Momentum Grows for Nuclear Thermal Space Propulsion

[Elderberry]

Space.com By Jeff Foust 5/28/2019

With congressional funding and industry support, nuclear thermal propulsion technology is making progress for potential use on future NASA deep space missions, although how it fits into the agency's exploration architectures remains uncertain.

The House Appropriations Committee approved May 22 a commerce, justice and science (CJS) appropriations bill that offers $22.3 billion for NASA. That funding includes $125 million for nuclear thermal propulsion development within the agency's space technology program, compared to an administration request for no funding.

"The bill's investment in nuclear thermal propulsion is critical as NASA works towards the design of a flight demonstration by 2024," said Rep. Robert Aderholt (R-Ala.), ranking member of the CJS appropriations subcommittee, during that subcommittee's markup of the bill May 17. He offered similar comments in support of that project at the full committee markup.

The $125 million comes on top of $100 million that Congress provided in 2019, of which $70 million was earmarked for a flight demonstration by 2024. The report accompanying the House bill makes no mention of a 2024 date for a flight demonstration, but does call on NASA to develop "a multi-year plan that enables a nuclear thermal propulsion demonstration, including the timeline associated with the space demonstration, and a description of future missions and propulsion and power systems enabled by this capability."

More: https://www.space.com/nuclear-thermal-space-propulsion-momentum-grows.html

[Joe Wooten]

We'll be starting all over here. All the guys who participated in the NERVA/KIWI tests in the late 60's and early 70's are mostly dead.

Also, to get those reactors into orbit will require a Saturn 5 class heavy lift rocket.

[thackney]

We'll be starting all over here. All the guys who participated in the NERVA/KIWI tests in the late 60's and early 70's are mostly dead.

Also, to get those reactors into orbit will require a Saturn 5 class heavy lift rocket.

I thought there were smaller versions currently in development/research.

https://www.bwxt.com/what-we-do/nuclear-thermal-propulsion-ntp

[Joe Wooten]

I thought there were smaller versions currently in development/research.

https://www.bwxt.com/what-we-do/nuclear-thermal-propulsion-ntp

The reactors  they feature are for unmanned probes only. 10 to 200 kW of power would not be enough for propulsion for a big manned ship. You need to get into the megawatt range, probably at least 200 MW if not more. That will be substantially heavier. I also do not think liquid hydrogen would be an optimal working fluid. Too bulky, and you'd have to spend a LOT of power to keep cryogenic for a multi year mission. It would be another thing to break, and it would since there would be a lot of active components in the refrigeration system. Ammonia or water would work better. I think water would work better since if you make the reactor a dual mode for both power and propulsion, you can cycle the water through the reactor for heat and back to the storage tank(s). One of the main problems found during the NERVA testing was poor cooling of the core from trying to cram too much hydrogen through the channels between the fuel rods. 

There's more info at http://www.projectrho.com/public_html/rocket/enginelist2.php#ntrsolidnerva

The NERVA and PeeWee engines tested ran about 200 MW (NERVA) and 500 MW (PeeWee).

[thackney]

The reactors  they feature are for unmanned probes only. 10 to 200 kW of power would not be enough for propulsion for a big manned ship. You need to get into the megawatt range, probably at least 200 MW if not more. That will be substantially heavier. I also do not think liquid hydrogen would be an optimal working fluid. Too bulky, and you'd have to spend a LOT of power to keep cryogenic for a multi year mission. It would be another thing to break, and it would since there would be a lot of active components in the refrigeration system. Ammonia or water would work better. I think water would work better since if you make the reactor a dual mode for both power and propulsion, you can cycle the water through the reactor for heat and back to the storage tank(s). One of the main problems found during the NERVA testing was poor cooling of the core from trying to cram too much hydrogen through the channels between the fuel rods. 

There's more info at http://www.projectrho.com/public_html/rocket/enginelist2.php#ntrsolidnerva

The NERVA and PeeWee engines tested ran about 200 MW (NERVA) and 500 MW (PeeWee).

Asking because I do not know, would you really need a refrigeration system or just keep a solar shade between that tank and the sun?

[Elderberry]

NASA is handed $125 million to develop nuclear rocket propulsion

https://www.digitaltrends.com/cool-tech/nasa-nuclear-thermal-125m/

NASA has been awarded a sum of $125 million to develop nuclear thermal propulsion systems for its future spacecraft. First reported by Space.com, the award was given as part of a total $22.3 billion of funding for NASA in a commerce, justice, and science (CJS) appropriations bill approved by the House Appropriations Committee this month.

“The bill’s investment in nuclear thermal propulsion is critical as NASA works towards the design of a flight demonstration by 2024,” said Robert Aderholt, the U.S. Representative for Alabama’s fourth congressional district, during the subcommittee’s markup of the bill earlier in May.

More at link.

[Joe Wooten]

Asking because I do not know, would you really need a refrigeration system or just keep a solar shade between that tank and the sun?

You'll need a refrigeration system and a solar shade.

[thackney]

You'll need a refrigeration system and a solar shade.

Thanks.  I thought there would be next to no transfer of heat without the solar radiation in the vacuum of space.  While the rocket is running there is cooling from the evaporation as the rocket is fed.  LNG fuel systems on ships stay cooled by the boil-off as the engine runs.

[Elderberry]

  While the rocket is running there is cooling from the evaporation as the rocket is fed.  LNG fuel systems on ships stay cooled by the boil-off as the engine runs.

A Deep Space vehicle's engine does not operate for most of the voyage. There is the initial burn setting the vehicle up on its planned velocity and trajectory for the mission. There may be several course correction burns if necessary. And then a burn to achieve a capture orbit at the destination planet.

[thackney]

A Deep Space vehicle's engine does not operate for most of the voyage. There is the initial burn setting the vehicle up on its planned velocity and trajectory for the mission. There may be several course correction burns if necessary. And then a burn to achieve a capture orbit at the destination planet.

Thank you.  I was thinking of constant acceleration halfway followed by constant deceleration.

But there really isn't that need for speed, range makes more sense.