Nuclear power in space

OK, I've not seen this one lately.

I noted in news that there is to be a push to get reactors going that are
able to run in space unattended for long periods. A few questions come to
mind here.

Would these be screened, and if so, surely this would make them very heavy.

If they were to be used for a manned vehicle, say some kind of
interplanetary shuttle, they would need to screen it.

Even on an unmanned probe, surely the radiation would upset the science
instruments?

Also, the environmental impact of a failed launch with a reactor on board
would be a nightmare, and I'm sure the idea would be ought by the lobby.

So, anyone out there know what exactly is planned? From the sci.space.news
text, it looks like they are also going to look into a better version of the
thermo electric system used now.


Brian

--
Brian Gaff....
graphics are great, but the blind can't hear them
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In article ,
says...
OK, I've not seen this one lately.

I noted in news that there is to be a push to get reactors going that are
able to run in space unattended for long periods. A few questions come to
mind here.

Would these be screened, and if so, surely this would make them very heavy.

If they were to be used for a manned vehicle, say some kind of
interplanetary shuttle, they would need to screen it.

Even on an unmanned probe, surely the radiation would upset the science
instruments?

Also, the environmental impact of a failed launch with a reactor on board
would be a nightmare, and I'm sure the idea would be ought by the lobby.

So, anyone out there know what exactly is planned? From the sci.space.news
text, it looks like they are also going to look into a better version of the
thermo electric system used now.

The thermo-electric system (Radioisotopic Thermal Generators, or RTGs)
are certainly the historically preferred approach to "nuclear energy"
sources in American space probes. While I can't say for certain that the
U.S. hasn't flown any actual nuclear reactors (i.e., moderated fission
piles) on spacecraft, I know that the Soviets are far more well known for
having done this, especially on their ocean surveillance radar
satellites. (One of those was the one that had an uncontrolled entry
over Canada a couple of decades ago.)

The Soviet mishap obviously is one of the reasons why anti-nuclear
lobbies would object to flying fission reactors in space. Also, AIUI, a
fission reactor requires a far larger mass of fissile material than an
RTG does to provide power, so reactors pose a greater threat in case of
impact with Earth or any other body.

However, that said, nuclear reactors also offer more efficient power and
propulsion for interplanetary flight than the currently available
technologies. A Pluto probe, for example, with a nuclear reactor-driven
propulsion system could get to Pluto in only a few years and have the
energy available to orbit the planet. A Mars mission could reach Mars in
a matter of three or four weeks, rather than the six to nine months a
minimum-energy transfer orbit would require. The savings in life support
and maintenance systems for such a vehicle are obvious.

It's a double-edged sword. And you're right, the anti-nuclear lobbies
might bring so much pressure to bear that using such systems (for
propulsion, especially) might be very difficult. But the benefits,
especially in travel times to other planets, are damned attractive.

--

Do not meddle in the affair of dragons, for | Doug Van Dorn
thou art crunchy and taste good with ketchup |

"Brian Gaff" wrote in

I noted in news that there is to be a push to get reactors going that are
able to run in space unattended for long periods. A few questions come to
mind here.

Would these be screened, and if so, surely this would make them very heavy.

Typical designs use a more-or-less bare reactor with a "shadow shield"
placed between the reactor and the rest of the spacecraft. Also
typically, the reactor is mounted on a boom to get it away from
the rest -- thus the shadow shield can be smaller/lighter and the
distance further attenuates the radiation that does get through
the shield. You need to be careful when operating such a system
in the vicinity of other radiation-sensitive objects, of course. :-)


Even on an unmanned probe, surely the radiation would upset the science
instruments?

It's a design consideration, not a show-stopper except for some very
special cases.

Also, the environmental impact of a failed launch with a reactor on board
would be a nightmare, and I'm sure the idea would be ought by the lobby.

Typical concepts use a uranium-fueled reactor that never goes critical
until it's in a no-return orbit/trajectory and is designed not to
be able to go critical accidentally even in an extreme crash scenario.
Such designs aren't all that hard to come up with.

So, anyone out there know what exactly is planned? From the
sci.space.news text, it looks like they are also going to look
into a better version of the thermo electric system used now.

At the moment, I get the impression that there is a dual track
program, with more/better RTGs on one track and something like
son-of-SP-100 on the other. Nuclear thermal rockets and other
stuff may come along at some point.

"Doug..." wrote in message
...
| In article ,
| says...
| OK, I've not seen this one lately.
|
| I noted in news that there is to be a push to get reactors going that
are
| able to run in space unattended for long periods. A few questions come
to
| mind here.
|
| Would these be screened, and if so, surely this would make them very
heavy.
|
| If they were to be used for a manned vehicle, say some kind of
| interplanetary shuttle, they would need to screen it.
|
| Even on an unmanned probe, surely the radiation would upset the science
| instruments?
|
| Also, the environmental impact of a failed launch with a reactor on
board
| would be a nightmare, and I'm sure the idea would be ought by the lobby.
|
| So, anyone out there know what exactly is planned? From the
sci.space.news
| text, it looks like they are also going to look into a better version of
the
| thermo electric system used now.
|
| The thermo-electric system (Radioisotopic Thermal Generators, or RTGs)
| are certainly the historically preferred approach to "nuclear energy"
| sources in American space probes. While I can't say for certain that the
| U.S. hasn't flown any actual nuclear reactors (i.e., moderated fission
| piles) on spacecraft, I know that the Soviets are far more well known for
| having done this, especially on their ocean surveillance radar
| satellites. (One of those was the one that had an uncontrolled entry
| over Canada a couple of decades ago.)
|
| The Soviet mishap obviously is one of the reasons why anti-nuclear
| lobbies would object to flying fission reactors in space. Also, AIUI, a
| fission reactor requires a far larger mass of fissile material than an
| RTG does to provide power, so reactors pose a greater threat in case of
| impact with Earth or any other body.
|
| However, that said, nuclear reactors also offer more efficient power and
| propulsion for interplanetary flight than the currently available
| technologies. A Pluto probe, for example, with a nuclear reactor-driven
| propulsion system could get to Pluto in only a few years and have the
| energy available to orbit the planet. A Mars mission could reach Mars in
| a matter of three or four weeks, rather than the six to nine months a
| minimum-energy transfer orbit would require. The savings in life support
| and maintenance systems for such a vehicle are obvious.
|
| It's a double-edged sword. And you're right, the anti-nuclear lobbies
| might bring so much pressure to bear that using such systems (for
| propulsion, especially) might be very difficult. But the benefits,
| especially in travel times to other planets, are damned attractive.
|
| --
|
| Do not meddle in the affair of dragons, for | Doug Van Dorn
| thou art crunchy and taste good with ketchup |

Really, a few weeks to Mars? I don't see how that could work, you would be
flying so fast you would need to slow down VERY quickly when you got there,
or slow down slowly from a long way out wohich would lengthen the trip time.

Brian

--
Brian Gaff....
graphics are great, but the blind can't hear them
Email:
__________________________________________________ __________________________
__________________________________






---
Outgoing mail is certified Virus Free.
Checked by AVG anti-virus system (http://www.grisoft.com).
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In article ,
says...

snip

Really, a few weeks to Mars? I don't see how that could work, you would be
flying so fast you would need to slow down VERY quickly when you got there,
or slow down slowly from a long way out wohich would lengthen the trip time.

We're talking a constant-thrust profile. You accelerate halfway out to
Mars, getting up to a pretty good clip, then you decelerate the rest of
the way. Doesn't have to be very high thrust, either, to achieve a
transit time of less than two months.

Franklin Chiang-Diaz has worked with NASA on a plasma propulsion system
that would do just that. I'm sure there are references to it on the web
somewhere...

--

Do not meddle in the affair of dragons, for | Doug Van Dorn
thou art crunchy and taste good with ketchup |

I'm very interested in nuclear-thermal rockets.

I've been wondering for a while if some sort of throttleable fusion-based
rocket with a non-radioactive exhaust would ever be possible. That would
really be the ultimate in rocket power, I think.