It's plenty strong enough -- it's based on the same technology (and the same materials, in fact) that skydivers have been using for close to twenty years: parafoils (commonly known as "square parachutes" back then) became practical in the early 70's. The Genesis parafoil is based on the design of a parachute long used for tandem skydiving instruction... long history there. (I've used similar devices a few thousand times myself; they work! And I don't just use 'em -- I design parachute systems for a living.)
And yeah, you can't just open it supersonically in Earth's atmosphere -- the vehicle slows considerably on its own, and it's further slowed by a drogue parachute before the parafoil opens at 20 Kft or so. IIRC the parafoil (at around 420 square feet planform area) weighs about fifteen pounds... not too shabby. You just have to remember that it's not extremely rigid: the airfoil shape is controlled by the ram-inflated fabric, but the load structure is all in the reinforcing tapes and suspension lines. My personal parachute weighs in at less than six pounds and is good for at least a thousand uses, and I'm not a little guy...
Your third reference, unfortunately, is either dreadfully misinformed or an outright nutcase (and I suspect the latter, after following a couple of his further links). I wouldn't quote his information as supportive of the Nemesis theory at all -- he doesn't even realize that Earth's rotation axis is dramatically inclined relative to the Sun's, nor that Polaris is over a thousand lightyears away and not associated with the Solar System at all.
And those are just a couple of the most glaring errors -- his short page is littered with them. There ain't no physics there.
You're right about the history of midair returns, but this one is different: the parachute is a parafoil, a ram-air inflated deployable flying wing. AFAIK this is the first time a spacecraft will be recovered in the air under a parafoil...
It makes a lot of sense: the parafoil gives a much lower rate of descent than an equivalent-weight round parachute could, and also gives a large horizontal velocity component -- so the relative closing speed of the helicopter is minimized, and it doesn't have to be in such a dive, either. IIRC the vertical rate is about 13 ft/sec, and horizontal is around three times that.
It's a pretty cool system; I got to work with it a bit, and saw quite a few of the test flights.
Lockheed Martin has the 2001 lander (virtually identical to the MPL), which was never launched because of the failure of the MPL. Basically, NASA freaked out over the MPL/Climate Orbiter failures, and refused to launch the next one... very typical of post-Challenger NASA.
It's mostly politics: JPL's Climate Orbiter failed, too, and JPL did one of the investigations into the two failures. Basically, they whitewashed their problems and crapped all over LockMart for what were very similar failings... not to excuse LockMart's bungling, just to point out another trait which NASA persistently exhibits.
If indeed the Young report's conclusions were correct, a line of code in the system controller's program would fix the problem: basically, when the legs deploy they tend to set the switches which tell the vehicle it's landed, thereby shutting down the landing motors as soon as they ignite -- simply reseting the registers after leg deployment does the job. In this case, LockMart wants to fix the code, and wants NASA to launch it (well, at least some of the LockMart employees want this).
If NIMA has found the MPL as described, however, then something else is wrong and there's no point in launching another (possibly fundamentally-defective) spacecraft. The Young report was pretty scathing: both JPL's MCO and LockMart's MPL were built for less than the wildly-successful Pathfinder lander, and both projects suffered from lack of supervision by experienced planetary spacecraft engineers, and from inadequate testing. It's not clear that all the potential problems have been identified, so NASA's decision to cancel the 2001 lander's launch may be a good call -- I have mixed feelings about it.
But in any case, NIMA's "discovery" is extremely tentative (despite the ridiculously misleading headline (for shame,/.!), and I wouldn't base any decision on it at the moment. Something tells me that NASA won't launch it under any circumstances, especially given the Bush administration's attitudes toward NASA in general... more's the pity.
It's been, what, 15 years since cold fusion was announced? I'm still waiting for the first demonstration of a working device.
Not that I disagree with you (cold fusion is problematical on energy considerations alone), but remember that it took over 50 years for Alfred Wegener's continental drift theory to be accepted -- he published it in 1915, and it was only around 1967 or so that the striped magnetic domains on the seafloor provided the inarguable evidence that he was right.
Fifteen years in science is nothing at all. The major paradigm shifts have to await the death of their opponents before they reach true acceptance.
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Re:IT Independence Transporter
on
What is 'IT'?
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· Score: 2
It's designed for people who are wheelchair-bound. Just for fun, why don't you get in a wheelchair and try to go about your life for juat a few hours, someday... and never even think about going to the beach, or the mountains. The only rule is, you can't get out of the wheelchair to do anything.
It won't be long before you come to think of it as "your own personal hovercraft or something." This thing's freedom itself for a lot of people!
I suspect you really don't mean that; "terraform" is usually used to denote the transformation of a planetary surface into a terrestrial environment, and there's no asteroid large enough for that -- they wouldn't hold water or an atmosphere.
If you meant "hollow it out and make a living environment inside," or even "use the materials to create a space habitat," I agree with you. Just being pedantic...;)
The gravitational attraction of Eros is small -- small enough that orbital velocity of NEAR Shoemaker is only a few miles per hour, like a brisk walking pace.
The problem is this: the spacecraft isn't going terribly fast, but it still has all its momentum... so when it hits, it's likely to tumble, shearing off solar collectors and anything else that protrudes. Even if it hits at just the right angle, it can't just slide to a stop -- there's not enough gravity for that (escape velocity is so low you could easily throw a rock into solar orbit); instead, it would take lots of bounces, hitting at new angles each time and tearing more stuff up.
I'm hoping it just "plonks" in, but I'm not counting on anything.
Why would someone even take the chance here when clearly they're stating they acknowledge issues surrounding their space projects.
They're not proposing they do it tomorrow; one might presume that in a decade or two they could acquire the necessary knowledge to do it better... after all, the US and USSR both had plenty of problems in their early days, but overcame them.
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Re:Pioneers, NOT tourists!
on
Space Tourism
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· Score: 2
This will never get anywhere. Oogling at the earth from 50 miles up will not accomplish any long term goals.
I disagree. While it doesn't directly accomplish your longterm goals (which I share, very enthusiastically!), it does help create both the infrastructure for space travel, and more importantly it creates an image of the possibility and the desirability of space travel.
I think these are all great things, and I wholeheartedly support space tourism because of it. (Just keep 'em out of the way of the serious folks, please...;)
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Re:Much better value than a trip to MIR
on
Space Tourism
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· Score: 1
I'm afraid I don't see the point.
Wow. So, how long have you been soul-dead?
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Re:Likely To Happen With Such A Long Wait :)
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Space Tourism
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· Score: 2
If even the gung-ho "Right Stuff" guys puked, what chance does a desk-jockey like me have of keeping it where it belongs?
Face it, the majority of the passengers will hurl. Just as with cruise ships, there'll be lots of "patches" behind the ears... it's what most people do in microgravity, and I think we won't change people, we'll just drug 'em.
There will be accidents, there will be deaths and some people may try to go legal.
There's actually a good model for this: skydiving. Go out to the local dropzone and sign up for a first-jump course: you'll sign a waiver which basically says you understand you might die, and that's your tough luck... These waivers regularly hold up in court, in part because few people are stupid enough to believe there's no risk, and they've been thoroughly warned that there is.
The other thing which helps is that there's rarely insurance, which prevents the development of a "deep pocket" for the lawyers to feed on. The Japanese might be relatively safe, since the lawsuits might have to be in their courts (as opposed to US courts, which are certifiably insane).
All we need now is for NASA to announce some reason to go to Mars (like huge gold mines below the surface), and we'll finally start seeing interplanetary travel.
Whoa! I didn't mean we can do it now -- only that there's nothing theoretically or physically impossible about it, as claimed in the earlier post.
We still don't have a drive that'll manage a hundredth of a gee for weeks on end... minor point.;) There are good reasons to believe that we'll have that tech in a while, but not yet!
Problems like this make it a nice gedanken experiment, but it's probably never going to be practical.
By the time you've addressed all the issues necessary for use of americium foil in a rocket, it will have been easier to just solve the problem of using antimatter as the energy source and water as the working fluid. Sure, you have to make the antimatter -- but that's not much harder than making the americium in situ... and turning it on and off is no doubt simpler (although probably breathtaking anyway).
...even if they accelerated at 1G half the way there and deccelerated at 1G the other half it would still take quite a while to reach mars...
Not really. I've still got the MathCad doc open from my earlier post, so here goes... Use the same 200 million kilometers for worst-case trip (opposition, fly around the sun) at 1 g constant acceleration: time to Mars is just under 40 hours, with turnover speed of 700 km/sec.
But you're right, 1 g constant acceleration for 40 hours is some trick!
Not at all: the site you link is talking about round-trip times, and erroneously assumes that you will have to wait for Earth and Mars to return to opposition for the return trip.
The truth of the matter is that if you have enough rocket, you can go directly to Mars from Earth at any point in their orbits, and you really won't care what the relative position is.
Just for fun, I took the one-way trip time for worst-case conjunction (100 million kilometers) with a 1/100 gravity continuous acceleration. This takes just under 12 days (accelerate half-way there, decelerate the other half); if you add a bit of time to match orbital velocity, you've still done it in under two weeks. (In fact, the coincidence of the numbers suggests to me that the value of 0.01 g is what the author was using...)
Now, I did this at conjunction (Earth and Mars on the same side of the sun, closest approach), although it was worst-case conjunction. If you want to go (or return) at opposition (meaning you'd go around the Sun en route, the trip's much longer -- on the order of 2.4 AU, or around 140 million klicks; let's use 200 million to make the argument, though, since we've got to miss the Sun by a little.
It now takes you 16.5 days, more or less. The reason it's so short is that you're continually accelerating: your velocity keeps growing, and adding just a little time at such a high velocity makes a big difference. FWIW, in the last case your velocity is over 70 km/sec at your halfway-point turnover; in the first case, traveling half the distance, it was under 50 km/sec.
Not impossible at all! Matter of fact, I'm open for a ticket right now...;)
You could then carry liquid rocket fuel in a plane-style lifting body to land on mars, which would be safer than parachuting...
Actually, this would be less practical than parachuting, which itself is not practical for the terminal descent onto Mars (that's why Pathfinder used an airbag, and why every other probe landed on Mars has done so with a rocket). The reason is that Mars' atmosphere is far too thin for these to be effective: Pathfinder, under a fully-open and functioning parachute, was still descending at around 185 ft/sec, which is faster than a skydiver in freefall! For comparison, on Earth the same parachute brought it down at less than 25 ft/sec.
While a lifting body would fly in Mars' atmosphere, it would be very, very fast -- and landing it would be effectively impossible. The lift-to-drag ratio of a lifting body is small (even for Shuttle, which has true wings, the L/D is only around 3:1), so the rate of descent would be impossibly high with any rational wing loading. Even on Earth, it's hard to land a highly-loaded lifting body -- this is why the X-38 Space Station "lifeboat" is landed with a large parafoil-type parachute, rather than simply landed... it's way too fast, even here.
While there are aircraft being designed for martian flight, they tend to resemble things like the Gossamer Condor and other manpowered aircraft, more than something you could use for descent from space; the vehicle would have to be all wing, and very lightweight wing at that, to work. Like mylar film over wireframe... not really great for re-entry.
Launching a rocket won't slow down earth's rotation; the rocket works by reacting its exhaust mass... it's not like the "kick" of a gun.
The "gravity whip" maneuver you originally mentioned probably did not involve "skipping a probe off the atmosphere." I'm sure it was a momentum exchange, using the earth's orbital momentum -- not the rotational momentum. Skipping a probe off the atmosphere would tend to slow the probe down, not speed it up, just in general. (It is possible to use it to change direction and potentially gain speed, but AFAIK that's not been reduced to practice yet.)
And I don't think they measured the change it made. They may have measured the change in momentum of the probe and calculated the change in earth's momentum, but earth's momentum (whether orbital or only rotational) is so huge that this sort of momentum exchange with any spacecraft yet built would be undetectable with present technology. Work out the numbers...
Just for an example: one of the things they can measure is the effects on the earth's rotation rate of motions of the entire terrestrial atmosphere. And the changes are tiny -- very small fractions of a second in the length of a day, from motions whick take days or weeks to complete. Have you any idea how massive the entire atmosphere is, compared to a manmade object of any kind whatsoever?
Not to arbitrarily bang on you, but your example was ill-chosen and then misunderstood...
There is no purpose to guns in a modern peaceful society.
Oh, what a sweet notion! [/sarcasm]
I wish you'd been there the time I needed a gun and didn't have it. Then they would have beat the crap out of you; and you, not I, would have spent the next several years in a spinal brace.
Just so you know, the next time they didn't touch me: I was armed. Nobody got hurt -- not me, not them. Sorta nice how that works... since societies aren't always peaceful. My offense? They just didn't like my haircut.
NASA needs to put some beef into man-rating the X-38 derivative CRV and certifying it for launch aboard an ELV (like a Delta) so that we can have a cheap way to put people in orbit.
Ummmm... the CRV will be man-rated; it has to be, since it will carry crew. Live crew, in fact...;)
It's already been noted that the CRV or some derivative thereof would make a fine low-cost mini-shuttle. ESA (the European Space Agency) is has been spending money on that, and are even working on their own version of the landing parafoil (ESA is providing funds and hardware for the X-38 program anyway). The Japanese are also rumored to be interested.
Matter of fact, I've seen some preliminary design work on the ESA ideas for this, at JSC in Houston (but don't quote me on that...).
By all accounts, Goldin is doing his level best to discourage this flight. I can't imagine NASA supporting it, even to keep the Russians from pulling off the first commercial space travel.
And there is no third choice. Not yet.
Tito wants to dance, so he's paying the only piper who'll take his money.
Slashdot Mirror
And yeah, you can't just open it supersonically in Earth's atmosphere -- the vehicle slows considerably on its own, and it's further slowed by a drogue parachute before the parafoil opens at 20 Kft or so. IIRC the parafoil (at around 420 square feet planform area) weighs about fifteen pounds... not too shabby. You just have to remember that it's not extremely rigid: the airfoil shape is controlled by the ram-inflated fabric, but the load structure is all in the reinforcing tapes and suspension lines. My personal parachute weighs in at less than six pounds and is good for at least a thousand uses, and I'm not a little guy...
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And those are just a couple of the most glaring errors -- his short page is littered with them. There ain't no physics there.
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It makes a lot of sense: the parafoil gives a much lower rate of descent than an equivalent-weight round parachute could, and also gives a large horizontal velocity component -- so the relative closing speed of the helicopter is minimized, and it doesn't have to be in such a dive, either. IIRC the vertical rate is about 13 ft/sec, and horizontal is around three times that.
It's a pretty cool system; I got to work with it a bit, and saw quite a few of the test flights.
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Nice and small, but plenty powerful, and extremely well-built -- of course you'd have to add a monitor...
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It's mostly politics: JPL's Climate Orbiter failed, too, and JPL did one of the investigations into the two failures. Basically, they whitewashed their problems and crapped all over LockMart for what were very similar failings... not to excuse LockMart's bungling, just to point out another trait which NASA persistently exhibits.
If indeed the Young report's conclusions were correct, a line of code in the system controller's program would fix the problem: basically, when the legs deploy they tend to set the switches which tell the vehicle it's landed, thereby shutting down the landing motors as soon as they ignite -- simply reseting the registers after leg deployment does the job. In this case, LockMart wants to fix the code, and wants NASA to launch it (well, at least some of the LockMart employees want this).
If NIMA has found the MPL as described, however, then something else is wrong and there's no point in launching another (possibly fundamentally-defective) spacecraft. The Young report was pretty scathing: both JPL's MCO and LockMart's MPL were built for less than the wildly-successful Pathfinder lander, and both projects suffered from lack of supervision by experienced planetary spacecraft engineers, and from inadequate testing. It's not clear that all the potential problems have been identified, so NASA's decision to cancel the 2001 lander's launch may be a good call -- I have mixed feelings about it.
But in any case, NIMA's "discovery" is extremely tentative (despite the ridiculously misleading headline (for shame, /.!), and I wouldn't base any decision on it at the moment. Something tells me that NASA won't launch it under any circumstances, especially given the Bush administration's attitudes toward NASA in general... more's the pity.
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Not that I disagree with you (cold fusion is problematical on energy considerations alone), but remember that it took over 50 years for Alfred Wegener's continental drift theory to be accepted -- he published it in 1915, and it was only around 1967 or so that the striped magnetic domains on the seafloor provided the inarguable evidence that he was right.
Fifteen years in science is nothing at all. The major paradigm shifts have to await the death of their opponents before they reach true acceptance.
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It won't be long before you come to think of it as "your own personal hovercraft or something." This thing's freedom itself for a lot of people!
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I suspect you really don't mean that; "terraform" is usually used to denote the transformation of a planetary surface into a terrestrial environment, and there's no asteroid large enough for that -- they wouldn't hold water or an atmosphere.
If you meant "hollow it out and make a living environment inside," or even "use the materials to create a space habitat," I agree with you. Just being pedantic... ;)
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If the aerospace industry went metric, everyone would have problems; now, NASA is the only one -- and then only if they don't bother to check...
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The problem is this: the spacecraft isn't going terribly fast, but it still has all its momentum... so when it hits, it's likely to tumble, shearing off solar collectors and anything else that protrudes. Even if it hits at just the right angle, it can't just slide to a stop -- there's not enough gravity for that (escape velocity is so low you could easily throw a rock into solar orbit); instead, it would take lots of bounces, hitting at new angles each time and tearing more stuff up.
I'm hoping it just "plonks" in, but I'm not counting on anything.
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They're not proposing they do it tomorrow; one might presume that in a decade or two they could acquire the necessary knowledge to do it better... after all, the US and USSR both had plenty of problems in their early days, but overcame them.
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I disagree. While it doesn't directly accomplish your longterm goals (which I share, very enthusiastically!), it does help create both the infrastructure for space travel, and more importantly it creates an image of the possibility and the desirability of space travel.
I think these are all great things, and I wholeheartedly support space tourism because of it. (Just keep 'em out of the way of the serious folks, please... ;)
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Wow. So, how long have you been soul-dead?
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Face it, the majority of the passengers will hurl. Just as with cruise ships, there'll be lots of "patches" behind the ears... it's what most people do in microgravity, and I think we won't change people, we'll just drug 'em.
There's actually a good model for this: skydiving. Go out to the local dropzone and sign up for a first-jump course: you'll sign a waiver which basically says you understand you might die, and that's your tough luck... These waivers regularly hold up in court, in part because few people are stupid enough to believe there's no risk, and they've been thoroughly warned that there is.
The other thing which helps is that there's rarely insurance, which prevents the development of a "deep pocket" for the lawyers to feed on. The Japanese might be relatively safe, since the lawsuits might have to be in their courts (as opposed to US courts, which are certifiably insane).
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Whoa! I didn't mean we can do it now -- only that there's nothing theoretically or physically impossible about it, as claimed in the earlier post.
We still don't have a drive that'll manage a hundredth of a gee for weeks on end... minor point. ;) There are good reasons to believe that we'll have that tech in a while, but not yet!
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By the time you've addressed all the issues necessary for use of americium foil in a rocket, it will have been easier to just solve the problem of using antimatter as the energy source and water as the working fluid. Sure, you have to make the antimatter -- but that's not much harder than making the americium in situ... and turning it on and off is no doubt simpler (although probably breathtaking anyway).
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Not really. I've still got the MathCad doc open from my earlier post, so here goes... Use the same 200 million kilometers for worst-case trip (opposition, fly around the sun) at 1 g constant acceleration: time to Mars is just under 40 hours, with turnover speed of 700 km/sec.
But you're right, 1 g constant acceleration for 40 hours is some trick!
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The truth of the matter is that if you have enough rocket, you can go directly to Mars from Earth at any point in their orbits, and you really won't care what the relative position is.
Just for fun, I took the one-way trip time for worst-case conjunction (100 million kilometers) with a 1/100 gravity continuous acceleration. This takes just under 12 days (accelerate half-way there, decelerate the other half); if you add a bit of time to match orbital velocity, you've still done it in under two weeks. (In fact, the coincidence of the numbers suggests to me that the value of 0.01 g is what the author was using...)
Now, I did this at conjunction (Earth and Mars on the same side of the sun, closest approach), although it was worst-case conjunction. If you want to go (or return) at opposition (meaning you'd go around the Sun en route, the trip's much longer -- on the order of 2.4 AU, or around 140 million klicks; let's use 200 million to make the argument, though, since we've got to miss the Sun by a little.
It now takes you 16.5 days, more or less. The reason it's so short is that you're continually accelerating: your velocity keeps growing, and adding just a little time at such a high velocity makes a big difference. FWIW, in the last case your velocity is over 70 km/sec at your halfway-point turnover; in the first case, traveling half the distance, it was under 50 km/sec.
Not impossible at all! Matter of fact, I'm open for a ticket right now... ;)
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Actually, this would be less practical than parachuting, which itself is not practical for the terminal descent onto Mars (that's why Pathfinder used an airbag, and why every other probe landed on Mars has done so with a rocket). The reason is that Mars' atmosphere is far too thin for these to be effective: Pathfinder, under a fully-open and functioning parachute, was still descending at around 185 ft/sec, which is faster than a skydiver in freefall! For comparison, on Earth the same parachute brought it down at less than 25 ft/sec.
While a lifting body would fly in Mars' atmosphere, it would be very, very fast -- and landing it would be effectively impossible. The lift-to-drag ratio of a lifting body is small (even for Shuttle, which has true wings, the L/D is only around 3:1), so the rate of descent would be impossibly high with any rational wing loading. Even on Earth, it's hard to land a highly-loaded lifting body -- this is why the X-38 Space Station "lifeboat" is landed with a large parafoil-type parachute, rather than simply landed... it's way too fast, even here.
While there are aircraft being designed for martian flight, they tend to resemble things like the Gossamer Condor and other manpowered aircraft, more than something you could use for descent from space; the vehicle would have to be all wing, and very lightweight wing at that, to work. Like mylar film over wireframe... not really great for re-entry.
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- Launching a rocket won't slow down earth's rotation; the rocket works by reacting its exhaust mass... it's not like the "kick" of a gun.
- The "gravity whip" maneuver you originally mentioned probably did not involve "skipping a probe off the atmosphere." I'm sure it was a momentum exchange, using the earth's orbital momentum -- not the rotational momentum. Skipping a probe off the atmosphere would tend to slow the probe down, not speed it up, just in general. (It is possible to use it to change direction and potentially gain speed, but AFAIK that's not been reduced to practice yet.)
- And I don't think they measured the change it made. They may have measured the change in momentum of the probe and calculated the change in earth's momentum, but earth's momentum (whether orbital or only rotational) is so huge that this sort of momentum exchange with any spacecraft yet built would be undetectable with present technology. Work out the numbers...
Just for an example: one of the things they can measure is the effects on the earth's rotation rate of motions of the entire terrestrial atmosphere. And the changes are tiny -- very small fractions of a second in the length of a day, from motions whick take days or weeks to complete. Have you any idea how massive the entire atmosphere is, compared to a manmade object of any kind whatsoever?Not to arbitrarily bang on you, but your example was ill-chosen and then misunderstood...
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Oh, what a sweet notion! [/sarcasm]
I wish you'd been there the time I needed a gun and didn't have it. Then they would have beat the crap out of you; and you, not I, would have spent the next several years in a spinal brace.
Just so you know, the next time they didn't touch me: I was armed. Nobody got hurt -- not me, not them. Sorta nice how that works... since societies aren't always peaceful. My offense? They just didn't like my haircut.
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Damn shame, but true. Texas...
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Ummmm... the CRV will be man-rated; it has to be, since it will carry crew. Live crew, in fact... ;)
It's already been noted that the CRV or some derivative thereof would make a fine low-cost mini-shuttle. ESA (the European Space Agency) is has been spending money on that, and are even working on their own version of the landing parafoil (ESA is providing funds and hardware for the X-38 program anyway). The Japanese are also rumored to be interested.
Matter of fact, I've seen some preliminary design work on the ESA ideas for this, at JSC in Houston (but don't quote me on that...).
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And there is no third choice. Not yet.
Tito wants to dance, so he's paying the only piper who'll take his money.
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