New Mars Forums

Ah, no sorry - not making myself clear. I'm not talking of a linear accelerator in terms of high-energy-physics, but rather the bucket launcher design proposed for lunar mining. Used as an engine in orbit it could accelerate raw material in buckets and throw it out the back at speeds unatainable in many nuclear types of propulsion. Including, I'm sorry to say, all forms of nuclear-thermal rockets.

GCNRs woudl be perfect if you wanted to fly around and between, say, the moons of saturn, and it's probably the closest we can get to the 'magic rockets' seen in science fiction. But for getting to places like saturn and back again a mass driver would probably be better because of the very high potential ISP and very high 'fuel' tollerances.

ANTIcarrot.

Oh no! That'll *never* work...

Speaking of orion alternatives though, linear accelerators in theory beat all other systems hands down in terms of ISP (except antimatter) and it's buildable with todays technology. After all, if atom-smashers can accelerate subatomic particles to .9C, then there's no reason something similar couldn't be built in space. More realistically, throwing significant amounts of matter backwards at 10-100kmps is very possible with todays technology. Though such a ship would be delicate, it could use anything as 'fuel' without the expensive/complex requirements of mining hydrogen.

ANTIcarrot.

Not to mention that while the orion nukes are travelling through the atmosphere to orbit, they can be stored in very secure and durable containers.

A NERVA though is, well, a nuclear reactor with a hole in the side. That seems a fundimental safety weakness to me. Though I'm sure it could be made 'safe' it could never be made as safe as a fully sealed orion nuke.

Though I would question the sanity of running the engine *inside* the atmosphere. And I worry the numer of anticipated deaths per launch is suspisiously low.

ANTIcarrot.

Hmm. Consider an ICBM. It's esentially a rocket that goes 80% of the way to orbit before falling down again. It's multi ton payload is designed to withstand reentry and 'land' with a high degree of accuracy. And they are designed to complte their mission with almost non-existant ground support.

True there's a big difference between an ICBM and an SSTO, but it makes a good half way house and might tell us a little about what might and might not work. So what ground facilities would be needed?

Spaceport facilities of a typical Altspace startup:
i) Launch-pad and landing pad. The second can probably be built from simple poured concrete with an automated landing system. The first would depend on the size (read: noise) of the launch vehicle.
ii) A very long runway for HTOL operations, and for delivery of goods via cargo plane.
iii) Standard ATC tower. Used to make sure nothing is over flying your rocket at time of take off. Includes links to national network to obtain and monitor flight corridor. Also used for some 'ground safety' concerns.
iv) Launch control. Room full of computers; similar to sealaunch.
v) Rocket & payload storage/servicing hanger.
vi)Cryogenic oxidiser and (maybe cryogenic) fuel storage.
vii) Misc vehicle stoage.
viii) Altspacecraft.
ix) 24/7 security service. Plain common sense & likely requirement of insurance policy.

Aside from (ii) and (viii) this is all fairly standard stuff for a small comercial or ex-military airport. What isn't standard can be easily accomadated in pre existing facilities.

Between launch and landing orbital flight and manouvering is autonymously handled by the altspacecraft (via GPS & P486s) with brief and occasional checks with the ground. When required the altspacecraft can use the same satellites intended for the shuttle. Naturally, the altspacecraft is reliable enough that it doesn't require a telemetry downlink.

ANTIcarrot.

Not quite the same thing IMHO. NASA was totally screwed because management incompetence and willful ignorance killed 7 people. That probably wouldn't be an issue with shuttle-C or any similar equipment.

You might loose a $5B spacecraft; but that would be a lesser issue. At least as far as public opinion/mourning is concerned.

ANTIcarrot.

Maybe the token woman on board should have sex equally p with all the men then?

I suppose gay men won't be allowed either? Better keep the blacks and jews away too. After all, you wouldn't want to upset one of your fine upstanding white male christian good-old-boy astronauts.

If NASA follows that kind of thinking all the success in the world wouldn't save them from the backlash.

ANTIcarrot.

Then we just have that niggling little issue of man rating. Plus the upper stage needed for ISS docking. Plus no-one has ever built a cargo module that can carry a large part of its weight as useful payload. Compare the launch capacity of the soyuz rocket with the payload capacity of a progress spacecraft. The *useful* capacity of any rocket can quickly be reduced by all sorts of things.

And then of course there's cost creep. Or perhaps cost sprint would be a better phrase...

I may be over reacting, but I'm just a little too synical to count my chickens before they're hatched, and in either I simply do not support another burn-the-blueprints campaign at NASA.

ANTIcarrot.

Great. From the logic that brought us McDonalds burger boxes and the destruction of the Kyoto protocol comes the idea of the disposable atmosphere.

I can't think of a quicker way to throw away the resources of the solar system than letting them leak away into space on Mars. What a wonderfully far-sighted idea.

I also can't help but wonder if Mars will ever be charged $46/barrel of replacement atmosphere...

ANTIcarrot.

What mars also has is a (comparatively) huge gravity well and a very solid wall at the end of colonisation. Even after terraforming, I seriously doubt mars could support as many as two billion people. And even if you do terraform it, it'll revert back to it's current state after a few thousand years because it simply isn't big enough to retain a decent atmosphere.

The asteroid belt alone can probably support closer to two trillion. True a M or C class can't support much life seperately, but it only take a small nudge to move two small M & C class asteroids so they they collide and 'stick' together. (In fact asteroids where this has happened naturally probably aren't rare.) And again, you can do this practically anywhere in the solar system you want. And to be perfectly honest that gravity problem was solved way back in the ninth grade, when the pecular motion of a ball on the end of a spinning string was observed.

Realistically it shouldn't be a case of one or the other, but both. Mars will probably come first though, as it is better known.

ANTIcarrot.

Actually Russia is fighting a civil war and the US is effecting a regime change. And both are pretty much screwing it up by using heavy handed tactics.

As to China being attacked... They might be strangely flattered. Terrorists tend to only go after the important countries after all.

China could easily dump a couple of million troops into Iraq without noticable impact on their economy or military. Which is kinda a problem really, as the US would oppose such activity.

This may be a major fear for them; China retaliating against a terrorist nation and seizing control of the natural resources as a 'side effect'. If that nation was Saudia Arabia (for instance) whom the US is technically allied with...

ANTIcarrot.

A quick reality check. According to a technical analysis of the problems involved:

1) A *real* space elevator could be grounded at possible one or two spots in the entire world. You don't put it where you wants, you put it where physics and weather says it has to go. With the second or third you might get more choice, but not the first.
2) A space elevator will hang, not stand. If you fly an aircraft into it at 10km high, and you cut it, only ~10km will fall. The rest will not. The elevator will probably have enough spare spool to compensate for this easily.
3) Even if it did, it's made olut of cardon (read coal) and will easily burn up.
4) The base of it will amount to a military airbase in the same way the NASA facilities in Florida do. Terrorists have yet to pull off that kind of attack successfully.

http://www.isr.us/Downloads/niac_pdf/co … tents.html

ANTIcarrot.

Erm... Eh?

Try getting take off permission (or even fueling permission!) for your 1000ton bomb at a place like Heathrow. You won't get it. The big commercial airports will not want to risk their runways. You are therefore restricted to building your own, using abandoned airbases that all have overflight problems, or using NASA facilities.

And agreed that we ned a spacecraft that operates like a 747 - but that doesn't mean it has to look like a 747.

GCNR...

It isn't really, but it lets you land in bad weather and solves cross range problems. Most people accept it as a given that one of the things that screwed up the shuttle was the cross range requirement. With jet engines it could afford to reduce the gliding cross range significantly, as long as the jet engines can compensate.

Paragliders land with accuracy all the time. NASA's X-38 landed roughly where they wanted it IIRC. A VTOL would probably have a powered last minute and a soft touch down on the pad.

Yeah yeah yeah. Something you've said many times. I'm still waiting though for that application that can't be broken down into two ton sections. You've had enough time to think of one.

So in other words, that are exactly the same size. And again you're compairing apples and oranges. A TSTO VTOL would be able to carry more into orbit without being significantly bigger than a SSTO VTOL.

The only thing on your checklist which couldn't be just as easily be applied to a VTOL TSTO design is
-Lift body design - Prototyped by Russia, X-38 ACRV, various ground tests and confirmed modeling
-NASA experience with spaceplanes of high complexity - 20+ years and counting

To which I counter:
*Capsule design - prototyped by everyone who've ever recovered something.
*NASA's experience with capsules. Getting on for 40 years now.

ANTIcarrot.