Nuclear Powered Spacecraft

publiusr said:
A recent book on nuclear spacecraft
Amazon.com
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A copy of that arrived here yesterday.
Have only skimmed through it at this point.
Looks good.
Was published April 16, 2023; is print on demand and this copy was printed January 23 in the little burg of Monee, Illinois, just south of Chicago.

Just for fun, here's a 2009 NASA interview with the author,

Here's the beginning of it,

Wright: Today is March 25th, 2009. This oral history interview with Manfred “Dutch” von Ehrenfried is being conducted for the Johnson Space Center Oral History Project in Lago Vista, Texas. The interviewer is Rebecca Wright, assisted by Sandra Johnson. We thank you so much for taking time this afternoon to sit down and visit with us for this project.

von Ehrenfried: Well, this ought to be fun.

Wright: We’re looking forward to it. We would like to start today by you sharing with us how you first became involved with NASA.

von Ehrenfried: Okay. I was going down to Langley [Air Force Base], [Hampton] Virginia to join the Air Force, and I was teaching school, and I was applying for jobs at the national laboratories, having just gotten a degree in physics. I thought I would be a physicist. But they would send me back little terse letters like, “Well, when you get your PhD, give us a call.” In the meantime I realized that I wasn’t going to go to a national lab. But I was interested in flying. So I went down to Langley, took my physical, flunked it—because I checked item 12, had asthma as a child, or something like that. Flunked me on the spot. I walked out the door with my head between my tail and just was really depressed. I saw a sign that said NASA [Langley Research Center]. I said, “Well, I’ve heard of them.” Knocked on the door, so to speak, interviewed with Chris [C.] Critzos, who showed me around, and met Gene [Eugene F.] Kranz and John [D.] Hodge and a few others. Sort of hired me on the spot, like, “You’re just what we needed.”
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Relevant to the realm of nuclear-electric propulsion,

Electric spacecraft propulsion may soon take a leap, thanks to new supercomputer
News
By Keith Cooper
published 25 January 2025

Electric propulsion is being increasingly used on space missions and could ultimately replace thrusters using chemical rockets.

www.space.com

Electric spacecraft propulsion may soon take a leap, thanks to new supercomputer

Electric propulsion is being increasingly used on space missions and could ultimately replace thrusters using chemical rockets.
www.space.com www.space.com

"For missions that could last years, [electric propulsion] thrusters must operate smoothly and consistently over long periods of time," Chen Cui of the University of Virginia School of Engineering and Applied Science said in a statement.

Before solutions can be put in place to protect a spacecraft from these backscattered electrons, their behavior in an ion-engine plume must first be understood, which is where Cui and Joseph Wang of the University of Southern California come in. They've performed supercomputer simulations of an ion engine's exhaust, modeling the thermodynamic behavior of the electrons and how they affect the overall characteristics of the plume.

"These particles may be small, but their movement and energy play an important role in determining the macroscopic dynamics of the plume emitted from the electric propulsion thruster," said Cui.

What Cui and Wang found was that the electrons in the plume behave differently depending upon their temperature and their velocity.

"The electrons are a lot like marbles packed into a tube," said Cui. "Inside the beam, the electrons are hot and move fast. Their temperature doesn't change much if you go along the beam direction. However, if the 'marbles' roll out from the middle of the tube, they start to cool down. This cooling happens more in a certain direction, the direction perpendicular to the beam's direction."

In other words, the electrons in the core of the beam that are moving fastest have a more or less constant temperature, but those on the outside cool off faster, slow down and move out of the beam, potentially being back-scattered and impacting the spacecraft.

Now that scientists better understand the behavior of the electrons in the ion plume, they can incorporate this into designs for future electric propulsion engines, looking for ways to limit the back-scatter, or perhaps confine the electrons more to the core of the beam. Ultimately, this could help missions powered by electric propulsion to fly farther and for longer, pushed by the gentle blue breeze of its ion plume.
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publiusr said:
To Titan

www.space.com

Pulsar Fusion unveils vision for ‘Sunbird’ nuclear rocket to reach Mars in half the time (video)

This superfast propulsion system could aid humanity's exploration goals someday.
www.space.com www.space.com
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Cutting the time to travel to Mars in half? So it's not even a centigee, not even a milligee?

My spreadsheet says that rocket would make about 0.0085 m/s/s, assuming constant burn and average distance between Earth and Mars.

*deep breath*

Baby steps, Scott. Baby steps...
 
Twice the average speed is actually quite impressive. With acceleration that slow it indicates ~4 x the peak speed, which if we say the current rocket-based burnout speed is ~12km/s gives almost 50km/s Vmax.
 
One use would be to burn to near depletion as a probe approachs Jupiter and do a reverse gravity assist. The payload might be a sundiver sail.

In this way, it doesn’t really matter if your destination isn’t exactly in Jupiter’s path…working best if Jupiter is across the solar system from where you want to go?
 
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Forest Green said:
Twice the average speed is actually quite impressive. With acceleration that slow it indicates ~4 x the peak speed, which if we say the current rocket-based burnout speed is ~12km/s gives almost 50km/s Vmax.
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Eh, yes and no.

A sub-milligee constant burn isn't anywhere near enough to really make a good case for hauling humans to Mars without some very massive shielding (probably mostly water, which is generally useful anyways)

But a centigee, 10cm/s/s, will get you to Mars in a month.
 
Scott Kenny said:
Eh, yes and no.

A sub-milligee constant burn isn't anywhere near enough to really make a good case for hauling humans to Mars without some very massive shielding (probably mostly water, which is generally useful anyways)

But a centigee, 10cm/s/s, will get you to Mars in a month.
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Closest distance to Mars is ~55 million km. 25km/s average gets you there in 2.2 millions seconds or 25 days. At average distance of 225m km, it becomes ~104 days. For longer journeys, the maths of this new powerplant vs rocket power becomes even better.
 
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Forest Green said:
Closest distance to Mars is ~55 million km. 25km/s average gets you there in 2.2 millions seconds or 25 days. At average distance of 140m km, it becomes ~65 days. For longer journeys, the maths of this new powerplant vs rocket power becomes even better.
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My math was using average distance of ~225mil km
 
Scott Kenny said:
My math was using average distance of ~225mil km
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Well I just noted that depending on whether the 'half the time' quote is for shortest distance or average, the further Mars is away the greater the increase in speed. E.g. if the 25km/s average speed is for 55m km, then for 225m km it may be 100km/s!
 
Today's phys.org paper

"Intelligent neural network model enhances space reactor shield design."

Seemingly unrelated story:
"New study reveals how solar coronal holes spray solar wind like a sun garden hose."

Now that made me think a statute using actual sunlight pressure might release starwisp-type magsails...but then I remembered M2P2.

Might a nuclear electric craft make even better use of solar wind fountains?

A starwisp is doomed to coast at some point. NTRs can't use the Sun--but might NEPs be a dual threat--as it were?
 
Forest Green said:
Well I just noted that depending on whether the 'half the time' quote is for shortest distance or average, the further Mars is away the greater the increase in speed. E.g. if the 25km/s average speed is for 55m km, then for 225m km it may be 100km/s!
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Sure.

If we assume the minimum distance between Earth and Mars, this drive is pushing 0.015m/s/s. 1.5 Milligee.



publiusr said:
Today's phys.org paper

"Intelligent neural network model enhances space reactor shield design."
Click to expand...
I'm not sure how exactly that would work, is that paper open access?



publiusr said:
Seemingly unrelated story:
"New study reveals how solar coronal holes spray solar wind like a sun garden hose."

Now that made me think a statute using actual sunlight pressure might release starwisp-type magsails...but then I remembered M2P2.

Might a nuclear electric craft make even better use of solar wind fountains?

A starwisp is doomed to coast at some point. NTRs can't use the Sun--but might NEPs be a dual threat--as it were?
Click to expand...
Starwisps are doomed to coast, but so are M2P2/MagSails. And I don't remember which one has the velocity advantage.

Starwisps, of course, are best used with farking ginormous green lasers for propulsion, if we're sending them to another star. I'm talking terawatts of beam output.

I suspect that MagSails would have an advantage for inner solar system runs. Not fast like a nuke-thermal torch drive, but better than Hohman Transfer orbits.
 
A couple of papers about nuclear ramjet powered flyers to explore the Jovian atmosphere, The first is based on the MITEE nuclear rocket, this is a compilation of two figures taken from the report:

Jovian nuclear ramjet flyer.jpg
 

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