Space travel: Looking to build spaceship within 100 years | Hacker News Reader

Space travel: Looking to build spaceship within 100 years

latimes.com

43 pointsantr30 comments

proton-boron fusion producing high speed (~ 0.03c) alpha particles reflected by magnetic field

http://en.wikipedia.org/wiki/Fusion_power#p-11B_fuel_cycle

It will let us to comfortably get to the solar system planets and to launch first multi-decade travel to the nearest star.

(Google for Bussard)

There's also always the Orion drive - basically dropping nuclear bombs out of the back of a ship and riding on the blast. Do you know how it and the Bussard Ramjet (which I think is what you meant) compare in terms of mass needed to run? Of course, a Ramjet would probably be much better for long missions, since it gives you a source of power as well as not requiring carrying reaction mass, which avoids running out of fuel.

Bussard's ramjet is too far fetched still. I meant more along the lines of http://www.emc2fusion.org/2006-9%20IAC%20Paper.pdf and http://www.ibiblio.org/lunar/school/InterStellar/Explorer_Cl...

The EMC2 is (was) his corporation that gets [though very small compare to other causes government spends money on] real funding and making real progress today, just as we speaking :) though i'd not discount the Z-pinch (Sandia) approach and think that ultimately working system may be a combination of these 2 approaches. The Z-pinch, dense plasma focus and other similar dynamic (inertial) confinement approaches is, in principle, the Orion, only with very small "bombs".

Bussard ramjets are non-starters. Firstly, as it turns out the drag from the ramjet would be much higher than the thrust generated by the fusion reaction. Secondly, a pure Bussard drive would be hugely difficult because proton-proton fusion is enormously challenging and would require very, very high temperatures to occur in a practical amount of time within a rocket.

Don't know why more research hasn't been done on Boron fusion. Since it gives off an electron you don't need any turbines or heavy equipment just a transformer. Instead we spend billions on H2 H3 fusion. Makes no sense to me.

except for D/T (and D/D), most of other fusion reactions which don't involve exotic components (like He3) don't seem to be confine-able by the mainstream magnetic confinement (tokamak). The inertial confinement is starting to come back and with it the promise of the other reactions.

It's unclear whether it's possible to reach a breakeven point.

That's true for any controlled fusion reaction.

the lowest upper bound we have is 5-10Kt thermonuclear bomb. I.e. we do know that using at least one type of confinement - inertial - with X rays as driver it is possible to get energy-net-positive on the scale of such a small bomb. On the other side, ie. the lower bound - the Z machine at Sandia is generating X rays with power enough to drive the reaction similar to how the fusion is driven by X rays in the H bomb, just on the much smaller scale, and we do know that scaling it up or the other existing designs, like the tokamak or polywell or laser driven device like NIF, does increase the reaction efficiency. Somewhere between is the practical energy-net-positive reactor. It can be order or 2 of magnitude bigger than ITER - well, the modern coal burning or nuclear plant is several orders of magnitudes bigger than the campfire of the cavemen where it started from.

We have yet to achieve the plasma densities, temperatures, and confinement levels to attain self-sustaining fusion with even D/T or D/D reactions. These are the lowest energy reactions, which is why we are pursuing them at the moment. D/He3 and p-B11 fusion are orders of magnitude harder to achieve. If we can't get D/T fusion past break-even we'll just be that much farther from getting p-B11 fusion to work too. As far as actual commercial fusion plants, such things may be dependent on more advanced fusion fuels and aneutronic reactions, but we are far from being capable of building even test reactors for such fuels.

This is a dream coming true. I wish I could be part of the team in that space ship. I'd do anything to actually be a part of space travel. That's all I want in my life.

SpaceX is growing, and they aren't the only ones. Space travel is going to happen.

I'd do anything to actually be a part of space travel. That's all I want in my life.

If you really mean it, then make it happen.

Yeah, I was at SpaceX in L.A the other month touring the manufacturing floor. It was amazing.

I really mean it. The only reason I work hard right now is to attempt to make enough money to even be involved with the process of making my dreams come true in space ($$$).

John Glenn was 77 on STS-95. In other words: you have a while. You better stay in good shape and actively follow projects by groups like SpaceX and Copenhagen Suborbitals :)

I don't know about propulsion ect, but IMO the best approach without magic levels of technology or antimatter is going to look something like:

2 stage craft, first stage uses solar sail to shift into a highly parabolic orbit that goes from close to the sun into the and back out to the ort cloud. Passengers meet up with craft as it's heading toward the sun on final passage. And ignite rocket near sun for maximum gravity assist on it's final flight through the solar system.

PS: Probes get's to skip the docking part of the trip.

Could you explain the gravity assist portion a bit more please? A gravity slingshot only works when you transition from a regime dominated by one body (sun for example) to a regime dominated by another body moving relative to it (Jupiter for many outbound probes).

I guess you could use a scheme similar to Cassini where you're doing multiple gravity assist swings off anything at all to get every last erg of thrust but my gut feeling is that you're not gaining much relative to the delta v needed for your complete voyage.

It would make for a fun app though. Design your own Interstellar Mission!

I believe he's talking about the Oberth effect.

Consider the total kinetic energy of a spacecraft in free fall (in orbit) and after a delta V has been applied. When farthest away from the Sun the KE after the spacecraft has finished firing its rocket will be proportional to (low-v + delta-v)^2, whereas if the firing is done at closest approach to the Sun the KE will be proportional to (high-v + delta-v)^2. You'll get a 2free-fall-speeddelta-v energy boost, so being at the highest relative speed possible to start is definitely advantageous, since this KE boost will translate into higher final speeds as well.

> It would make for a fun app though

Like this one? http://orbit.medphys.ucl.ac.uk/

Orbiter is a space sim with accurate orbital mechanics (including the Oberth effect ;).

It's a lot of fun. You can use realistic current vehicles for accuracy, or unrealistic ones with huge power-to-weight for fun.

Why you exclude antimatter? I think it has the most perspective as the energy source of the starship, now scientist can hold antimatter for minutes, until we'll have other technologies for star travel - they will learn to create much more of it and hold it for much longer.

Keeping ~10^6th protons contained for minutes is a long way from 10^28th protons contained for years. Anyway even with antimatter you are still bound by the E=V^2 problem so launching a large ship at 1g for 2 months might be possible with anti matter but the energy requirements become insane. For that matter generating atimatter is ridiculously inefficient, if you had perfect containment and converted the all the world electricity production into antimatter using current methods you would not be able to launch a bottle rocket let alone a useful ship.

The funding has long been moving away from space exploration and more towards information technology, robotics, and medical/biological research. The picture in my mind of interstellar travel in a century looks much more like sending an unmanned craft at high acceleration with frozen, fertilized embryos and robotic caretakers, than attempting to shuffle soft pudgy mammals across the galaxy.

well, a little bit more of "technology, robotics, and medical/biological research" and may be these mammals can be made a little less soft and pudgy :) . Especially considering that any promising high specific impulse propulsion systems are expected to have low trust (thus low acceleration for long period of time)

They should start by trying to design a Starwisp:

http://en.wikipedia.org/wiki/Starwisp

I seriously doubt a government sponsored project can remain coherent for 100 years.

I don't think the point is a 100 year project so much as a plausible inspiring 100 year "plan".

Actually, the British Royal Navy used oaks that had been planted some 200 years earlier specifically for the navy.

From http://www.centauri-dreams.org/?p=11894 which talks about long term thinking for interstellar flight:

  The British oak used in the ships that fought the 
  Napoleonic wars was planted during the reign of the 
  Stuarts some 200 years earlier and allocated for future 
  use in the Royal Navy. Knowing this, Collingwood went on 
  to encourage the planting of oaks that would be made 
  ready for future Royal Navy ships, oaks that matured long 
  after the heyday of sailing ships.

True, but once you plant an oak, there is little you have to do for it to mature. With developing and building a starship, there is a lot to do.

It's possible if they work with this group:

http://www.icarusinterstellar.org/

http://news.discovery.com/space/tau-zero-project-daedalus-ic...

I think USA is going to do it alone.

Neyland sounds like an enthusiastic and genuine guy, but you gotta be f*cking kidding me with that $500k prize. Their budget is $3.2bn.

In these times, with all of the troubles on Earth, it may seem to be foolhardy to focus on space, much less a hundred years into the future. But whether it's escapist or actually preparing for the long-term, it's good to dream higher.

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