Did Galileo/Cassini anti-nuke crowd go AWOL?

Mike Chan schreef in berichtnieuws
...

[snip]

The Galileo/Cassini anti-nuke crowd held that Galileo/Cassini were
public relations openings by NASA as a front for military use of
nuclear power in space. RTG's can be designed to survive launch
explosions and re-entry from LEO; direct risks from RTG's in these
types of accidents are insignificant. RTG's have not been used in
LEO, because solar energy works well and is plentiful and cheaper in

I believe this is not correct. I vaguelly recall some weather-satellite
named NIMBUS that was powered with RTGs. Can anybody verify this?

Earth orbit (kilowatts with lower cost solar arrays vs hundreds of
watts electrical for an expensive RTG). This goes even for the
military. Nuclear power does have have a lower volume / cross
sectional area than a solar array; this might get some play in better
survivability from a conventional ASAT near miss. If the military
wanted to go nuclear in space, they would do it without regard to
Galileo/Cassini.

Filip De Vos

In article ,
dinges wrote:
...RTG's have not been used in
LEO, because solar energy works well and is plentiful and cheaper...

I believe this is not correct. I vaguelly recall some weather-satellite
named NIMBUS that was powered with RTGs. Can anybody verify this?

Correct. Some of the Nimbus experimental weather satellites had both
solar arrays and RTGs. Also, some of the Transit navigation satellites
had RTGs. Back in the days when solar arrays were new and not that good,
and anti-nuclear jitters were largely absent, using isotope power in LEO
was quite a respectable idea.
--
MOST launched 1015 EDT 30 June, separated 1046, | Henry Spencer
first ground-station pass 1651, all nominal! |

"Henry Spencer" wrote in message
...
In article ,
dinges wrote:
...RTG's have not been used in
LEO, because solar energy works well and is plentiful and cheaper...

I believe this is not correct. I vaguelly recall some weather-satellite
named NIMBUS that was powered with RTGs. Can anybody verify this?

Correct. Some of the Nimbus experimental weather satellites had both
solar arrays and RTGs. Also, some of the Transit navigation satellites
had RTGs. Back in the days when solar arrays were new and not that good,
and anti-nuclear jitters were largely absent, using isotope power in LEO
was quite a respectable idea.

Also the Russian radarsats (such as the one that crashed in Henry's
backyard) used nuclear energy. They orbited at a fairly low altitude and
the drag from solar arrays large enough to power them would have caused them
to reenter to quickly.


--
MOST launched 1015 EDT 30 June, separated 1046, | Henry Spencer
first ground-station pass 1651, all nominal! |

(Henry Spencer) wrote in message ...
In article ,
dinges wrote:
...RTG's have not been used in
LEO, because solar energy works well and is plentiful and cheaper...

I believe this is not correct. I vaguelly recall some weather-satellite
named NIMBUS that was powered with RTGs. Can anybody verify this?

Correct. Some of the Nimbus experimental weather satellites had both
solar arrays and RTGs. Also, some of the Transit navigation satellites
had RTGs. Back in the days when solar arrays were new and not that good,
and anti-nuclear jitters were largely absent, using isotope power in LEO
was quite a respectable idea.

Good catch. I was thinking more recent history, not the 60's SNAP's.
I should have written "RTG's have not been used _much_ in LEO." The
point was that designing containment for an RTG against an accidental
LEO re-entry is less difficult than against a re-entry from solar
orbit. The Aquarius SNAP-27 apparently made it thru, but that was at
a relatively low incidence angle entry. Granted Cassini and Galileo
would have had to miss by a lot to plow head on into Earth, future
missions with RTG's should avoid Earth flybys by using a bigger LV and
lower injected mass, e.g., New Horizons.

Eventually, NEP should be the way to go for outer planets.

(Henry Spencer) wrote in message ...
In article ,
dinges wrote:
...RTG's have not been used in
LEO, because solar energy works well and is plentiful and cheaper...

I believe this is not correct. I vaguelly recall some weather-satellite
named NIMBUS that was powered with RTGs. Can anybody verify this?

Correct. Some of the Nimbus experimental weather satellites had both
solar arrays and RTGs. Also, some of the Transit navigation satellites
had RTGs. Back in the days when solar arrays were new and not that good,
and anti-nuclear jitters were largely absent, using isotope power in LEO
was quite a respectable idea.


Didn't one of the Nimbus RTG's break up in the atmosphere and did
indeed vaporize? I believe later Nimbus RTG designs were meant to keep
the heat source intact during reentry. What about Apollo 13's RTG? Did
the heat source stay intact? When I worked on RTG's, the heat source
was encased in iridium as I recall. We also had some experimental
designs that used beryllium copper too. BeCu was aslo used on ICBM
reentry vehicles IIRC.

Gene

In article ,
Greg D. Moore \(Strider\) wrote:
Correct. Some of the Nimbus experimental weather satellites had both
solar arrays and RTGs. Also, some of the Transit navigation satellites
had RTGs...

Also the Russian radarsats (such as the one that crashed in Henry's
backyard) used nuclear energy.

Indeed so, although that was a slightly different case -- reactors rather
than RTGs.
--
MOST launched 1015 EDT 30 June, separated 1046, | Henry Spencer
first ground-station pass 1651, all nominal! |

In article ,
Gene DiGennaro wrote:
Didn't one of the Nimbus RTG's break up in the atmosphere and did
indeed vaporize?

If memory serves -- references are not handy -- a Transit RTG reentered
and vaporized, as they were then designed to do. That caused changes in
policy, in favor of designing for intact survival.

I believe later Nimbus RTG designs were meant to keep
the heat source intact during reentry.

Correct. I don't believe any of them have reentered, but there was a
Nimbus that failed to reach orbit. Its RTGs were found on the bottom,
recovered, refurbished, and reflown.

What about Apollo 13's RTG? Did the heat source stay intact?

Yes. A slightly different case, because the ALSEP RTGs were not launched
with heat sources installed -- the heat source was launched in a
protective cask, and was transferred to the RTG by the astronauts during
ALSEP setup on the lunar surface. Apollo 13's reentry path was chosen to
put the cask in deep ocean. Extensive air and water sampling was done
afterward to confirm that the cask had survived intact; it did.
--
MOST launched 1015 EDT 30 June, separated 1046, | Henry Spencer
first ground-station pass 1651, all nominal! |

(Henry Spencer) wrote in message ...
In article ,
Gene DiGennaro wrote:
Didn't one of the Nimbus RTG's break up in the atmosphere and did
indeed vaporize?

If memory serves -- references are not handy -- a Transit RTG reentered
and vaporized, as they were then designed to do. That caused changes in
policy, in favor of designing for intact survival.

I believe later Nimbus RTG designs were meant to keep
the heat source intact during reentry.

Correct. I don't believe any of them have reentered, but there was a
Nimbus that failed to reach orbit. Its RTGs were found on the bottom,
recovered, refurbished, and reflown.

What about Apollo 13's RTG? Did the heat source stay intact?

Yes. A slightly different case, because the ALSEP RTGs were not launched
with heat sources installed -- the heat source was launched in a
protective cask, and was transferred to the RTG by the astronauts during
ALSEP setup on the lunar surface. Apollo 13's reentry path was chosen to
put the cask in deep ocean. Extensive air and water sampling was done
afterward to confirm that the cask had survived intact; it did.

Thanks Henry,
I knew there were only three RTG's reentries. Forgot about Transit, it
was indeed intended to vaporise and as we all know everyone everywhere
has lung cancer!
I found some of my notes on RTG reentry from my days at Teledyne. It's
just like you said. Look for the t-shirt in the mail Henry!

Gene