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Benford on Space Exploration
gid-goo writes "Gregory Benford looks at what we should do in the aftermath of the Columbia accident. Is the shuttle, or the International Space Station for that matter, useful? Or just payola to aerospace interests and a means for keeping Russian rocket scientists employed?" Benford's comments about the necessity of a closed biosphere and of some way for astronauts to stop muscle and bone loss are far more insightful than the usual discussions about where our space exploration priorities should lie.
According to this article mentioned earlier on Slashdot:
I code, therefore I am.
The main part of the Benford's article is that the primary problem of space travel is dealing with the lack of gravity to maintain human bone and organ health.
Cats spend up to 20 hours a day sleeping and yet still manage to stay fitter than most human gymnasts.
Purring creates vibrations through the cat's body helping to maintain muscle and bone density.
Transducers in an astronaut's suit could produce similar resonant vibrations. These vibrations could simulate the stresses of g-forces by rapidly moving the astronaut a very small distance back and forth.
Sorry I didn't connect the dots for you in the original post.
- A new spaceplane, designed for crew. See the Orbital Space Plane [orbital.com].
Wings add greatly to the weight, and there are lots of tradeoffs, like high landing speeds. Arguably adding wings to the Shuttle killed Columbia, certainly it was a wing failed, and the tiles are necessary because of the aerodynamic shape required, and the slower reentry that wings impose/allows, leading to overall higher heat load (compared to Apollo, Shuttle has to cope with a somewhat lower temperature but for much longer).A new technology, reusable launch vehicle. See the Space Launch Initiative [slinews.com].
The SLI has been cancelled.
Continuing with the Prometheus Project [space.com]. We fucked up when we stopped persuing NERVA/Rover [astronautix.com].
Prometheus is a development of a nuclear power plant for space use; it is for ion drives. NERVA will not be supported under this program.
Mars. Need I say more? [nw.net] I'd also like to see a space elevator persued, but I don't know that we have the tech yet. Then again, I haven't looked into it that much either.
It seems doable with hardly much more technology than we have right now. Scaling up the production of carbon nanotubes to production of tonnes rather than milligrams is required, and a demonstration of a few percent more strength, and a reasonably large wodge of cash- about $15 billion ;-)
-WolfWithoutAClause
"Gravity is only a theory, not a fact!"This article on spacefuture.com has a pretty good analysis of what centripetal forces we should be looking for in deciding to build a rotating space station. It takes into account not only the physics, but also the effects of this artificial gravity on humans (since there is a significant effect due to Coriolis forces that make it behave differently from natural gravity).
The escape velocity of Mars is 5.03kps as compared with Earth's 11.2kps escape velocity. That figure is based on its gravaty.
As for the atmosphere, here is more info out of a Newsletter from the Coconino Astronomical Society about what is in the atmosphere and how they know. You may want to read the whole letter at http://www.lowell.edu/cas/news/2002_sep. pdf (warning! it gets boring fast).
In order to determine if a gas is retained by a planet, the following formula is used.
Escape velocity of molecules = the square root of (2 times Boltzmann's constant times the effective temperature / molecular weight times the mass of the hydrogen atom).
The escape velocity of Mars is three miles per second. Therefore, Mars has carbon dioxide and no water vapor in its atmosphere. Carbon dioxide has a molecular weight of 44; water has a molecular weight of 18. Obviously, water vapor requires much less energy to escape the Martian gravitational pull than carbon dioxide. Hydrogen and helium molecules are not present in any of the inner planets because of their atomic weights of one and four, respectively
Laika! But she was kind of a bitch.
Really - Valentina Tereshkova, the pilot of Vostok 7. The only thing remarkable about Sally Ride (or other "female firsts") is that women in the west were prevented from pursuing that field for so long. The Soviet Union had no shortage of flaws, but they were more equal-opportunity than the West.
And actually I rather dislike the story of Laika. She was sent to her death (an unpleasant one, slow suffocation, dehydration, or burning up) and they knew they had no way to get her down. The Americans weren't much better, killing lots of monkeys and chimps. At least by the time they actually managed to get a primate in orbit it was late enough that they were also able to land it safely. Maybe there's a message there about prematurely putting humans in space...
I think Benford had a much larger centrifuge in mind than either the STS90 or STS107 experiments.
Boeing designed a centrifuge module for the ISS that was a bit larger--2.5 meters or so, but it's not for human use.
It seemed to me that Benford was talking about the long-term effects of centrifugal motion on the human body. Those experiments weren't keeping the subjects under continuous centrifugal motion for months at a time, so I think his point is still valid. Spinning the shuttle for a few minutes is hardly a test of long-term effects.
I'm not sure putting our priorities on designing the next shuttle is what's really needed since it is basically a truck to LEO. In retrospect, in the early 70's NASA would have been much better off ramping up production and building scores of Saturn V's, a hundred Saturn 1B's and a few dozen Skylabs. With 20/20 hindsight, big dumb boosters were probably the best way to go three decades ago and that probably still holds true today. Who knows, maybe we still would have lost 1 out of 50 Saturn launches as well, but at least would have a lot more interesting stuff everywhere between LEO and the Moon for the same money.
For me I'm much more interested in spending the bulk of NASA's limited budget on interesting payloads that leave LEO rather than developing trucks to deliver the payloads to LEO. After all, 60's technology was fine for getting us to LEO and the Shuttle isn't going to take NASA to Mars.
Since the beginning of the shuttle program there were plans for a shuttle derived unmanned heavy lift vehicle that basically looked like a huge boxcar strapped to the side of the external tank. The only recoverable parts were the engines themselves, which would parachute to Earth after entering the atmosphere with an ablative heat shield. I believe that with most of the weight of the shuttle structure, wings, and crew cabin removed, such a booster would have had nearly the capacity of the Saturn V. It seems that such plans could be resurrected and within a year or two we have a heavy lift vehicle that can take advantage of economies of scale for shuttle solid rocket boosters and external tanks which I believe, ironically, are the cheapest parts of the shuttle. NASA can then use the proven Soyuz (thank you very much Russia for keeping the rocket and capsule assembly lines going) to get human crews into orbit until some suitable replacement is made.
Once NASA again has heavy lift capability it can then concentrate on truly interesting payloads that can take us to Mars and beyond. I'll cry if NASA does get the go ahead for a Mars mission and comes up with a scheme where dozens of shuttle missions (either the remaining three vehicles or next generation shuttles) are required to build the spacecraft in orbit from small components.
You say there's nothing in space you can't get cheaper here. Try 50 terawatts of power. The world currently runs on 10-12 terawatts and that's with a lot of it stuck in the dark ages. If we were to liberate the 4/5ths of mankind stuck under repressive regimes and they would start to have the ability to purchase power because of higher standards of living, there simply isn't enough uranium, coal, oil, or natural gas available on the planet to do it.
Yes, we do need space resource extraction, not least of all to provide energy for all those liberated people who aren't dying of malaria et al and want to live a modern life.
Here's a good paper on the subject. It's a 15mb pdf, but worth the download.
In it, a good many of the technical problems are solidly examined, and reasonable solutions are proposed.
The approach presented is to launch an initial spool of very thin cable into geosynchronous orbit. This spool will be some thousands of kg in mass; this won't be *that* much harder than putting up a communications satellite. Then you lower that cable down to earth (and raise spool-unreeling spacecraft up past geosynch. as a counterweight), and you have a sort of "mini" space elevator that can haul up a mere 1200 kg. A series of climbers then ascend, each epoxying on a new layer of cable. Continue for 2 years, and you have a cable that can carry up as much as the shuttle. Continue for 5 years, and you have one that can lift a million kg.
All the solutions to the technical problems will require lots of research/testing to truly overcome, so it'd likely still be decades away, even with full effort. And that's also assuming the cable itself can be built.
I think that's the paper's main weakness, actually: its reliance on finding an epoxy to construct the cable with, that will allow the overall cable strength to be similar to the inherent nanotube strength. The proposal calls for 3-cm lengths of carbon nanotube to be assembled into the cable (in a mostly flat ribbon shape) with the epoxy. This is because such lengths of carbon nanotubes have indeed been produced, and the paper is trying to go with known technology as much as possible.
Now it seems to me that finding an epoxy strong enough to hold on to the fibers would require finding a substance with nearly as much strength as the fibers themselves. Otherwise, the epoxy will fail when the load becomes great, and the fibers will just slip out. A strong rope does you no good if you can't hold onto it!
Though perhaps there's something about epoxying materials from fibers that I don't understand. Anyone? Anyone? Bueller?
The terrorist-threat angle is another concern. Though a terrorist attack would presumably occur at the low end of the cable, which would have minimal effect on the earth.
The main environmental risk is that of the cable breaking at a high point, possibly at the counterweight. The paper say that if this happens, "About 3000 kg of 2 square millimeter cross-section cable ... may fall to Earth intact and east of the anchor." It goes onto say that further study/simulation is necessary to determine the full threat.
So again, for me, I'm not so sure that the epoxy technique of cable construction will work. We may have to wait until we have enough nano-scale control to be able to construct the cable with full-cable-length nanotube, finely interwoven. Of course, once we can make nanotubes like that, a lot of other possibilities for space travel may open up.
"Orthodoxy is unconsciousness" - Orwell
In a big way. Well put, my feelings exactly (spelling errors and all
As for the article, pure rubbish. Unrelentless ranting. Science fiction.
Space is about as safe as a highway of drunk drivers, always has been, always will be. How can you say for one minute NASA should make it look easy to go 100km up at 17,580mph, in 394 degrees K tempatures, sustain it, and then accurately drop back to the planet and hit a runway in Florida, startng the decent as far back as the Pacific?
NASA and all the others who have worked on the Shuttle have worked miracles over the years. I for one am glad they went ahead at whatever the cost, because wasteful or not, we're further ahead of where we were.
Perhaps then, along the articles lines of thinking, we should ban cars, because they have failed more than once, and the auto industry is just pissing awaay our hard earned dollars. I suspect the author uses a computer with Windows? Better not save any data on it, as "Microsoft wants us to believe our hard drives are safe, when in fact they are not. Once is an accident, twice is a defect."
(OK Maybe he'd be right on the last one.)
My point is: Shit happens. There will be accidents. Build a new space plane, it will crash at least once. So will the next one. And the one after. Let us not forget, launching a rocket into space that comes back down safely is the most dangerous, costly, complex thing mankind has ever done. And with good reason: It is the greatest thing mankind has ever done.
CAn'T CompreHend SARcaSm?
- It would be a money sink that would never pay back its construction costs - a tax money sink, because no commercial firm could ever get investment funding (not this side of AD 3000 anyhow).
The cost is actually quite modest. Figures between $5bn and $40bn have been mentioned. At the lower end of the scale, this is about 15 shuttle launches. At the high end, it's a tiny fraction of the US defence budget. The benefits to the first company or government who does this are the ability to launch satellites at a tiny cost, build further space elevators for (relatively) next to nothing, and in the long term the full exploration and exploitation of natural resources in space.- It would be the worst sort of governmental monopoly, a choke point where everyone must bow and scrape to the groundbound owners, in order to get a lift.
This is certainly true in the short term. In the longer term, many elevators can be built by different companies and governments. (Only the first elevator is expensive - once that's working the others are cheap to build).- It would be The Definitive Terrorist Target - and the bad guys only have to get lucky once. It would be utterly indefensible from a simple kamikaze attack, being so long that no weapons installation could keep cover over its whole length without weighing it down.
The proposal is to have an exclusion zone around of the order of 10-100 miles. It would be extremely hard to fly unnoticed into such an area. Attacks from underneath (submarines, etc) and attacks from people actually travelling on the elevator are harder to deal with. In the end it doesn't matter however. Once one elevator is up, you build more, and you keep a few reels of carbon nanotubes "parked" in space to cover this eventuality and natural disasters.- And it would be a catastrophe waiting to happen, when (not if) it snaps and rains megatons of carbon cable down upon the ground below.
Yes, we've all read Kim Stanley Robinson too. He's a good writer, but not a great scientist. A break in the cable is most likely to happen in the first 20-40 miles (ie. in the atmosphere). So the 20-40 miles of cable drops down - into the exclusion zone which is just a harmless area of sea. The top part slowly drifts off into space. There's even the possibility of repairing a broken cable by lowering more down to earth before it drifts off.Rich.
libguestfs - tools for accessing and modifying virtual machine disk images
Robert Zubrin puts forward a credible scheme in his (rather biased but scientifically thorough) book "The Case for Mars". You send an unmanned return vehicle ahead, with a fuel generator to make fuel from the Martian atmosphere (yes, it's possible). The crew only goes once there's a ticket home already there. For added safety, you send two return vehicles. The crew has a rover so they can drive to the nearest ascent vehicle when their time is up, and everything's cool. Meanwhile, there's a habitat left behind which you can use to start a persistent presence there.
Freedom: "I won't!"
Mars exploration is a thought, at least it's dramatic enough that it might grab people's attention. I submit that we would be better off pursuing a goal in space with some obvious practical benefit, e.g. this scheme of Robert Kennedy of the Ultimax Group:
Apparently NASA "studied" the SPSS idea again a few years back. They said it looked good, but they needed to reduce launch costs "a problem which is being addressed" (by the space shuttle?):Mirrors & Smoke: Ameliorating Climate Change with Giant Solar Sails;
Topic: Mirrors & Smoke, and Other Shady Schemes
Bright Future for Solar Power Satellites
Complete bollocks. Specficially, if it cost $20G to build (they say $10G), it need only make $2G/a to handily beat bank loans and stuff as a payback means. So double the $100/kg lift costs to $200/kg, big deal in the face of the $10,000-$30,000/kg it is now. $2G / $100/kg extra profit == 20Mt/a, 55,000t/day, 2300t/hr, a 400t load every 10 minutes.
Need to halve that load? Triple the price instead of doubling it. Or use the elevator to build more, and amortise the costs between them.
And we don't have one now? Go ahead, build your own Saturn V or Energia-Groza, be my guest.
Once they have half a dozen of these up, owned by 3 or 4 countries or consortia (I'd guess USA, EU, China, Russia, India, Brasil), that starts to break down anyway. If Australia wanted to build the first one, that would cost us $10,000 a head. If it built the 8th one, maybe $500 a head and every Australian gets their first 2kg hauled to space for free. If the people living in Perth pooled their gree kilograms, we could loft a 3000 tonne satellite.
Ever tried to hit something a meter wide from 10 km away? With defenses on the elevator shooting back at you and at your shells?
Clearing a corridor 10km wide around this would be no problem, and keeping it clear with SDI technology (near the ground, a perfectly ordinary Vulcan radar-guided cannon would do the job) relatively simple. Can you outfly a laser? Could your aircraft or missile survive several hundred unexpected megawatts of microwaves tuned to some vital dimension? How about a smart remote-targeted crowbar dropping in on you from LEO at mach 20?
Any concievable replacement would be worse.
It would have to be a clever piece of space-junk, smaller than a peanut and yet more destructive than a nuke. You haven't had a look at the design, have you?
If they were kind enough to put the elevator up on the Equator (not necessary, but it helps), it (or more specifically the defenses on it) would actually make a pretty good street-sweeper for the space industry.
That statement just betrayed your complete ignorance of how the elevator would work.
Of the 100,000km length, less than 100km would be in atmosphere. Take what is presumably the worst case: the cable snaps about 50km up. 50km of cable fall to earth, the top 30km or so burning up on re-entry, the balance stays in orbit. That's right, losing 0.05% of the cable makes very little difference to its orbit. Soon the lost 50km is replaced by shipping it out along another cable and unreeling it off the next segment above the damaged one.
But what about the bottom 20km? Even if it were heavy (did you read the line saying `paper-thin?'), it would fall into the ocean. Even if they anchored it at, say, Kununurra (in the far north of Western Australia) and it were heavy, you'd still only lose a stripe of desert a few m wide and 20km long. Big deal.
Now, important step, visit High Lift Systems and RTFM. Then come whinging back here.
Got time? Spend some of it coding or testing
The Problems with the shuttles:
1. They cost inordinate amounts of money
2. They provide no significant gain (If your goal is to study stuff to save human lives, the money is better spent researching stuff on Earth)
3. They're obselete(going to space in the shuttle is like going online with a PDP-11)
The Gains from the shuttle:
1. Nearly meaningless science that has very little, if any, practical value.
2. Vast numbers of jobs.
3. The ability to say, "Hey, we're in low Earth orbit!"
The problems with going to Mars:
1. Radiation
2. Physical effects of prolonged zero gravity.
3. Actually getting there and getting back alive.
The gains of going to Mars:
1. The ability to say, "We're on a whole nother fricking planet!"
2. Entry in every history book
3. Vast numbers of jobs
4. Science that is actually worth doing and justifies the cost.
5. Knowing that we have taken a step forward and not a step back
Which would you pick?(rehetorical Question)
There's a growing sense that even if The Future comes,
most of us won't be able to afford it.
-- Lemmy
Actually, Lockheed-Martin beat out others and won a contract to build a half-size sub-orbital prototype of a single stage to orbital next generation shuttle. The prototype was called the X-33. The full blown bird would have been VentureStar.
It had a lot of new techonologies. One has a new design fuel tank make of a new composite material. The first time they tried filling it up with liquid hydrogen, it ripped open. They told the government that they needed a ton of money more, over and above the original bid to fix it. The government said, forget it and the project was abandoned.
I'll bite.
The ribbon would weight 7.5 kg/km (yes, that's per kilometer). So the whole ribbon with its 100,000 km would weight 750,000 kg. Of course only the portion below the severed point would fall back. If that happens at an altitude of 1,000 km (region of space debris), only a mere 7,500 kg would fall back to Earth.
7,500 kg...
1 megaton = 1,000,000 t = 1,000,000,000 kg
Your apocaliptic image of "rains megatons of carbon cable" is off by 6 orders of magnitude. Not to mention that with its low density, the ribbon would not plummet down, but would probably be picked up by winds and fall quietly, much like a piece of cloth.
Just watch out for the climber. Oh here it comes! "INCOMING!"
I code, therefore I am.