The military wants nuclear propulsion to the Moon???

[Exoscientist]

 I was surprised when reading this:

DARPA moving forward with development of nuclear powered spacecraft.  by Sandra Erwin — May 4, 2022 https://spacenews.com/darpa-moving-forward-with-development-of-nuclear-powered-spacecraft/

  The article discusses that DARPA is funding nuclear powered propulsion to cislunar space. This is space in the vicinity of the Moon.  The only reason why you would want it nuclear powered is you want to get there rapidly, in a matter of hours instead of days. What military purpose could there be for getting to the Moon in hours?

   Robert Clark

[kerbiloid]

They want it again.

https://en.wikipedia.org/wiki/Jupiter_Icy_Moons_Orbiter

Because others are having wanted it a little earlier.

https://ru-m-wikipedia-org.translate.goog/wiki/Нуклон_(космический_комплекс)?_x_tr_sl=ru&_x_tr_tl=en&_x_tr_hl=ru&_x_tr_pto=wapp

Anything but Orion.

[sevenperforce]

15 minutes ago, Exoscientist said:

The only reason why you would want it nuclear powered is you want to get there rapidly, in a matter of hours instead of days. What military purpose could there be for getting to the Moon in hours?

Nuclear thermal propulsion won't get you to the moon in a matter of hours.

[darthgently]

11 minutes ago, Exoscientist said:

 I was surprised when reading this:

DARPA moving forward with development of nuclear powered spacecraft.  by Sandra Erwin — May 4, 2022 https://spacenews.com/darpa-moving-forward-with-development-of-nuclear-powered-spacecraft/

  The article discusses that DARPA is funding nuclear powered propulsion to cislunar space. This is space in the vicinity of the Moon.  The only reason why you would want it nuclear powered is you want to get there rapidly, in a matter of hours instead of days. What military purpose could there be for getting to the Moon in hours?

   Robert Clark

If a foreign power were to get established on the Moon they might start hurtling rocks down upon the US.  We need to demonstrate that we can get there fast and nuke any rock chucker as a deterrent.  With a surname like Clark I'm a bit surprised you posed this question, lol. 

Fine Print Disclaimer: I have no inside knowledge, am only an avid sci-fi reader and nothing in the preceding should be considered financial, legal, or existential advice

[kerbiloid]

9 minutes ago, darthgently said:

I have no inside knowledge, am only an avid sci-fi reader and nothing in the preceding should be considered financial, legal, or existential advice

Too late.
https://en.wikipedia.org/wiki/The_Moon_Is_a_Harsh_Mistress

[sevenperforce]

People assume that nuclear rocket engines must be wildly, wildly overpowered, but they really aren't.

The specific impulse of a rocket engine is primarily a function of three things: chamber temperature, expansion ratio, and propellant molecular weight. Believe it or not, the peak chamber temperature of the RS-25 (3,300°C) is actually 29% higher than the chamber temperature of a NERVA nuclear thermal engine (2,500°C). The reason NERVA gets higher specific impulse is not because it imparts greater energy to its propellant, but because its propellant is pure hydrogen, which has a much lower molecular weight than the mixture of hydrogen and water that comes spewing out the back end of an RS-25.

 

If you're planning a mission and you want as much Δv as possible for a small payload, you're actually going to opt for a high-thrust engine on your upper stage with less efficient propellants, because your mass fraction is going to be the biggest factor. On the other hand, if you have a very large payload and a relatively low Δv requirement, you're going to want to maximize specific impulse, since your mass fraction is limited by the size of your payload. So a nuclear thermal engine is good for sending big payloads, not for sending small payloads fast.

An NTR would be great for sending very large monolithic payloads to the moon. It would not get you to the moon in a matter of hours.

[darthgently]

27 minutes ago, kerbiloid said:

Too late.
https://en.wikipedia.org/wiki/The_Moon_Is_a_Harsh_Mistress

Ackshully, that is the book I was implying when I referenced OP's surname (spelling diff notwithstanding) and the story line.  So, you sir, are too late 

[darthgently]

1 hour ago, sevenperforce said:

People assume that nuclear rocket engines must be wildly, wildly overpowered, but they really aren't

I can only imagine the USSF must be considering Orion for all the reasons you outline

[JoeSchmuckatelli]

2 hours ago, sevenperforce said:

An NTR would be great for sending very large monolithic payloads to the moon

Would bulldozer sized work probes count?  And could we give them a little plutonium battery that would keep them warm and working during the long night?

[DDE]

2 hours ago, Exoscientist said:

The article discusses that DARPA is funding nuclear powered propulsion to cislunar space.

Given the last time I've heard of NTRs in the context of US national security, I'm disinclined to take the article above at face value. The article below proposes use of NTRs for (ostensibly purely defensive) Earth-orbit warfare.

https://www.defensenews.com/opinion/commentary/2021/07/08/maneuver-warfare-in-space-the-strategic-imperative-for-nuclear-thermal-propulsion/

My initial reading of this was that someone overdosed on the word "maneuver", read how spacecraft are sitting ducks due to lack of a middle-ground in thrust and ISP, found out that NTRs occupy said middile ground, and ignored their poor responsiveness that makes them unusable as an emergency dodge engine.

However, now that there's a funded program, this seems a lot less silly. The possibility of someone still chasing the word "maneuver" without an articulated end goal should not be discount, but to assume your en... adversaries are stoooooopid is a conclusion preferably avoided.

NTRs are the most readily available option for a military spacecraft designed for intense and frequent orbit changes and dodging. That's likely the totality of the motivation, and it's a somewhat alarming one. Much has been done to differentiate the development of weapons that only briefly enter space, including planet-based anti-space weapons, and the placement of attack capabilities in space proper. It's a major red line.

[SunlitZelkova]

5 hours ago, Exoscientist said:

The article discusses that DARPA is funding nuclear powered propulsion to cislunar space. This is space in the vicinity of the Moon.  The only reason why you would want it nuclear powered is you want to get there rapidly, in a matter of hours instead of days. What military purpose could there be for getting to the Moon in hours?

What @DDE said is a great explanation. I’ll tack on to it in case you are wondering why the idea of military operations around the Moon is even a concept worthy of discussion in the first place.

Without turning this into politics, basically one side (side A) misinterpreted the scientific missions of the other side’s (side B) probes, and side B thinks side A is taking advantage of such poor analyses to establish a monopoly over speculative lunar resources.

Also there are a number of potential military applications for cislunar space, like putting reconnaissance assets there out of reach of Earth orbit ASAT. Obviously placing a military asset somewhere invites attack, so there is a potential for combat around the Moon.

So now theories are flying and accusations are trading and it is looking like the Moon could end up just like LEO did (a mess of lack of clarity and control and the ever present danger of a disaster in orbit).

[tater]

3 hours ago, DDE said:

NTRs are the most readily available option for a military spacecraft designed for intense and frequent orbit changes and dodging. That's likely the totality of the motivation, and it's a somewhat alarming one. Much has been done to differentiate the development of weapons that only briefly enter space, including planet-based anti-space weapons, and the placement of attack capabilities in space proper. It's a major red line.

Orbit changes can also be so they are less predictable from a recon standpoint, though honestly constellations are making this somewhat moot—and recon sats are not cislunar.

[RCgothic]

1 minute ago, tater said:

Orbit changes can also be so they are less predictable from a recon standpoint, though honestly constellations are making this somewhat moot—and recon sats are not cislunar.

You can't hide your surface assets from satellites if there are *always* satellites overhead.

[kerbiloid]

Routine monthly delivery to build and support a lunar base. No need in high thrust.

A revival of the Project Horizon without the need in a hundred of Saturn V launches.

***

But first of all, several decades of funding.

[farmerben]

It doesn't make sense.  For a Moon to Mars ferry sure it would make sense, but not just to the Moon and LEO.  For "military maneuvers" , hypergolic thrusters make more sense.

[kerbiloid]

Project Horizon required 100+ Saturn launches to establish the tier 1 lunar base with just 12 infantrymen in it.

That's why it had been cancelled/postponed before even Mercury could fly.

Several low-thrust nuke tugs could be spiralling there and back again and significantly reduce the amount of chemical flights.

(But as a tiny Luna-16-like lunar bug is able to nuke it up in a signle flight, so the R&D funding looks self-valuable itself. )

[farmerben]

Maybe they are talking about this:

https://en.wikipedia.org/wiki/Kilopower

It's probably one of the first things you want on a Moon base, where night lasts 28 days.  It's not a propulsion system though.

[DDE]

17 minutes ago, farmerben said:

Maybe they are talking about this:

https://en.wikipedia.org/wiki/Kilopower

It's probably one of the first things you want on a Moon base, where night lasts 28 days.  It's not a propulsion system though.

Nope. "Nuclear thermal rocket engine" is mentioned both in the article body (which, given a technology-literate source, would be credible enough on its own) and in a direct quote from DARPA. This is unambiguous.

[kerbiloid]

2 hours ago, farmerben said:

Maybe they are talking about this:

https://en.wikipedia.org/wiki/Kilopower

It's probably one of the first things you want on a Moon base, where night lasts 28 days.  It's not a propulsion system though.

1 kW is pathetic. Even the Zeus/Nucleon is wannabe 1..3 MW.

[DDE]

On 11/2/2022 at 8:23 PM, kerbiloid said:

1 kW is pathetic. Even the Zeus/Nucleon is wannabe 1..3 MW.

Kilopower aims to cover hotel needs, I believe. Definitely not enough to even start talking about industrial uses.

[kerbiloid]

52 minutes ago, DDE said:

Kilopower aims to cover hotel needs, I believe.

One man hotel. Fridge vs clothes iron.

[Nuke]

On 11/1/2022 at 8:47 AM, DDE said:

Given the last time I've heard of NTRs in the context of US national security, I'm disinclined to take the article above at face value. The article below proposes use of NTRs for (ostensibly purely defensive) Earth-orbit warfare.

https://www.defensenews.com/opinion/commentary/2021/07/08/maneuver-warfare-in-space-the-strategic-imperative-for-nuclear-thermal-propulsion/

My initial reading of this was that someone overdosed on the word "maneuver", read how spacecraft are sitting ducks due to lack of a middle-ground in thrust and ISP, found out that NTRs occupy said middile ground, and ignored their poor responsiveness that makes them unusable as an emergency dodge engine.

However, now that there's a funded program, this seems a lot less silly. The possibility of someone still chasing the word "maneuver" without an articulated end goal should not be discount, but to assume your en... adversaries are stoooooopid is a conclusion preferably avoided.

NTRs are the most readily available option for a military spacecraft designed for intense and frequent orbit changes and dodging. That's likely the totality of the motivation, and it's a somewhat alarming one. Much has been done to differentiate the development of weapons that only briefly enter space, including planet-based anti-space weapons, and the placement of attack capabilities in space proper. It's a major red line.

cant imagine it would be too much trouble to have a high thrust but short lived srb kick motor for such emergency situations. enough to dodge an incoming projectile long enough to get the drive online. might pull a few gs for a few seconds. of course the missile will probibly have the same thing. ive made the cheetah vs gazelle analogy before. cheetah is the missile and the gazelle is the ship. if the ship can survive the initial moments of the engagement then it stands a good chance of out sustaining the missile and can win by endurance alone. one or more kick motors might enable that.

3 hours ago, kerbiloid said:

One man hotel. Fridge vs clothes iron.

i dont think wrinkles would be much of an issue in zero g. 

[kerbiloid]

24 minutes ago, Nuke said:

i dont think wrinkles would be much of an issue in zero g. 

That's not for wrinkles...

Spoiler

 

[Exoscientist]

 

 This article suggests nuclear thermal propulsion could get to the Moon in hours:

The US military is getting serious about nuclear thermal propulsion
“Activity in cislunar space is expected to increase considerably in the coming years.”
ERIC BERGER - 6/15/2020, 8:18 AM
“With the DRACO program, the US Defense Department could potentially move large satellites quickly around cislunar space. For example, moving a 4-ton satellite from point A to point B might take about six months with solar electric propulsion, whereas it could be done in a few hours with nuclear thermal propulsion.”
https://arstechnica.com/science/2020/06/the-us-military-is-getting-serious-about-nuclear-thermal-propulsion/

   Robert Clark

[DDE]

3 minutes ago, Exoscientist said:

This article suggests nuclear thermal propulsion could get to the Moon in hours:

No, it doesn't. "Move around cislunar space"