[B]NASA Unveils New Public Web Portal for Research Results[/B]

Press release: [URL]https://www.nasa.gov/press-release/nasa-unveils-new-public-web-portal-for-research-results[/URL]

[URL="http://www.bbc.co.uk/news/science-environment-37167390"]Earth-sized world 'around nearest star'[/URL]

We already have the technology to go there and investigate in detail. Whether we have the political and economic will to embark on a project which won't give results until the early 22nd century is another matter entirely.

There are a whole bunch of technologies, perhaps the most promising are sub-1kg light sails boosted by sunlight and terrestrial (or NEO) lasers. Send off a thousand or so and some will arrive in good enough shape to report back. They only need to reach 0.05c to report back in a century or less.

[URL="https://www.reddit.com/r/spacex/comments/50a032/press_release_ses10_launching_to_orbit_on_spacexs/"]Reddit - Press release: "SES-10 Launching to Orbit on SpaceX's Flight-Proven Falcon 9 Rocket. Leading satellite operator will be world's first company to launch a geostationary satellite on a reusable rocket in Q4 2016"[/URL]

[URL="http://www.latimes.com/business/la-fi-spacex-rocket-20160829-snap-story.html"]LA Times: SpaceX signs first customer for launch of a reused rocket[/URL]
[QUOTE]There also was “no material change” in the insurance rate compared to using a new Falcon 9 rocket, indicating insurers’ confidence in the launch vehicle, Halliwell said.[/QUOTE]

[QUOTE=xilman;440602][URL="http://www.bbc.co.uk/news/science-environment-37167390"]Earth-sized world 'around nearest star'[/URL]

We already have the technology to go there and investigate in detail. Whether we have the political and economic will to embark on a project which won't give results until the early 22nd century is another matter entirely.

There are a whole bunch of technologies, perhaps the most promising are sub-1kg light sails boosted by sunlight and terrestrial (or NEO) lasers. Send off a thousand or so and some will arrive in good enough shape to report back. They only need to reach 0.05c to report back in a century or less.[/QUOTE]

Maybe my math is not so ok. Going there with current technology would be a waste of effort and time and i doubt we could produce equipment that doesn't break down for such long period of time.

However you might want to calculate a more practical goal.

How large do we need to make a telescope in space (its primary mirror) to be able to take a picture of the planet nearby proxima centauri?

Right now we only have indirect evidence by making picture of the star.

building a huge telescope in space existing out of many panels might not be such stupid idea. At earth there is gravity for example, which makes a huge telescope already soon very heavy.

With future technology delivering cargo cheaper in space we might be able to construct a massive telescope in space that can make great pictures.

Right now all telescopes are like "launch in 1 go" type telescopes that go to space.

Yet think larger. Think of autonomeous small robots in space that maintain a large structure that gets built in space. I'm not an expert in knowing at which orbit it should be.

Yet the advantages of it would be obvious. You can grow it very large over time. If something hits panels, you just need the robots to replace that panel and service it (if that's still possible). If no humans are involved you suddenly can do very cheap service flights to such project in space.

Risky Musk type rockets then might be a good solution.

So from payment viewpoint it's affordable.

[QUOTE=xilman;440602][URL="http://www.bbc.co.uk/news/science-environment-37167390"]Earth-sized world 'around nearest star'[/URL]

We already have the technology to go there and investigate in detail. Whether we have the political and economic will to embark on a project which won't give results until the early 22nd century is another matter entirely.

There are a whole bunch of technologies, perhaps the most promising are sub-1kg light sails boosted by sunlight and terrestrial (or NEO) lasers. Send off a thousand or so and some will arrive in good enough shape to report back. They only need to reach 0.05c to report back in a century or less.[/QUOTE]

If we calculate price of such mission it's soon 5 billion dollar for the first mission. Now maybe there is reduction in price and launchcosts should go down considerable in future if you produce a lot.

However if you really want to send 1000 to Proxima Centauri, that's gonna be a very expensive mission. Even the most careful estimate i would guess in the order of 300 billion dollar.

This where most likely around Proxima Centauri there isn't any planet that has any life - as the star is big in radiation.

Paying such huge cost for a mission to a star that with high certainty can't support any life in orbit around it, is tough to find funding for.

On other hand - go do some math with a huge telescope in space existing out of many panels serviced by small (semi-)autonomeous robots. Though i would rather want to call it dedicated robots rather than autonomeous.

[QUOTE=diep;441075]Maybe my math is not so ok. Going there with current technology would be a waste of effort and time and i doubt we could produce equipment that doesn't break down for such long period of time.[/QUOTE]
I don't see why your math should be a problem. What is the conceptual problem?

There are a number of space probes which are still working after twenty years. Of necessity they were built with technology now decades out of date. The Voyager probes are the best known examples but others exist.

Unsurprisingly, some terrestrial equipment has also worked perfectly for decades without maintenance. I've some computers in my loft which are over thirty years old, have never had any maintenance and still work perfectly AFAIK. Those are consumer-grade equipment which was never designed to last.

Longevity is not the problem, IMO. Political will is the major problem to be addressed before launching an interstellar mission.

That's not to say we shouldn't build a telescope as you describe. I whole-heartedly support the idea, not least because it would be useful for much more than looking in the close neighborhood of Proxima Centauri. Nonetheless, it is very unlikely to provide the wealth of detail that a close pass by a swarm of probes would give.

[QUOTE=diep;441075] How large do we need to make a telescope in space (its primary mirror) to be able to take a picture of the planet nearby proxima centauri?[/QUOTE]

Specify the size of the planet and the working wavelength of the imager and the computation of an approximation to the telescope aperture is straightforward. What follows is a first attempt. The estimate will be wrong but should be good to within a factor of two or so.

Assumptions[LIST][*]Working wavelength is 1 micron = 1e-6 m[*]Distance to Proxima is 1.3 parsec = 4e16 m[*]Maximum separation of planet from star is 0.05 AU or 7.5e9 m[*]Diameter of planet, assumed slightly larger than Earth's = 1.5e7 m[*]Desired number of pixels in diameter of planetary image = 10[/LIST]
To put the desired imaging capailities into familiar terms, the human eye has a resoution of 1 arcmin and the moon is 30 arcmin in diameter. Consequently, the telescope designed below will give an image showing markedly less detail than can be seen on the moon with the naked eye.

First note that much of the time the planet will not be at maximum elongation from the star but the desired image scale is such that the separation will be 10 * 7.5e9 / 1.5e7 pixels. This is 5000 pixels, so scattered starlight will be insignificant for almost all of the time.

The resolution element at the planet is (diameter / pixel size) = 1.5e6 m.

The ratio (pixel size) / (distance to planet) is thus 1.5e6/4e16 = 4e-11

Diffraction limit of an aperture diameter d working at wavelength lambda is approximately lambda / 2d. Accordingly we have 4e-11 = 1e-6 / 2d. Rearranging gives d = 1e-6 / (2 * 4e-11) = 1.3e4 m

I[B]n round numbers, a ten-kilometre optical telescope will do it.[/B]

The largest optical telescope on the earth is 0.01km across, the largest radio telescopes are 0.3-0.5km in diameter. Neither are steerable and neither need surface accuracies (much) better than 1 micron.

So you are asking for an optical telescope to be built in orbit which has a thousand times the aperture of bleeding edge ground-based instruments. In my considered opinion such a facility would be vastly more expensive to build than a thousand interstellar probes. The launch costs would be vastly more expensive. System maintenance, though possible, is also certain not to come cheap.

[QUOTE=xilman;441080]I don't see why your math should be a problem. What is the conceptual problem?

There are a number of space probes which are still working after twenty years. Of necessity they were built with technology now decades out of date. The Voyager probes are the best known examples but others exist.

Unsurprisingly, some terrestrial equipment has also worked perfectly for decades without maintenance. I've some computers in my loft which are over thirty years old, have never had any maintenance and still work perfectly AFAIK. Those are consumer-grade equipment which was never designed to last.

Longevity is not the problem, IMO. Political will is the major problem to be addressed before launching an interstellar mission.

That's not to say we shouldn't build a telescope as you describe. I whole-heartedly support the idea, not least because it would be useful for much more than looking in the close neighborhood of Proxima Centauri. Nonetheless, it is very unlikely to provide the wealth of detail that a close pass by a swarm of probes would give.[/QUOTE]

None of those probes will survive another century though.

For such telescope you first want to see a simple magnification calculation what size you would require to make a photo, even if it's a few pixels, of a planet orbitting another star. Such math is doable long before the concept turns into a serious plan.

What you propose is to ship unproven technology, assume the probe will survive for 2 centuries, something still unproven as well, somehow it must then be able to communicate back to us 2 centuries from now, and to ship it to a star which with near to 100% sureness according to how we use logics can't support any form of life as we know it, which then all together is gonna cost in the hundreds of billions if not more.

If something can't work in advance, companies are gonna keep that a secret. People making money are very good at getting contracts.

They also kept something quiet around hubble in that sense. They d** well knew something was wrong - and deliberately didn't investigate it as they knew something was wrong. And 'they' being the CEO's of the small tiny company grinding the mirrors.

A multibllion dollar project that for a contract of what was it 20 million dollar or so, had to spend another few billion fixing something. This where probes that travel for 2 centuries to a remote star, with the traveltime an assumption, you can't correct anything on them.

Unproven technology that's gonna travel for an unproven period of time, that's gonna pass through all sorts of belts where particles can tank the probe, and where hundreds of billions are possible to get made. The conceptual problem is that with 100% sureness some frauds will manage to get contract jobs and mess up - even if conceptual it would be possible. They are long dead and gone when their shortcuts that render every single probe useless, get unveiled.

Speaking of math. Please calculate the difference of the hubble primary versus the same primary that would be parabolic primary.

You'll figure out the difference is less than 0.1 nanometer. In short that's factors less than the grinding accuracy they could achieve in 1979.

In short they didn't need some complicated manner of testing that primary mirror, which you need for a hyperbolic primary mirror. A simple laser interferometer would have done - of course they took that shortcut.

Then the next question is: how the h*** could they mess that up?

Well they DID.

When one of the grinders noticed that something might be wrong - the leadership of that company took care not a single test was done that would've found the problem.

Of course they already knew that something went wrong...

The conceptual problem of a 300 billion project with zero control possible the probes actually will work for another 2 centuries during the life of those CEO's delivering junk - the conceptual problem is that someone will be carrying out the project for 150 billion dollar and mess up with 100% sureness.

[QUOTE=diep;441078]If we calculate price of such mission it's soon 5 billion dollar for the first mission. Now maybe there is reduction in price and launchcosts should go down considerable in future if you produce a lot.

However if you really want to send 1000 to Proxima Centauri, that's gonna be a very expensive mission. Even the most careful estimate i would guess in the order of 300 billion dollar.[/QUOTE]The actual probes should not cost very much each. A few grams of graphene for a square-metre sail and a wafer-sized chip. In thousand-off quantities they might cost a million USD each, for a total cost of a billion.

The launch facility will be expensive, no doubt, but again economies of scale come into play. A phased-array of numerous lasers uses relatively cheap mass-produced components. A few billion USD should cover the manufacturing and installation.

Development costs are much less easily estimated. I'd guess something in the range 1-10 billion USD.


If I'm anywhere near the right ballpark, a mission cost of, say, 20 billion USD will cover it. This is more than an order of magnitude lower than your estimate. To put things in perspective, the Apollo project cost close to 100 billion USD in 2010 dollars.

[QUOTE=diep;441085]None of those probes will survive another century though.

For such telescope you first want to see a simple magnification calculation what size you would require to make a photo, even if it's a few pixels, of a planet orbitting another star. Such math is doable long before the concept turns into a serious plan.

What you propose is to ship unproven technology, assume the probe will survive for 2 centuries, something still unproven as well, somehow it must then be able to communicate back to us 2 centuries from now, and to ship it to a star which with near to 100% sureness according to how we use logics can't support any form of life as we know it, which then all together is gonna cost in the hundreds of billions if not more.

If something can't work in advance, companies are gonna keep that a secret. People making money are very good at getting contracts.

They also kept something quiet around hubble in that sense. They d** well knew something was wrong - and deliberately didn't investigate it as they knew something was wrong. And 'they' being the CEO's of the small tiny company grinding the mirrors.

A multibllion dollar project that for a contract of what was it 20 million dollar or so, had to spend another few billion fixing something. This where probes that travel for 2 centuries to a remote star, with the traveltime an assumption, you can't correct anything on them.

Unproven technology that's gonna travel for an unproven period of time, that's gonna pass through all sorts of belts where particles can tank the probe, and where hundreds of billions are possible to get made. The conceptual problem is that with 100% sureness some frauds will manage to get contract jobs and mess up - even if conceptual it would be possible. They are long dead and gone when their shortcuts that render every single probe useless, get unveiled.

Speaking of math. Please calculate the difference of the hubble primary versus the same primary that would be parabolic primary.

You'll figure out the difference is less than 0.1 nanometer. In short that's factors less than the grinding accuracy they could achieve in 1979.

In short they didn't need some complicated manner of testing that primary mirror, which you need for a hyperbolic primary mirror. A simple laser interferometer would have done - of course they took that shortcut.

Then the next question is: how the h*** could they mess that up?

Well they DID.

When one of the grinders noticed that something might be wrong - the leadership of that company took care not a single test was done that would've found the problem.

Of course they already knew that something went wrong...

If I'm in at least the right
The conceptual problem of a 300 billion project with zero control possible the probes actually will work for another 2 centuries during the life of those CEO's delivering junk - the conceptual problem is that someone will be carrying out the project for 150 billion dollar and mess up with 100% sureness.[/QUOTE]Your duration assumptions are wildly wrong.

Current plans are for the probes to travel at 0.05 to 0.2c. Flight time is therefore 20 to 80 years. Results return at the speed of light so add another four years.

As I noted, large amounts of stuff has been shown to work perfectly for decades without any maintenance.

[QUOTE=xilman;441087]Your duration assumptions are wildly wrong.

Current plans are for the probes to travel at 0.05 to 0.2c. Flight time is therefore 20 to 80 years. Results return at the speed of light so add another four years.

As I noted, large amounts of stuff has been shown to work perfectly for decades without any maintenance.[/QUOTE]

That's probes with nuclear batteries from which we know how long they last. They won't make it that much longer.

I hear wildly ideas through each other. First i hear something about solar parachutes and then suddenly something about lasers. Well let's forget about the lasers for now. Our lasers aren't powerful enough.

Then i hear something about weight. You do realize you need some power to ship back signals from Proxima Centauri to here?

[QUOTE=xilman;441086]The actual probes should not cost very much each. A few grams of graphene for a square-metre sail and a wafer-sized chip. In thousand-off quantities they might cost a million USD each, for a total cost of a billion.

The launch facility will be expensive, no doubt, but again economies of scale come into play. A phased-array of numerous lasers uses relatively cheap mass-produced components. A few billion USD should cover the manufacturing and installation.

Development costs are much less easily estimated. I'd guess something in the range 1-10 billion USD.


If I'm anywhere near the right ballpark, a mission cost of, say, 20 billion USD will cover it. This is more than an order of magnitude lower than your estimate. To put things in perspective, the Apollo project cost close to 100 billion USD in 2010 dollars.[/QUOTE]

Everything in space, first square the price and then the only question is whether it needs to get squared again.

To make some good pictures you need to equip each probe with a bunch of sensors and a good camera. You only get 1 shot at it with such mission so you want to equip it with really a lot of sensors.

You definitely need to ship something that's quickly 500 kilo or so. That would be something totally unprotected. We just gamble in such case nothing in space will hit it (as you ship a 1000 anyway).

How large does the sun parachute need to be in that case?

New Horizons launch mass was 478 kilo - yet that's without parachute.

[QUOTE=xilman;441086] ....
Development costs are much less easily estimated. I'd guess something in the range 1-10 billion USD.
[/quote]

Well on development costs. Here i have a different opinion than how it currently works. I simply assume next:

a) spacecraft get ever more advanced and need to get more advanced
b) software you don't build with the same 2 persons that hacked together the spacecraft...

If we look how New Horizons was rushed together by just 2 persons that's not how it should go.

I'm in favour of a nonstop development team that develops great software and hardware solutions for future missions so that components are ready that can get used that work well and have been tested well.

First of all it reduces launch weight. Right now that mission we discuss probably needs to get hacked together by 2 persons within 1 year - before no more funding is there.

Either something gets funded now or not at all - and when it does get funded - you usually have little time to build something and deliver it.

That's dead wrong approach simply. A much better approach is not easy to find. Yet you simply want the best software guy to develop the software and the best hardware guy to develop the hardware. Right now that's not how it happens.

[QUOTE=diep;441089]Everything in space, first square the price and then the only question is whether it needs to get squared again.

To make some good pictures you need to equip each probe with a bunch of sensors and a good camera. You only get 1 shot at it with such mission so you want to equip it with really a lot of sensors.

You definitely need to ship something that's quickly 500 kilo or so. That would be something totally unprotected. We just gamble in such case nothing in space will hit it (as you ship a 1000 anyway).

How large does the sun parachute need to be in that case?

New Horizons launch mass was 478 kilo - yet that's without parachute.[/QUOTE]Once more: your assumptions are wildly inaccurate.

Each probe has a mass of under a kilogram. You are out by three orders of magnitude.

You don't launch one probe. You fire off a thousand or so. Who cares if even a hundred of them fail to work on arrival?

You don't get one shot. You get a thousand shots.

Not all probes need to be identical and carry a complete set of instruments. A hundred, say could be optimised for observing magnetic fields, another hundred for optical imaging, another hundred for measuring dust properties, another hundred for measuring the thermal properties of the planetary and stellar atmospheres another hundred for measuring the chemical compostition of the same. Let's see, I'm up to five hundred probes so far. Another five hundred still to be allocated.

A multi-megapixel camera and optics weigh a gram or less costs a few dollars at present.

The "sun parachute" (actually a light sail) is about a metre across.

The light sail is also the communications antenna. Communication back to the solar system is by laser. Diode lasers are also dirt cheap and very low mass.

New Horizons used almost totally different technology, rendering your comparison not particularly useful.

Please read [url]https://breakthroughinitiatives.org/Initiative/3[/url] and related material to bring yourself up to date on the proposals and technology I'm discussing. You appear still to be thinking about 1980's systems. I'm thinking about 2020-technolgy.

[QUOTE=xilman;441094]Not all probes need to be identical and carry a complete set of instruments. A hundred, say could be optimised for observing magnetic fields, another hundred for optical imaging, another hundred for measuring dust properties, another hundred for measuring the thermal properties of the planetary and stellar atmospheres another hundred for measuring the chemical compostition of the same. Let's see, I'm up to five hundred probes so far. Another five hundred still to be allocated.[/QUOTE]

Indeed. And even without guidance, they will all take different hyperbolic trajectories.

Should be a good and informative time.

[QUOTE=xilman;441094]Once more: your assumptions are wildly inaccurate.

Each probe has a mass of under a kilogram. You are out by three orders of magnitude.

You don't launch one probe. You fire off a thousand or so. Who cares if even a hundred of them fail to work on arrival?

You don't get one shot. You get a thousand shots.

Not all probes need to be identical and carry a complete set of instruments. A hundred, say could be optimised for observing magnetic fields, another hundred for optical imaging, another hundred for measuring dust properties, another hundred for measuring the thermal properties of the planetary and stellar atmospheres another hundred for measuring the chemical compostition of the same. Let's see, I'm up to five hundred probes so far. Another five hundred still to be allocated.

A multi-megapixel camera and optics weigh a gram or less costs a few dollars at present.

The "sun parachute" (actually a light sail) is about a metre across.

The light sail is also the communications antenna. Communication back to the solar system is by laser. Diode lasers are also dirt cheap and very low mass.

New Horizons used almost totally different technology, rendering your comparison not particularly useful.

Please read [url]https://breakthroughinitiatives.org/Initiative/3[/url] and related material to bring yourself up to date on the proposals and technology I'm discussing. You appear still to be thinking about 1980's systems. I'm thinking about 2020-technolgy.[/QUOTE]

For optics you'll need something that's like 8 inches at least in diameter, probably 10 would be better. Doesn't weigh that much though. Optics are optics simply.

For communications using the light sail seems suspected to me.

I'm not so sure using carbon technology is a good idea for something that has to get dead old. In space all carbon structures have the habit to shrink and vanish.

Lots of those 2020s technologies still need to get tested out and majority won't work.

[QUOTE=diep;441111]I'm not so sure using carbon technology is a good idea for something that has to get dead old. In space all carbon structures have the habit to shrink and vanish.[/QUOTE]

Just in case you are not aware, known life (including us) is carbon technology....

[QUOTE=chalsall;441112]Just in case you are not aware, known life (including us) is carbon technology....[/QUOTE]

We get protected by earth from the sun there. structures in space that use carbon technology, such as hubble - they have a limited life - they keep shrinking.

[QUOTE=diep;441113]structures in space that use carbon technology, such as hubble - they have a limited life - they keep shrinking.[/QUOTE]

Please support that statement with documentation.

You can simply look it up at the hubble pages from NASA.

[QUOTE=diep;441116]You can simply look it up at the hubble pages from NASA.[/QUOTE]

You made the claim sir. Support it.

[QUOTE=diep;441111]For optics you'll need something that's like 8 inches at least in diameter, probably 10 would be better. Doesn't weigh that much though. Optics are optics simply.

For communications using the light sail seems suspected to me.

I'm not so sure using carbon technology is a good idea for something that has to get dead old. In space all carbon structures have the habit to shrink and vanish.

Lots of those 2020s technologies still need to get tested out and majority won't work.[/QUOTE]Where do you get the figure of 8 to 10 inches (I prefer 20 to 25 cm but there again I'm British and more accustomed to SI units) for the size of the optics? My entire phone is only a fraction of that size and manages to take entirely adequate pictures as well as performing all its other functions.

A light sail, by definition is a reflector of light. Suitably curved it could focus a comms laser beam from earth on to the probe for software updates. It could also act as the transmitter antenna in the reverse direction, though I suspect that just pointing a laser back at the solar system will be better.

You are thinking about carbon fibre which does indeed tend to shrink. However, it's not the carbon at fault but the resin which holds the fibre together. It slowly evaporates in the hard vacuum.

The proposed structural material is essentially pure carbon, graphite for the probe body and graphene for the sail. Silica has also been proposed for the former. Even nicer, in many ways, would be a diamond structure but artificial diamonds circa 10-20 cm in diameter are not currently possible.

I fully agree that making square-metre scale sheets of graphene has not yet been demonstrated in the public literature. That is definitely some 2020-technology which needs to be demonstrated. I see absolutely no reason why it should not be possible within the next few years.

Custom developed diamond device technology is proceeding:
[QUOTE]Under an operating microscope, doctors will cleanly chop through both spinal cords—with a $200,000 diamond nanoblade, so thin that it is measured in angstroms, provided by the University of Texas.[/QUOTE]
[URL="http://www.newsweek.com/2016/05/06/first-human-head-transplant-452240.html"]DOCTOR READY TO PERFORM FIRST HUMAN HEAD TRANSPLANT[/URL]

[QUOTE=diep;441113]We get protected by earth from the sun there. structures in space that use carbon technology, such as hubble - they have a limited life - they keep shrinking.[/QUOTE]Hubble has been in orbit for something over 26 years now. It is still working and the shrinkage you allege has not yet caused it to fail. A trip of 4 light years at 0.2c takes twenty years.

Before you comment, I'm well aware that Hubble has been serviced. Such servicing was of the optical and ancillary equipment, [b]not[/b] the structural components.

[QUOTE=only_human;441147][URL="http://www.newsweek.com/2016/05/06/first-human-head-transplant-452240.html"]DOCTOR READY TO PERFORM FIRST HUMAN HEAD TRANSPLANT[/URL][/QUOTE]
Didn't click it yet (busy here!) but wondering: is that a head transplant, or a body transplant? If you take the heart out of a guy (whose body is damaged) and put it inside other guy's chest (whose heart was damaged), that is a heart transplant, which makes the second guy function, using "spare parts" from the first. But if you take the brain out of a guy X (with a damaged body) and place it inside the scull of other guy Y (whose brain is damaged), is that a brain transplant, or a body transplant? Because when (and if) the "functioning" guy wakes up, he is X, in a new body. And not Y with a new brain. All the knowledge, memories, logic, un-logic, whatever, is from the X guy....

[QUOTE=LaurV;441158]Didn't click it yet (busy here!) but wondering: is that a head transplant, or a body transplant?..[/QUOTE]
Head transplant onto a donor body ... as you say it could be called a body transplant but when you move a plant into a bigger pot we call that a plant transplant instead of a pot transplant. This ethically challenged procedure will be moving a head into a bigger pot.
[URL="http://www.theatlantic.com/magazine/archive/2016/09/the-audacious-plan-to-save-this-mans-life-by-transplanting-his-head/492755/"]The Audacious Plan to Save This Man’s Life by Transplanting His Head[/URL]
[QUOTE]Spiridonov’s head would float across the operating theater to the donor body on a customized crane, hanging by Velcro straps. Surgeons would align the spinal stumps and bind the two ends together, using peg to fuse Spiridonov’s spinal cells with the donor’s. The surgeons would also implant an electrical paddle near the fusion site, because studies have shown that bursts of electricity help establish communication across a severed spinal cord.

At the same time, another team of surgeons would begin the long, messy process of attaching a head to a body. With the hour ticking down, establishing blood flow to Spiridonov’s brain would take priority. After that, surgeons would install the spinal bones, trachea, and esophagus, then attach the color-coded muscles. One vital step would involve connecting the nerves that carry signals from the brain to the heart and to the muscles that pump the lungs, so Spiridonov’s new body could breathe and regulate its heartbeat.

Thirty-six hours after entering surgery, the new Spiridonov would roll out the door, sitting upright.[/QUOTE]

[QUOTE=xilman;441149]Hubble has been in orbit for something over 26 years now. It is still working and the shrinkage you allege has not yet caused it to fail. A trip of 4 light years at 0.2c takes twenty years.

Before you comment, I'm well aware that Hubble has been serviced. Such servicing was of the optical and ancillary equipment, [b]not[/b] the structural components.[/QUOTE]

Hubble has been designed such that it could survive some decades of shrinkage.

Yet there is a limit to it when the motors no longer can compensate for it.

No service mission would help in the end. Yet from my viewpoint i wonder already for a long time why they didn't design it such that it could get serviced by robots.

A robot of a few kilo's, maybe even lighter, is a lot cheaper to launch to low orbit than a human being with a space suit, survival gear and so on.

Note that telescope apertures usually work in inches just like your plumbing tubing does.

Even though the inches that plumbers use are total outdated as nowadays improved production techniques take care the thickness of the pipes has improved a lot.

My telescope here is 10 inch.

Yet the entire math regarding the rest is in millimeters :)

Graphene type structures are highly poisenous.

I'm not so sure we soon will see industry grade materials that are easy to proces from graphene as there is only some industrial purposes to it.

Right now in a lab they have like 1 atom thick layer material or something and largest size ever produced you still need a microsope - would be amazed if it's above 1 square inch by now.

That'll take decades.

In space using graphene i'm not so sure that would be a good idea - yet i'm no material expert in that sense. The carbon structures in space all shrink.

After graphene has been produced on earth it still needs to be tested in space of course.

Why can't the parachute be from some other material?

If you want to use it as a laster disk i assume aluminium is a good material?
Highly reflective!

Yet something travelling that far away i assume such parabolic sphere needs to be pretty large. Maybe diameter 10 meters would be enough?

Note that i remember that pluto photos from recently were taken with a camera with 10 inch lenses - yet i do that from memories from some time ago - so you might want to dive into that one.

If you don't like the quality of those pictures, your probe to other stars will need to carry larger camera's with it.

Probably you want it to have at least 2 camera's as getting back pictures is most important.

Quite probably you want better camera's as well - which basically means larger enlargements - so that means wider apertures - as you are going to take pictures from further away most likely from planets.

As for shipping probes out to discover outside our system - please realize i'm a fan of that.

Yet it'll require a better approach than past missions. Spending billions for probes that get hacked together by 2 men within a year time - without KNOWING it works ok - i call that amateuristic work.

A professional probe to discover far far away systems - it'll require some testing and tests - as well as maybe more than we were used to have. Like having its own autonomeous robots that can move outside to repair and inspect - remove dirt and so on. Can be very tiny robots and maybe some service robot that can do welding / 3d printing of materials to repair small damages.

If you ship something - please ship something professional :)

[QUOTE=diep;441175]Graphene type structures are highly poisenous.
[/quote]Evidence please. This is the first I've heard of the claim --- an admission of ignorance on my part.

Anyway, what does it matter if they are poisonous? Hypergolic rocket fuels and Pu radioisotopes are highly poisonous too, but space missions use them regardless.

[QUOTE=diep;441175]
That'll take decades.
[/QUOTE]Why? Anyway, the project assumes a 20-year span for research and construction, so we have decades.

[QUOTE=diep;441175]
In space using graphene i'm not so sure that would be a good idea - yet i'm no material expert in that sense. The carbon structures in space all shrink.
[/QUOTE]Once more: you are talking about carbon fibre composites, where it is the binder which shrinks, not the carbon fibres themselves. Graphene sails and graphite (or diamond) structures are pure carbon and are extremely unlikely to shrink. If you have evidence to the contrary, please produce it.

It's far more likely that a graphite spacecraft structure will expand rather than shrink. Experience with graphite moderated reactors shows that the crystal structure is damaged by radiation in such a way that atomic-sized voids are created as carbon atoms are displaced by high energy radiation. Interstellar gas travelling at 0.2c [i]is[/i] high energy radiation. Fortunately its density is so low that significant damage to the graphite crystal structure won't occur. Note that this is easy to test in the lab. Creating 0.2c proton and helium beams is easy. Heavier atoms too, but they are much less common in the ISM.

[QUOTE=diep;441175]
After graphene has been produced on earth it still needs to be tested in space of course.
[/QUOTE]Agreed. Easily enough to do, and on earth too. Vacuum chambers exist down here; they can be kitted out with UV radiation, heating and cooling, ionizing radiation, mechanical vibrations and so forth. This is [i]old[/i] technology. It was used over fifty years ago in the Apollo project.
[QUOTE=diep;441175]
Why can't the parachute be from some other material?
[/quote]It can. Graphene is very much lighter and stronger than other known materials.
[QUOTE=diep;441175]
If you want to use it as a laster disk i assume aluminium is a good material?
Highly reflective!
[/quote]Aluminium is reflective but weak. Light-weight mirrors generally use a thin plastic, such as mylar, on which very thin layer of Al (or Au for infrared mirrors) has been deposited.
[QUOTE=diep;441175]
Yet something travelling that far away i assume such parabolic sphere needs to be pretty large. Maybe diameter 10 meters would be enough?[/QUOTE]
You can assume anything you like. Your views would be taken much more seriously if you first read and then understood the proposals before commenting on them. I've already provided you with the starting point for your investigations.

Oh boy where to start.

Nearly all cheap mirrors have an aluminium reflective coating for visible light spectra.

Gold reflects better yet doesn't cover the entire visible light spectrum. Gets used especially for infrared.

Silver on paper is reflecting very well - yet it oxidizes too fast.

In space gold gets used most for reflection. On earth aluminium most.
My own telescope has aluminium coating.

If you want that parachute behind the probe to also act as radio antenna, you'll need to give it an aluminium, silver or gold coating in short.

Why not directly make it out of aluminium then?

Much easier.

I don't see any use for graphene type materials there - asking for troubles.

Diamond reflects to all direction - no use for it as a parabolic antenna.

The reason for a parabolic antenna is to get a larger surface area to communicate. In short that shape needs to be very precisely a parabola.
You need a very stiff material. If you go toy with some plastic or carbon that bends a lot you no longer can communicate home.

The tensile strength of graphene is unrivalled - yet that's not what you need.

p.s. i don't think graphite ever will be used :)

[QUOTE=diep;441205]Oh boy where to start.

Nearly all cheap mirrors have an aluminium reflective coating for visible light spectra.

Gold reflects better yet doesn't cover the entire visible light spectrum. Gets used especially for infrared.

Silver on paper is reflecting very well - yet it oxidizes too fast.

In space gold gets used most for reflection. On earth aluminium most.
My own telescope has aluminium coating.

If you want that parachute behind the probe to also act as radio antenna, you'll need to give it an aluminium, silver or gold coating in short.

Why not directly make it out of aluminium then?

Much easier.

I don't see any use for graphene type materials there - asking for troubles.

Diamond reflects to all direction - no use for it as a parabolic antenna.

The reason for a parabolic antenna is to get a larger surface area to communicate. In short that shape needs to be very precisely a parabola.
You need a very stiff material. If you go toy with some plastic or carbon that bends a lot you no longer can communicate home.

The tensile strength of graphene is unrivalled - yet that's not what you need.

p.s. i don't think graphite ever will be used :)[/QUOTE]A pure aluminium mirror weighs far too much for use as a light sail. Metallic coated thin films are very much lighter for the same performance, as long as you don't demand high-quality imaging. The tensile strength of graphene is [i]exactly[/i] what you need. It lets you use extremely thin films and hence extremely low mass films for a given reflecting area. Mass is of crucial importance in this project. Each probe has to have a mass under one kilogram for everything: sail, structure, detectors, comms, power supply, the lot.

For comms use, imaging isn't very important as there is only one detection element. Anything which increases the signal to noise ratio is useful for this purpose. It's nice to get more signal on the detector but if doubling the signal costs too much mass, then just use a more powerful transmitter. If the comms to the spacecraft uses a visible light laser, Al is better than Au for coating. If the laser is in the near infrared the opposite is true. Given that the sun is brightest in the optical [i]and[/i] light from the solar system will be red-shifted by 20% or so, using near-infrared communications makes a lot of sense to me as it stands out better from sunlight.

OTOH, I don't yet know whether the launch laser would be better working in the visible or the IR, though I suspect the latter given what little I know about the achievable average power of current lasers. A 100W optical laser is quite unusual, AFAIK, whereas multi-kilowatt IR lasers are widely used in industrial cutting and machining.

Graphite (or possibly diamond, that's my suggestion not the "official" one) is suggested for the spacecraft structure, not the sail.

[QUOTE=xilman;441211]A pure aluminium mirror weighs far too much for use as a light sail. Metallic coated thin films are very much lighter for the same performance, as long as you don't demand high-quality imaging. The tensile strength of graphene is [i]exactly[/i] what you need. It lets you use extremely thin films and hence extremely low mass films for a given reflecting area. Mass is of crucial importance in this project. Each probe has to have a mass under one kilogram for everything: sail, structure, detectors, comms, power supply, the lot.

For comms use, imaging isn't very important as there is only one detection element. Anything which increases the signal to noise ratio is useful for this purpose. It's nice to get more signal on the detector but if doubling the signal costs too much mass, then just use a more powerful transmitter. If the comms to the spacecraft uses a visible light laser, Al is better than Au for coating. If the laser is in the near infrared the opposite is true. Given that the sun is brightest in the optical [i]and[/i] light from the solar system will be red-shifted by 20% or so, using near-infrared communications makes a lot of sense to me as it stands out better from sunlight.

OTOH, I don't yet know whether the launch laser would be better working in the visible or the IR, though I suspect the latter given what little I know about the achievable average power of current lasers. A 100W optical laser is quite unusual, AFAIK, whereas multi-kilowatt IR lasers are widely used in industrial cutting and machining.

Graphite (or possibly diamond, that's my suggestion not the "official" one) is suggested for the spacecraft structure, not the sail.[/QUOTE]

Under 1 kilo you won't be able to produce something that can produce good pictures and ship them back home. Otherwise your probe could take that picture already from here and doesn't need to travel to that star.

It's all about aperture of the camera's lenzes....

Which is why i say: first calculate how large of a telescope you need to build here in orbit of earth, to take a picture of planets at other stars.
That calculation is interesting to see :)

I don't understand why you are busy with lasers at these huge distances.

At such huge distance a laser is total useless.

Typical machine that uses laser cutter is like 60 watt laser (the motors on the other hand consume kilowatts not seldom - even the steppers i have here have their own PSU each one of them :))

p.s. graphite is something else than graphene.

Xilman, In this all the thing most underestimated seems to be how tough it is to communicate with the homefront.

The sorts of signals we analyze here from remote sources are things like quasars and big bursts of stars.

That's huge things. How to communicate back to the homefront with something under 1 kilo and no power source at all or at most some small battery?

Suppose your thing flies at 0.05c, though i know some experts are disputing all that, yet me not being an expert there will say simply: "let's continue pondering and make plans".

Or in the words here of Batalov: "Plot. Scratch your forehead. Analyze. Plan ahead. Keep it simple".

The KISS manner of communicating back to the homefront is some huge parabolic antenna. Let's say a meter or 30 diameter. Then use megawatts of electricity and try to get a signal back home and pray it gets detected.

At a speed of 0.05c you got just a few minutes to zoom in onto the planets and seconds to make a photograph of each planet you detect and then you crash into the star.

If your probe does have some sort of telescope say with diameter 1 meter, you make more of a chance to detect planets quickly and make that photo.

Then you have seconds to communicate back to earth prior to impact into the star.

In case of some star with circumstances similar to the Sun, your odds are even worse - you'd crash into the jupiter equivalent there prior to be able to take pictures.
At most your chances of making a photo of something similar like 'earth' is 25% at most in those few seconds you have prior to crashing into the 'jupiter equivalent'.

How do you communicate back?

[QUOTE=xilman;441146] Even nicer, in many ways, would be a diamond structure but artificial diamonds circa 10-20 cm in diameter are not currently possible.[/QUOTE]
Indeed, we can't make single-crystal diamonds this size today, but
a while ago I did read something about diamond powder sintering,
giving polycristalline diamonds the size of some cm^3. I wonder
how big this thingies could be made if someone really tried.

But why would diamond be nicer than, for example, Al2O3 or SiC?
They have lower density, thermal and chemical stability is
quite nice, mechanical load on the structures should be low...
Radiation effects?

[QUOTE=J F;441221]Indeed, we can't make single-crystal diamonds this size today, but
a while ago I did read something about diamond powder sintering,
giving polycristalline diamonds the size of some cm^3. I wonder
how big this thingies could be made if someone really tried.

But why would diamond be nicer than, for example, Al2O3 or SiC?
They have lower density, thermal and chemical stability is
quite nice, mechanical load on the structures should be low...
Radiation effects?[/QUOTE]

I assume because he wants to keep a souvenir as i see no other use in diamonds in a space crafts hull.

I'd build it out of a combination of metals not any sort of carbon idiocy at all.

Xilman - seems something interesting is this link:

[url]http://www.nasa.gov/mission_pages/hubble/science/pluto-20100204.html[/url]

That's one of the better pictures taken by Hubble of pluto.

If you are at 0.05c (i give you this speed for free out of appreciation) you will need to take photographs from quite a distance.

Realize Hubble is a ritchey-chretien telescope that can make very accurate pictures with a 2.4 meter diameter aperture.

So if you pass with a small probe a specific star - you've got minutes to determine what the planets are - and to take a good picture you simply need a big aperture or you will just have 1 or 2 pixels at most.

We already know there are planets - we just want good pictures from them - the rest really is not so interesting.

You need a huge aperture to make a good picture. At the distance of hubble <=> pluto, this is the maximum you can get - and taking this picture by hubble probably took quite some time.

If you'd equip the probe with a hubble sized camera the picture will be a lot worse than the hours hubble can spend taking a single picture.

[QUOTE=diep;441224][url]http://www.nasa.gov/mission_pages/hubble/science/pluto-20100204.html[/url]

That's one of the better pictures taken by Hubble of pluto.
.....

You need a huge aperture to make a good picture. At the distance of hubble <=> pluto, this is the maximum you can get - and taking this picture by hubble probably took quite some time.

If you'd equip the probe with a hubble sized camera the picture will be a lot worse than the hours hubble can spend taking a single picture.[/QUOTE]You obviously did not read the caption in the link that you posted, nor the article.
Those are generated images from multiple images taken. The data were then calculated and rendered. Pluto is bright enough that Hubble does not need 'quite some time'.

Paul also (I can safely assume) has some answers to some of the imaging issues that you think that you are bringing up. There are many answers that he has up his sleeve that you have not progressed far enough in your understanding to receive. I have been watching the discussion and know that you are making some real errors in knowledge, understanding, and logic.:popcorn:

[QUOTE=Uncwilly;441239]You obviously did not read the caption in the link that you posted, nor the article.
Those are generated images from multiple images taken. The data were then calculated and rendered. Pluto is bright enough that Hubble does not need 'quite some time'.

Paul also (I can safely assume) has some answers to some of the imaging issues that you think that you are bringing up. There are many answers that he has up his sleeve that you have not progressed far enough in your understanding to receive. I have been watching the discussion and know that you are making some real errors in knowledge, understanding, and logic.:popcorn:[/QUOTE]

All images are rendered from multiple photos.

There is no other way. The previous photo taken which took quite some time from pluto by hubble, some years before that - it's just some blue pixels.

Taking photos from a large distance is very very complicated.

A kilo heavy probe is just like proposing transporting cargo between UK and China by using floating miniature containers.

[QUOTE=diep;441240]All images are rendered from multiple photos.

There is no other way. The previous photo taken which took quite some time from pluto by hubble, some years before that - it's just some blue pixels.

Taking photos from a large distance is very very complicated.

A kilo heavy probe is just like proposing transporting cargo between UK and China by using floating miniature containers.[/QUOTE]
Here is a list of challenges identified so far in the Breakthrough Starshot high speed lightsail program:
[url]https://breakthroughinitiatives.org/Challenges/3[/url]

[QUOTE=diep;441240]All images are rendered from multiple photos.

There is no other way. The previous photo taken which took quite some time from pluto by hubble, some years before that - it's just some blue pixels.

Taking photos from a large distance is very very complicated.[/QUOTE]You are just plain wrong. To see how wrong you are take your phone outside on a clear moonlit night and point it at the moon at full zoom. Take a picture.

You will end up with a photo of the moon at a distance of 400 thousand km with a camera which has an aperture of a few millimetres and a mass of a gram or so.

All that bullshit about crashing into the star is just that: bullshit. It would take extremely precise targeting to hit the star and why would anyone want to do that? Unless a decision is made to impact something the odds are overwhelmingly likely that all the probes will just pass clean through the Proxima system.

[QUOTE=diep;441240]All images are rendered from multiple photos.

There is no other way. The previous photo taken which took quite some time from pluto by hubble, some years before that - it's just some blue pixels.

Taking photos from a large distance is very very complicated.

A kilo heavy probe is just like proposing transporting cargo between UK and China by using floating miniature containers.[/QUOTE]

You are just plain wrong. To see how wrong you are take your phone outside on a clear moonlit night and point it at the moon at full zoom. Take a picture.

You will end up with a photo of the moon at a distance of 400 thousand km with a camera which has an aperture of a few millimetres and a mass of a gram or so. Further, your camera has not been specifically optimized within those physical parameters to take especially high quality images because a phone camera has to be dirt cheap to be sold by the billion to people who really don't care that much about image quality.

All that bullshit in your other post about crashing into the star is just that: bullshit. It would take extremely precise targeting to hit the star and why would anyone want to do that? Unless a decision is made to impact something the odds are overwhelmingly likely that all the probes will just pass clean through the Proxima system.

By the time the probes get there we should know the location of the planet to within a thousand km or so. In other words, the photo could be taken from much closer than 400,000 km. Motion blur could be an issue but could be mitigated by scanning the camera field of view or by subsequent deconvolution of the blurred image. Even if the former isn't practical from mass and / or energy considerations, the latter has been standard practice for 20 years or more already.

[QUOTE=diep;441224]We already know there are planets - we just want good pictures from them - the rest really is not so interesting.[/QUOTE]That may be all you are interested in. I can assure you that there are many others who are nowhere near as blinkered in their desire for knowledge and understanding. Why did you think I posted about magnetic fields, chemical composition, thermal structure, and so forth?

[QUOTE=diep;441213]p.s. graphite is something else than graphene.[/QUOTE]I know.

Why do you think I referred to graphene only in the context of the light sail, which needs to have a large area in as small a mass as possible but doesn't need to be rigind, and graphite as a candidate for the probe's structure on which the science instruments are mounted, which needs to be rigid and as small a mass as possible?

Please pay attention to what I'm typing and please read the supplementary material to which I have given you an excellent entry point.

[QUOTE=J F;441221]Indeed, we can't make single-crystal diamonds this size today, but
a while ago I did read something about diamond powder sintering,
giving polycristalline diamonds the size of some cm^3. I wonder
how big this thingies could be made if someone really tried.

But why would diamond be nicer than, for example, Al2O3 or SiC?
They have lower density, thermal and chemical stability is
quite nice, mechanical load on the structures should be low...
Radiation effects?[/QUOTE]Single crystals have nice mechanical properties, in particular it's relatively easy to deposit microelectronic and MEMS devices on them. Graphite, being a conductor, would presumably need an insulating layer between the physical structure and the active devices. Monocrystalline diamond has wonderful mechanical, electrical, thermal and radiation hardness properties. Its density is lower than alumina (3.52 vs ~4.0) but 10% larger than SiC (3.2).

The killer is that we don't yet know how to make big enough single crystals of diamond. Sintered polycrystalline diamond (IMO, I don't know for sure) is likely to have too great a surface roughness for standard semiconductor technology to build reliably working devices on top of it. I agree SiC is a fine candidate material and easy to make in large single crystals but please remember that the diamond proposal is (AFAIK) entirely my own idea and I'm quite prepared to be convinced that it is a bad one.

[QUOTE=xilman;441253]I know.

Why do you think I referred to graphene only in the context of the light sail, which needs to have a large area in as small a mass as possible but doesn't need to be rigind, and graphite as a candidate for the probe's structure on which the science instruments are mounted, which needs to be rigid and as small a mass as possible?

Please pay attention to what I'm typing and please read the supplementary material to which I have given you an excellent entry point.[/QUOTE]

There is a fundamental problem of exploration:

a) communication back to the home front
b) a good description of what you saw back to the homefront

A) you keep ignoring in this. 1 meter light sail in diameter is gonna get lost in all the sounds and noises that the stars make. You need something that points to planet earth. Radio communication goes at light speed. You need a huge parabolic radio antenna to communicat to the homefront. The light sail as you pointed out you want light and very huge. Let's make it 500 meters in diameter ok and very light. No big problem.

But then we still need a huge parabolic radio antenna that points back to earth or maybe even to some point far away from the Sun as an 'in between radio station', who will say?

B) to take a good picture, regardless at which frequency you want to take it, you need to catch enough light. So the computer chip you use might be very tiny and light - yet the tube and lenses or mirrors used will be significant in diameter. For such expensive mission you definitely do not want some sort of space version of the apple iphone camera. That's not gonna cut it. You're gonna need a big diameter aperture or lenses.

For a close pass by of a planet you already will need 10 inch - yet at a speed of 0.05c you can't garantuee a close pass by - even if we do figure out somehow more details like which different planets specific stars might have or do not have and even if we might have some clue where at which moment planets are rotating based upon future telescopes (E-Elt etc).

You still are gonna need a far superior camera over other probes to generate enough data for the mission.

I'm no expert there but we're soon looking at 16 inches diameter.
That's gonna weigh something.

That 1 kilo idea is not realistic.

300 is more realistic for the total probe - and that will already require serious design and improvements over anything that was there so far.

[QUOTE=xilman;441094]Not all probes need to be identical and carry a complete set of instruments. A hundred, say could be optimised for observing magnetic fields, another hundred for optical imaging, another hundred for measuring dust properties, another hundred for measuring the thermal properties of the planetary and stellar atmospheres another hundred for measuring the chemical compostition of the same. Let's see, I'm up to five hundred probes so far. Another five hundred still to be allocated.
[/QUOTE]
We here really like that idea! Warcraft in space! (or is that called starcraft, or spacecraft?) - for who didn't play warcraft, you command an army of little guys, all with different abilities, and you can send them around to gather different types of resources, or to carry on the fights with your neighbors (computer IA or other human players) which also command an army of little guys... etc. Now, every one of the little guys have different abilities and knowledge, and [U]different weaknesses[/U], and the practice (in all games and simulations) showed that the best army (for the same resources spent on upgrades, etc) is that one which is the most non-homogeneous, i.e. you must have a little bit of all types of the little guys in the group, as opposite to an army composed only from the "best" (fastest, most aggressive, most intelligent, most upgraded, most expensive, whatever) unit type. In different confrontation situations, the army composed only by the "best" type of little guys will doubtless find its match, i.e an enemy which exploits its weakness, and kills it. See also my argument for "diversity" which I repeatedly raised it here around. Our force stands in the fact that we are different.

[QUOTE]
Diode lasers are also dirt cheap and very low mass.
[/QUOTE]
Well... not, not here. We do not agree now... Laser diodes which are bloody cheap have also a very short life time. Like 4000 hours or so. That is because they suffer a phenomenon called COD (Catastrophic Optical Damage). A powerful COD-free laser diode costs millions. We need to change the laser guns for our production laser markers from time to time (like every 20k hours or so) and it costs 40k USD each (and those are not totally COD-free). Therefore the high price of the products which are laser marked (as opposed to pad-printed), i.e. few cents more per piece, etc (the marking is very fast, few seconds, etc, depending on the logo/text/image that is marked.

[QUOTE=diep;441264]There is a fundamental problem of exploration:

a) communication back to the home front
b) a good description of what you saw back to the homefront
[/quote]
True.
[QUOTE=diep;441264]
A) you keep ignoring in this. 1 meter light sail in diameter is gonna get lost in all the sounds and noises that the stars make. You need something that points to planet earth. Radio communication goes at light speed. You need a huge parabolic radio antenna to communicat to the homefront. The light sail as you pointed out you want light and very huge. Let's make it 500 meters in diameter ok and very light. No big problem.

But then we still need a huge parabolic radio antenna that points back to earth or maybe even to some point far away from the Sun as an 'in between radio station', who will say?

[/quote]
You keep ignoring what I say.
You persist in ignoring what others have to say.
You keep making bald assertions about what you believe to be necessities which you fail to justify and ignore alternatives.

Where did I say that the information sent back to earth had to be by radio? Please read [URL="https://breakthroughinitiatives.org/index.php?controller=Forum&action=viewforum&id=13&page=3"]this[/URL]

You are correct that there is background noise, primarily from the star. Please do a little bit of reading and calculate the power per unit bandwidth to be expected from Proxima Centauri. The formulae are straightforward and the raw data on Proxima are easily available. I'll even make it easy for you by pointing you at [url]https://en.wikipedia.org/wiki/Planck's_law[/url] and [url]https://en.wikipedia.org/wiki/Proxima_Centauri[/url]

Then consider the power per unit bandwidth of a diode laser. Assume, say, 1W with a bandwidth of 30GHz operating at a frequency of 300THz (a wavelength of about a micron) which are fairly typical values for easily obtainable lasers. Compare that with the blackbody radiation from the star. To optimize your design, choose the diode's operating frequency (red-shifted of course) to be the same as a deep absorption line in the stellar spectrum and compare once again.

It should go without saying that the detector at earth should also be tuned to the (red-shifted) laser wavelength and have an equally narrow bandwidth.

I obliged your curiosity and calculated fthe size of an imaging telescope for you. Please do your own computations from now on. I'll give you pointers, as above, if you need the raw data but you ought to be able to use a search engine for yourself by now.

BTW, do you still think it would be cheaper to build a 10-20km diffraction-limited optical telescope in earth orbit? Cheaper than even your (IMO excessive) $300G estimate for an interstellar mission? I estimated $20G in total and $1M per probe. My estimates are 2-4 times larger than those at [url]https://breakthroughinitiatives.org/News/4[/url]

[QUOTE=diep;441264]

B) to take a good picture, regardless at which frequency you want to take it, you need to catch enough light. So the computer chip you use might be very tiny and light - yet the tube and lenses or mirrors used will be significant in diameter. For such expensive mission you definitely do not want some sort of space version of the apple iphone camera. That's not gonna cut it. You're gonna need a big diameter aperture or lenses.

For a close pass by of a planet you already will need 10 inch - yet at a speed of 0.05c you can't garantuee a close pass by - even if we do figure out somehow more details like which different planets specific stars might have or do not have and even if we might have some clue where at which moment planets are rotating based upon future telescopes (E-Elt etc).

You still are gonna need a far superior camera over other probes to generate enough data for the mission.

I'm no expert there but we're soon looking at 16 inches diameter.
That's gonna weigh something.

That 1 kilo idea is not realistic.

300 is more realistic for the total probe - and that will already require serious design and improvements over anything that was there so far.[/QUOTE]
You state unambiguously that you are not an expert and go on to make a dogmatic claim that a 40cm-diameter camera is necessary. You are completely ignoring the views of those who are experts who believe, and can justify their beliefs, that a camera a hundred times smaller is sufficient.

[B]Added in edit:[/B] My apologies, I was naively assuming that the camera optics needed to be localized to a small area of the spacecraft, leading to an incorrect view that the aperture would be of order one cm or less. There is no need for such a restriction and the effective aperture could be essentially the size of the spacecraft itself, or 10cm. My assumption was that a filled aperture telescope would be necessary. It quite clearly is not.


Once more: please read [url]http://www.breakthroughinitiatives.org/Initiative/3[/url] and links therein. Another [i]excellent[/i] resource is [url]http://arxiv.org/abs/1604.01356[/url] (referenced from the Breakthrough Initiatives site) which goes into very precise detail about the light sail propulsion mechanism for spacecraft of all sizes, from sub-kilogram probes reaching 0.2c to 100-ton human-rated spacecraft for solar-system travel at 0.0026c (760 km/s). A 100kg craft (Voyager-class) would reach Mars in about a day at a speed of 0.015c. Note that we are considering only fly-by and/or long duration missions here so don't need to consider how to slow down again at the destination. (Incidentally a 100kg probe would reach Proxima in around 280 years, which is substantially longer than I believe we are currently willing to contemplate.

Figure 13 in that paper addresses communication back to earth from a sub-kg probe. The scenario considers a 1g spacecraft structure 10cm in diameter and does [i]not[/i] use any other optical component such as the 1 metre sail for comms.

When you can back up your claims with sound and detailed physics and engineering computations I will be inclined to take them seriously. Until then you give every appearance of spouting ill-informed nonsense.

Explosion at SpaceX launch site: [url]http://www.bbc.com/news/world-us-canada-37247077[/url]

[QUOTE=Mark Rose;441321]Explosion at SpaceX launch site: [URL]http://www.bbc.com/news/world-us-canada-37247077[/URL][/QUOTE]
Ah Shoot! Dang! etc. :davieddy:

[QUOTE=xilman;441307]
Another [i]excellent[/i] resource is [url]http://arxiv.org/abs/1604.01356[/url] [/QUOTE]

Thanks very much for posting that link; that's the resource I've been looking for ever since hearing about this proposal. Fascinating ideas, but on first hearing about it, I couldn't tell what was realistically doable in the future versus what was completely fantasy. Really neat.

Norm

[QUOTE=Spherical Cow;441338]Thanks very much for posting that link; that's the resource I've been looking for ever since hearing about this proposal. Fascinating ideas, but on first hearing about it, I couldn't tell what was realistically doable in the future versus what was completely fantasy. Really neat.

Norm[/QUOTE]You're welcome.

I had hoped that those interested would have found it by themselves --- it's not difficult given the heavy hints I'd already posted --- but it became clear that diep at least had failed to do so.

The SpaceX explosion is a massive setback -- at least as massive as the CRS-7 setback, and they came out on the relatively bright side of that (6 month turnaround is a lot less than I would have guessed going into that).

In this case, 6 months is again absolute best case scenario I imagine. Depends of course on what the initial analysis is -- not to mention rebuilding the pad, which they didn't need to do last time.

(Regarding the other conversation in this thread, perhaps it would be wise to split that off to a separate thread? Possibly titled "What "wee need" is a space mission -- to Proxima Centauri!")

[QUOTE=kladner;441327]Ah Shoot! Dang! etc.[/QUOTE]

Woke up this morning at 0623 local time with electrical power having just been cut off (island wide power outage; still to be explained by BL&P).

Woke up again this morning at 0803 with no mains water (Barbados pumps water up hills using electricity into large tanks to provide gravity feed to water consumers).

Finally(!) get Power, Cellular and terrestrial Internet back at about 1135.

Immediately check my news feeds... Trump has lied again, and SpaceX's rocket blew up during fuelling for a preflight test firing.

A bit of a bummer of a day.... :sad:

@Paul: My thanks, as well. I've already fired off the links to a friend who should really appreciate them. I have started on the PDF: Roadmap to Interstellar Flight. Some of the math is a bit dense for me, but I get the idea, at least in proportions. 0.26 C is a stunning possibility.

[QUOTE=LaurV;441302]Well... not, not here. We do not agree now... Laser diodes which are bloody cheap have also a very short life time. Like 4000 hours or so. That is because they suffer a phenomenon called COD (Catastrophic Optical Damage). A powerful COD-free laser diode costs millions.[/QUOTE]

I hope you don't mind me discussing this with you a little bit on this topic...

Assuming most of the energy for interplanetary, or interstellar, investigations was sender sent, would this not be possible within ten years or so?

One would assume that upgrades to the sent craft would not be possible.

On the other hand, upgrades to the orbitals lasers powering said crafts is simply a question of money, rather than physics.

Please correct me if I am wrong.

What do you mean "sender sent"? Oh, do you propose to have the lasers [U]here[/U], and only have some "mirrors" or whatever, on the spaceships? I was assuming the other way around, for I don't know which reason, I was thinking that the lasers have to be on board :blush: But you may also need lasers for propulsion?

Actually, hm.. the lasers for communication (if they are separate) will only need to work from time to time, and the lasers for propulsion (if they are separate) can work until they are exhausted, to bring the ship to speed (well, keep a little for steering). So, somehow, you can not mix them (make an "all in one" laser), as they have different working habits. And you need lasers for propulsion on board if you are talking about speeds comparable to c. But the idea of having the communication lasers here, that may work.

Or the proposal is to have all the lasers here and create a "laser wind" (by analogy with the solar wind) to push the ships all the way? Is that feasible? (I honestly have no idea!)

[QUOTE=LaurV;441382]Or the proposal is to have all the lasers here and create a "laser wind" (by analogy with the solar wind) to push the ships all the way? Is that feasible? (I honestly have no idea!)[/QUOTE]That is the idea, though the push lasts for only a short time. For the lightest craft around 10 minutes of thrust gives a final velocity of 0.2c or more. Thereafter it coasts for the other 99.999% or so of the journey.

Lasers on the space craft are used for two things: attitude control and communication back to the solar system. The latter is short term, the former very intermittent.

Much more detail in the links already posted.

[QUOTE=xilman;441385] For the lightest craft around 10 minutes of thrust gives a final velocity of 0.2c or more. Thereafter it coasts for the other 99.999% or so of the journey.

[/QUOTE]

That is one of the most fascinating aspects- the acceleration to 0.2c is so quick. When I first read about this is in the "normal" news, I assumed the lasers would need to be pushing for years to get the craft up to speed.

Norm

A complete tangent, if I may...

As a young person, I read Larry Niven and Jerry Pournelle's /The Mote in God's Eye/. The aliens were detected approaching us because their laser propulsion system was noticed

A reasonably good read.

[QUOTE=chalsall;441415]A complete tangent, if I may...

As a young person, I read Larry Niven and Jerry Pournelle's /The Mote in God's Eye/. The aliens were detected approaching us because their laser propulsion system was noticed

A reasonably good read.[/QUOTE]Not a complete tangent, IMAO. The information transferred by the lasers in that story was only a few bits. The roadmap paper linked previously points out that two 10-km laser launch sites could communicate at ethernet speeds over a distance of more than gigaparsec. Ping times would be rather lengthy.

Interstellar communication within our galaxy at bandwidths of megabytes per second is already well within present-day capabilities. A 10-metre telescope and a 100kW laser at each end will do it. The current problem is arranging for the two ends to have the equipment and to know where to point it.

[QUOTE=xilman;441417]Ping times would be rather lengthy.[/QUOTE]

Yeah. Welcome to Earth. :wink:

[QUOTE=xilman;441417I]The current problem is arranging for the two ends to have the equipment and to know where to point it.[/QUOTE]

I understand this is currently being worked.

[QUOTE=chalsall;441415]A complete tangent, if I may...

As a young person, I read Larry Niven and Jerry Pournelle's /The Mote in God's Eye/. The aliens were detected approaching us because their laser propulsion system was noticed

A reasonably good read.[/QUOTE]
I think of Mote as an ultimate Malthusian warning. It would be well for humankind to pay attention. In this household, we blame Pournelle for all the royalty/nobility stuffed into a good story. I guess you gotta have some social framework, though.

Juno send her first few images, and it's stunning
[URL]http://www.jpl.nasa.gov/news/news.php?feature=6613[/URL]

[QUOTE=kladner;441421]I think of Mote as an ultimate Malthusian warning. It would be well for humankind to pay attention. In this household, we blame Pournelle for all the royalty/nobility stuffed into a good story. I guess you gotta have some social framework, though.[/QUOTE]

Niven was the brain. Pournelle was the mouth.

I also don't like Pournelle that much (mostly because of his Byte writings about computing).

Niven has written a lot of worthy stuff independently. Ringworld, for example (levering on Dyson, and leveraged upon by Pratchett).

You can bounce but you can not hide
 

[URL="http://www.bbc.co.uk/news/science-environment-37276221"]So that's where the damned thing has been trying to hide.[/URL]

[QUOTE=xilman;441755][URL="http://www.bbc.co.uk/news/science-environment-37276221"]So that's where the damned thing has been trying to hide.[/URL][/QUOTE]

Unfortunate that the anchor didn't fire. (Bounce, bounce, bounce...)

Perhaps next time there will be redundancy.

[URL="https://www.youtube.com/watch?v=H08tGjXNHO4"]Ambition the film[/URL] by ESA was pretty cool.

But, then again, so was the [URL="https://www.youtube.com/watch?v=Ki_Af_o9Q9s"]Seven Minutes of Terror: The Challenges of Getting to Mars[/URL] video by NASA.

A pity the latter video had the audio drowned out by unnecessary music.

That previously was a bloody good video, serous engineers talking seriously.

[URL="http://www.space.com/34029-elon-musk-seeks-help-solving-rocket-explosion.html"]Elon Musk Asks for Help Solving SpaceX Rocket Explosion[/URL]
[QUOTE]Musk tweeted about the loss of the Falcon 9 hours after the incident, noting that the explosion appeared to originate "around upper-stage oxygen tank" but the cause was "still unknown." SpaceX provided more updates about the incident on Sept. 2.

Then, Musk's account went quiet until about 12:30 a.m. EDT this morning (0030 GMT), when he began tweeting actively about the explosion.

"Still working on the Falcon fireball investigation. Turning out to be the most difficult and complex failure we have ever had in 14 years," Musk wrote. "Important to note that this happened during a routine filling operation. Engines were not on, and there was no apparent heat source.

"Particularly trying to understand the quieter bang sound a few seconds before the fireball goes off. May come from rocket or something else," he said.

Musk also answered questions and responded to comments from the public.

When Twitter user @ashwin7002 tweeted at Musk that "there are some videos on YouTube claiming something hit the rocket. Any reality there?" Musk replied, "We have not ruled that out."

Twitter user Matt Stohrer wrote, "that sound at 0:54 sounds like a metal joint popping under stress. e.g. weld failing on strut, welded seam bursting, etc." Musk replied, "Most likely true, but we can't yet find it on any vehicle sensors."[/QUOTE]

[URL="http://kck.st/2bfaFkN"]Red Heaven Kickstarter project[/URL]

They are making a documentary about pretending to be on Mars.

It stars the wife of a friend of mine.

Let's get off this rock.

[QUOTE=chappy;442311][URL="http://kck.st/2bfaFkN"]Red Heaven Kickstarter project[/URL]

They are making a documentary about pretending to be on Mars.

It stars the wife of a friend of mine.

Let's get off this rock.[/QUOTE]
I'm kind of hoping dark energy is something we can imitate and maybe we can get off the planet for way cheaper than it is now. The LHC keeps coming up with new stuff, so who knows.

But then the problem would be how do you prevent idiots from trying to go to the moon in their cars?

SpaceX Mars Announcement from IAC starts in 1.5 hours!

[url]https://spacex.com/mars[/url]

[QUOTE=Dubslow;443609]SpaceX Mars Announcement from IAC starts in 1.5 hours!

[URL]https://spacex.com/mars[/URL][/QUOTE]
A bit disappointing. It looked a lot like advertising, he didn't seem "prepared" for the talk, a lot of "aaaaarrr" and "eeerrrrr", he didn't say anything about the cosmic radiation and all the dangers of the trip, etc. Looked like he only wanted to boast about his luxury design with restaurant on board, etc, and the 200k tickets (i think they are still expensive, the real cost could be cut to at least a third), and about how much money is he going to collect, to be spent on March and nowhere else...

[QUOTE=LaurV;443798]and the 200k tickets (i think they are still expensive, the real cost could be cut to at least a third), and about how much money is he going to collect, to be spent on March and nowhere else...[/QUOTE]The BBC had a discussion on this issue. I pointed out that a good number of British baby-boomers could easily afford $200K if they wanted to because they had had a free university education and now own their (greatly inflated) houses outright. The only other qualification was that (by and large) some had not reproduced and so didn't need to support their offspring directly or through bequests.

Reaction was mixed. 7 voted up my post, 16 voted down.

FWIW. I could afford a $200K ticket for the reasons outlined above. In practice I will probably be too old for the likely time period when tickets go on sale, even if I wanted to emigrate to Mars, though the idea is very tempting. At my age, I don't give a damn that I'm 20% more likely to develop a radiation-induced cancer because it's almost certain that I'm going to die of something in the next 40 years.

[QUOTE=LaurV;443798]A bit disappointing. It looked a lot like advertising, he didn't seem "prepared" for the talk...[/QUOTE]

LOL... I watched a recent interview with Musk a little while ago, a one-on-one interview, where he hadn't even shaved properly.

[QUOTE=Dubslow;443609]SpaceX Mars Announcement from IAC starts in 1.5 hours!

[url]https://spacex.com/mars[/url][/QUOTE]

So I guess the whole vacuum-tubes-will-revolutionize-mass-transport-worldwide thing fizzled ... onward and outward!

What this is really about is Musk feeding a steady diet of disruptive-innovation-foo to the legions of headline-scanning bots tied into HFT platforms worldwide. The bots only care about the big splashy initial announcement, not whether anything ever comes of it.

[QUOTE=chalsall;443832]LOL... I watched a recent interview with Musk a little while ago, a one-on-one interview, where he hadn't even shaved properly.[/QUOTE]

LOL... Found the video... [url]https://www.youtube.com/watch?v=tnBQmEqBCY0[/url]

The man's worth billions of dollars, but can't afford (or, at least, doesn't know how to use) a good razor....

[QUOTE=chalsall;443868]The man's worth billions of dollars, but can't afford (or, at least, doesn't know how to use) a good razor....[/QUOTE]You is jealous of smth bro?

Let's examine the content, not the delivery method. Can?

[QUOTE=retina;443872]Let's examine the content, not the delivery method. Can?[/QUOTE]

Can. Should. Must.

Musk is only (one) human. There are many others involved in this project.

We will pat them on their bottoms for their good work once we take control.

[QUOTE=retina;443872]You is jealous of smth bro?
Let's examine the content, not the delivery method. Can?[/QUOTE]
That was nothing about the man himself. I was talking about the content. There are a lot of problems and issues with his design. That is not a "software guy with no idea about space traveling" (that is me) talking, but experts on web have similar concerns.[URL="http://jalopnik.com/heres-how-to-fix-the-big-problems-with-elon-musks-mars-1787163420"] Here is one[/URL] that puts it in layman terms.

[QUOTE=LaurV;443882]That was nothing about the man himself.[/QUOTE]My reply was for a different recipient. Your reply was cool bro.

[QUOTE=LaurV;443798]A bit disappointing. It looked a lot like advertising, he didn't seem "prepared" for the talk, a lot of "aaaaarrr" and "eeerrrrr", he didn't say anything about the cosmic radiation and all the dangers of the trip, etc. Looked like he only wanted to boast about his luxury design with restaurant on board, etc, and the 200k tickets (i think they are still expensive, the real cost could be cut to at least a third), and about how much money is he going to collect, to be spent on Mars* and nowhere else...[/QUOTE]
I swear to any god you want that I didn't read[URL="http://www.theverge.com/2016/9/28/13086980/spacex-elon-musk-mars-plan-problems-breathing-radiation-death"] this article[/URL] before posting the comment above. But i agree with every word the reporter there says, is like I thought it and wrote it by myself. He even uses my words! (but much better than I did or I could do). I am also an incurable optimist, and felt exactly the same as the reporter, hearing/watching Musk.


----
* I corrected the typo, it was written "March" in the initial post. In my language there is not as much difference as in English, they both come from the war's god Mars/Martius.

First, Musk is known to not be a good public speaker. Every interview/speech he's ever done, he has stutters and hesistations. That's just how he his, please don't knock the content for it.

As for the content itself, SpaceX has 14 years of history to prove that the skeptics on the outside, while right to be skeptical (in the scientific sense) were generally underestimating SpaceX. When they first suggested landing rockets on barges, much less boosting back to land, people thought that was crazy, and yet here we are 5 years down the road.

If anyone can pull off something that others don't think is possible, it would be SpaceX. So far they've generally followed up on what they said they could do (with the notable exception of generally being a lot slower about it then they state).

Edit: I just read the articles LaurV linked, and I agree with 2.5 of the 3 points made.

The first article mentions separating planetary habitats from vacuum habitats, and I think that's an excellent idea.

It also mentions changing the refueling paradigm, which I only partially agree with. The reason the tankers are launched after the main spaceship in Musk's original plan is because of propellant boil off issues. Essentially, cryogenic propellants (especially LOx and especially especially LH2, the latter of which isn't used for this among other reasons) are extremely difficult to store for any long term duration. This is why the [URL="https://en.wikipedia.org/wiki/Falcon_9_Flight_22#Launch_attempts"]SES-9 launch earlier this year was delayed multiple times[/URL], because SpaceX was still learning how to properly load the subcooled LOx in 30 minutes as opposed to the couple of hours previously used by SpaceX and just about every other provider. Two hours is simply too long for subcooled LOx to be out of active cooling. Now, the partial agreement with this proposal is that it would be possible to make an infrastructure investment to have an active cooling and storage system in the proposed garage, however it would be significantly more expensive and difficult than he seems to think.

The third point by the second article is also quite a problem IMO. I remember when Musk was asked about radiation for the trip and he kind of waved it away, that was one of the few moments when I thought to myself "Uh... okay then Mr Musk, but that's actually a serious problem".

All this being said though, SpaceX has definitely shown that they are capable of reacting to new problems as they are presented, and fixing them or working around them as necessary. I'm quite certain that the manner in which they land rockets now is quite different from the initial vision they had however many years ago, but they've still pulled it off all the same.

So although it may not necessarily look like the presentation Musk made (in physical look or in the architecture of the missions), I am still quite confident that SpaceX will achieve what they set out to do in one form or another.

Rosetta died today. lasts image sent are here
[url]http://www.esa.int/spaceinimages/Images/2016/09/Comet_from_51_m_wide-angle_camera[/url]
this one from 51 meters above the surface of the comet, scale is 5 mm by pixel.
There is another picture taken 10 sec before impact and a gif but I have no direct link.

[url]http://acomik.com/post/151142093006/low-iq-a-patreon-twitter-instagram[/url]

[QUOTE=Dubslow;443890]Now, the partial agreement with this proposal is that it would be possible to make an infrastructure investment to have an active cooling and storage system in the proposed garage, however it would be significantly more expensive and difficult than [the author of the article, not Musk] seems to think.[/QUOTE]

Agreed. However, it is worth noting that there is a great deal of energy, and thermal differences, available in space which could be used for cooling. Heck, just launch a tanker full of liquid nitrogen every so often and let it boil off in the vacuum behind a sun-shade to sub-cool down the LOX and liquid methane.

[QUOTE=Dubslow;443890]The third point by the second article is also quite a problem IMO. I remember when Musk was asked about radiation for the trip and he kind of waved it away, that was one of the few moments when I thought to myself "Uh... okay then Mr Musk, but that's actually a serious problem".[/QUOTE]

So always orient the ship with it's back end pointed towards the sun (the largest source of dangerous radiation). All those engines, the tank of liquid methane, the tank LOX, the tank(s) of water, and the cargo would probably help quite a bit.

[QUOTE=Dubslow;443890]So although it may not necessarily look like the presentation Musk made (in physical look or in the architecture of the missions), I am still quite confident that SpaceX will achieve what they set out to do in one form or another.[/QUOTE]

Or, at the very least, they will push the state of the art forward. As Musk himself said, they're likely to fail. But at least they're working the problems.

And, without question, the plan will evolve over time. Slowly spinning the ship, for example, makes a lot of sense.

[QUOTE=chalsall;443935]Slowly spinning the ship, for example, makes a lot of sense.[/QUOTE]How slow? Trying for one G requires a lot of structural support apparently so is infeasible at this time due to weight considerations. Even one atm is hard enough, we still don't do that on commercial aircraft.

[QUOTE=retina;443937]How slow? Trying for one G requires a lot of structural support apparently so is infeasible at this time due to weight considerations. Even one atm is hard enough, we still don't do that on commercial aircraft.[/QUOTE]

Why would you try to achieve 1G when your destination is only 0.38? Not to mention the Coriolis effect in a small radius.

Similarly, while one ATM is maintained on the ISS, there is no need to do so during interplanetary (or even innerplanetary) travel.

[QUOTE=retina;443937]How slow? Trying for one G requires a lot of structural support apparently so is infeasible at this time due to weight considerations. Even one atm is hard enough, we still don't do that on commercial aircraft.[/QUOTE]Only a small fraction of the ship needs to be at high gravity. The connection between those points and the core structure will be in tension, which is much easier to arrange with a low mass budget than are compression or sheer. Nonetheless it's an interesting engineering problem.

[QUOTE=xilman;443943]Nonetheless it's an interesting engineering problem.[/QUOTE]

It's a ferris wheel. A rotating frame of reference.

Been there; done that.

Hope to go again....

[QUOTE=chalsall;443950]It's a ferris wheel. A rotating frame of reference.

Been there; done that.

Hope to go again....[/QUOTE]Indeed, but with differences. A Ferris wheel doesn't have such a tight mass budget as the spacecraft equivalent. It has to withstand a slightly varying g-force which averages 1 g [i]in one constant direction[/i] whereas the spacecraft should produce a uniform acceleration acting purely radially.

[QUOTE=xilman;443959]A Ferris wheel doesn't have such a tight mass budget as the spacecraft equivalent. It has to withstand a slightly varying g-force which averages 1 g [i]in one constant direction[/i] whereas the spacecraft should produce a uniform acceleration acting purely radially.[/QUOTE]

Agreed. A Ferris wheel doesn't have /as much/ of tight mass budget, but it does have one. And I was reflecting on your point that it would be a tension structure; just like a bicycle or some car wheels.

My fundamental point was that rotating tension structures are well studied and widely used. And since the spaceship is going to need gyros anyway, why not use some of them to provide "artificial gravity" to the passengers?

Snipper...
 

So, an internet meme has manifested about the possibility that a rifle took out SpaceX's rocket carrying a satellite owned by an Israeli company while it was fuelling on the pad.

I have no idea how this is going to play out, but I suspect SpaceX are going to have a *whole* lot more high-speed and high resolution cameras and microphones recording at all times.

They might want to talk with NewTek. Their NDI solution domain is pretty cool.

I've heard rumors that they didn't have much in the way of audio recordings, though they certainly will moving forward.

It certainly didn't help that they requested access to the roof of a ULA building on the basis of some white blobs and shadows from far off video. (ULA eventually allowed Air Force investigators to investigate; they found nothing.) Not exactly the best PR to let out.

[QUOTE=Dubslow;444198]I've heard rumors that they didn't have much in the way of audio recordings, though they certainly will moving forward.[/QUOTE]

Indeed. Multiple widely distributed microphones each tied with a GPS receiver for extremely accurate time stamping could have been very useful for triangulation in this investigation.

Such GPS time coordination is widely used in the communications, electrical power distribution and financial trading industries, to give only a few examples.

SpaceX rarely makes the same mistake twice.