Lightweight Nuclear Electric Space Propulsion With Ten Times the Power

The Swarm-Probe Enabling ATEG Reactor, or SPEAR, is a nuclear electric propulsion spacecraft that uses a new, lightweight reactor moderator and advanced thermoelectric generators (ATEGs) to greatly reduce overall core mass. This will subsequently require a reduction in operating temperatures and reduce the total power levels achievable by the core. However, the reduced mass will require reduced power for propulsion, resulting in a small, inexpensive nuclear electric spacecraft.

The ATEG system they previously proposed would have 15,000 watts of thermal energy about 3000 watts of electrical energy. The best RTG that NASA has flown was about 300 watts. GPHS-RTG or General Purpose Heat Source — Radioisotope Thermoelectric Generator, was used on Ulysses, Galileo, Cassini-Huygens, and New Horizons missions. The GPHS-RTG has an overall diameter of 0.422 m and a length of 1.14 m. Each GPHS-RTG has a mass of about 57 kg and generates about 300 Watts of electrical power at the start of mission (5.2 We/kg), using about 7.8 kg of Pu-238 which produces about 4,400 Watts of thermal power.

The phase I effort showed that a low mass probe was feasible and that key component- the ATEG conversion system- had extremely high potential for efficient, solid-state power conversion.

The Phase II effort will build on these findings to demonstrate a functioning ATEG unit and show the increased efficiency in a working unit. This will be done by creating a boron based ATEG and operating it at a test reactor at KSU to simulate the radiation field created by the SPEAR. The ionizing radiation will improve the material properties of the TEG feet (as demonstrated in phase I) and show unequivocally that the performance improves.

The major tasks in this phase will include:

Demonstrating performance of the improved ATEG units.
Improving the computational model for the ATEG performance prediction so that new combinations of materials can be used in the future.
Optimizing the SPEAR reactor to minimize mass and cost.
Identifying detailed trajectory and mission info for orbital insertion and Cubesat orbits to gather data from Europa plumes.
Creating a low mass NEP system will open many new opportunities for research in the future. Using smaller rockets will provide flagship class results with much smaller missions. Additionally, the development of the ATEG units and small reactors can provide power to other rovers, surface bases, satellites, or a number of other missions.
Development of the SPEAR probe will show that inexpensive, effective nuclear technologies can be achieved for future space exploration.

Prior Work on Space Nuclear Power and Propulsion

Here is a 2015 presentation – Radioisotope-Based Propulsion System Enabling Exploration with Small Payloads. Nuclear and Emerging Technologies for Space 2015, Albuquerque, New Mexico

24 thoughts on “Lightweight Nuclear Electric Space Propulsion With Ten Times the Power”

  1. Small numbers. Things tend to get out of hand when you try and ram the number up to something useful. Build them is space. No one should care space is radioactive already. You could even launch Thorium or Uranium 238 and use a linear accelerator to make them fissile.

  2. Should look into what it would cost to make fissile material in orbit or on the moon. We are going to need a more powerful energy source for interplanetary exploration. And I doubt people would be too happy about the launching of radioactive material from earth.

  3. As is sadly usual for Brian, he has smooshed together two similar sounding, but fundamentally different articles.

    One article is about a radio-isotope-thermal-electric generator. The other article is about a radio-isotope thermal source with turbine generators strapped to it.

    One uses electric ion drives. The other feeds gas straight through the isotope core to get nuclear-thermal propulsion.

    Hence the confusing text and images.

    And I think he’s buried the lede here. If someone actually does manage a 20% radio-isotope heat to electricity conversion rate, that opens ALL SORTS of cool possibilities. You can run a self charging EV on that. (May have legal difficulties…)

  4. That certainly is a bit odd. Maybe something to due with ATEG’s boron absorbing radiation for power boost, maybe improving reactor local radiation profile? But that still favors putting the shadow shield closer. Maybe the shadow shield composition might be easier to make at that size, or something about it’s composition makes it a convenient structure for the chassis bus?

  5. Please don’t fall for the trick of calling an RTG a reactor. The figure should not call it a nano-reactor, but an RTG.

  6. Then the next pandemic and the next shutdown will yield the same results. On the plus side, it will afford another opportunity for everyone to say the same things.

  7. Is it just me or is it also very small? IMO, go as large an engine as the Starship can carry and as powerful as we can make it. Go big or go home. If this concept works, would it be hard to scale up?

  8. I have no authority and made no choices, but I have been very consistent about my convictions and where I stand on COVID19 – that the lockdown was BS and that it will not be portrayed well in historical context. The history will show it as a profound mistake – mass hysteria.

    Now, get on with it and eat up the spaceX stories. Back to normal now. Chop, chop! On to the next thing.

  9. The threat of tragedy is quickly vaporizing. I can’t wait for the finger-pointing. I want to see people hang for the bad decisions that crashed the economy in a pilot-induced oscillation.

    The best outlook; what guides me: The rain wets me; the sun dries me.

    Get over it. You got suckered – you jumped on the bandwagon.

    Yes, I know. Infirm people are dying and the death rate in NYC tops 200% of expected for the last 3 weeks. Did the virus kill them or their failing kidneys/hearts/livers/lungs? Remember, it was cool to smoke for most of the 20th century. My old Chevy has ashtrays in the back seat.

    Could have handled NYC covid patient spillover in the neighboring states – shipped them to Nebraska if needed.

    We should build a monument out of the hundreds of thousands of ventilators that are coming down the pipeline – use them like bricks – build a cathedral to the god of worry.

  10. His crack team told him it will take 6months to recover, anyone know when in the next election?
    Everyone have their own priorities.

  11. You know why he’s so desperate to re-open the country? All of his real estate properties are shut down, and he’s going rapidly broke. So the next big story will be about how he let people die in order to save his business.

  12. “the next impeachment or whatever”

    Probably going to be “Trump is guilty of mass, premeditated murder!!1!”

  13. Why isn’t the shadow shield next to the reactor so it can be smaller and thus lighter? Isn’t as if the neutron flux/gamma flux is usefully reduced by moving the shadow shield 3.5 meters away from the reactor but the size of the shadow shield (and thus its mass) is greatly increased by being moved 3.5 meters away from the reactor.

  14. For two months literally nothing but COVID19 stories – maybe 6 stories about TESLA or SPACEX – but 35 articles about COVID.

    Now that the news WRT the disease has taken a turn for the better, Brian is back on track with the staple diet of space travel and quantum computers.


    It is very anti-cathartic tho.

    I expect to see a lot more of that as the MSM winds down from this crisis and is calm for a spell before it spins up again on the next impeachment or whatever.

    One thing is for sure. There will be no strong action on climate change based on any ‘scientist’ models of the infinitely complex system of the biosphere.

    Oh sure. We can all notice that the rivers are dirty and the fish and animals are gone* and the soil is running off, but I believe it was all getting better, but slowly.

    *I do not make light of extinction. It pains me greatly.


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