Nuclear Wave Rotor Propulsion Could Get Ten Times Chemical Rocket Speeds

Nuclear Thermal Propulsion (NTP) is one of the best options for manned missions throughout the solar system with over double the ISP of chemical rockets. A new NASA NIAC study will look at improved nuclear propulsion with a Wave Rotor combined with Nuclear Electric. This could enable four times the ISP of nuclear thermal and up to ten times the ISP of chemical rockets while also having high thrust levesl.

The state-of-the-art NTP cycle is based on solid core Nuclear Engine for Rocket Vehicle Application (NERVA) class technology that is envisioned to provide a specific impulse (Isp) of 900 seconds doubling chemical rocket performance (450 seconds). Even with this impressive increase, the NTP NERVA designs still have issues providing adequate initial to final mass fractions for high DeltaV missions.

Nuclear Electric Propulsion (NEP) can provide extremely high Isp (over 10,000 seconds) but with only low thrust and limits on mass to power ratios. The need for an electric power source also adds the issue of heat rejection in space where thermal energy conversion is at best 30-40% under ideal conditions.

A novel Wave Rotor (WR) topping cycle is proposed that promises to deliver similar thrust as NERVA class NTP propulsion, but with Isp in the 1400-2000 second range. Coupled with an NEP cycle, the duty cycle Isp can further be increased (1800-4000 seconds) with minimal addition of dry mass. This bimodal design enables the fast transit for manned missions (45 days to Mars) and revolutionizes the deep space exploration of our solar system.

22 thoughts on “Nuclear Wave Rotor Propulsion Could Get Ten Times Chemical Rocket Speeds”

  1. Maybe I’m wrong but this looks exactly like a wave rotor jet engine. The seals are the problem in this. They can get them to work…for a little while.

  2. This should be something Musk should ask our self-interested legislators to partner up with. Delivery of reactor core elements to lunar orbit would keep their vanity rocket viable. SLS, being a creature of government, already meets government requirements for cis-lunar deliveries of sensitive materials and Federal employees. DOE would have a prominent role, and NASA would be overseeing some major construction project.
    Plenty of graft to go around.

    • Until Musk actually achieves moon landings, please stop acting like he’s the only one that knows how to do it. This cult of Elon Musk worship is ridiculous.

  3. There was also Project Timberwind. How useful would that have been for civilian space exploration?

    “For a number of reasons, Timber Wind has a legendary status among people familiar with NTRs, but isn’t well reported on, and a lot of confusion has built up around the project. It’s also interesting in that it was an incredibly (and according to the US Office of the Inspector General, overly) classified program, which means that there’s still a lot we don’t know about this program 30 years later.”


  4. So, is the MEGA drive going to end up as just another false lead?

    “Called a Mach-Effect Gravitational Assist (MEGA) drive, the device only requires a power source to gain thrust.

    Preliminary trials have shown mixed results. Woodward himself was able to demonstrate only a modest amount of thrust, while other teams tried to replicate his experiments with little or no thrust.”


    • I don’t think it’s any accident that basically all tests of these sorts of ‘drives” fail basic standards for experimental design for measuring tiny forces.

      The Cavendish experiment in 1797 was able to measure the gravitational attraction between two iron balls in a lab. If you know anything about physics, you know that required exquisite delicacy. Techniques that were developed since, and are now in the realm of a good HS science fair experiment, are capable of measuring the photon pressure of an LED.

      And yet you continually see crappy experimental design for tests of ‘reactionless drives’.

      I’ve been forced to conclude that if the people doing these tests are not outright frauds, they’re self-sabotaging to avoid definitively proving that nothing is really going on.

  5. DARPA is also collaborating with NASA on new propulsion technology:

    Watch Live: NASA and DARPA Discuss New Advanced Propulsion Tech

    “The 2023 American Institute of Aeronautics and Astronautics (AIAA) SciTech Forum is officially underway in National Harbor, Maryland. The theme for this year’s confab is to “explore the frontiers of aerospace,” and it will run from today through to Friday at the Gaylord National Resort & Convention Center. Forum speakers will touch upon the future of space and planetary exploration, aeronautics, climate research, and Earth sciences, among other topics.”


  6. The old NERVA design was rated at 4GW of power at a mass of only 8600 kg. That’s a specific power of 470 kW/kg…if there was a system to convert that thermal energy into electricity that was massless. That’s why systems like Kilopower have a max specific power of only 6 watts per kg. Very little mass comes from the heat source. The rest is shielding, heat pipes, and Stirling engine for extracting useful work from the reactor. Having a light -weight system to generate electricity from the NTR reactor would provide a lot of power for electric propulsion systems.

  7. What we need is to mass-produce and used nuclear rocket engines. We have been looking at them for over fifty years. They shouldn’t be that complex.

    • At best NTP is an incremental improvement over burning hydrolox, and the benefit can’t be fully realized because of material science issues, which is ALWAYS the case with high energy extensions of current nuclear technology (from MSRs to NTP).

      Q. Why don’t we do X?
      A. Because it will quickly melt/foul/erode/break and always… make a mess.

      With NTP, the power to weight ratio is similar to an M1A2 battle tank.

      BWXT with a $100M DOD grant may eventually re-develop a 4GWt NTP core (cermet or TRISO) the size of a washing machine that will heat LH2 from 20K to nearly whatever white hot surface temperature is possible with a solid heating element… for about as long as a top fuel drag racing motor will make 3000 PS out of a 10L v8 on nitromethane (not long). How durable is an incandescent lamp filament? Not very.

      I personally wouldn’t want to be in the same zip code as an NTP rocket – any kind of flow instability or surging changes nuclear power. Imagine the system choking/chugging drying/wetting with a moderator and temperature gradients of 2000K. Moronic.

      We don’t even have a mission that needs the incremental improvement in ISP. We have lots of missions that need a quantum leap in propulsion and not many that need to double ISP at the expense of adding an expensive, super-high-powered, super heavy liability, super regulated power source.

      I know, I know. Conquer Mars, yada yada. Go for it Musk.

  8. Sadly, none of the accounts of this I’ve found so far give any more detail than the stub of a report above. Which is to say, basically nothing but some buzz words.

    • Strange, looks like it chops the flow through the nozzle, but the diagram doesn’t even show where it fits. Could it be that Salvatore Pais works for NASA now? Looks intentionally vague and misleading, or worse (lazy).

      • Going on the tiny bit of information provided, the engine is “bimodal”, which is to say it can run in two different modes.

        They reference nuclear thermal propulsion, where you’re using the reactor to heat reaction fluid and spewing it out the back. NERVA, basically.

        They also reference nuclear electric, where the reactor feeds power into an ion engine, VASMR, or something similar.

        So, putting this together, what we at first glance appear to have is a proposal to use the same reactor in a NERVA mode when high thrust is needed, and at other times in a power producing mode driving a plasma thruster, for a much higher ISP but lower thrust.

        But the wave rotor topping cycle has no use in that interpretation.

        A wave rotor topping cycle essentially uses coupled oscillations to concentrate energy from one flow into another.

        So, maybe the idea here is that when not needing the high thrust, you run most of the gas on a closed cycle through the reactor, and use the topping cycle to boost the temperature of a small portion of it for exhaust purposes, achieving nuclear electric like ISP without the power conversion.

        But for this to actually work you WOULD have to recirculate and cool most of the flow through the reactor; If you dumped it instead there would be no reduction in mass flow out of the rocket, and thus no gain in ISP; You can’t boost ISP by just redistributing energy inside the mass flow, if you’re dumping all of it.

        The illustration shows no cooling fins. Really, it’s just a stock NERVA illustration and a stock wave rotor topping cycle illustration pasted together.

        No details, and they really cheaped out on the illustrations. This is not giving me warm feelings of trust that there’s substance here.

        • Allegedly the wave rotor topping cycle is a replacement for the LH2 turbopump at twice the efficiency (engine bleed driven wave rotor compressor complex versus engine bleed driving a conventional rocket turbopump).

          • Doubling the efficiency of the turbopump isn’t going to significantly increase ISP, though. It’s not consistent with the claims they’re making.

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