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Fusion Thrusters For Space Travel

Soulskill posted more than 3 years ago | from the trimming-parsecs-off-the-kessel-run dept.

Space 192

kgeiger writes "John J. Chapman, a physicist and electronics engineer at NASA's Langley Research Center, envisions a laser-pumped fusion drive. Chapman estimates the drive can produce thrust 40 times more efficiently than existing ion engines such as those on the Dawn mission now exploring the asteroid belt."

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research! (4, Insightful)

k6mfw (1182893) | more than 3 years ago | (#36605384)

Alrighty so I haven't RTFA but this is the kind of stuff NASA should be doing more. Hire ambitious smart people with grand ideas, give them resources and turn 'em loose! Probably much of what they do will amount to nothing but you just never know (a great concept may become reality).

Re:research! (1)

sortius_nod (1080919) | more than 3 years ago | (#36605404)

In the first golden age of space, that's what happened. Maybe we're about to see the second golden age of space?

One can only hope.

Re:research! (1, Interesting)

Nethemas the Great (909900) | more than 3 years ago | (#36605632)

That's easily answered. No. Not from government at any rate. If private enterprise can get a better hold on things sure but we need laws that promote the commercialization of space before even they will care. In the mean time we'll happily spend more than NASA's present budget to bring air conditioning to uninsulated tents out in the desserts of the middle east in support of our troops blowing holes in the sand.

Re:research! (3, Interesting)

WindBourne (631190) | more than 3 years ago | (#36606070)

Really? Please show me what advanced R&D do you see coming from private enterprise on their own?
1) SpaceX's rockets? The engines were developed by NASA in the 90's, but squelced by 1996 CONgress.
2) Perhaps SpaceX's tank's? Again development by NASA, but squelced by 2001 W/CONgress destruction of X-33.
3) Inflatable space stations? Transhab that was crush by 1996 CONgress, but allowed into private enterprise by Clinton
4) Laser Drilling? Crushed by 1996 CONgress, but allowed to go to Colorado Mines by Clinton.
5) VASIMR? Crushed by 1996 CONgress, but allowed to go private by Clinton.

The list goes on and on and on. NASA does a LOT of R&D, but it is CONgress and typically short-sighted pres (nixon and W being the worst 2) that destroy it. You will be hard pressed to find any ORIGINAL SPACE R&D by private enterprise that is NOT an off branch of something that NASA came up with and funded.

Fiscal Sanity? (0)

Anonymous Coward | more than 3 years ago | (#36606132)

Look, you do know that money doesn't grow on trees, right? If everybody with a powerpoint presentation got billions of dollars, then there'd be nothing left to spend.

Re:Fiscal Sanity? (4, Interesting)

fyngyrz (762201) | more than 3 years ago | (#36606844)

We spend the equivalent of a huge forest of money trees on USELESS aggression; bring those troops and ships home, destroy deployed equipment in place, sell it to the locals, or bring it home if practical, leave the military brought home employed for a strong standing defense, and (a) we'd be acting morally for the first time in decades and (b) the money spent on the standing army, now home, would go right back into our OWN economy, and (c) we'd have huge overall spending reductions we could apply to the debt and perhaps once again, someday, have money to spend for our actual benefit.

Our budget problems are 100% solvable. All you need to do is get the cowards out of congress. Somehow.

Re:Fiscal Sanity? (1)

WindBourne (631190) | more than 3 years ago | (#36606902)

True. It is time to roll back all those expense that the neo-cons saddle us with. They are destroying America.

Re:research! (3, Informative)

Anonymous Coward | more than 3 years ago | (#36606740)

1. Spacex's rockets were based on a concept engine called Fastrac, killed in 2001. Spacex have scaled up the thrust by a factor of four and the ISP from 260 seconds to 300.

2. Spacex's aluminium-lithium friction stir welded tanks were developed by LockMart for the SLWT first flown by the space shuttle in 1998. X-33 used experimental composite tanks and ignored the lighter FSW technology because it wasn't "Space Age" enough. This is why X-33 failed.

3. Transhab was not killed by the 1996 congress. Transhab didn't exist in 1996. Transhab was killed by House Resolution 1654 in 2000 to prevent NASA from even thinking about Mars. If NASA had called it an Orbhab instead of a Transhab then it wouldn't have been killed.

4. Nope.

5. VASIMR barely existed on paper in 1996. It didn't exist as a national program and there was nothing for congress to kill.

Re:research! (1)

Nethemas the Great (909900) | more than 3 years ago | (#36606944)

That's neat and all, not sure you have all those correct, but it doesn't argue against what I just said. If anything it provides evidence demonstrating it. NASA will not be the one that brings it from conception through to delivery. Like it or not (in your case quite obviously the later) NASA is unable to see any of their advanced research through to a finished deliverable. However, you will note that business when it picks up a university/government research project or in some rarer cases original work, it has a pretty good track record of delivering. This is why I said commercialization is the only way we'll see a "golden age of space."

Re:research! (1)

FrellMeDead (1367815) | more than 3 years ago | (#36606430)

I know it's all the rage to rag on the Government for a certain part of the country but you do realize that the Government does do a lot for the people. I agree that there are problems a lot of which is due to B.S. political games. To defund NASA just because it is supported by the Government is stupid. Maybe a cross between Government and private enterprise would be better but it still comes with the requirement for oversight to prevent mistakes, over spending, etc. To allow true scientists, inventors, and people that are naturally inquisitive among others is what needs to be done and funding needs to be provide regardless of who it comes from. I do agree trying to a\c the tents in the desert is stupid and but maybe if we had people that are motivated to think instead of just going along with stupid moves then we would have provided temp structures that are easily movable/collapsible as well as insulated.

Re:research! (2)

hairyfeet (841228) | more than 3 years ago | (#36606822)

The problem with that is this: Sadly since there is no loner a Ruskie threat to give a weapon to NASA against them in its current form NASA has become a black hole for Sen Porker and Congressman kickbackus to "bring home the bacon" no matter how much money it blows or how badly it screws things up.

See how the shuttle building and support was shotgunned all over the damned country or how Orion would have had to reuse a bunch of crap shuttle parts that frankly made no sense and probably would have been dangerous, just so Porker and Kickbackus could say they are "keeping those lines open for the people!" and ensure they stay in office until they take that cushy contractor job or get caught with a rent boy.

Sadly like everything else in government, no matter how noble or pure the original intentions were, Kickbackus and Porker will find a way to subvert and pervert the funds into their own pockets and the pockets of their friends. This is why we are still building aircraft carriers like we have WWIII planned for next Tuesday even though we have something like 1000% more of the things than the next possible threat, why we blew boatloads of cash on the F-22 and are blowing even more truckloads of cash on the F-35 when frankly we've already reached the point that with current designs they can pull more Gs than a human body can stand and UCAVs can do the job faster, cheaper, and safer.

So I'm sorry but like everything else once good in this country NASA has been turned to shit by Porker and Kickbackus. Most likely the next golden age of space will come from China, where they still have the ability to execute treasonous bastards instead of letting them reward their treason with cushy contractor jobs for their families and big fat checks for themselves.

Re:research! (1)

Nethemas the Great (909900) | more than 3 years ago | (#36606974)

I don't recall ever claiming it wasn't NASA/"the governments" place, or that NASA should be defunded. Quite the opposite I think there's a lot to be accomplished if the sciences were given their proper funding. However, advanced research is where the money should be being sent so that they may incubate the technology of the future that business will later commercialize. Business by its nature can't field advanced, high risk research but they are quite good a turning a profit off of other's work. NASA appears to get that. That's why I think they're trying to support ventures like SpaceX in any way they can. They recognize how hard it is to complete big projects given such a fickle legislative and executive branch.

Re:research! (2)

fyngyrz (762201) | more than 3 years ago | (#36606894)

Reading TFA, it strikes me that this might make an awesome power reactor -- there's provision for electrical capture already, and the thrust might be converted into mechanical energy. Plus, it's damn near a beryllium sphere... ok, a boron sphere, but hey. :^)

Re:research! (3, Insightful)

youn (1516637) | more than 3 years ago | (#36605484)

I think if Nasa was only allowed to carry projects from start to finish... and not successive radical change in direction mid projects... lots more cool stuff could come out. The problem, every time a new administration comes out big buzz words are introduced to completely change the direction, forcing many times redevelopment of the wheel.

Re:research! (1)

Nyeerrmm (940927) | more than 3 years ago | (#36605668)

That conventional wisdom (which I have my own issues with, but I digress) only applies to projects that consume a large fraction of NASA's budget and are thus highly visible.

Plenty of small-ish projects get along just find without fear of national politics ending them. A small project just needs to stay on-time, on-budget, and not piss off the more immediate managers.

Re:research! (1)

youn (1516637) | more than 3 years ago | (#36605844)

I totally agree with you, lots of great projects Nasa have brought (and are still bringing) awesome science, notably robotic missions... like the mars missions still bringing in useful data or the now extra solar probes. Though I still believe >more cool stuff would come out (I understand you disagree ;) if projects were allowed to go through until the end and budgets decisions were more results focused. It is sad to see so many promising yet abandoned projects... including lunar exploration. Today, to go back to the moon (men... and women too ;), a lot of the expertise has to be re-developed because no one is around to say how they did things.

Re:research! (0)

Runaway1956 (1322357) | more than 3 years ago | (#36605932)

The problem is - NASA spends way to much money, for to little return. I've said before that the ultimate goal of space exploration is to provide more habitable space in our solar system, off of the earth, so that a single cataclysmic event cannot end the human race. NASA's missions and goals do not seem to mesh with that ultimate goal. SpaceX seems to be the way forward. In the western world, at least, they seem the most likely to achieve the heavy lift capacity required to put some kind of habitat out there - even if a very limited version, woefully inadequate to meet my stated goals.

But, if the goal is to be achieved, SOMEONE has to go first! If I were a wealthy man, like Bill Gates, I would invest my billions into SpaceX. IMHO, there is no more altruistic use for all that money.

Re:research! (2)

lymond01 (314120) | more than 3 years ago | (#36606088)

I think the issue with government versus private is that private won't do anything unless there's money in it. The government will do lots of things for the greater good, not only roads and bridges, but science.

Re:research! (2)

cavreader (1903280) | more than 3 years ago | (#36606232)

Outside of launching satellites I don't see a whole lot to commercialize yet. To do anything else in space we need to come up with an efficient, safe, and cost effective way of reaching orbit. About the only space related project I see the government spending money on is anti-satellite weapon platforms and possibly orbit to ground weapon platforms. If you want the government to fund expensive projects with little or no immediate return on investment you need to include at least one aspect that might have a military application.

Re:research! (2)

WindBourne (631190) | more than 3 years ago | (#36606090)

Elon Musk would never take money from Gates. Paul allen perhaps, but not Gates. Gates has a LONG history of screwing everybody that he does deals with.

NASA is NOT spending much money at all. And they get far more returns than any single other group.

Re:research! (1)

cplusplus (782679) | more than 3 years ago | (#36606174)

I just read today that the US Military spends $20 billion per year on expenses related to *air conditioning* in Iraq. That's more than NASA's entire budget. I hear things like that, and it really puts the the "way too much money for too little return" argument in to perspective. We need to learn a lot more about space and space travel before we can venture forth, so any kind of money spent on studying those complicated (and expensive issues) is worth it.

Re:research! (0)

Anonymous Coward | more than 3 years ago | (#36605502)

Two words for you: Tea Party.

Don't want no dag gum taxes paying for stuff I ain't gonna use.

Re:research! (1)

WindBourne (631190) | more than 3 years ago | (#36606100)

The tea party have joined neo-cons in pushing SLS (a communist approach to space) while fighting against helping private enterprise into space. America sits on the edge of our next 'Internet style economy', but neo-cons and tea* alike are stopping it.

Re:research! (2, Insightful)

Anonymous Coward | more than 3 years ago | (#36605720)

If only they had a more reasonable budget.

I mean look at this. [wikipedia.org]

1963-1968 gave them a pretty darned reasonable budget. Then, until 1987 they had CRAP. Starting from 1987 they started to get a halfhearted budget that fluctuated up and down.

Also it's pretty depressing their underwhelming budget represents 35% of the budget for academic scientific research in the US.

Re:research! (1)

Wyatt Earp (1029) | more than 3 years ago | (#36605746)

So let DARPA do it instead of NASA?

http://en.wikipedia.org/wiki/DARPA [wikipedia.org]

Today's news for DARPA
http://www.pcmag.com/article2/0,2817,2387672,00.asp [pcmag.com] - project ahead of schedule.

Re:research! (1)

JonySuede (1908576) | more than 3 years ago | (#36606950)

this is incredibly insightful, it redistribute the wealth (as long as you exclude the big companies) and does not encourage laziness. It also boost patriotism as the people helped designed the weapon

Re:research! (1)

WindBourne (631190) | more than 3 years ago | (#36606018)

That is exactly what ppl like Obama and Bolden are pushing. NASA was actually built to be an R&D for Aerospace. Now, it has been turned into a jobs bill by the likes of Shelby, Wolf, Hutchinson, Hatch, Coffman, etc. We need to allow private space to do these launches and then have NASA focus on doing R&D like this.

Re:research! (1)

PylonHead (61401) | more than 3 years ago | (#36606216)

I totally read your comment in the the voice of Cave Johnson, CEO of Aperture Science.

Re:research! (1)

wagnerrp (1305589) | more than 3 years ago | (#36606564)

I won't lie to you. We're just throwing science at the wall to see what sticks.

Let those words run by your ears... (2, Insightful)

Anonymous Coward | more than 3 years ago | (#36605398)

*LASER*-pumped *FUSION* drive... Say that out loud...

Are we living in the future yet?

Re:Let those words run by your ears... (0)

Anonymous Coward | more than 3 years ago | (#36605468)

Are we living in the future yet?

No. But we're making cool pictures of it.

Re:Let those words run by your ears... (1)

CCTalbert (819490) | more than 3 years ago | (#36605486)

Uhhh... that makes me HARD ! :)

If you like the sound of that... (1)

memorycardfull (1187485) | more than 3 years ago | (#36605630)

Would you like to check my assembly for the monitor unit of the inverse klystron tube transmitter?

Re:If you like the sound of that... (1)

hey! (33014) | more than 3 years ago | (#36605900)

He said *Laser*-pumped, not *Maser*-pumped.

Do try to keep up, dear chap. It's not like we're knapping flint here, old boy.

Re:If you like the sound of that... (1)

memorycardfull (1187485) | more than 3 years ago | (#36606160)

TFA mentions use of a traveling wave tube, basically an inverse klystron tube, to reclaim some of the energy from the emitted alpha particles and convert it into electricity to power other vehicle systems. It does this using condensers out of your accelerator circuits, solenoids from your gyro stabilizers, and the Lavallois technique.

Re:Let those words run by your ears... (1)

Nethemas the Great (909900) | more than 3 years ago | (#36605652)

No, didn't you RTFA? It's 10 years away. 10 years not the typical 20 because we're going to use boron instead of helium-3.

Re:Let those words run by your ears... (1)

Hal_Porter (817932) | more than 3 years ago | (#36605822)

What about this

http://www.centauri-dreams.org/?p=1275 [centauri-dreams.org]

As we move into the realm of ChipSats, Peck has my full attention. Take the ChipSat to its logical conclusion and you can envision thousands of tiny spacecraft slung out from the Solar System at ten percent of lightspeed to make the journey to the Centauri stars. "When these small craft arrive," says Peck (I'm quoting from Larry's story again), "they might send back a single, simple signal; one bit of information confirming or denying some scientific principle, such as is there a blue-green planet, for example."

Michio Kaku suggested "emailing" DNA samples to a spacestation built by nanobots that were sent out at 0.1c to a nearby star. There the colonists would be assembled. Of course to make the process work you'd need to email their mental state too which requires some non trivial discoveries to get working. But the fact we could send nanonprobes at 0.1c seems pretty damn impressive to me.

How cool is that?

Re:Let those words run by your ears... (1)

TheCouchPotatoFamine (628797) | more than 3 years ago | (#36606196)

Why send their mental states? Teach them via educational software, and we cannot be killed by a single planetary event. That proviso is too attached to individuality. Let it go.

Re:Let those words run by your ears... (1)

melikamp (631205) | more than 3 years ago | (#36606406)

If nanobots are intelligent enough to build a space-station at Alpha Centauri, then why would they need us there at all? When Humans arrive, they will be treated as tourists at best, or at worst as original Italian immigrants to US.

Re:Let those words run by your ears... (1)

Roachie (2180772) | more than 3 years ago | (#36606340)

I think what you would end up with is a FUSION pumped LASER?

Didnt this happen back in the 80s- they hired some nerd to layout a design for an x-ray laser and he was all like "Oh, cool you could make holograms of cell organelles, it will be a boon to medical science!" That is until he worked the numbers and you would need kilotons to pump it. "Why this would be totally impractical, not only would this medical diagnostic devices destroy the patient but the city that they live in -why... its better suited to be a weapon... waitaminit... Ima pacifist!!!! EEEEeeee!"

Hold on (0)

Anonymous Coward | more than 3 years ago | (#36605402)

Fusion drives allow travel at 4 parsecs per turn and ion drives at 6. Physicist and engineer? Pah!

Re:Hold on (1)

MobileTatsu-NJG (946591) | more than 3 years ago | (#36605442)

Fusion drives allow travel at 4 parsecs per turn and ion drives at 6.

Put the research into increasing our population, then you can get a 10 parsec drive and get just as far in as many turns.

Re:Hold on (2)

dakameleon (1126377) | more than 3 years ago | (#36606334)

Put the research into increasing our population,

I'm happy to help with that research!

Re:Hold on (2)

rubycodez (864176) | more than 3 years ago | (#36605586)

that's about the feeling I got with their "300 watts" nonsense, an amount of boron will give an amount of energy. Han Solo type bragging with nonsense units. Power would only be known after knowing at time interval.

Re:Hold on (0)

Anonymous Coward | more than 3 years ago | (#36606316)

"Power would only be known after knowing at time interval."

No, dimwit, that's ENERGY. You clearly don't have a clue; stick to software, it's more your speed.

Re:Hold on (1)

wagnerrp (1305589) | more than 3 years ago | (#36605648)

Masters of Orion?

Mmmm, fusion (0)

Anonymous Coward | more than 3 years ago | (#36605446)

Yummy AND efficient!

Nice Idea, but There Are Concerns (1)

BJ_Covert_Action (1499847) | more than 3 years ago | (#36605522)

I RTFA. The guy has an interesting idea to be sure. However, as he acknowledges, that level of technology is at least a decade away from a flying prototype (I'd wager more like two decades). Furthermore, the whole article was a bit scant on other details. Specifically, I would like to know the power requirements for a piece of equipment like this. If its reaction can sustain the apparatus's own power draw, that would be a huge point in its favor. However, something tells me this particular thruster would require a lot of electricity.

Furthermore, I'd like to see some thermal numbers for the thing. How hot/cold does it need to be to oeprate? Also, how much waste heat does it produce. If it requires a ten square meter black body radiator attached to it to function, it may not prove to be the miracle thruster that it claims to be. All in all it is an interesting concept. I would be surprised to see a prototype developed before 2030 or so though.

Re:Nice Idea, but There Are Concerns (1)

Wyatt Earp (1029) | more than 3 years ago | (#36605756)

Fusion has been 10-20 years away for the last 60 years.

Re:Nice Idea, but There Are Concerns (1)

multi io (640409) | more than 3 years ago | (#36606010)

Specifically, I would like to know the power requirements for a piece of equipment like this. If its reaction can sustain the apparatus's own power draw, that would be a huge point in its favor.

Well, I doubt that it could do that, because if it could, then we should have a working fusion power station on earth based on the same principles years before someone manages to build a rocket engine with it.

Re:Nice Idea, but There Are Concerns (1)

c0lo (1497653) | more than 3 years ago | (#36606322)

Specifically, I would like to know the power requirements for a piece of equipment like this.

Computations on the back of a napkin:
TFA: A beam with energy on the order of 2 x 10^18 watts per square centimeter, pulse frequencies up to 75 megahertz, and wavelengths between 1 and 10 micrometers is aimed at a two-layer, 20-centimeter-diameter target.

Assumption: the entire target is hit.
– Area of the target: 314 sq cm. => Total power required/pulse: 0.6e+21 W.
– Considering a femptosecond pulses [wikipedia.org] => Total energy/pulse: 0.6e+6 J
– Taking into consideration the frequency of pulses (75MHz) => Laser source power (no efficiency considerations): 45e+12 W
Hell, this can't be! Not for the TFA's: Each pulse of the laser should generate roughly 100 000 particles, making the method tremendously efficient, says Chapman.

Assumption: the laser beam is focused
–With a maximum wave-length of 10 micrometers, let's say the laser is focused to a circle with a radius 10 times the wave-length.
– Redoing all the math for a targeted area of 0.2 mm diameter - would still lead to a needed value of 450 kW for the laser source (again, at 100% efficiency).
And all of this to get 100000 alpha particles? Meaning 33333 reactions of 8.7 MeV each=290000MeV=4.65e-8 J? Put the pulse frequency again and, per second, the generated kinetic energy is <3.5 J?

Nah, something IS fishy!

Re:Nice Idea, but There Are Concerns (1)

wagnerrp (1305589) | more than 3 years ago | (#36606744)

Based off the operational design of existing ION thrusters, your power source is irrelevant. Assume you have a huge solar array, and power is unlimited. The only thing that matters is how fast you can accelerate your consumable fuel source. Traditional rockets dump exhaust at thousands of meters per second. ION drives do so at tens of thousands of meters per second. Using the several billion kelven reaction temperature, and a magnetic nozzle, you're looking at exhaust velocities in the millions of meters per second. Higher exhaust velocity means higher total delta V, assuming you don't kill yourself in engine mass.

But... (0)

Anonymous Coward | more than 3 years ago | (#36605526)

Someone smarter than me will obviously fill in the details but it's not that simple. There is an international ban on nuclear anything or another in space iirc.

Re:But... (1)

Boronx (228853) | more than 3 years ago | (#36605624)

They allow RTGs [wikipedia.org] into space.

Re:But... (0, Troll)

DarthBart (640519) | more than 3 years ago | (#36605852)

If you can *get* them into space without the treehuggers freaking out over "What if the whole thing explodes on the pad and scatters radioactive material across the entire country".

Re:But... (1)

wagnerrp (1305589) | more than 3 years ago | (#36606114)

That's easy. All you have to do is beat them with it to show that they are better armored than a main battle tank, and won't be harmed by something so trivial as the detonation of several million pounds of rocket fuel.

Right thinking. (1)

w0mprat (1317953) | more than 3 years ago | (#36605534)

I've always thought that we'd have viable fusion rockets long before we have practical fusion power generation. The reasoning being, power could come from another source (fission reactor) to trigger the fusion, the resulting high-velocity particles would be a source of thrust alone. This seems to be exactly what TFA describes. Proton-boron fusion spits out high-energy alpha particles that are easily deflected into thrust... clever.

With todays tech something like electrostatic inertial confinement fusion (like an Ion drive, but can reach energy levels for some fusion) could gain a bit of extra thrust from fusion, even if it was a long way off being able to generate useful power. But using a laser is novel ... and "The specific power of the proton-triggered boron fuel would be so great that a mere mole of it (11 grams) would yield roughly 300 megawatts of power. " (!) the efficiency sounds awesome.

Re:Right thinking. (2)

wagnerrp (1305589) | more than 3 years ago | (#36605712)

"The specific power of the proton-triggered boron fuel would be so great that a mere mole of it (11 grams) would yield roughly 300 megawatts of power. " (!) the efficiency sounds awesome.

Come on IEEE, I expected better of you. Power output is irrelevent. We care about energy output. 11 grams of boron fuel will get you 300 megawatts for what duration?

Re:Right thinking. (1)

steveha (103154) | more than 3 years ago | (#36606642)

Come on IEEE, I expected better of you. Power output is irrelevent. We care about energy output. 11 grams of boron fuel will get you 300 megawatts for what duration?

I am not a physicist, but I think the info you want is in the article.

pulse frequencies up to 75 megahertz

Each pulse of the laser should generate roughly 100 000 particles

a mere mole of it (11 grams) would yield roughly 300 megawatts of power.

So a mole is 6.0221415e23, right?

Now, please correct me if I'm wrong, and I may be wrong, but:

6.02e23 / 100 000 == 6.02e18 pulses to process one mole of boron

6.02e18 / 75e6 == 8.02e11 seconds to process one mole of boron

300e6 W / 8.02e11 seconds == 3.7e-3 W/sec

I can't tell you how that compares with an ion drive.

steveha

Re:Right thinking. (1)

pclminion (145572) | more than 3 years ago | (#36606800)

I am not a physicist

We can tell, because W/s is not a unit of energy. It's not a commonly used unit at all, really. You want to MULTIPLY watts by seconds to get joules.

I'm pretty certain some number has been quoted incorrectly. 300 megawatts * 8e11 seconds is the equivalent of about 3000 kg of mass energy. The answer is nonsense.

Re:Right thinking. (2)

newcastlejon (1483695) | more than 3 years ago | (#36606930)

Now, please correct me if I'm wrong, and I may be wrong, but:

6.02e23 / 100 000 == 6.02e18 pulses to process one mole of boron

6.02e18 / 75e6 == 8.02e11 seconds to process one mole of boron

300e6 W / 8.02e11 seconds == 3.7e-3 W/sec

I can't tell you how that compares with an ion drive.

steveha

Sorry, but I think you are wrong. wwagerrp wanted to know the energy the machine would get from 1 mol of boron fuel, the article gives us something in watts, and you gave something in watts/second when in fact what is needed will be in watt-seconds (or joules as most people say).

This might be better: 75e6 * 1e5 gives 75e11 particles released per second. But, the article doesn't say how many of those go on to fuse, etc so this is all academic. Assuming it wasn't, though, 300e6 (Joule/second) / 750e11 (1/second) gives 4e-6 Joules/particle. 8.7 MeV ~= 1.4e-12 Joules so there's something definitely wrong here.

To sum up, article on spectrum is light on details and written pretty badly. If you want to actually know how this thing is supposed to work try and find the paper because frankly I've seen better science reporting in the free paper they have on the bus.

Re:Right thinking. (1)

LWATCDR (28044) | more than 3 years ago | (#36606278)

Well maybe if we used a Polywell reactor to power it. :)
I wish I was 20 years younger :)

Tanks (3, Funny)

avandesande (143899) | more than 3 years ago | (#36605546)

How will the shark tanks work in space with zero Gs?

Re:Tanks (1)

Anonymous Coward | more than 3 years ago | (#36605560)

They will have to be made of transparent aluminum

Re:Tanks (1)

Grog6 (85859) | more than 3 years ago | (#36606302)

And the lasers in the sharks' frickin' heads will be the result of genetic manipulation, to get around those pesky environmentalists!!

Plausible? (1)

gman003 (1693318) | more than 3 years ago | (#36605582)

We haven't gotten fusion to be a net energy gain here on Earth yet (outside tritium-boosted or thermonuclear atomic bombs). While I'm sure it will eventually happen, what makes it so that it's easier to make fusion work in space, compared to Earth?

Re:Plausible? (2)

John Hasler (414242) | more than 3 years ago | (#36605854)

This isn't about net energy gain. It's about specific impulse.

Yes, probably. (2, Informative)

Anonymous Coward | more than 3 years ago | (#36605880)

On Earth, we want to use fusion to power homes, ground vehicles, etc. However, the amount of work and energy we put into fusion gives us much less gain when compared to the amount of energy we can extract with fission, wind, solar, waves, geothermal, oil and coal. We attempt this with deuterium and tritium to produce neutrons. As the article puts it; [To make use of neutrons, "you need an absorbing wall that converts the kinetic energy of the particles to thermal energy," he says. "In effect, all you’ve got is a fancy heat engine, with all its resultant losses and limitations."]

According to the article, he's suggesting using Aneutronic fusion using Boron-11 as a fuel source to produce alpha particles (Helium-4 and Beryllium) via a laser which will yield 60% - 70% efficiency and 100,000 particles with each pulse. Boron will yield 300 MW of power per 11 mg, whereas Helium-3 isotopes as a fuel source would yield 493 MW in equal quantities. However, Helium-3 is scarce whereas Boron is not so it makes more sense to go with Boron instead. He claims it would be 40% more efficient than current deep space ion engines.

Keep in mind, that these engines have to run for long periods of time over great distances. They have all the time in the world to increase their acceleration to their mass potential. It's Hare vs the Tortoise, on Earth we need our power *right now* in large quantities and quickly. Whereas, in space you have patience because the distances are already so vast, you don't have much room to store fuel, and there is little or no friction so you can take your time building up speed.

Hope that helped you make heads or tails of this.

mostly the radioactivity... (1)

Grog6 (85859) | more than 3 years ago | (#36606330)

The output is three alpha particles; not exactly the same as three helium atoms...

It seems more fission than fusion (4, Informative)

Michael Woodhams (112247) | more than 3 years ago | (#36605594)

The reaction is
1H + 11B -> 12C -> 4He + 8Be -> 4He + 4He + 4He
so there are more output nuclei than input.

However, I suppose it is true that all of the energy is coming from fusion, as 12C -> 4He + 4He + 4He is exothermic. (The reverse reaction is an energy source for stars under some circumstances.)

12C is normally stable, so for this reaction to go as stated the nucleus must be created in some suitable excited state.

Re:It seems more fission than fusion (1)

farnsworth (558449) | more than 3 years ago | (#36606028)

The reaction is 1H + 11B -> 12C -> 4He + 8Be -> 4He + 4He + 4He so there are more output nuclei than input.

However, I suppose it is true that all of the energy is coming from fusion, as 12C -> 4He + 4He + 4He is exothermic. (The reverse reaction is an energy source for stars under some circumstances.)

12C is normally stable, so for this reaction to go as stated the nucleus must be created in some suitable excited state.

Is there some physics version of the Web Bullshit Generator [dack.com] ?

Re:It seems more fission than fusion (1)

Michael Woodhams (112247) | more than 3 years ago | (#36606352)

Make a substantive criticism, and I'll consider it, as I have for my other responder. Otherwise you're just a source of noise.

Re:It seems more fission than fusion (1)

farnsworth (558449) | more than 3 years ago | (#36606646)

Make a substantive criticism, and I'll consider it, as I have for my other responder. Otherwise you're just a source of noise.

I'm sorry if the humor didn't come across. It was not meant as any kind of substantive criticism, it was meant to make light of the fact that you are talking over the heads of probably 98% of the people who read what you wrote. I have no way of knowing if what you said was accurate or not, and that wasn't even part of what I was trying to communicate. If anything, I was teasing you for using such dense language with such little context. Really, though, what happened is that I read what you wrote, thought to myself, "this is what engineers experience when they hear management using highly specific language to describe business models", and I thought of that funny buzzword generator. It's funny, right?!

No offense, and I'm sorry that my terse comment was misunderstood.

Re:It seems more fission than fusion (1)

Michael Woodhams (112247) | more than 3 years ago | (#36606826)

OK, thanks for the explanation, sorry to misunderstand you.

I suspect I'm only over the heads of 75-90% of the readers - many have science background or self education. (As demonstrated by the fact I've had two people correct me already...)

Re:It seems more fission than fusion (1)

Waffle Iron (339739) | more than 3 years ago | (#36606984)

98%? There wasn't really anything in his discussion that would be out of place in an honors high school science class.

Re:It seems more fission than fusion (1)

Co0Ps (1539395) | more than 3 years ago | (#36606080)

I don't think you can just count the number of input and output nuclei and come to that conclusion. Both fission and fusion reactions can involve decay into smaller particles while fusion reactions always has at least one element merging with another, in this case a free proton (hydrogen) and boron. E.g. the 1H + 11B -> 12C part (a neutron is not an "element" hence fission != fusion).

Re:It seems more fission than fusion (1)

Michael Woodhams (112247) | more than 3 years ago | (#36606304)

Well, I was actually saying it was both. (My thoughts moved on a bit as I was composing, and perhaps I should have gone back and edited my heading.)

The Cambridge dictionary defines (nuclear) fission as "the splitting of the nucleus of an atom, which results in the release of a large amount of energy". Similarly, Websters says "the splitting of an atomic nucleus resulting in the release of large amounts of energy." I would not have made energy release part of the definition, but it seems the dictionaries disagree with me.

I think we're in danger of arguing about words (which is boring and pointless) rather than arguing about the world (which is interesting and useful.)

The reaction involves fusion, and is accurately described as 'fusion powered', so I'll accept "fusion thrusters" as a description, but still note that it is odd that more particles come out than went in.

Re:It seems more fission than fusion (3, Interesting)

newcastlejon (1483695) | more than 3 years ago | (#36606616)

When the proton hits the boron-11 nucleus they fuse giving an excited (that bit's important) carbon-12, which in very short order (sorry, the exact time escapes me) splits into a helium nucleus and a beryllium-8 nucleus, which in turn splits into another two helium nuclei. So what you have in effect is a fusion-fission reaction but the fission part isn't usually mentioned - something to do with OMG nuke! types, perhaps?

However, I suppose it is true that all of the energy is coming from fusion, as 12C -> 4He + 4He + 4He is exothermic. (The reverse reaction is an energy source for stars under some circumstances.)

Actually, the triple-alpha process, which produces carbon in some stars is closer to this:

He + He -> Be

Be + He -> C

I expect that the probability of a 3-body collision between 3 helium nuclei is so vanishingly small as to be insignificant, but hopefully someone who knows this subject well can fill in that particular blank.

As for why the carbon that gets produced doesn't immediately decay like the one made in a p+B11 fusion reactor, I couldn't say as IANANP (just an interested layman) but I imagine it's something to do with that business of being in an excited state I touched upon earlier.

P.S. A dictionary isn't a good place to start learning about nuclear physics; try an encyclopaedia instead. In fact, here [focusfusion.org] is a good article, which was the second result Google gave when I searched for p+B11. To address your issue with particles: yes, more atoms come out than go in, but the number of nucleons remains the same.

Re:It seems more fission than fusion (2)

chgros (690878) | more than 3 years ago | (#36606706)

12C -> 4He + 4He + 4He is exothermic. (The reverse reaction is an energy source for stars under some circumstances.)
You meant endothermic then.

Re:It seems more fission than fusion (1)

Michael Woodhams (112247) | more than 3 years ago | (#36606796)

*facepalm*. You're right, sorry.

My math may be wrong, but... (1, Interesting)

plindse (1873276) | more than 3 years ago | (#36605742)

10^18 Watts/cm^2 with a 20cm disk for 1 picosec == 87.2 KWH ?
2.9 MeV per alpha particle * 100,000 ~= 0.00000047 joules

I'm not into engine building, but that seems like a tiny amount of force for 87.2 KWH.

Re:My math may be wrong, but... (1)

John Hasler (414242) | more than 3 years ago | (#36605866)

Force is not measured in joules.

Re:My math may be wrong, but... (0)

Anonymous Coward | more than 3 years ago | (#36605990)

Is it measured in the amount of voices going silent at the same time?

Re:My math may be wrong, but... (1)

plindse (1873276) | more than 3 years ago | (#36606142)

Duly corrected...

10^18 Watts/cm^2 with a 20cm disk for 1 picosec == 87.2 KWH ?
2.9 MeV per alpha particle * 100,000 ~= 0.00000046 n M

I'm not into engine building, but that seems like a tiny amount of thrust for 87.2 KWH.

Re:My math may be wrong, but... (1)

Anonymous Coward | more than 3 years ago | (#36606220)

Minus some issues converting units etc there is one large assumption, which is the actual size of the beam. The article says:
"...A beam with energy on the order of 2 x 10^18 watts per square centimeter, pulse frequencies up to 75 megahertz, and wavelengths between 1 and 10 micrometers is aimed at a two-layer, 20-centimeter-diameter target. The first layer is a 5- to 10-m-thick sheet of conductive metal foil. It responds to the teravolt-per-meter electric field created by the laser pulse by "acting as a de facto proton accelerator," says Chapman..."

Its not really clear how the "TeV per Meter" electric field is generated (either entirely by the laser or if there's secondary effects going on). Without knowing the beam size we cannot really calculated the input work required. At a worst-case we can assume its 2 x 10^18 watts/cm^2 for the entire 314.2 cm^2 of the disk:

2×10^18 W/cm^2 (watts per square centimeter) (314.2 cm^2 (square centimeters)) (1 ps (picosecond)) = 174.55 kW h (kilowatt hours) = 628.4 MJ
http://www.wolframalpha.com/input/?i=2+10^18+watts%2Fcm^2+times+314.2cm^2+for+1+picosecond

convert 290000 MeV (megaelectronvolts) to megajoules = 4.646312×10^-14 MJ (megajoules)
http://www.wolframalpha.com/input/?i=290000+mev+to+megajoules

Maximum input work (ignoring losses): 628.4 MJ
Esitmated output work: 4.646312×10^-14 MJ

Unfortunately at this point we can't determine the force created because we don't know the distance the energy is acting over. Newton Meter is a unit of energy which is equivalent to a Joule (disregarding semantics), however a Newton is a unit of force which is Nm / Distance.

Re:My math may be wrong, but... (1)

multi io (640409) | more than 3 years ago | (#36606750)

Esitmated output work: 4.646312×10^-14 MJ

Unfortunately at this point we can't determine the force created because we don't know the distance the energy is acting over. Newton Meter is a unit of energy which is equivalent to a Joule (disregarding semantics), however a Newton is a unit of force which is Nm / Distance.

The energy is used to accelerate alpha particles from zero to the velocity v corresponding to 2.9 MeV of kinetic energy of an alpha particle, so you can use F=d(m*v)/dt, with m = 100000 times the mass of one particle, and dt=1ps. (that gives the force during the time when the laser is on; for getting the net force you'd best use dt=1s and m=75e6*100000*(mass of one particle)).

Re:My math may be wrong, but... (1)

wagnerrp (1305589) | more than 3 years ago | (#36606130)

The laser will be far more focused than a full square centimeter.

in the 90's they called it... (0)

Anonymous Coward | more than 3 years ago | (#36605744)

A Fission-fragment rocket. Saw it on a program called Beyond 2000.

Power Plant for X (0)

Anonymous Coward | more than 3 years ago | (#36605784)

My question here is why only use it in space? Over 300MW of generated power is quite a bit. How small is the device? How often do the boron fuel plate and other metal plate need to be replaced? Are the components dangerous for the average person to be around once they have been used up? These devices could be scaled down to power electric vehicles such as cars, trucks, trains, and aircraft as well as our homes without the need for fossil fuels. What do you think?

Re:Power Plant for X (1)

newcastlejon (1483695) | more than 3 years ago | (#36606682)

These devices could be scaled down to power electric vehicles such as cars, trucks, trains, and aircraft as well as our homes without the need for fossil fuels. What do you think?

I think that scaling isn't as simple as that and also that maintaining a hard vacuum is probably a lot easier in space.

Mr. Jones needs to learn the difference... (1)

John Hasler (414242) | more than 3 years ago | (#36605826)

...between power and energy.

It makes me sad (4, Insightful)

hamburgler007 (1420537) | more than 3 years ago | (#36605834)

When I think about how much more the US could do if we didn't squander our money on bullshit

Re:It makes me sad (1)

asylumx (881307) | more than 3 years ago | (#36606134)

I'm confused. Are you saying this technology is bullshit and we shouldn't spend money on it, or are you saying we should be spending our money on this instead of all the other bullshit?

Re:It makes me sad (1)

Anonymous Coward | more than 3 years ago | (#36606356)

War = Bullshit

Thrusters? (1)

dicobalt (1536225) | more than 3 years ago | (#36605954)

Starfleet ships only use those during docking procedures.

Re:Thrusters? (1)

newcastlejon (1483695) | more than 3 years ago | (#36606700)

The impulse engines are canonically fusion drives with a magic inertia-mitigating field thrown in for good measure; as memory serves they ran on deuterium.

40x efficiency (1)

Bryan3000000 (1356999) | more than 3 years ago | (#36606054)

So if the other engines had an efficiency of 2%, this could get 80%? And if they operated at more than 2.5% efficiency, it would be fusion with a net energy gain - a real reactor? It might easily not take diversion of much of the thrust to produce the energy necessary to sustain the reaction.

So what if getting a sustainable fusion reaction requires a thruster design - that's easy to engineer around.

First on the ground? (1)

B.Stolk (132572) | more than 3 years ago | (#36606474)

We can't do fusion with net energy gain on earth.
So why would we be able to do this in space?
First build a working fusion reactor that generates energy on the ground.
And only then take it to the skies and stars.

old news? (2)

recharged95 (782975) | more than 3 years ago | (#36606734)

Sanger proposed this way back in the early 1950's.

And Spencer wrote about it later:
Spencer, Dwain F. "Fusion Propulsion for Interstellar Missions". Annals NY Academy of Sciences 140, 407-418 (1966).
.
Robert Forward documented all the above in a book I have on my shelf, but for the life of me can't remember the title. Heck, I was doing solar sail research/simulations on an x86 back in the 80's and we were proposing fusion drives as a power source for sails when the vehicle was in interstellar space.

It's great for today's visionaries to talk about their theories, but we all need to remember our ideas are based on the shoulders of those before us, whether they are giants or not.

Not a bad start (0)

Anonymous Coward | more than 3 years ago | (#36606890)

While this isn't a full-blown warp core, fusion drive is what is used to go slow between planets. "Full Impulse" is the usual term, but its good enough to go extra-terrestrial. If you want to go inter-galactic, you need that warp core. Right now physics says 'no'. 110 years ago, physics and flying were equations on paper and nothing more. There was nothing feasible. 50 years ago, it was hot stuff (crappy engines and glorified kites of the first decade of flight --still miracles at the time-- had been replaced by better engines and wing surfaces in the second decade, faster engines pressurized cabins, high altitude bombing and millions of flight hours per year after the third decade, jets and faster commercial flight after the next decade, space flight after the next and on it went. Ships started off as boats. Boats started off as logs that people floated across the river with. A bit of work and the log went better if it was pointy at both ends. You didn't get wet if it was hollowed out inside and you were in it. You didn't have to get wet hands if you had a flat stick to push the water. Later, steel hulls and turbine shafts made going across the ocean more routine. Right now we are at the 'logs' end of space flight. For going across the ocean, logs to turbines was more than 3000 years. When I was 4 years old, people were all jumping up and down because some guy was the first guy to step foot on the moon *ever* and he came back to talk about it! We will get there. Likely not in my lifetime, but we *will* get there.

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