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The pusher plate means that the Orion craft is at least 4,000 tonnes. This is 4,000,000 kg, or about twice the total liftoff weight of the Shuttle, orbiter, stack and all. This is the minimum, and least efficient weight.
Out of that, you get 1,000 tonnes of steel, and 3,000 tonnes of structure, payload, etc. You're already down to 75%. And you dont have power, yet.
The NERVA engine weighed 10 tonnes. And gave a good deal of power. Yes, Orion outperforms the thrust of NERVA, however, due to the weight of the pusher plate, mathematically, it would only take about 12 NERVA engines to lift the payload equivalent of an Orion launch--120 tonnes of reactor, 10% of the mass of the pusher plate.
They are far superior to chemical rockets-even the lowliest NTR has twice the isp and better thrust conversion than the best chemical engines.
There are gas core designs that employ active reactor wall cooling, which allow Isps of up to 7,000 seconds. These reactors would be large, but 7,000 seconds is a tremendous Isp. They could also get at least 6x the thrust of a solid core engine. Not too shabby.
And before I have to go, one quick last point. Orion is blocked by the Test Ban Treaty, which bans firing nuclear weapons in space. Orion's bomblets classify as nuclear weapons.
I doubt it does at all, itll likely shatter before it hits the surface. And its too small to make a major orbital impact on the planet.
Which brings me to another point, what has tens of thousands of years of human development done to the orbit of Earth? Sorry, but the idea that development may alter the orbit is amusing, at best. We, as a whole can't begin to compare to the mass of a planet or Sun.
So you would rather us stay on Earth forever?
Don't worry Shaun, take a look over at the SETI forum at space.com and you'll find loads of similar...bunk.
What others do you need?
I was reading about Buzz Aldrin's idea for a TSTO reusable booster/spaceplane-a booster cased in an airplane (Boeing 747, I believe-I know it was a 7x7), with the payload on top. The plane would then fly back down.
It sounded pretty good-but I don't know how an airplane would fare with liquid fuel and a booster inside.
Ask Zubrin-he is the biggest proponent of nuclear reactors for Mars.
But a full size nuclear reactor can be brought along with the initial flights.
AA: what do you think of Bristol's design? I think its a fairly conservative design with strong potential.
And what do you think about SCs capsule, the Nova 2/Thunderbird, that they just revealed?
If we use a nuclear reactor to begin with, power to extract the water shouldn't really be a problem, considering the large amount of water now estimated to be close to the surface.
This would save money in the short term, which allows quicker establishment of bases on Mars. The quicker we can develop it, the more funding the bases can get. Then we can develop large scale ecosystems.
I've talked about before the possibility of using an NTR-that could carry fuel into orbit, and slow down before reentry. Turn off the reactor when the descent begins, and glide down to landing.
Oh, BTW, Bill, I've always maintained that anarchy would be best suited for an economical / technological plateau, so I can agree with what you said.
Yeah, according to grandiose theories. You can say whatever you want, real economics will have to be applied on Mars.
I've refuted anarchy's "obvious advantages." Anarchy is a load of economic...poop.
I have to agree with clark.
Right, but there are other alternatives, already being R&D'ed, that would allow commercial passenger flights from airports, which is more convenient for the "customers."
Since mountain tracks are less likely to be as ubiquitous as airports, they may be better served towards devoting themselves to the payload launch markets.
I dont base my history on sci fi tv shows.
What do you mean by very specific land points ?! Obviously, once you reached LEO you can land just about anywhere you want with the vehicle.
Sorry, you are right, I meant very specific launch points, which is not in any way desireable for passenger flight.
The potential i see in this is for payload launches.
I think RBCCs and similar designs, that could launch from airstrips, would be more viable for commercial applications (convenience, flexibility, existing infrastructure).
Thus, I think that you would want to truncate the runway, because for payload, g load is less important, and a shorter runway means less maintenance, and greater launch rates.
No system could exist unregulated. A system without laws is no different, in any case, from what Alexander described.
Well, they say subsequent elevators could be built for under $5 billion, which means you could have dozens of elevators (the equator is rather huge, and more advanced designs may not need equatorial positioning). So if one goes down, no problem, just send up a new ribbon/strand, and get back to work.
The X-33 was designed to test the feasiblity of a concept-it wasn't cancelled, it was successful. I don't believe it was ever intended as an actual vehicle.
How many people have the resources to build a full city? Even a single mission would nearly bankrupt Bill Gates.
The rich entity may pave the way, but to make profits, they will have to sell some of this property to less affluent entities, which transfers the property. It is almost entirely impossible for a single entity to monopolisze a planet.
Like I've said before, I'm all for regulated capitalism economies, with democratic/republican representation. For reasons I've stated before, I think the best way to get into space and stay there is by making money.
But I really don't want to get into another economics discussion, because it's always a circular loop.
But I will say that I'd like to see an interplanetary government, that allows for individual sovereignty. General rules (i.e. no warships in space), but nothing that would restrict commerce for a specific entity (ex: restricting asteroid mining would be unfairly harmful to say, Mars).
Right, but the thing is, you have very specific launch and land points, which would not be suitable to commercial activity.
However, this has great potential for launches. Why not use a steam driven catapult to jumpstart it, and then run it through a maglev track? You could significantly truncate the track, and get the same benefits.
Well, I made a thread called "Carriers" that talked about belt-based fusion/fission powered outposts, that would basically be based around a single huge vessel at first (which would have processing facilities, docks, quarters, and so on), and then evolve around that (with factories, trade vessels, hangars, etc.). This could be a center of interplanetary commerce, and could serve as a base for outer solar system missions.
Another important factor is the potential of space elevators. If they work out, these plans will be much more feasible.
Any numbers on mass ratio capacity?
How about combining this with ramjet + scramjet systems, to get a real kick?
The problem I see is that this would have to be used primarily for payload launch, and could never fit the mass market (i.e. good for satellites and space stations but not for people transportation). So, it could do very well for its role, but it would have a specific role.
If and when Mars does become geothermally active, could you imagine an eruption of Olympus Mon? How much damage would a volcano of that size cause?
The chunks would weigh less, and a lot of it would probably never reach the bottom, so on a serious note, I don't think it would be all that dangerous, unless you set up shop on the mountain.
Where would it launch from?
I don't like the Moon. It's a rock. Now, Mars has potential. If we are to settle anywhere, it should be Mars first. It has everything we need.
The Moon's greatest purpose may be as an observatory, and as a materials base/shipyard. Not a home, imho.