X-SpaceX Raptor designer has ready for development designs for nuclear rocket that will be up to 7 times better than BFR

John Bucknell created the pre-conceptual design for the SpaceX Raptor engine. It will be the advanced full-flow staged combustion rocket engine for the SpaceX BFR. He designed and built the subscale Raptor rocket for proof of concept testing able to test eighty-one configurations of main injector.

John Bucknell says the nuclear turbo rocket technology and his designs are ready for development. The air-breathing nuclear thermal rocket will enable 7 times more payload fraction to be delivered to low-earth orbit and it will have 6 times the ISP (rocket fuel efficiency) as chemical rockets. The rocket will have two to three times the speed and performance of chemical rockets for missions outside of the atmosphere.

UPDATE

Video for the talk is up on a follow-up Nextbigfuture article.

More details

The fully reusable nuclear rocket will be a single stage to orbit system which will be able to make space-based solar power several times cheaper than coal power. Using the 11-meter diameter version of this rocket to build space-based solar power will enable solar power at less than 2 cents per kilowatt-hour.

Besides being cheaper and vastly higher performing that the SpaceX BFR, the Bucknell Nuclear turbo rocket will to do things which the SpaceX BFR cannot.

Bucknell’s proposed air-breathing nuclear thermal rocket propulsion cycle called the Nuclear Thermal Turbo Rocket (NTTR) improves payload fraction to Low Earth Orbit (LEO) by a factor of 5-7 relative to State of the Art chemical rockets.

Mission Average Specific Impulse: 1430 to 1788 sec (About 5-6 times better than 350-400 ISP chemical rockets)

The Nuclear Thermal Turbo Rocket (NTTR) is a supercharged air-augmented nuclear thermal combined cycle rocket architecture.

Nuclear turbo rockets already offer the highest Specific Impulse (Isp) of launch-capable pure rocket propulsion systems, whereas launch to hypersonic turbine combined cycle systems offer far higher Isp. The NTTR combines both modes.

The Turbo Rocket architecture represents a new paradigm for access to space economics.
Large payload fractions of 35-50%, Low Construction Cost and Full Reuse
Cost to LEO: less than $85/kg w/10 flights
Cost to Luna: less than $715/kg w/10 flights
Staged Combustion: Lowest Cost to LEO
Nuclear Thermal: Lowest Cost for Near Earth Return and Larger Payloads to Everywhere

The Turbo Rocket architecture is the first such known to be able to achieve payload fractions to LEO above 44%, representing an order of magnitude improvement over the state of the art.

John answered questions on his air-breathing nuclear thermal rocket last year on Nextbigfuture.

81 thoughts on “X-SpaceX Raptor designer has ready for development designs for nuclear rocket that will be up to 7 times better than BFR”

  1. How would the SCTR do with cryogenic methane, with the same diameter and design benefits (steel/heat shield) as the Starship?

  2. Love the nuclear concept. We really need more nuclear engines, as well as nuclear power. However, Space based power, save for disaster areas and military, is one of the worst ideas going. Look, right now, we have a climate that is heating up due to increased GHG, esp CO2. These trap the heat, and do not allow them to be reflected. Now, we are talking about taking electricity and beaming it to earth. Unless it is 100% efficient, it will mean that it is being converted into heat. Well, beaming will be at best 50% efficient. IOW, this will pump loads of heat into our atmosphere. And considering how CHina continues to build out MASSIVE amounts of coal plants, I could see them easily switching to SBP regardless of the consequences.

  3. Love the nuclear concept. We really need more nuclear engines as well as nuclear power. However Space based power save for disaster areas and military is one of the worst ideas going. Look right now we have a climate that is heating up due to increased GHG esp CO2. These trap the heat and do not allow them to be reflected.Now we are talking about taking electricity and beaming it to earth. Unless it is 100{22800fc54956079738b58e74e4dcd846757aa319aad70fcf90c97a58f3119a12} efficient it will mean that it is being converted into heat. Well beaming will be at best 50{22800fc54956079738b58e74e4dcd846757aa319aad70fcf90c97a58f3119a12} efficient. IOW this will pump loads of heat into our atmosphere. And considering how CHina continues to build out MASSIVE amounts of coal plants I could see them easily switching to SBP regardless of the consequences.

  4. Okay, I read that wrong and thought the SCTR is effectively trying to use a nuclear teakettle to run the turbopumps to get pumped performance without preburning, same as the endrun of using electric pumps on RocketLab’s rocket? So nuclear teakettle has a closed loop helium turbine driving LH2 and LOX turbo pumps, using LH2 turbopump output to cool the helium loop somehow. SCTR seems to be a bit of a combo between SERJ and and NASA’s GTX concept (lots of duct/nozzle pressure tricks to use a rocket chamber nozzle that is vacuum optimized at sea level by effectively increasing ambient to prevent overexpansion) and maybe shades of SCAAT, though GTX pumped unburnt fuel into the duct directly (igniting near the shockwave fronts farther back in the engine), rather than preburner output which will probably ignite immediately after exiting the fan tips. It sorta keeps SERJ’s use of tip drive fan, but rather than an outrunner scenario it is actually exhausting directly from the fan tips. That umbrella gulper mouth inlet still bothers me though, compared to some kind of more traditional translating cone/frustrum inlet setup. Mouth wobble would be harsh. I wonder if you could do a “tip drive” like setup for a RamGen style rampressor as a substitute for the fan, where radial separator blade aft ends end in bluff body fuel (preburner combustion product) injectors.

  5. Okay I read that wrong and thought the SCTR is effectively trying to use a nuclear teakettle to run the turbopumps to get pumped performance without preburning same as the endrun of using electric pumps on RocketLab’s rocket? So nuclear teakettle has a closed loop helium turbine driving LH2 and LOX turbo pumps using LH2 turbopump output to cool the helium loop somehow.SCTR seems to be a bit of a combo between SERJ and and NASA’s GTX concept (lots of duct/nozzle pressure tricks to use a rocket chamber nozzle that is vacuum optimized at sea level by effectively increasing ambient to prevent overexpansion) and maybe shades of SCAAT though GTX pumped unburnt fuel into the duct directly (igniting near the shockwave fronts farther back in the engine) rather than preburner output which will probably ignite immediately after exiting the fan tips. It sorta keeps SERJ’s use of tip drive fan but rather than an outrunner scenario it is actually exhausting directly from the fan tips.That umbrella gulper mouth inlet still bothers me though compared to some kind of more traditional translating cone/frustrum inlet setup. Mouth wobble would be harsh.I wonder if you could do a tip drive”” like setup for a RamGen style rampressor as a substitute for the fan”””” where radial separator blade aft ends end in bluff body fuel (preburner combustion product) injectors.”””

  6. Avoiding a nuclear variant for Earth to LEO deals with the objections I’ve voiced. As I said before, so long as you start the reactor from a stable orbit, I’m fine with using nuclear propulsion.

  7. Avoiding a nuclear variant for Earth to LEO deals with the objections I’ve voiced. As I said before so long as you start the reactor from a stable orbit I’m fine with using nuclear propulsion.

  8. Because the goal of nuclear waste disposal was to make nuclear energy unaffordable, not safe. Otherwise they’d have used Pournelle’s disposal method: Pick an area of desert with next to no rainfall, fence it off with multiple walls and fences adorned with warnings in many languages including pictographs, and just dump the waste there unshielded.

    Anybody stupid enough to ignore the warnings can contribute a decorative skeleton.

  9. As with similar environmental objections, people often don’t grasp the vast difference of scales that makes their objections irrelevant. The amount of energy naturally coming in and leaving Earth completely dwarfs any human energy production. Space based power won’t even move the needle at current global energy use scale. To put some numbers on it, we need to compare natural energy flow to the expected energy flow from these satellites. According to Wikipedia: > [i]Globally, over the course of the year, the Earth system – land surfaces, oceans, and atmosphere – absorbs and then radiates back to space an average of about 240 watts of solar power per square meter.[/i] Earth’s surface area is 510 million km^2, or 510e12 m^2. Multiplying by 240 W/m, we get a total of 1.2e17 W of energy flow over the entire Earth. That’s 120 petawatts. Another article places the average annual solar radiation arriving at the top of Earth’s atmosphere at roughly 1360 W/m^2, which gives a total value of 700 petawatts. This latter value is defined as Kardashev I level. I’m not sure where the difference of over 1000 W/m^2 goes. At least some of is likely absorbed by plants for photosynthesis. Regardless, even the smaller value dwarfs human energy production. For comparison, our total global energy production is just shy of 20 terawatts, or 2e13 W. Four orders of magnitude less than the natural energy flow. Even if we increased our global energy use by a factor of 10, and supplied all of it from space-based solar, that’d still be less than 0.2% of the natural energy flow – hardly enough to affect global temperatures. We’d have to get much closer to Kardashev I level before our waste heat starts becoming a problem. Finally, if we have the technology and logistics to build space solar on that scale, then we also have what it takes to build enough orbital sun shades to balance things out.

  10. As with similar environmental objections people often don’t grasp the vast difference of scales that makes their objections irrelevant. The amount of energy naturally coming in and leaving Earth completely dwarfs any human energy production. Space based power won’t even move the needle at current global energy use scale.To put some numbers on it we need to compare natural energy flow to the expected energy flow from these satellites. According to Wikipedia:> [i]Globally over the course of the year the Earth system – land surfaces oceans and atmosphere – absorbs and then radiates back to space an average of about 240 watts of solar power per square meter.[/i]Earth’s surface area is 510 million km^2 or 510e12 m^2. Multiplying by 240 W/m we get a total of 1.2e17 W of energy flow over the entire Earth. That’s 120 petawatts. Another article places the average annual solar radiation arriving at the top of Earth’s atmosphere at roughly 1360 W/m^2 which gives a total value of 700 petawatts. This latter value is defined as Kardashev I level.I’m not sure where the difference of over 1000 W/m^2 goes. At least some of is likely absorbed by plants for photosynthesis. Regardless even the smaller value dwarfs human energy production.For comparison our total global energy production is just shy of 20 terawatts or 2e13 W. Four orders of magnitude less than the natural energy flow. Even if we increased our global energy use by a factor of 10 and supplied all of it from space-based solar that’d still be less than 0.2{22800fc54956079738b58e74e4dcd846757aa319aad70fcf90c97a58f3119a12} of the natural energy flow – hardly enough to affect global temperatures. We’d have to get much closer to Kardashev I level before our waste heat starts becoming a problem.Finally if we have the technology and logistics to build space solar on that scale then we also have what it takes to build enough orbital sun shades to balance things out.

  11. Bucknell is leveraging off technology developed in the 1960s and abandoned by 1972. Almost 5GW of power was generated in a small package called, I believe, Kiwi or Phoebe. To address the issue of an exploding reactor core, the technologists had to resort to high explosives to test the integrity of the reactor. The core might melt but it would not explode, and the chemical detonation just spread reactor debris all over the place and no radioactivity was released and the ensuing debris was not radioactive. If the core were to drop into the ocean, any subsequent release of radioactivity would be, after some period of time, indistinguishable from ambient levels. If the dropped core were assembled to dissolve rapidly in sea water, the disbursal would be very fast. I have often wondered why such schemes were not adopted to drop nuclear wastes on the mid-ocean volcanic ridges to simply dispose of wastes in a safe manner.

  12. Bucknell is leveraging off technology developed in the 1960s and abandoned by 1972. Almost 5GW of power was generated in a small package called I believe Kiwi or Phoebe. To address the issue of an exploding reactor core the technologists had to resort to high explosives to test the integrity of the reactor. The core might melt but it would not explode and the chemical detonation just spread reactor debris all over the place and no radioactivity was released and the ensuing debris was not radioactive. If the core were to drop into the ocean any subsequent release of radioactivity would be after some period of time indistinguishable from ambient levels. If the dropped core were assembled to dissolve rapidly in sea water the disbursal would be very fast. I have often wondered why such schemes were not adopted to drop nuclear wastes on the mid-ocean volcanic ridges to simply dispose of wastes in a safe manner.

  13. Because the goal of nuclear waste disposal was to make nuclear energy unaffordable, not safe. Otherwise they’d have used Pournelle’s disposal method: Pick an area of desert with next to no rainfall, fence it off with multiple walls and fences adorned with warnings in many languages including pictographs, and just dump the waste there unshielded.

    Anybody stupid enough to ignore the warnings can contribute a decorative skeleton.

  14. We won’t need a nuclear variant for access to Low Earth Orbit – it is more expensive and can come later if we want to go further.

  15. We won’t need a nuclear variant for access to Low Earth Orbit – it is more expensive and can come later if we want to go further.

  16. Review the first paper for detail, but neutron shielding is necessary to prevent propellant heating fore of the reactor, and gamma shielding is all the way around – but thickest fore and large enough in diameter to shield most of tankage. Gamma shield is tungsten carbide – 228mm fore, 48mm all other sides in thickness. Boron Carbide for neutron, inside the gamma – 100mm thick. All told, 6500kg for mass budget for 1GW reactor of 700mm right circular cylinder dimensions – core is only 420kg. Tungsten is strong enough to contain core even if dropped from very high. Payload gets integrated dose of 0.05 rad per launch, ignoring propellant shielding. Observers at 2 mile from launch get zero due to atmospheric shielding, launch pad gets 1 rad per launch at 20 ft.

  17. Review the first paper for detail but neutron shielding is necessary to prevent propellant heating fore of the reactor and gamma shielding is all the way around – but thickest fore and large enough in diameter to shield most of tankage. Gamma shield is tungsten carbide – 228mm fore 48mm all other sides in thickness. Boron Carbide for neutron inside the gamma – 100mm thick. All told 6500kg for mass budget for 1GW reactor of 700mm right circular cylinder dimensions – core is only 420kg. Tungsten is strong enough to contain core even if dropped from very high. Payload gets integrated dose of 0.05 rad per launch ignoring propellant shielding. Observers at 2 mile from launch get zero due to atmospheric shielding launch pad gets 1 rad per launch at 20 ft.

  18. You mention using a shadow shield in your presentation in the link, this means that in every direction *except* the eponymous “shadow” left by this shield the reactor is, effectively, unshielded. If I misunderstand and you are planning on surrounding the reactor with heavy shielding, I want to see your mass budgets for that. Also, even if you are planning on using as much low neutron capture cross-section material as you can, I will still need considerably more convincing that, once the reactor starts operating, you won’t have a potential radioactive witches brew, should there be an accident. We are not talking Kosmos or SNAP sized reactors here, we’re talking gigawatt scale.

  19. You mention using a shadow shield in your presentation in the link this means that in every direction *except* the eponymous shadow”” left by this shield the reactor is”” effectively unshielded. If I misunderstand and you are planning on surrounding the reactor with heavy shielding I want to see your mass budgets for that. Also even if you are planning on using as much low neutron capture cross-section material as you can I will still need considerably more convincing that once the reactor starts operating you won’t have a potential radioactive witches brew should there be an accident. We are not talking Kosmos or SNAP sized reactors here”” we’re talking gigawatt scale.”””

  20. Using the 11-meter diameter version of this rocket to build space-based solar power will enable solar power at less than 2 cents per kilowatt-hour.” In Italy the current price goes from 0,19 €/kWh to 0,48 €/kWh (taxes included). Is it just my opinion the current F9H is good enough to let SPS be competitive with that? And Italy is not the only with such outrageous prices. A lot of small / medium islands )seasteadings in the not far future) have high energy costs because they MUST rely on oil power (or solar with different costs) to produce electricity. Electricity Puerto Rico United States Residential 24.40 cents/kWh 12.99 cents/kWh Commercial 27.97 cents/kWh 10.47 cents/kWh Industrial 22.42 cents/kWh 06.64 cents/kWh I suggest SPS could, initially, target these markets. Another interesting type of market is the military: FOBs need a lot of energy and make a lot of sense to have a power source that can not be seized by the enemy.

  21. Using the 11-meter diameter version of this rocket to build space-based solar power will enable solar power at less than 2 cents per kilowatt-hour.””In Italy the current price goes from 0″”19 €/kWh to 0″”48 €/kWh (taxes included).Is it just my opinion the current F9H is good enough to let SPS be competitive with that?And Italy is not the only with such outrageous prices. A lot of small / medium islands )seasteadings in the not far future) have high energy costs because they MUST rely on oil power (or solar with different costs) to produce electricity.Electricity Puerto Rico United StatesResidential 24.40 cents/kWh 12.99 cents/kWhCommercial 27.97 cents/kWh 10.47 cents/kWhIndustrial 22.42 cents/kWh 06.64 cents/kWhI suggest SPS could”” initially”” target these markets.Another interesting type of market is the military: FOBs need a lot of energy and make a lot of sense to have a power source that can not be seized by the enemy.”””””””

  22. 1) Thank You for the work done. 2) I like the concept and I don’t fear radiations, but the big problem with your solutions is using nuclear energy. It attract a lot of unwanted government attention and regulation. 3) IF (BIG IF) Rossi’s high temperature eCat is commercially released it could solve a lot of problems for the energy source and its management (no radiations, granular control, etc.).

  23. 1) Thank You for the work done.2) I like the concept and I don’t fear radiations but the big problem with your solutions is using nuclear energy. It attract a lot of unwanted government attention and regulation.3) IF (BIG IF) Rossi’s high temperature eCat is commercially released it could solve a lot of problems for the energy source and its management (no radiations granular control etc.).

  24. Seems pointless to have broken down the cost projections as the image shows. The only thing that counts is $/lb to LEO over the lifetime of the vehicle, and it is a figure of merit which should be calculable for all, NTTR, BFR, F9Rb5, etc.

  25. Seems pointless to have broken down the cost projections as the image shows. The only thing that counts is $/lb to LEO over the lifetime of the vehicle and it is a figure of merit which should be calculable for all NTTR BFR F9Rb5 etc.

  26. Several factual errors here: Reactor is heavily shielded – payloads and observers get very small radiation doses. Also, everything is constructed of neutron-transparent materials (primarily carbon fiber composites) and can’t get activated. I am doing this work strictly voluntarily for the betterment of all, and it would be horribly wrong to trade performance for safety. The primary message from this latest publication is that there are multiple solutions to access to orbit, and the Turbo Rocket in non-nuclear form is the least expensive by far. I will upload the video of the presentation in the next few days.

  27. Several factual errors here: Reactor is heavily shielded – payloads and observers get very small radiation doses. Also everything is constructed of neutron-transparent materials (primarily carbon fiber composites) and can’t get activated. I am doing this work strictly voluntarily for the betterment of all and it would be horribly wrong to trade performance for safety.The primary message from this latest publication is that there are multiple solutions to access to orbit and the Turbo Rocket in non-nuclear form is the least expensive by far.I will upload the video of the presentation in the next few days.

  28. There are a number of issues that I think John either fails to address or else intentionally diverts attention from. The fact that he is planning on running an unshielded reactor in the atmosphere, combined with the fact that, once the reactor starts running, neutron activation will make the whole engine into a radioactive nightmare, tasks like loading the rocket, to say nothing of maintaining the engine or any other part of the rocket,become a mite… tricky. And while it is true that explosions aren’t as easy to experience as in chemical rocket motors, the vehicle cracking up and spreading radioactive crap all over the place like a mobile Chernobyl IS a failure mode that is all too easy to envision. I do think that nuclear engines have their place in space travel, but that place is not Earth to LEO. This is particularly true now that SpaceX seems on the way to achieving reusability by successive approximation. Tell me that you are only going to fire up your reactor once you have already achieved stable orbit and now want to go somewhere else (the Moon, Mars, etc.) and I won’t have any problem with that. I would also point out that, unlike in orbit, on Earth there might be objects around which could scatter the radiation, potentially defeating the effect of a shadow shield. In addition I have a question about how he plans to keep the engine from melting itself to (radioactive) slag when it is not producing thrust. In the linked article he talks about a gigawatt (thermal) reactor, scaling up to 5 gigawatts for a single stage to Mars variant, that is a f*ck of a lot of waste heat to deal with.

  29. There are a number of issues that I think John either fails to address or else intentionally diverts attention from. The fact that he is planning on running an unshielded reactor in the atmosphere combined with the fact that once the reactor starts running neutron activation will make the whole engine into a radioactive nightmare tasks like loading the rocket to say nothing of maintaining the engine or any other part of the rocketbecome a mite… tricky. And while it is true that explosions aren’t as easy to experience as in chemical rocket motors the vehicle cracking up and spreading radioactive crap all over the place like a mobile Chernobyl IS a failure mode that is all too easy to envision.I do think that nuclear engines have their place in space travel but that place is not Earth to LEO. This is particularly true now that SpaceX seems on the way to achieving reusability by successive approximation. Tell me that you are only going to fire up your reactor once you have already achieved stable orbit and now want to go somewhere else (the Moon Mars etc.) and I won’t have any problem with that. I would also point out that unlike in orbit on Earth there might be objects around which could scatter the radiation potentially defeating the effect of a shadow shield. In addition I have a question about how he plans to keep the engine from melting itself to (radioactive) slag when it is not producing thrust. In the linked article he talks about a gigawatt (thermal) reactor scaling up to 5 gigawatts for a single stage to Mars variant that is a f*ck of a lot of waste heat to deal with.

  30. AFAIK there was $18.8m funding from NASA with BWXT Nuclear Energy to help design the reactor, which I believe helped to get the concept to the current state when John published the powerpoint presentation and is asking for comments and views to his design which according to his own words is “ready to be made”.

  31. AFAIK there was $18.8m funding from NASA with BWXT Nuclear Energy to help design the reactor which I believe helped to get the concept to the current state when John published the powerpoint presentation and is asking for comments and views to his design which according to his own words is ready to be made””.”””

  32. What if one blows up in the atmosphere? Won’t it contaminate the atmosphere for a long time and have long term effects?

  33. What if one blows up in the atmosphere? Won’t it contaminate the atmosphere for a long time and have long term effects?

  34. I don’t mean to be a pessimist, but has there been any news of funding for this development? In my cursory glance through Google I haven’t been able to find any other mention of this concept before July 17th of 2017. Just wondering if anyone has heard anything new over the last year?

  35. I don’t mean to be a pessimist but has there been any news of funding for this development? In my cursory glance through Google I haven’t been able to find any other mention of this concept before July 17th of 2017. Just wondering if anyone has heard anything new over the last year?

  36. John answered the question last year. Link was at the bottom of this article. Question set 1. Is the rocket reusable? Is it intended for reuse? What happens if the rocket explodes in flight? (how strong is fuel containment) How much gamma/neutron radiation near the launch pad at takeoff? Any numbers for a single stage to Mars surface mission profile? Question 1 answer Exploding is not a thing with a monopropellant rocket (how often do aircraft explode?). As for fuel containment/reactor structure – if the rocket were to have a RUD event the core/shielding is largely metallic with a tungsten carbide gamma shield (six of the seven tons of core mass). It would put a large dent in anything it landed on, but that is a risk with any rocket (ie why launches are over water). The radiation shielding included in the rocket is probably overkill – it keeps exposure to both payloads and launch site below terrestrial background radiation (0.2 rad/y) if less than five flights a year are flown. Gamma shielding is fully surrounding the reactor (tungsten carbide), and lithium hydride for neutron fore for payload protection. Details in the paper. Question 2. How is exhaust radioactivity prevented or dealt with? Would I be correct to say that the hydrogen propellant doesn’t stay long enough in the reactor to be transmuted to tritium, and any fission fragments are contained by the fuel cladding? Answer. What exhaust radioactivity? There are no fission fragments with this fuel arrangement as core temperature is kept low for effectively zero material loss. Hydrogen spends milliseconds in the core, so mass of tritium generated is negligible. 3. What are the risks for catastrophic failures inside the atmosphere, and how would they be dealt with? See answer 1 above

  37. John answered the question last year. Link was at the bottom of this article.Question set 1. Is the rocket reusable? Is it intended for reuse?What happens if the rocket explodes in flight? (how strong is fuel containment)How much gamma/neutron radiation near the launch pad at takeoff?Any numbers for a single stage to Mars surface mission profile?Question 1 answerExploding is not a thing with a monopropellant rocket (how often do aircraft explode?). As for fuel containment/reactor structure – if the rocket were to have a RUD event the core/shielding is largely metallic with a tungsten carbide gamma shield (six of the seven tons of core mass). It would put a large dent in anything it landed on but that is a risk with any rocket (ie why launches are over water).The radiation shielding included in the rocket is probably overkill – it keeps exposure to both payloads and launch site below terrestrial background radiation (0.2 rad/y) if less than five flights a year are flown. Gamma shielding is fully surrounding the reactor (tungsten carbide) and lithium hydride for neutron fore for payload protection. Details in the paper.Question 2. How is exhaust radioactivity prevented or dealt with? Would I be correct to say that the hydrogen propellant doesn’t stay long enough in the reactor to be transmuted to tritium and any fission fragments are contained by the fuel cladding?Answer. What exhaust radioactivity? There are no fission fragments with this fuel arrangement as core temperature is kept low for effectively zero material loss. Hydrogen spends milliseconds in the core so mass of tritium generated is negligible.3. What are the risks for catastrophic failures inside the atmosphere and how would they be dealt with?See answer 1 above”

  38. An Air-Breathing Nuclear Engine has one small problem: it spews radioactive fragments of the core into earth’s atmosphere. Hence, these engines have been called “flying Chernobyls”, and are prohibited by Nuclear test Ban treaties. Solving the pollution problem is a good idea, but would involve a lot of expensive development.

  39. An Air-Breathing Nuclear Engine has one small problem: it spews radioactive fragments of the core into earth’s atmosphere. Hence these engines have been called flying Chernobyls””” and are prohibited by Nuclear test Ban treaties. Solving the pollution problem is a good idea”” but would involve a lot of expensive development.”””

  40. Bucknell is leveraging off technology developed in the 1960s and abandoned by 1972. Almost 5GW of power was generated in a small package called, I believe, Kiwi or Phoebe. To address the issue of an exploding reactor core, the technologists had to resort to high explosives to test the integrity of the reactor. The core might melt but it would not explode, and the chemical detonation just spread reactor debris all over the place and no radioactivity was released and the ensuing debris was not radioactive. If the core were to drop into the ocean, any subsequent release of radioactivity would be, after some period of time, indistinguishable from ambient levels. If the dropped core were assembled to dissolve rapidly in sea water, the disbursal would be very fast. I have often wondered why such schemes were not adopted to drop nuclear wastes on the mid-ocean volcanic ridges to simply dispose of wastes in a safe manner.

  41. As with similar environmental objections, people often don’t grasp the vast difference of scales that makes their objections irrelevant. The amount of energy naturally coming in and leaving Earth completely dwarfs any human energy production. Space based power won’t even move the needle at current global energy use scale.

    To put some numbers on it, we need to compare natural energy flow to the expected energy flow from these satellites. According to Wikipedia:

    > [i]Globally, over the course of the year, the Earth system – land surfaces, oceans, and atmosphere – absorbs and then radiates back to space an average of about 240 watts of solar power per square meter.[/i]

    Earth’s surface area is 510 million km^2, or 510e12 m^2. Multiplying by 240 W/m, we get a total of 1.2e17 W of energy flow over the entire Earth. That’s 120 petawatts. Another article places the average annual solar radiation arriving at the top of Earth’s atmosphere at roughly 1360 W/m^2, which gives a total value of 700 petawatts. This latter value is defined as Kardashev I level.

    I’m not sure where the difference of over 1000 W/m^2 goes. At least some of is likely absorbed by plants for photosynthesis. Regardless, even the smaller value dwarfs human energy production.

    For comparison, our total global energy production is just shy of 20 terawatts, or 2e13 W. Four orders of magnitude less than the natural energy flow. Even if we increased our global energy use by a factor of 10, and supplied all of it from space-based solar, that’d still be less than 0.2% of the natural energy flow – hardly enough to affect global temperatures. We’d have to get much closer to Kardashev I level before our waste heat starts becoming a problem.

    Finally, if we have the technology and logistics to build space solar on that scale, then we also have what it takes to build enough orbital sun shades to balance things out.

  42. Love the nuclear concept. We really need more nuclear engines, as well as nuclear power.

    However, Space based power, save for disaster areas and military, is one of the worst ideas going.
    Look, right now, we have a climate that is heating up due to increased GHG, esp CO2. These trap the heat, and do not allow them to be reflected.
    Now, we are talking about taking electricity and beaming it to earth.
    Unless it is 100% efficient, it will mean that it is being converted into heat. Well, beaming will be at best 50% efficient. IOW, this will pump loads of heat into our atmosphere.
    And considering how CHina continues to build out MASSIVE amounts of coal plants, I could see them easily switching to SBP regardless of the consequences.

  43. Okay, I read that wrong and thought the SCTR is effectively trying to use a nuclear teakettle to run the turbopumps to get pumped performance without preburning, same as the endrun of using electric pumps on RocketLab’s rocket? So nuclear teakettle has a closed loop helium turbine driving LH2 and LOX turbo pumps, using LH2 turbopump output to cool the helium loop somehow.
    SCTR seems to be a bit of a combo between SERJ and and NASA’s GTX concept (lots of duct/nozzle pressure tricks to use a rocket chamber nozzle that is vacuum optimized at sea level by effectively increasing ambient to prevent overexpansion) and maybe shades of SCAAT, though GTX pumped unburnt fuel into the duct directly (igniting near the shockwave fronts farther back in the engine), rather than preburner output which will probably ignite immediately after exiting the fan tips. It sorta keeps SERJ’s use of tip drive fan, but rather than an outrunner scenario it is actually exhausting directly from the fan tips.

    That umbrella gulper mouth inlet still bothers me though, compared to some kind of more traditional translating cone/frustrum inlet setup. Mouth wobble would be harsh.

    I wonder if you could do a “tip drive” like setup for a RamGen style rampressor as a substitute for the fan, where radial separator blade aft ends end in bluff body fuel (preburner combustion product) injectors.

  44. Avoiding a nuclear variant for Earth to LEO deals with the objections I’ve voiced. As I said before, so long as you start the reactor from a stable orbit, I’m fine with using nuclear propulsion.

  45. Review the first paper for detail, but neutron shielding is necessary to prevent propellant heating fore of the reactor, and gamma shielding is all the way around – but thickest fore and large enough in diameter to shield most of tankage.

    Gamma shield is tungsten carbide – 228mm fore, 48mm all other sides in thickness. Boron Carbide for neutron, inside the gamma – 100mm thick. All told, 6500kg for mass budget for 1GW reactor of 700mm right circular cylinder dimensions – core is only 420kg. Tungsten is strong enough to contain core even if dropped from very high.

    Payload gets integrated dose of 0.05 rad per launch, ignoring propellant shielding. Observers at 2 mile from launch get zero due to atmospheric shielding, launch pad gets 1 rad per launch at 20 ft.

  46. You mention using a shadow shield in your presentation in the link, this means that in every direction *except* the eponymous “shadow” left by this shield the reactor is, effectively, unshielded. If I misunderstand and you are planning on surrounding the reactor with heavy shielding, I want to see your mass budgets for that. Also, even if you are planning on using as much low neutron capture cross-section material as you can, I will still need considerably more convincing that, once the reactor starts operating, you won’t have a potential radioactive witches brew, should there be an accident. We are not talking Kosmos or SNAP sized reactors here, we’re talking gigawatt scale.

  47. “Using the 11-meter diameter version of this rocket to build space-based solar power will enable solar power at less than 2 cents per kilowatt-hour.”

    In Italy the current price goes from 0,19 €/kWh to 0,48 €/kWh (taxes included).
    Is it just my opinion the current F9H is good enough to let SPS be competitive with that?

    And Italy is not the only with such outrageous prices. A lot of small / medium islands )seasteadings in the not far future) have high energy costs because they MUST rely on oil power (or solar with different costs) to produce electricity.

    Electricity Puerto Rico United States
    Residential 24.40 cents/kWh 12.99 cents/kWh
    Commercial 27.97 cents/kWh 10.47 cents/kWh
    Industrial 22.42 cents/kWh 06.64 cents/kWh

    I suggest SPS could, initially, target these markets.

    Another interesting type of market is the military: FOBs need a lot of energy and make a lot of sense to have a power source that can not be seized by the enemy.

  48. 1) Thank You for the work done.

    2) I like the concept and I don’t fear radiations, but the big problem with your solutions is using nuclear energy. It attract a lot of unwanted government attention and regulation.

    3) IF (BIG IF) Rossi’s high temperature eCat is commercially released it could solve a lot of problems for the energy source and its management (no radiations, granular control, etc.).

  49. Seems pointless to have broken down the cost projections as the image shows. The only thing that counts is $/lb to LEO over the lifetime of the vehicle, and it is a figure of merit which should be calculable for all, NTTR, BFR, F9Rb5, etc.

  50. Several factual errors here: Reactor is heavily shielded – payloads and observers get very small radiation doses. Also, everything is constructed of neutron-transparent materials (primarily carbon fiber composites) and can’t get activated.

    I am doing this work strictly voluntarily for the betterment of all, and it would be horribly wrong to trade performance for safety.

    The primary message from this latest publication is that there are multiple solutions to access to orbit, and the Turbo Rocket in non-nuclear form is the least expensive by far.

    I will upload the video of the presentation in the next few days.

  51. There are a number of issues that I think John either fails to address or else intentionally diverts attention from. The fact that he is planning on running an unshielded reactor in the atmosphere, combined with the fact that, once the reactor starts running, neutron activation will make the whole engine into a radioactive nightmare, tasks like loading the rocket, to say nothing of maintaining the engine or any other part of the rocket,become a mite… tricky. And while it is true that explosions aren’t as easy to experience as in chemical rocket motors, the vehicle cracking up and spreading radioactive crap all over the place like a mobile Chernobyl IS a failure mode that is all too easy to envision.

    I do think that nuclear engines have their place in space travel, but that place is not Earth to LEO. This is particularly true now that SpaceX seems on the way to achieving reusability by successive approximation. Tell me that you are only going to fire up your reactor once you have already achieved stable orbit and now want to go somewhere else (the Moon, Mars, etc.) and I won’t have any problem with that. I would also point out that, unlike in orbit, on Earth there might be objects around which could scatter the radiation, potentially defeating the effect of a shadow shield. In addition I have a question about how he plans to keep the engine from melting itself to (radioactive) slag when it is not producing thrust. In the linked article he talks about a gigawatt (thermal) reactor, scaling up to 5 gigawatts for a single stage to Mars variant, that is a f*ck of a lot of waste heat to deal with.

  52. AFAIK there was $18.8m funding from NASA with BWXT Nuclear Energy to help design the reactor, which I believe helped to get the concept to the current state when John published the powerpoint presentation and is asking for comments and views to his design which according to his own words is “ready to be made”.

  53. How it will blow up? Another answer from John: “Exploding is not a thing with a monopropellant rocket. As for fuel containment/reactor structure – if the rocket were to have a RUD (Rapid Unscheduled Disassembly) event the core/shielding is largely metallic with a tungsten carbide gamma shield (six of the seven tons of core mass). It would put a large dent in anything it landed on, but that is a risk with any rocket (ie why launches are over water).”

  54. The system didn’t published the link. But it is the same as the one at the end of the article. “John answered questions on his air-breathing nuclear thermal rocket last year on Nextbigfuture”

  55. I don’t mean to be a pessimist, but has there been any news of funding for this development? In my cursory glance through Google I haven’t been able to find any other mention of this concept before July 17th of 2017. Just wondering if anyone has heard anything new over the last year?

  56. John answered the question last year. Link was at the bottom of this article.

    Question set 1. Is the rocket reusable? Is it intended for reuse?
    What happens if the rocket explodes in flight? (how strong is fuel containment)
    How much gamma/neutron radiation near the launch pad at takeoff?
    Any numbers for a single stage to Mars surface mission profile?

    Question 1 answer

    Exploding is not a thing with a monopropellant rocket (how often do aircraft explode?). As for fuel containment/reactor structure – if the rocket were to have a RUD event the core/shielding is largely metallic with a tungsten carbide gamma shield (six of the seven tons of core mass). It would put a large dent in anything it landed on, but that is a risk with any rocket (ie why launches are over water).

    The radiation shielding included in the rocket is probably overkill – it keeps exposure to both payloads and launch site below terrestrial background radiation (0.2 rad/y) if less than five flights a year are flown. Gamma shielding is fully surrounding the reactor (tungsten carbide), and lithium hydride for neutron fore for payload protection. Details in the paper.
    Question 2. How is exhaust radioactivity prevented or dealt with? Would I be correct to say that the hydrogen propellant doesn’t stay long enough in the reactor to be transmuted to tritium, and any fission fragments are contained by the fuel cladding?

    Answer. What exhaust radioactivity? There are no fission fragments with this fuel arrangement as core temperature is kept low for effectively zero material loss. Hydrogen spends milliseconds in the core, so mass of tritium generated is negligible.

    3. What are the risks for catastrophic failures inside the atmosphere, and how would they be dealt with?

    See answer 1 above

  57. Seems that this is pretty much sorted already: https://www.nextbigfuture.com/2018/02/nasa-has-small-18-8-million-nuclear-thermal-rocket-research-project.html
    “How is exhaust radioactivity prevented or dealt with?

    Answer. What exhaust radioactivity? There are no fission fragments with this fuel arrangement as core temperature is kept low for effectively zero material loss. Hydrogen spends milliseconds in the core, so mass of tritium generated is negligible.”

  58. An Air-Breathing Nuclear Engine has one small problem: it spews radioactive fragments of the core into earth’s atmosphere. Hence, these engines have been called “flying Chernobyls”, and are prohibited by Nuclear test Ban treaties. Solving the pollution problem is a good idea, but would involve a lot of expensive development.

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