Gingrich Space Plan

[GIThruster]

I don't personally believe a "golden age" of space travel, where the average joe can fly to the moon like he can now fly across a continent; is possible using propellant based transport of any kind. There aren't many ways to drive the cost down further than what SpaceX intends, especially if they can reuse all the components save perhaps the Dragon trunk. That is still too expensive for the average person to pay for.

OTOH, if we can build something like a 1 N/W MLT or UFG, then we can reduce price to the Moon round trip to less than NY to LA and back.

When I think about rockets, I don't ever think about maikng them safe enough, quick enough, convenient enough or economical enough for a golden age of space travel. I don't think they'll ever be. They are sufficient though, to enable exploration until we can work out propellantless propulsion.

[Skipjack]

I think that something like a fusion rocket engine could be the technologic breakthrough that we need. That would lower the price enough that everyone will be able to at least go to LEO once in their life.

[Betruger]

Anyone know what happened to the DIRECT team? Their tentative DIRECT v2 webpages suggested ~400$/kg to LEO with their Leviathan rocket. Also projected 3 Leviathan launches to put an ISS up, vs two orders of magnitude more using historical STS and other launchers, and even more orders of magnitude in $ difference.

http://www.filedropper.com/directp2

[CaptainBeowulf]

Again, this brings us back to Bussard's Polywell rocket idea. If Polywell works out and it can be implemented, I could see relatively routine space access being feasible. I could see about 10x the cost of a plane ticket, so $5000-$10 000 to take a flight to a space hotel. Of course, the stay would cost more, or a trip to a moon hotel would be extra too - but this would still bring it within the range of your average millionaire (people worth $2 or $3 million up to $100 million), instead of super-millionaires and billionaires. The former is actually probably a market of tens to hundreds of thousands of people worldwide, while the latter is thousands, maybe only hundreds.

Polywell would also provide an in-space drive, or a power source for "turbocharged" ion drives or VASIMR.

I actually think we're nearly there with in-space drives. I agree with others that what we're nowhere close to solving is earth-to-orbit.

If a company can make money on space tourism then it can move on to mining asteroids, which would also be profitable if transportation is cheap enough.

My suspicion is that, although SpaceX may achieve some major cost to LEO reductions combined with greater reliability/shorter notice launch, they will encounter problems that will cause them to fall short of their goals. They will be *successful* in a limited market, but to grow the market on a large scale chemical rockets are just too big, expensive, and frangible, no matter how you design them.

So... hoping that Park & co. are having some success... my immediate economic interest in Polywell is lowering the cost of power on the North American electrical grid and performing an end run around carbon emissions concerns and taxes (whether or not AGW is "real," it's a political problem). This could create a competitive advantage and bring industry back to the continent, and create a new period of rapid GDP growth which would help the U.S. government pay off its debts. But, I would also like to see Polywell as a space enabler (and, of course, the navy's interest: an enabler for a new generation of warships with a strategic edge).

And yes, I know that Polywell is still a long-shot. I'd just like to see us get a "lucky streak."

[CaptainBeowulf]

Direct were the guys who wanted a straightforward SDHLV rather than the Ares V which was getting out of control. They pretty much got what they wanted with the current Congress/Senate approved system, except rather late in the game, so there's a large gap between shuttle and SDHLV launches and most of the workforce vanishes and has to be rebuilt.

The Leviathan sounds like they're turning around and advocating the sort of monstrosity that Ares V was after all... so why did they work so hard to kill it in the first place? At most, use a modified shuttle ET with payload on top and three or four engines underneath, with 5-segment SRBs and the existing VAB, crawlers and concrete trackways. Wait and see if SpaceX matches its performance at lower cost with Falcon Heavy/Falcon X/Falcon XX... and if so, ditch the SDLVs altogether and go with private launch contracts.

(Again, I'm impressed by SpaceX's performance so far but I think it'll take them longer than they and their more enthusiastic proponents expect to get a true heavy lift vehicle developed... although I hope I'm proven wrong).

[Betruger]

Come on, read the literature you argue. They present Leviathan as almost fully reusable.

[KitemanSA]

I don't personally believe a "golden age" of space travel, where the average joe can fly to the moon like he can now fly across a continent; is possible using propellant based transport of any kind.

I was about to argue with you until I saw the modifier bolded above. You are probably right if the entire trip is rocket (propellant) driven. Tethers on the other hand would bring on such an age.

[Skipjack]

Again, this brings us back to Bussard's Polywell rocket idea.

Which is why I am here.

Direct were the guys who wanted a straightforward SDHLV rather than the Ares V which was getting out of control. They pretty much got what they wanted with the current Congress/Senate approved system

The SLS is a huge waste of money. It will cost a furtune and fly once every two years because there is no money to fly it more often. It currently does not even have a mission yet. The money is now of course missing from commercial crew and they will have to reduce the number of participants which increases the risk and reduces the benefits of the commerical crew project. But I guess that was the idea of the supporters of the SLS to make CCDev worse so the SLS looks better.

The Leviathan is even a worse idea. A monstrosity that would cost billions per launch and that would launch very rarely. The most important thing about an RLV is launch rate!

[D Tibbets]

I figure SpaceX could get astronauts on the moon inside 4 years, if there was compelling cause and funding. Using 2 launches of the Falcon Heavy:
First launch puts a lander module in lunar orbit or at L1. Second launch puts a Dragon capsule on course to rendezvous with the lander. Astronauts take the lander down, leaving the Dragon parked, then rendezvous with the Dragon for the trip home.

Sustainable would take longer, with a reusable lander, orbit transfer craft, and transfer/refueling station, among other infrastructure.

I don't think two launches would do it. Perhaps 3-4 might. I don't think the Dragon capsule is meant for use for more than a few days in LEO. To protect the crew and provide the propellent for Lunar insertion and return, another module (like the Soyuz orbital module) would be needed. Even then it might not provide enough fuel.

Dan Tibbets

[Robthebob]

I still dont quite understand why we're talking about this. why is it that everyone obsessed with pedaling a tricycle across a state? I'm personally interested only in the science, and we can do science cheaply. Until we're at least this tall, we shouldnt be allowed to ride the rollercoaster, that's just the way it is.

I mean it's not that building ships and whatnot will increase our abilities to make better ships in the future; it will, but one very fundamental thing is very lacking, that's the fuel energy density, before we tame nuclear fusion, what's the point?

For science? no
For engineering? not really, there's a very fundamental problem that needs to be dealt with first
For fun? no thanks.

[KitemanSA]

I mean it's not that building ships and whatnot will increase our abilities to make better ships in the future; it will, but one very fundamental thing is very lacking, that's the fuel energy density, before we tame nuclear fusion, what's the point?

Nuclear Fission?

[GIThruster]

I mean it's not that building ships and whatnot will increase our abilities to make better ships in the future; it will, but one very fundamental thing is very lacking, that's the fuel energy density, before we tame nuclear fusion, what's the point?

Nuclear Fission?

Rob, chemical has higher energy density than fission, and fission has higher energy density than fusion.

AFRL did a parametric study some years ago (that is posted somewhere here at T-P) that showed what they believed can be built using fusion for propulsion. It's a very tricky task. Many of the calculations for fusion thrusters are rubbish. For instance, if you'll look here:

http://nextbigfuture.com/2007/11/fusion ... usion.html

you'll find a very pro-fusion series of documents that make extraordinary performance predictions. These should all be taken with a grain of salt. For the most part, NONE of this stuff is possible for the simple reason that we don't have materials to contain thrust Isp's beyond about 5,000. If you look at these notes, you'll see supposed Isp's all the way up to 1.2 million. Since the proposed propulsion systems using fusion that give these fantastically cheap transportation numbers are based upon Isp's we cannot and will never be able to harness, all this following calculation is pretty worthless.

Sorry to be a wet blanket, but I don't think anyone will ever build a 1.2 million Isp engine of any kind. When you see the LEO to Titan numbers, and this requires constant thrust at 70,000 seconds, you're seeing an engineer's wet dream, not a real possibility, IMHO. To get to Titan we need propellantless thrust.

[quixote]

chemical has higher energy density than fission, and fission has higher energy density than fusion.

Can you elaborate on what you mean here? What you said is the exact opposite of my understanding of the relationship between these energy sources. Or did you mean the thrust or power vs weight ratio?

[Betruger]

I'm personally interested only in the science, and we can do science cheaply.

Navel gazing

Until we're at least this tall, we shouldnt be allowed to ride the rollercoaster, that's just the way it is.

Sure. Doesn't mean some fraction of a percent is excessive for the rest of us who know better than "you must be this tall" admonitions.

I mean it's not that building ships and whatnot will increase our abilities to make better ships in the future; it will, but one very fundamental thing is very lacking, that's the fuel energy density, before we tame nuclear fusion, what's the point?

Economies of scale perhaps. No way to know for sure unless we try. A truly motivated attempt (IE no bullshit approach - lucid and spartan) would easily make one hell of a dent in the orbital access $$$ bottleneck, even with only the current budget proportion. Because that proportion's as small as it is, 200% of it is still chump change in the budgetary big picture -- so not only is current budget, properly tasked and managed, enough to make that big dent, but any increase would equate to significant additional results..

Many of the calculations for fusion thrusters are rubbish. For instance, if you'll look here:

http://nextbigfuture.com/2007/11/fusion ... usion.html

you'll find a very pro-fusion series of documents that make extraordinary performance predictions. These should all be taken with a grain of salt. [...]

Curious what Tom Ligon, who wrote those slides, has to say.

[GIThruster]

chemical has higher energy density than fission, and fission has higher energy density than fusion.

Can you elaborate on what you mean here? What you said is the exact opposite of my understanding of the relationship between these energy sources. Or did you mean the thrust or power vs weight ratio?

Fission has lower thrust to weight than chemical. This is why the TRITON is not as promising as one could hope--its chief advantage is combining the power generation for a spacecraft with the thruster--you get your long term, high power generation as part of the package--but the thruster weighs much more than a chemical engine and even though you get higher Isp, the Isp will only make up for the extra weight in some systems. TRITON is not especially good for a launch system. Many people don't think it has the thrust to weight to be engineered into practical launch systems at all. It certainly has enough thrust/weight to be used in launch from any smaller body, Mars, the Moon, Titan; but it's generally not a good choice for Earth launch. (TRITON was designed almost a decade ago around a max Isp of ~900s. It is possible that mateterials science advancements could by now give it better numbers. http://www.pwrengineering.com/dataresou ... 4-3863.pdf but for Isp's nearer 5,000, you need a gas core or nuclear lightbulb.)

Fussion is another step in the same direction. It has the advantage that you don't necessarily need so much shielding, but you do have X-rays and most guesses are they will never go away entirely so you still need shielding. How much we don't know. We do know that you have to have large banks of capacitors and some heavy power equipment. When AFRL did their study, they found that Fusion is capable of building "starfighters" that could fly from Earth into space but the payload mass fraction was exceedingly low. So low its doubtful it would ever be worth building them and certainly not with pilots. Bussard's Poly launcher has this trouble too. Realize in his thumbnail sketches and calculations, he doesn't come to terms with the materials science limits to Isp, he doesn't look at thermal protection systems at all, etc. Despite this, he's still got fusion rockets that have tiny payload fraction. Until someone has a working Poly to crunch numbers with, it's not a good guess to assume it can be used for a launch system, any more than can TRITON.

It's important to note though, ultra-high Isp is what you want for deep space. Fission and fusion can drive Isp to the limits of their materials and chemical cannot; so for human transport in deep space, fission and fusion may be the best choices apart from propellantless.