NASA backed fusion engine could fly to Mars in 30-90 days

[Lord Relvenous]

http://www.theregister.co.uk/2013/04/10 ... mars_trip/

Based off of using magnetism to compress lithium or aluminum bands around a pellet of deuterium-tritium the size of a grain of sand. It's very cool stuff, and they have a target date of 2020 for a fully operational model (which would be cut shorter by additional funding). So its a little more immediate than some of the other ideas for new propulsion techniques. Apparently the research team has tested all the parts in the lab, and just need to assemble the tech into a functioning model. I would post the article, but I'm on my phone.

Overall, very awesome science. It sounds like this has a good chance of going somewhere instead of being one of those ideas that runs into an insurmountable issue and dies.

[Isolder74]

So when are they building this?


This is looking very cool. The big if is if they can manage to get the funding to build a spacecraft to test the engine on. A powerful engine able to lower travel times is always a awesome thing to develop for a manned long range space mission.

[Lord Relvenous]

So when are they building this?

This is looking very cool. The big if is if they can manage to get the funding to build a spacecraft to test the engine on. A powerful engine able to lower travel times is always a awesome thing to develop for a manned long range space mission.

Unless we can develop much more mass-efficient shielding materials to protect astronauts from cosmic radiation, it's a necessity for a long range mission. And this is a huge step. The needed fuel mass is so much lower (which means we can put on more shielding) while also presenting more acceleration, and the engine design is electric so it can run off solar power. I mean, that is a crazy list of benefits.

If they can get the engine to work, NASA would throw money at them, I'd guess.

[Broomstick]

Cutting the trip time down to 30 days each way solves some enormous problems presented by the multi-year timescale of current propellent technology. It would still be dangerous as hell and difficult, but much more possible.

Question: given that the fuel sources are heavy water and lithium and/or aluminum, could the asteroid fields provide fuel for future ships? Does this cut down round-trip to the asteroid belt to a feasible level? It would definitely be for the more distant future but if fuel for space could be found and refined in space and not hoisted out of a gravity well that would prove a significant boon to interplanetary space travel.

[LaCroix]

I doubt you'd ever make commercial round-trip style travel to the asteroid belt, especially since this drive allows you to put a really good carussell into place you could dock on with orbital shuttle ferries. You could make orbital corrections on the earth leg ( I don't know if solar would work so well near the asteroid belt, that's about twice the orbital distance of earth.), and if that fuel could not be processed in space, shuttles could simply pay their "fare" by lifting some extra processed fuel pellets up from earth to transfer to the orbiter, which is much easier considering the new fuel weight.

[Bedlam]

With a 30 day trip assuming constant acceleration up to the half way and then deceleration on the way back how many g's would the crew be under.

I have no idea how to calculate this type of thing, I imagine it being a significant number but someone will probably tell me now that its actually a tiny number.

[ray245]

With a 30 day trip assuming constant acceleration up to the half way and then deceleration on the way back how many g's would the crew be under.

I have no idea how to calculate this type of thing, I imagine it being a significant number but someone will probably tell me now that its actually a tiny number.

Even if it is impossible for humans to survive under that conditions, using that ship to deploy robots would be extremely useful.

[Hawkwings]

With a 30 day trip assuming constant acceleration up to the half way and then deceleration on the way back how many g's would the crew be under.

I have no idea how to calculate this type of thing, I imagine it being a significant number but someone will probably tell me now that its actually a tiny number.

Yeah, it's a tiny number. 0.008 m/s^2, or a bit less than one-thousandth of a g.

[Starglider]

This is looking very cool. The big if is if they can manage to get the funding to build a spacecraft to test the engine on.

Trying to build a spacecraft based on magentised target fusion makes as much sense as trying to build the Daedelus space probe before we've even got net-power laser inertial confinement fusion working in the lab. In fact this is extremely similar to the 70s/80s hype about laser-ICF, new approach supposed to make fusion power just around the corner, naturally people start talking about powering spaceships with it as well. Just like z-pinch and tokamaks / stellerators before though, lots of new problems became apparent as soon as the machines scaled up, and we still don't have net-power ICF despite all the money poured into the National Ignition Facility and new concepts like HIPER. In short if this actually worked it would be easier to build as an earth-bound fusion generator rather than a spaceship engine, but research has been ongoing since the late 90s and no one is close yet. As such MTF should be considered a 'promising idea' on the same level as Polywell, not something that is in any way certain to work or ready to fly.

Unless we can develop much more mass-efficient shielding materials to protect astronauts from cosmic radiation,

Which we just aren't, without getting into the far-out science-fantasy 'picotech' ideas. Radiation absorbtion works at the atomic level, changing how those atoms are arranged doesn't make a lot of difference. Viable magnetic shielding against ions is a seperate question and much more promising.

Question: given that the fuel sources are heavy water and lithium and/or aluminum, could the asteroid fields provide fuel for future ships?

Firstly, tritium is very hard to produce (essentially you have to stick lithium in a nuclear reactor and then put it through a refining process). Secondly laser ICF pellets are highly precise and difficult to machine, MTF ones probably are for the same basic reason (any slight instability quenches the reaction). So 'in theory yes but in practice probably not without major infrastructure'.

[Eternal_Freedom]

With a 30 day trip assuming constant acceleration up to the half way and then deceleration on the way back how many g's would the crew be under.

I have no idea how to calculate this type of thing, I imagine it being a significant number but someone will probably tell me now that its actually a tiny number.

If you read the article it says that the 30-day mission would be three days accelerating at the start and three days decelerating at the end with the rest of the time spent coasting.

[MrDakka]

More links here including the original paper http://nextbigfuture.com/2013/04/compon ... clear.html

Correct me if I'm wrong but isn't this concept similar to the mini mag orion except it uses MTF instead of a z-pinch fission reaction?

[Simon_Jester]

Question: given that the fuel sources are heavy water and lithium and/or aluminum, could the asteroid fields provide fuel for future ships?

Water will not be a problem in the asteroid belts, chondrites are fun! Aluminum is probably available (we'd want to experiment first).

If you can get to Mars in 30 days you can get to the asteroids in a few months, so it's doable. One interesting design scheme is a 'slowboat' that uses more radiation armor and thus protects the crew, but takes longer to get there; this might actually pay off for exploring the outer system.

Deuterium from the asteroids, I don't know. It's trivially available in Jupiter orbit, but the problem with Jupiter is that it's stupidly far away for solar panels- panels that give X watts in Earth orbit will give X/27 or so watts in Jupiter orbit. You'd need a different power source- RTGs might be a bit lightweight for the job, but you might get a full-up nuclear reactor out there with the right infrastructure.

With a 30 day trip assuming constant acceleration up to the half way and then deceleration on the way back how many g's would the crew be under.

[/quote]If the drive were continuous, let's see...

x=0.5a*t^2

gives us the distance to the turnover point. Distance to Mars at opposition (closest approach) is about 60-90 million kilometers. Let's be pessimistic, that's 9*10^9 meters, or 4.5*10^10 meters to turnover, in 15 days or 1.3 million seconds. Average acceleration is 0.053 meters per second squared, or about 0.005 to 0.006 gravities. Top speed is 70 kilometers per second, after a LONG period of buildup.

Note that this would be for continuous acceleration. The engine does not provide continuous acceleration, being as how it works by detonating tiny, tiny, carefully contained fusion explosions. The microseconds when you are lighting off tiny nuclear firecrackers under your ship's engine section involve considerably higher accelerations, although this is a much less serious problem than with the 'Orion' nuclear pulse propulsion system from what I gather.

[Broomstick]

Deuterium from the asteroids, I don't know. It's trivially available in Jupiter orbit, but the problem with Jupiter is that it's stupidly far away for solar panels- panels that give X watts in Earth orbit will give X/27 or so watts in Jupiter orbit. You'd need a different power source- RTGs might be a bit lightweight for the job, but you might get a full-up nuclear reactor out there with the right infrastructure.

Isn't the area immediately around Jupiter also full of insane amounts of radiation? Something to do with Jupiter's magnetic field or something.

[Aleva13]

Isn't the area immediately around Jupiter also full of insane amounts of radiation? Something to do with Jupiter's magnetic field or something.

Yes, like the Van Allen belts, only bigger.

[Simon_Jester]

True. You might not be safe approaching the place in anything less than a hollowed-out asteroid.

Then again, if we really wanted to, one of the simplest feats of terraforming would be to clear the van Allen belts; doing it on Jupiter would be orders of magnitude more difficult, but that doesn't make it impossible or even all that impractical.

[LaCroix]

True. You might not be safe approaching the place in anything less than a hollowed-out asteroid.

Then again, if we really wanted to, one of the simplest feats of terraforming would be to clear the van Allen belts; doing it on Jupiter would be orders of magnitude more difficult, but that doesn't make it impossible or even all that impractical.

I don't know if clearing the belts and eliminating .16 to 1.18 rads exposure while crossing int very quickly is worth the potentional downsides. (I guess they do form some kind of additional barrier against solar flares, given that the third one was washed away by one.)

[Simon_Jester]

I was thinking more of the Jovian version of the belts. Protecting Jupiter (and inhabited orbital structures and moons) from solar flares may be less important than protecting it from the native radiation environment, when you get out that far.

[Darth Herobrine]

Developing a fusion engine is unnecessary. There's already a powerful engine that could send a manned spacecraft to Mars in 39 days: VASIMR. A fission powered plasma rocket like VASIMR would be far cheaper and a interplanetary ship could be operational by 2018 using this existing tech.

[Simon_Jester]

VASIMR is not a powerful engine, just an efficient one. It would work, and work reasonably well once you get your ship into orbit- but that doesn't mean other possibilities should be ignored.

For reference, the only "existing technology" VASIMR rocket that exists as a space-rated thruster is the VF-200. To get the 0.053 m/s^2 acceleration proposed for the Mars ship out of a VF-200, you need a pretty light spacecraft- 100 kg, roughly from the figures I have available. I suspect the thruster unit itself weighs more than 100 kg, let alone the power plant that goes behind it.

So no, some development is required; VASIMR is right now in about the same place liquid fuel rocketry was in the late 1930s. A good place, lots of promise, I'm all for it- but not to the exclusion of other R&D concepts that might turn out NOT to require a megawatt-range external power supply.

[Lord Relvenous]

Developing a fusion engine is unnecessary. There's already a powerful engine that could send a manned spacecraft to Mars in 39 days: VASIMR. A fission powered plasma rocket like VASIMR would be far cheaper and a interplanetary ship could be operational by 2018 using this existing tech.

While the propulsion element of such a ship may very well be possible by 2018, saying the ship itself could be operational is just silly. There are very significant hurdles to interplanetary travel, and propulsion is just one of them.

[His Divine Shadow]

So when are they building this?

This is looking very cool. The big if is if they can manage to get the funding to build a spacecraft to test the engine on. A powerful engine able to lower travel times is always a awesome thing to develop for a manned long range space mission.

Unless we can develop much more mass-efficient shielding materials to protect astronauts from cosmic radiation, it's a necessity for a long range mission. And this is a huge step. The needed fuel mass is so much lower (which means we can put on more shielding) while also presenting more acceleration, and the engine design is electric so it can run off solar power. I mean, that is a crazy list of benefits.

If they can get the engine to work, NASA would throw money at them, I'd guess.

It does seem if we want to establish a long-term presence in space (and we do, we must) we're going to have to build large and heavy ships and habitats. I also believe some form of active magnetic shielding might be required if we ever want to have smaller ships, which in turn will require some hefty power sources, Nothing impossible but still very far away.

[Algebraist]

As I understand it VISIMR generates a plasma in a magnetic field and uses this for propulsion. All the energy for this comes from a fission reactor but the electricity conversion efficiency is about 99% so very efficient. However with a fission reactor needed in addition this is never going to be that light.
So this new fusion rengine which generates its own power is going to be much lighter as an overall system. Its clearly got further to go with developement but if its shown to work this could be the way to go.

[Sky Captain]

I somehow doubt it would be possible to build a fusion engine before a ground based fusion power plant is built where saving mass is not an issue. It is kinda like building high performance jet engine before a steam engine is invented.

[Simon_Jester]

I somehow doubt it would be possible to build a fusion engine before a ground based fusion power plant is built where saving mass is not an issue. It is kinda like building high performance jet engine before a steam engine is invented.

Not quite. It's more like building an atomic bomb before building a nuclear reactor.

See, the challenge in a fusion reactor is getting the reaction to be efficient and complete enough to pass breakeven- to power itself, and generate significant electrical power besides. We already know how to induce fusion in pellets of hydrogen, we've been doing it for years; the problem is getting sustainable, breakeven-beating fusion.

This fusion rocket does not require us to hit the breakeven point. It is reliant on external power sources (solar cells) like VASIMR; the main difference seems to be in how much thrust you get from a given amount of external power. If the figures in the article are accurate, this fusion rocket would get you a lot more acceleration for your constant 200 kW power input than a VASIMR thruster would.

So just as we were able to achieve short bursts of nuclear fission which did not provide net electric power gain a decade or more before it became practical to build commercial nuclear reactors, we may be able to achieve short bursts of fusion for rocket propulsion a decade or more before it becomes practical to build commercial fusion reactors.

[Sky Captain]

This fusion rocket does not require us to hit the breakeven point. It is reliant on external power sources (solar cells) like VASIMR; the main difference seems to be in how much thrust you get from a given amount of external power. If the figures in the article are accurate, this fusion rocket would get you a lot more acceleration for your constant 200 kW power input than a VASIMR thruster would.

Not sure if I understand this correctly, but how you could get a lot more acceleration from same 200 kW input than ion or VASIMR engines would produce if there aren't significant net power gain from fusion reaction. This of course assume specific impulse remain the same for both engines. You have to pass brekeven point to get more exhaust power than input of electricity.