
NASA-backed fusion engine could cut Mars trip down to 30 days - kristianp
http://www.theregister.co.uk/2013/04/10/nasa_fusion_engine_fast_mars_trip/
======
rdl
Arguably we've had "fusion drive" for spaceships ever since Project Orion.
Very simply, build a ship with a big shield in the back, throw nuclear bombs
out behind the ship, detonate, the shock and radiation hits the plate (some
ablates, but it's still fairly study and safe), and some kind of shock
absorber system pushes the spaceship forward. Repeat. You can feasibly get to
0.10c with this, using 1960s technology, and really big ships.

I think most of the earlier designs involved fission bombs, but there's no
reason you couldn't use fusion bombs, and maybe even some kind of laser or
magnetic means of initiating fusion. Which seems to be exactly what UW is
talking about here.

[http://en.wikipedia.org/wiki/Project_Orion_(nuclear_propulsi...](http://en.wikipedia.org/wiki/Project_Orion_\(nuclear_propulsion\))

A _lot_ of the engineering and physiological problems of a Mars mission go
away if you have the ability to move huge masses between Earth and Mars fast.
You can skip the low energy launch windows and just go for a short on-Mars
trip, rather than needing to loiter for a year or two between windows. You
don't need to worry about supplies in space and radiation issues for a year-
long transit. etc.

~~~
n0mad01
and you think that getting x nuclear bombs into orbit is safe?

and even when all bombs go into space without incidents, having them there
until start is no risk neither?

i think something more conventional would be better, even when less
economically ...

~~~
daliusd
Well, combustion engine in my car is not very conventional either by XIX
century standards. Maybe we should ride horses?

Why you make assumption that bombs must be delivered to space vs constructed
there from resources mined in asteroids?

~~~
CapitalistCartr
Plutonium is a synthetic element, requiring a nuclear reactor to create, then
must be purified. Uranium is currently unknown in asteroids, and even if it
were found would require refining with thousands of large centrifuges.

Converting uranium to uranium hexafluoride, centrifuging it over and over,
then converting it back requires massive industrial facilities, currently
impossible in space.

~~~
daliusd
What about moon?

I'm pretty sure that smart people will figure out the solution. I just wanted
to point out that most probably we can find solutions that are safe enough and
the only limiting factor is our imagination (or lack of it specifically).

------
lutusp
Something is rotten in Denmark. If this project achieves a sustained fusion
reaction as claimed, that represents a huge breakthrough, and not just for
space propulsion, but for the general topic of fusion power.

If it succeeds, it would sweep away all present fusion reaction prototype
methods, including the well-tested but so far ineffective( * ) tokamak and
laser-fusion approaches.

* By "ineffective" I mean none of them has reached the break-even point, that point where more energy is released than is required to initiate the reaction in the first place.

The article doesn't say whether the prototype device has actually succeeded in
igniting a sustained fusion reaction. If it does, it would quickly move beyond
its present goal of producing a more effective source of space acceleration
and would answer some longstanding questions about fusion power itself.

The fact that this isn't being discussed leads to my statement above --
something is rotten in Denmark. Either the project is overselling its
possibilities, and/or it can't really achieve fusion break-even.

Speaking hypothetically, if the device could produce a sustained fusion
reaction with substantial power, it could be scaled up and used to propel a
spacecraft to Mars in much less than 30 days. Assuming a sustained
acceleration of 1 g, the hypothetical craft could accelerate for 1/2 the trip,
turn around and decelerate for the other 1/2 of the distance, arriving at Mars
with zero velocity. Apart from minimizing travel time, this hypothetical
profile would prevent the bone loss that accompanies sustained time at zero-g.

Making the above assumptions, and assuming that Mars is at a close approach
point in its orbit, the travel time could be as little as ... wait for it ..
50 hours.

Derivation:

1\. Distance d (meters) for acceleration a (m/s^2) and time t (seconds): d =
1/2 a t^2

2\. Time t for distance d and acceleration a, assuming 1/2 acceleration and
1/2 deceleration: t = 2 sqrt(d/a)

3\. Result for Mars close approach (7.834e10 meters) and acceleration of 1 g:
49.64 hours.

Again, speaking very hypothetically. I still think something is rotten in
Denmark.

~~~
wazoox
> _Something is rotten in Denmark. If this project achieves a sustained fusion
> reaction as claimed, that represents a huge breakthrough, and not just for
> space propulsion, but for the general topic of fusion power._

Achieving fusion in a tokamak or with lasers has been a solved problem for a
couple of decades.

The problem with fusion power is generating more energy from the fusion than
consumed to power the lasers or tokamak.

There is no such problem here as I understand it; the system isn't supposed to
sustain itself from fusion, but instead will rely on solar panels or some
other energy source to power the fusion reactor.

~~~
lutusp
> Achieving fusion in a tokamak or with lasers has been a solved problem for a
> couple of decades.

I should have been more clear -- I mean sustained fusion _generation_ ,
meaning a net energy gain over that required to start the reaction in the
first place. That hasn't been achieved.

> There is no such problem here as I understand it; the system isn't supposed
> to sustain itself from fusion ...

Not according to the NASA documents (see below). If that were true, there
would be no point in using the system. If the fusion reaction produces less
power than it requires, the designers would be better off using the source
electrical power to drive an ion thruster.

The claim being made is that the fusion scheme creates more power than is
required to start it -- by using electrical power to initiate a fusion
reaction that produces more power than it requires. If this were not true, the
amount of converted solar energy described in the project (i.e. 200 KW) is not
enough to propel the relatively massive spacecraft to Mars in 30 days using
other methods.

Here's the evidence:

Link:
[http://www.nasa.gov/directorates/spacetech/niac/2012_phaseII...](http://www.nasa.gov/directorates/spacetech/niac/2012_phaseII_fellows_slough.html)

Title: "The Fusion Driven Rocket: Nuclear Propulsion through Direct Conversion
of Fusion Energy"

Quote: "an in-depth analysis of the rocket design and spacecraft integration
as well as mission architectures enabled by the FDR need to be performed.
Fulfilling these three elements form the major tasks to be completed in the
proposed Phase II study. A subscale, laboratory liner compression test
facility will be assembled with sufficient liner kinetic energy (~ 0.5 MJ) _to
reach fusion breakeven conditions_." [emphasis added]

Which brings us back to square one. If this project were to succeed, it would
instantly replace the existing approaches (i.e. tokamak and laser inertial
confinement) as the most promising candidate for large-scale fusion power
generation.

As I said before, something is rotten in Denmark -- why isn't this project
being described as a candidate for earthly fusion power generation, given that
it must achieve break-even to accomplish its mission?

~~~
Vivtek
The thing about a fusion _rocket engine_ is that the energy is used to throw
stuff out the back. In a fusion _generator_ this would not be considered a
feature - if you want a stationary generator that doesn't melt your city you
have to contain that plasma, which is very, very energy-intensive.

~~~
lutusp
Yes, true, but neither scenario has a working model of a fusion generator with
power gain > 1.

> if you want a stationary generator that doesn't melt your city you have to
> contain that plasma, which is very, very energy-intensive.

Actually, if you think about it, a rocket engine that can create a fusion
reaction and direct the energy out "the back" as you put it, and a power
generator that also directs fusion energy to a secondary process, are very
similar. In the extreme case, you could take the space device, put it in a
vacuum chamber, and direct the thrust into a steam generator.

------
lifeisstillgood
Hmm, a little goggling gives a hint this may not be BS after all.

I am unclear on the exact methods, but there appears to be existing research
into generating a plasma "pinch" via compression of aluminium around a core of
detrinium-tritium. This generates a massive magnetic-flux (which seems to be a
result of actual fusion during the compression) and if it is held in a
magnetic cage with an out at the back, you have propulsion.

(1) <http://en.wikipedia.org/wiki/Pinch_(plasma_physics)>
(2)[http://en.wikipedia.org/wiki/Explosively_pumped_flux_compres...](http://en.wikipedia.org/wiki/Explosively_pumped_flux_compression_generator)
[http://en.wikipedia.org/wiki/Explosively_pumped_flux_compres...](http://en.wikipedia.org/wiki/Explosively_pumped_flux_compression_generator)

------
dchichkov
Love to watch (and support with my money) all these low cost space propulsion
projects. This kickstarter project
[http://www.kickstarter.com/projects/2027072188/plasma-jet-
el...](http://www.kickstarter.com/projects/2027072188/plasma-jet-electric-
thrusters-for-spacecraft/posts) was particularly amazing to watch. Best
donation / entertainment money spent ever. And I hope B612 foundation would
result in some great fun as well ;) Or not :)

And another thing. And advice for kids looking for summer internships. Don't
do these 'iPhone games' startups. Try something real, like NASA or Lockheed,
or whatever. If you good, who knows, maybe a few lines of your code will have
a chance flying into space.

~~~
quahada
Former aerospace, current iPhone app guy here. Each career path has its pros &
cons. Working at a place like NASA or Lockheed lets you work on some very cool
projects, often times you are working on some project that never sees the
light of day (canceled due to budget cuts and what not). Also, the bureaucracy
at large aerospace organizations can be stifling.

Having said that, Space X seems like it offers the best of both worlds.

~~~
dchichkov
I should have been slightly more precise, the advice was specifically about
taking an internship in aerospace as a kid. I don't have any advice about
having a career in aerospace industry... Haven't had one. I only had a short
internship as a high school student at aero/space R&D company back in Russia.
But that [aero/space R&D, not Russia ;)], I can highly recommend.

I think actually, a more general advice is to take an internship in any high
tech industry area in which a cost of software or design failures is very,
very high.

------
Vivtek
From the article: _Given the tight financial strictures of the US government
this is unlikely_

This is what pisses me off about the last decade. Plenty of money to bail out
the richest people the planet has ever seen. Plenty of money to kill brown
people. Making a fusion drive? Making sure we all have medicine? Sheesh, we're
not made of money!

------
anigbrowl
_The FDR is one of only ten projects to get Stage Two funding from the
program. This $600,000 award will provide the proof-of-concept FDR system over
the next 18 months, and a working spacecraft would be ready as soon as 2020,
Pancokti predicted – but if NASA wanted to throw money at the project, this
timescale could be cut._

There's a lot of people on HN who could double that budget without blinking,
he hinted.

~~~
lifeisstillgood
Reading lutusp post, anyone on HN who got sufficient funds to double the
budget, would also have learnt to look very closely at extraordinary claims
with only ordinary evidence.

Be nice if it was true, and one day I am sure it will be (I mean the Sun DES
this all the time and not even a single Phd was involved)

~~~
vectorjohn
I'm not saying this FDR is guaranteed to work or be the best idea, but I'm
pretty sure lutusp is trolling or something. He is clearly not understanding
any of the issues. Repeatedly he talks of needing to create a steady reaction,
and talks about needing to meet the same requirements of a fusion electric
generator. Neither of these things is proposed by the FDR project. It is
pulsed, and it generates only kinetic energy (much like an H-bomb, relatively
old and proven technology). Further, he talks of ion thrusters as an
alternative, which would take months to get to Mars, whereas this is talking
about 30 days.

------
jbattle
The once a minute firing of the engines feels like it'd be a very unpleasant
sensation - I wonder what the momentary acceleration experienced would be.

Also - this craft sounds perfectly suited for laser-transmitted power (rather
than carrying a large solar array) - have one or more earth-orbiting lasers
beaming energy to the craft. Though I'm not sure if we have the technology
today to aim & focus a laser at that range (?)

~~~
jes5199
I saw George Dyson give a talk about the Orion project - where they were
planning to set off conventional atomic bombs in a series to propel spacecraft
- and he had found a paper that had done the math and claimed that the crew of
the spacecraft would only feel low-frequency sound, like the bass at a loud
rock concert.

------
omegant
What kind of residues leaves that kind of engine? is it gas or solid? because
small solids at that speed will surely make the earth orbit in a quite
dangerous shooting range in no time. What is the expected coherence of a gas
cloud flying that fast? Is it going to be dangerous? or will simply dissolve
in to space. Would the material expelled fly away from earth orbit?. Sorry,
too many questions..

~~~
kristianp
My guess would be that the products would be gases. Pinching a little ball of
deteurium would make it very hot, and vaporise the metal that squishes it.

~~~
omegant
Are gases dangerous at 30km/sec?. I mean, of course they are, but are they
still dangerous in space?. Will the cloud keep more or less cohesive or will
it disperse?

~~~
chad_oliver
It will disperse. Gas is made up of atoms going in many different different
directions; even if some gas doesn't seem to be moving that's just a
statistical average.

Thus, in space all those different particles will fly off in different
directions at 30km/sec. They'll be harmless in microseconds.

------
iwwr
This is very early, preliminary research. Actual fruits of a manned or
otherwise fusion rocket to Mars may be decades ahead. Even at NASA's slow pace
they could get there by the 2030es (or 2020es if they listen to Zubrin).

Edit: at 150 tons payload for low orbit (early estimate) it's not exactly easy
to launch. If you can do that on a man-rated rocket you're all ready for Mars
on just chemical propulsion (in a Mars-direct/Mars-semidirect scenario).

~~~
quahada
Not even the Saturn V could launch 150 tons into LEO (though it could come
close). No current rocket even comes close.

------
elboru
Columbus took almost one month to pass through the Atlantic Ocean, who could
imagine something like this even one century ago?

------
nnq
Maybe I misunderstand everything, but why couldn't such a system be use on
Earth as fusion power plant? (it seems to produce more energy than is consumed
to produce the fuel, right?)

~~~
lutusp
> Maybe I misunderstand everything, but why couldn't such a system be use on
> Earth as fusion power plant?

That was my question also (see my other post in this thread) -- if they really
achieve fusion break-even (i.e. produce more power than they require to start
the reaction) then they have done something that many decades of fusion
research have so far failed to achieve. If their device can really do what
they claim, it has implications far beyond the described project.

~~~
lifeisstillgood
I am not validating these sources but suggest that there is a known approach
that collapses aluminium over a core deuterium tritium. It is not self
sustaining, but it generates some net positive energy, thus enough I guess to
throw a pellet out the door

[http://www.alternative-energy-action-now.com/general-
fusion....](http://www.alternative-energy-action-now.com/general-fusion.html)

~~~
lutusp
If this method actually worked, I think we would all know by now. Achieving
break-even in a controlled laboratory fusion reaction is the "holy grail" of
fusion research and would produce instant worldwide headlines, not unlike the
(ultimately false) claims made by Pons & Fleischmann, who thought they had
achieved room-temperature fusion some time ago:

<http://en.wikipedia.org/wiki/Cold_fusion>

So I don't think so. It's a matter of how much a positive result would
completely change the fusion research landscape. It's something that people
would know about right away.

~~~
emp_zealoth
You insist on a misnomer. Achieving electrical breakeven haven't been done yet
(and even if it will be)

~~~
emp_zealoth
Sorry, this site really doesn't like pinch to zoom. I'm having a little
trouble - the post wasn't even supposed to be posted, but oh well.

I was doing research and apparently I was wrong too, depending on a definition
of fusion breakeven (which I was unable to find) Care to explain what is
yours?

If you achieve even smallest amount of fusion, technically you have more
energy than you started with. Electrical break even would be the holy grail of
fusion research, but even then you have to reach economic feasibility (produce
enough power to pay back the cost of a plant)

~~~
lutusp
> I was doing research and apparently I was wrong too, depending on a
> definition of fusion breakeven (which I was unable to find) Care to explain
> what is yours?

Fusion break-even means the reaction produces more than or equal to the power
required to initiate it. Apart from stars and weapons, it has never been
achieved.

<http://en.wikipedia.org/wiki/Fusion_energy_gain_factor>

Quote: "The fusion energy gain factor, usually expressed with the symbol Q, is
the ratio of fusion power produced in a nuclear fusion reactor to the power
required to maintain the plasma in steady state. The condition of Q = 1 is
referred to as breakeven."

> If you achieve even smallest amount of fusion, technically you have more
> energy than you started with.

Yes, but with serious problems. One of them is that you have to continue
providing more power than the reaction creates, in order to keep the reaction
going. This means the overall available power is less than the input power.
The reaction is using up much of the power to sustain itself, and that power
can't be applied to another purpose. So even though technically there is a lot
of power present, it cannot be applied to any purpose other than energizing
the plasma. This means the net available power is less than the input power.

This is a bit hard to visualize, so let's say that we have 1000 watts
available to apply to some ordinary purpose, or to sustain a fusion reaction.

We discover that the fusion reactor requires all 1000 watts to keep its plasma
activated and fusing, but the fusion reaction only produces 250 watts. So,
even though there is 1,250 watts of power in the system, 1000 watts of that is
required to sustain the plasma in its fusing state and is therefore
unavailable. That means only 250 watts is available for any other purpose.

Hence the importance of break-even. :)

------
mschuster91
I really hope this works out! But the real question is: could this be used for
atmospheric thrusters on Earth?

~~~
rurounijones
Based on the amount of thrust it produces for the weight of the machine, not a
chance.

Only works in an environment with very low friction. i.e. space

~~~
james4k
Why not? Aren't rocket-fueled thrusters much heavier due to the weight of the
fuel alone?

~~~
WhaleBiologist
Pretty much. More mass to lift = more fuel = more mass = more fuel etc., plus
burning fuel isn't the most efficient way of getting kinetic energy into the
thing you are lifting.

I would say it is unsuitable for atmospheric engines because of the way it
runs. Earth to Mars in 30 days will need you to be travelling at almost 90
km/second. The engine has to fire for 3 days straight because the delta v you
need is retardedly high, so it pulses the engine once a minute so that the
passengers don't die and the ship doesn't break up due to huge g-forces.

Lifting something into orbit needs to be done fast, because most of your
energy is spent counteracting gravity, not air resistance. A slow pulsing
engine would not be enough to get you up.

~~~
omegant
Three days of hammering impulse is not going to be fun!

~~~
mschuster91
I guess you won't feel the pulsing that much...

------
Aardwolf
Alright count me in for this trip. At least if it includes a return ticket :)

~~~
blisterpeanuts
If it's in the 2040s or 2050s, and I'm into my dotage and pushing 100, I'll
spring for a one-way. They can fill my return slot with someone younger, or
bring home an extra 150lbs of Mars rocks.

