You are not logged in.
The science channel finally has a show worth watching(the others mostly on archaeology and bio are 'o.k.'), they have a great documentary on the Ruten commercial space project.
Seems, they've found a way to beat the reentry heat with composites, and a variable wing topology.
What about reentering from higher up you say? Look, if you try reentering at the orbital speeds of higher up, then you won't make it without a mercury capsule or better, but if you slow down to the orbital speeds such as the spaceshipone has already proven, then your entering at much reduced speeds, and as Rutan has already shown a new topology that reduces the terminal velocity of reentry, Ruten has solved the space problem!
From now on, all the other X-prizers will have to take into account Rutan's breakthrough and can only help by making breakthroughs elsewhere; like, maybe somebody can generalize to other reentry topologies; or maybe, somebody can find another better way to launch or maybe use scramjets in the future and so on and so forth.
What about getting higher masses up in space? That is solved by spaceX and the inflatable spacestations of Bigalo. The whole point of space stations as Von Brawn and all the prioneers is to leave all that mass up there instead of launching them up and down every time; the space station is no suppose to reenter!
The X-prize has solved the space problem!(the problem of getting humanity out in space); now, if industrial civilization can just keep from falling apart in the next twenty or so years . . . i really don't think a total nuclear anihilation is coming(one or a few nukes just might go off however . . . .); a new global war? We havn't had one of those in sixty to seventy years probably because of the spread of democracy by our admittedly imperialistic america and Britain and so on and so forth, but hey, maybe Ike and all them were right to a degree!
Mars Direct? It can be reformulated based on the X-prize breakthroughs!
Space civilization ho!
Offline
Uhhhhh. No.
Burt managed to keep his little "shuttlecock" Space Ship One from cooking at suborbital velocities (around Mach 3-5 generally) by adding alot of drag at high altitude where the air is thin... but if you tried to do that from orbital velocities (Mach 25+, over eight times faster), the wings would rip right off and the composite crew cabin would vaporize Columbia style, since you can't use high drag at such high speeds. Burt can't solve that problem with the current SSO design.
I ought to also point out that Burt's ship never made it to orbit. In fact, it never even got anywhere CLOSE to orbit. In order to go into space and stay in space, you have to not only reach an altitude of 200km or so (double what Burt's SSO did), but you must have a ground speed at Mach 25 (parallel to the Earth's surface). Burt's rocket burned every last drop of fuel and inertia to just barely get half way to orbital altitude, and up there it was basically stopped and had almost zero ground speed. In order to push SSO into orbit and carry the other nessesarry equipment that SSO lacks, it would need 200-300X (two or three hundred times) the fuel. It would be so big, it would hardly fit on a 747 jumbo jet.
And thats just for passengers, no payload at all.
If your hope was that the X-Prize was supposed to foster real development of orbital commertial infrastructure, then it failed badly.
MarsDirect, in its stock unmodified form, would NEVER work.
[i]"The power of accurate observation is often called cynicism by those that do not have it." - George Bernard Shaw[/i]
[i]The glass is at 50% of capacity[/i]
Offline
I think we have to realize something. SSO was not designed to go to 200km. It was designed to go to 100km. Given some clever staging the vehicle weight you are quoting (send me the math) could be brought down significantly.
The response to the XPrize was, exactly that, a response to a set of requirements. The money invested, the knowledge gained (whether you like it or not, Burt did have some exotic technology being evaluated on this trip) and the public awareness/interest that resulted in SSO is important.
GCN, I haven't read all of your emails, but are they all this defeatist and down? Maybe you could tell us what you think will work. Your profile doesn't reveal much.
Offline
"clever staging the vehicle weight you are quoting (send me the math) could be brought down significantly."
Nope. See, to get into orbit, reaching the 200km altitude is actually only a minor fraction of how much fuel you need: The real killer is getting up to orbital ground speed, which is about Mach 25 or higher. Burt's toy rocket couldn't even get up to altitude, and thats only a percent or two of the total push you would need.
There is something called the Rocket Equation you might want to look up, its simple to use and is a real eye-opener for just how hard it is to build an efficent spacecraft. The biggest thing to note is that as your desired payload or speed increases, the amount of rocket fuel you need doesn't increase linearly, it increases exponentially. So even though SSO probobly needs to go ten times as fast, it needs a hundred times the rocket fuel. There are a few major systems that SSO would need to be a practical orbital spacecraft too, so your vehicle gets even heavier, so you need even more fuel. Hence the 200-300X estimate.
There are some immuteable, unchangeable, unalterable constants that all rockets have to conquer, and throw all the tricks at them you want, but you'll never change the laws of physics. Gravity isn't going away, and you are limited in the amount of energy you get per-kilo/liter of rocket fuel. As long as you are using a rocket to get into space with chemical fuels, you cannot cheat the Rocket Equation.
I am not a pessimist as far as spaceflight goes, I aspire to be a realist who is tired of both the "we'll do it in 2050 when we have the technology and skills" as well as the AltSpace/X-Prize/etc people who "space is easy! we'll do it tomorrow for peanuts with our little rockets."
Imparticularly I am a critic of Burt Rurtan's Space Ship One and derivitives. It is so far away from a REAL space ship, that the name is a hypocritical lie. He hasn't really DONE anything that noteworthy that the Bell X-2 couldn't have in the 1950s/60s. His ship was not at all "exotic technology," and exuded low-tech other then its composite construction. It really gets me upset that people are so excited about it, when it is really nothing special.
[i]"The power of accurate observation is often called cynicism by those that do not have it." - George Bernard Shaw[/i]
[i]The glass is at 50% of capacity[/i]
Offline
The Tsiolkovsky Rocket Equation is exactly what I am talking about. You see I ran SSO's numbers through the rocket eq. and got results that did not agree with your numbers. I was just wondering if you had run the numbers yourself or if you were quoting someone.
Let me introduce you to one of the facets of the rocket eq. Staging is when you launch a rocket, and when you reach a particular altitude and/or velocity you disconnect your vehicle from part of your launch vehicle and continue on with reduced mass. This makes life a little easier. Then you could either dispose of the stage or have some method of sending it back to reuse later.
I'm not suggesting that SSO could launched on a conventional staged rocket. Re-entry from that velocity would be out of the question. This brings me back to SSO is not designed to be a conventional vehicle.
I can respect a realist. I also respect someone with vision. If you think that we're not ready for the sky until 2050, why are you here? Obviously, you have some kind of vision.
P.S. The 'exotic' technology I was referring to was the hybrid rocket motor. It's been conceived of, and even used experimentally to some lengths, but going from that to a human rated sub-orbital craft...exotic.
Offline
That would be because of the roughly added dry mass of the rocket fuel tankage that SSO would need to hold all the fuel to get to orbit. It could be tens of times the mass either way with staging events and additional SSO systems mass, but its still going to be about two orders of magnetude greater.
"Let me introduce you to one of the facets of the rocket eq"
Excuse me, but I happen to know what staging is, thank you.
"If you think that we're not ready for the sky until 2050, why are you here?"
You will note upon more thoughtful review of my previous post, that I said that I was tired of people who thought practical space travel was only a far-future proposition.
"The 'exotic' technology I was referring to was the hybrid rocket motor"
Nonsense. It was low tech, and the only engine Burt could come up with that wouldn't explode that he could afford.
[i]"The power of accurate observation is often called cynicism by those that do not have it." - George Bernard Shaw[/i]
[i]The glass is at 50% of capacity[/i]
Offline
Your saying Rutans rocket needs so much more to get up to mach 25, and then saying it has to reenter at mach 25? I'm saying it doesn't, although I have to say that I just realized that you may have to burn lots of fuel to get back down to speed.
Another thing is where the atmosphere; never mind that that is relative to how many atoms your counting in a given volume of space; does the atomsphere extend past the van allen belts? Sure, there's got to be a few atoms even out there. If you watch the Ruten rocket, it feels zero-gravity(I'm not saying this is orbital, but it is freefall); in fact, the last sso had to use retrorockets to stop it from spinning because there was no atmosphere to cause drag.
The real issue of whether we can avoid reentry heat is whether we can reduce speed to suborbital velocity before it hits the atomsphere which would take a lot of energy admittedly; maybe use space hooks(duck; i just know avenger is going to be throwing things at me from far away!).
Back to the scramjet thingy though; Rutans sso got up to mach 3 pretty fast, it could then engage a scramjet which would get it up to mach what 15?(hold on avenger) At the height mach 15 could achieve, there is no atmosphere worth worrying about, engage the rockets again from that substantially reduced atomosphere and gravity I should add and . . . drumroll? O.K., the ship probably would have to be scaled up here and there, but those space hooks again?
Offline
The amount of fuel you would need to carry to go from Mach 25 to a lower (say, Mach 10) would be a pretty good chunk of the fuel needed to go from 10 to 25, which would be dozens or hundreds of tonnes. And every gram of that would subtract from your payload... using rockets to slow down from orbital speed would completly eliminate all your payload. And more probobly.
The "skyhook" is a stupid plan cooked up by ameratures who don't have their heads grounded in reality (the kind of people I really get annoyed with). Its never going to be useful because its too hard to use and build.
Using a Scramjet to go from Mach 5 to 15 doesn't save you that much rocket fuel, and you would have to stay in the thick atmosphere down low for it to work, while regular rockets are out of the atmosphere when they reach these kinds of speeds. Making a spaceplane, with a Scramjet built into its body, that can handle the pressures, temperatures, and so on of Mach 15 travel in the atmosphere is very difficult. Way, way beyond Burt and company.
[i]"The power of accurate observation is often called cynicism by those that do not have it." - George Bernard Shaw[/i]
[i]The glass is at 50% of capacity[/i]
Offline
To GCN: No insult intended, it's just that I know what the Rocket Eq is too.
To Flash: The atmosphere does extend farther than Rutan's ship, but you have to remember the density of the atmosphere like the Ideal Rocket Equation, is exponential. So the higher you go, the faster the air thins.
Scramjets are a beautiful technology. You have to be going very fast though, and you have to have a fine tuned design. Because we know so little about the effects on air at that velocity it is difficult to make a robust craft. Another extremely important thing to keep in mind is that scramjets will not work outside the atmosphere, and their efficiency depends on the density of air. To go fast enough to use scramjets in air that is dense generates a lot of heat on the leading edges of your craft. So its a trade. But all of the projects that I have been on that have dealt with scramjets have shown that they can be help out a lot.
Quickly, a scramjet is simply a rocket. The only difference is where you're getting your oxidizer. You compress air using an inlet, and then ignite fuel in the flow (tricky). There is a technology called ACES (Air Collection and Enrichment System). This is used to collect O2 in flight (one so you can have it when you leave the atmosphere, and two so you don't have to take off with it, which might be prohibitive). It can be heavy though, so currently would only be useful on larger vehicles.
Offline
Well, after pondering some more things and cancelling the ideas, I'm left with one final idea; ionizing the atmosphere ahead of the rocket to reduce the drag, and how about ionizing the atomsphere upon reentry to reduce drag? This can be done using a superconducting magnet(expensive, but then again I have read some recent reports on superconducting magnets, but they are probably still pretty expensive)s.
Offline
"Quickly, a scramjet is simply a rocket. The only difference is where you're getting your oxidizer."
What? No, no it isn't. There is another BIG fundimental difference, that a rocket must carry every single gram of reaction mass, while an airbreathing engine not only gets free oxidizer, but free inert air to push on too. This changes matters considerably, and throws the rocket equation out the window since not all your reaction mass must be carried.
The limited top speed of a "run of the mill" Scramjet however doesn't help near enough, it still won't make a "small private spaceplane" possible.
ACES would be nice, but thats an awful lot of equipment you are talking about lugging I bet.
[i]"The power of accurate observation is often called cynicism by those that do not have it." - George Bernard Shaw[/i]
[i]The glass is at 50% of capacity[/i]
Offline
One more quick thing: Mars Direct won't see any direct benefit from the X-Prize. The best we can hope for there is that people might get excited and tell their governments to spend more on spaceflight and less on wars. Does anyone have the dollar amount spent on the 'war on terror' and the sum of NASA budgets since then for some head-to-head comparison?
Mars Direct is a ten year old plan. All ten year old plans have shortcomings. But I'm guessing that what you're implying by saying "stock unmodified" form is that you think it would work in some modified form?
Offline
Well, after pondering some more things and cancelling the ideas, I'm left with one final idea; ionizing the atmosphere ahead of the rocket to reduce the drag, and how about ionizing the atomsphere upon reentry to reduce drag? This can be done using a superconducting magnet(expensive, but then again I have read some recent reports on superconducting magnets, but they are probably still pretty expensive)s.
Huh? A magnet to make air ionize?
A superconducting magnet of that kind of power would be big and heavy too, bigger and heavier then a heat shield would be. And since they have to be kept at like -200C or below to work, even a little heating would destroy your ship.
Even if it did work, if you reduce the drag ahead of your ship, then you won't slow down very well and you would "skip" right off the top of the atmosphere back into orbit.
[i]"The power of accurate observation is often called cynicism by those that do not have it." - George Bernard Shaw[/i]
[i]The glass is at 50% of capacity[/i]
Offline
Scramjet top speed is mach 25 (maybe higher).
The rocket equation that you are talking about is the "ideal rocket equation". A rocket is just a device for momentum transfer. This doesn't mean that you have to bring all of your medium with you. Under these 'non-ideal' circumstances the equation has to be modified. Other things that can effect the rocket equation are aerodynamic effects.
Bringing a giant powerful magnet-superconductor would be prohibitive I think.
Small private scramjet planes are not feasible. Ramjet ...maybe. I think there is something on it at the Joint Propulsion Conference. Maybe I'll report back when I get back.
Offline
One more quick thing: Mars Direct won't see any direct benefit from the X-Prize. The best we can hope for there is that people might get excited and tell their governments to spend more on spaceflight and less on wars. Does anyone have the dollar amount spent on the 'war on terror' and the sum of NASA budgets since then for some head-to-head comparison?
Mars Direct is a ten year old plan. All ten year old plans have shortcomings. But I'm guessing that what you're implying by saying "stock unmodified" form is that you think it would work in some modified form?
The basic MarsDirect plan suffers from two basic fundimental "character flaws:"
1: It cuts too many corners. That the basic plan is not capable of working safely even as advertised, the "budgets" for mass, volume, and margins are obviously way below what is needed, much less with enough "headroom" for safety margins.
2: MarsDirect, even if it did work, is a terrible plan. Its capacity to perform science is badly limited by its smaller crew size, smaller science payload, and so on. More importantly however, any notions about MarsDirect evolving to be anything better then the basic plan are nonsense. MarsDirect is a dead end, and will never be anything more then it is... You can't make a base out of warn out HABs, and you can't turn it into a reuseable cycler.
The NASA DRM-III plan (perhaps using 100MT rather then 80MT pieces), using expendable nuclear TMI rockets and Mars aerobraking is the best plan I know of.
[i]"The power of accurate observation is often called cynicism by those that do not have it." - George Bernard Shaw[/i]
[i]The glass is at 50% of capacity[/i]
Offline
Scramjet top speed is mach 25 (maybe higher).
Small private scramjet planes are not feasible. Ramjet ...maybe. I think there is something on it at the Joint Propulsion Conference. Maybe I'll report back when I get back.
You are talking about an advanced "varient" of the Scramjet, a "Regenerative" scramjet. Such an engine could get you going faster, maybe like Mach 20 or something, but such an engine would be very hard to build. We're talking needing materials that can handle liquid hydrogen (-300C or so) on one side, and 2,000-3,000C+ on the other... and still conduct heat efficenctly, be extremely strong, and resist both ablation and Hydrogen embrittlement. Oh, and do it a hundred times without serious overhaul too.
"Small private spaceplane" is not going to happen for a very, very long time if its possible at all.
[i]"The power of accurate observation is often called cynicism by those that do not have it." - George Bernard Shaw[/i]
[i]The glass is at 50% of capacity[/i]
Offline
Does this operated like Nuclear Thermal Rocket? Would you launch from orbit?
Offline
The DRM would use small solid core nuclear thermal rockets, about the same thrust as today's little RL-10 engine. They would not be activated on Earth's surface or in the atmosphere, but only after reaching orbit. A Shuttle-derived heavy lift rocket called Magnum would put the nuclear TMI rocket into orbit using only conventional chemical engines. Since nuclear reactors don't become radioactive until activated, the nuclear engines are harmless even if they did accidently reenter Earth's atmosphere.
They are probobly the easiest, quickest route to Mars.
[i]"The power of accurate observation is often called cynicism by those that do not have it." - George Bernard Shaw[/i]
[i]The glass is at 50% of capacity[/i]
Offline
Yeah I don't think scramjets are very feasible for single person use. I'll have to give that one some more thought.
I completely agree that there are technology hurdles. Even though I have done research on the matter, I have my doubts at the same time. I'm an old-fashioned sort of guy when it comes to real hardware. Paper studies are one thing. But they are mostly thought experiments.
I am a strong proponent of NTRs. They are realistic, powerful, efficient, and can be built and operational sooner than air-breathers I think. There are legal hurdles though.
Offline
A nuclear engine won't be an either/or with an airbreathing engine, a nuclear engine would only be for getting from one orbit to another, and never for getting off the surface where an airbreathing engine is useful. The political hurdles and the real objective apolitical environmental risks are way too great.
For a big payload, like a Mars ship, you would need a big NTR engine if you are trying to get off of Earth's surface. You need lots of thrust, but as you know in space you don't, only a little will do. Having one of these "big" nuclear engines explode, or otherwise fail to reach orbit after firing, that would cause a nuclear nightmare.
[i]"The power of accurate observation is often called cynicism by those that do not have it." - George Bernard Shaw[/i]
[i]The glass is at 50% of capacity[/i]
Offline
I think what most people don't realize is that we have launched many nuclear powered vehicles (although RTG's and not what we're talking about). We have to be careful, but don't we always?
Offline
Using a large NTR engine for a launch vehicle is really a different kind of threat. RTGs carry only some kilos of mildly radioactive Pu238, which isn't too nasty being a whimpy Alpha emitter and is easily contained in its blast-hardend casing.
A fault with a nuclear engine is a whole different beast... even if you manage to turn the reactor off and avoid meltdown, it will still be producing extreme amounts of hard Gamma radiation and heat, and it will be coming back down on our heads. The radiation is produced by the radioactive waste made during operation, and it isn't going away. If that material were to be spread over an area, you would be talking serious casulties.
Building a blast-hardend nuclear rocket that big would also not be feasable, it would be too heavy, and there really isn't any kind of practical shielding that would be safe enough. If you add all the extra weight for armor and bigger fuel tanks (since it only uses low-density H2), then you are better off using the much cheaper and lighter chemical rockets.
If such an engine or power reactor melted down or blew up in orbit though, thats not so bad. The failed engine would stay in orbit for many years, and so most of the radioactivity would be gone as the majority of the radioactive waste decays quite quickly. Plus, since it would be at the top of the atmosphere moving very quickly, the debries would be very widely dispursed and be an inconsequential danger. Space-only reactors and engines can be much, much smaller then large NTR engines for launch vehicles too, so there is lots less radioactive material in the first place.
[i]"The power of accurate observation is often called cynicism by those that do not have it." - George Bernard Shaw[/i]
[i]The glass is at 50% of capacity[/i]
Offline
Coming back, i'm surprised I didn't bring up the nuclear ticket, but besides that, what I was really going to say was something I've been meaning to say but have been trying to build up slowly in other forums; we need to make a scientific society that is socially prepared to go to space. :realllymad: We need either so much chemical energy, and or exotic nuclear energy which is anethema to a conservative mind, that we need a society that is working towards going to space, not just living the lives to make ends meet by having dozens of babies just to go to school and all the other such crazy things going on. Even if by some miracle of miracles, our society spits out a lone space colony somewhere somehow, that colony will not survive in space if it is not socialy ready for the stars.
Offline
o.k. another way of putting this without even bringing up the space colonization issue is that the second law of thermodynamics is going to bite technological civilization in the ass sooner or later if we don't explore; but, if we don't have it in us socially as a society to go exploring, then we won't.
Offline
consider this; who's going to pay for a few other guys to go storming the heavens while everybody else stays here on earth to sweat and moan?
Offline