US Space Policy: Launch of Spacecraft Containing Space Nuclear Systems

[Dr Mordrid]

GAME ON; US space nuclear power memorandum.

This necessitated by NASA's development of a compact, simple and relatively inexpensive space capable nuclear reactor, which is expected to be used by both government and commercial space missions.

Propulsion, probes, bases, etc., even in remote Earth locations.

Imagine a SpaceX Starship or NASA NAUTILUS-X with a nuclear propulsion module...

WhiteHouse.gov...

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MEMORANDUM FOR THE SECRETARY OF STATE
THE SECRETARY OF DEFENSE
THE SECRETARY OF TRANSPORTATION
THE SECRETARY OF ENERGY
THE ADMINISTRATOR OF THE ENVIRONMENTAL
PROTECTION AGENCY
THE ADMINISTRATOR OF THE NATIONAL
AERONAUTICS AND SPACE ADMINISTRATION
THE CHAIRMAN OF THE NUCLEAR REGULATORY
COMMISSION
THE ASSISTANT TO THE PRESIDENT FOR NATIONAL
SECURITY AFFAIRS
THE ASSISTANT TO THE PRESIDENT FOR SCIENCE AND
TECHNOLOGY AND DIRECTOR OF THE OFFICE OF
SCIENCE AND TECHNOLOGY POLICY

SUBJECT: Launch of Spacecraft Containing Space Nuclear Systems

By the authority vested in me as President by the Constitution and the laws of the United States of America, I hereby direct the following:

Section 1. Purpose.

This memorandum updates the process for launches of spacecraft containing space nuclear systems. Space nuclear systems include radioisotope power systems (RPSs), such as radioisotope thermoelectric generators (RTGs) and radioisotope heater units (RHUs), and fission reactors used for power and propulsion.

The ability to use space nuclear systems safely and sustainably is vital to maintaining and advancing United States dominance and strategic leadership in space. For United States launches of space nuclear systems, the Federal Government must ensure a rigorous, risk informed safety analysis and launch authorization process. This memorandum establishes processes for Federal Government launches and launches for which the Department of Transportation (DOT) has statutory authority to license as commercial space launch activities (commercial launches). These processes include transparent safety guidelines and are forward-looking and amenable to effective use of space nuclear systems for heating, power, and propulsion.

Section 2. Policy.

The United States shall develop and use space nuclear systems when such systems safely enable or enhance space exploration or operational capabilities. The Secretary of Energy shall maintain, on a full cost recovery basis, the capability and infrastructure to develop, furnish, and conduct safety analyses for space nuclear systems for use in United States Government space systems. Executive departments and agencies (agencies) shall seek to ensure that safe application of space nuclear systems is a viable option for Federal Government and commercial space activities.
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DONALD J. TRUMP

[Dr Mordrid]

The other shoe drops

Jim Bridenstine ✔ @JimBridenstine
In partnership with @ENERGY, we’ve completed successful tests of #Kilopower, a new nuclear power technology that could provide safe, efficient and sun-independent energy for long-term human and robotic exploration during long lunar nights and within shadowed areas on the Moon.

IMG_20190822_125643.jpg

https://twitter.com/JimBridenstine/status/1164217912707690496

[Umfriend]

Given that these run for 12-15 years max, I would say beyond moon and mars it is gonna be a hard sell. What makes these reactors "safe"?

Can the fuel for the reactors be replaced and do other planets have U-235? And propulsion? Are these not far to small for that?

[Dr Mordrid]

Given that these run for 12-15 years max, I would say beyond moon and mars it is gonna be a hard sell.

Given advances in high thrust electric propulsion 10-15 years is enough for powering outer solar system probes launched with the high deltaV expendable Starship upper stage. It could launch several Voyager class missions in one shot, with the reactors only activating when needed.

What makes these reactors "safe"?

Design geometry and materials make it passively safe - can't melt down. As current draw goes up the core gets cooler, and if core temps go up the neutron flux declines - slowing the reaction.

Can the fuel for the reactors be replaced and do other planets have U-235?

They can be safely retired, with the fuel element being about the size of a paper towel roll's core.

For early bases on Mars several 40 KWe Kilopower reactors + ROSAs (Roll Out Solar Arrays, deployed from a box) will be enough to run the base and do ISRU propellant manufacturing. Later, Mars has thorium.

And propulsion? Are these not far to small for that?

As noted, electric propulsion has come a long ways. Where before a single electric thruster had millinewtons of thrust some now have several Newtons. More than enough for probes, and a high percentsge of satellites now use electric propulsion. SpaceX's StarLink satellites use a Krypton electric thruster.

For manned missions, both NASA and SpaceX have a renewed interest in nuclear thermal rocket propulsion modules. These produce very high thrust and a very high specific impulse.

[dZeus]

Given that these run for 12-15 years max, I would say beyond moon and mars it is gonna be a hard sell. What makes these reactors "safe"?

Can the fuel for the reactors be replaced and do other planets have U-235? And propulsion? Are these not far to small for that?

Russia already is playing with 'fission reactors used for power and propulsion' (in this case not for missions to outer space, but for the Burevestnik ICBM). Supposedly it was involved in the failed test on 8th August.
Monitoring the fallout should provide with some information on potential risk of using fissile material for rocket propulsion.

[UtwigMU]

The Burevestnik is allegeldy (based on some video by Russian physicist I watched) a ramjet that uses reactor to heat air.

[Dr Mordrid]

Correct, a nuclear ramjet.

The reactor could 1) directly heat scooped air or, 2) use a closed cooling loop filled with a liquid metal; lead, sodium, etc. This is pumped through a heat exchanger which super-heats scooped in air. In either case, the heated air becomes the reaction mass.

In principle, the range is limited by how long the core stays hot enough to sufficiently super-heat air.

In the US's Project Pluto (1960's) a directly heated nuclear ramjet successfully fired for 5 minutes.