Nuclear Powered Spacecraft

[X-39]

Nuclear Technology Set to Propel and Power Future Space Missions, IAEA Panel Says

Humanity is poised to embark on a new age of space travel to Mars, our solar system and beyond as nuclear power and related technologies promise to make interplanetary missions faster, more efficient and economical. These were the conclusions of a panel of international experts from the public...

www.iaea.org

Nuclear Technology Set to Propel and Power Future Space Missions, IAEA Panel Says​

Wolfgang Picot, IAEA Office of Public Information and Communication
Feb 18 2022

Humanity is poised to embark on a new age of space travel to Mars, our solar system and beyond as nuclear power and related technologies promise to make interplanetary missions faster, more efficient and economical. These were the conclusions of a panel of international experts from the public and private sectors at this week’s IAEA webinar, “Atoms for Space: Nuclear Systems for Space Exploration”.


Advances in both nuclear fission and fusion will be indispensable for deep-space travel, they agreed, also highlighting that nuclear energy could supply electricity for onboard systems and instrumentation, and power a sustained human presence on celestial bodies in the solar system[...]

[...]Rockets lifting off from Earth will depend on chemical fuels for the foreseeable future. However, once in orbit, nuclear engines could take over and provide propulsion to accelerate spacecraft through space.


“Crewed interplanetary missions of the future will almost certainly require propulsion systems with performance levels greatly exceeding that of today’s best chemical engines,” said William Emrich, former Lead Project Engineer at NASA, adding that a solid candidate to be used for space travel is nuclear thermal propulsion (NTP).


In NTP, a nuclear fission reactor heats up a liquid propellant, like hydrogen. The heat converts the liquid into a gas, which expands through a nozzle to provide thrust and propel a spacecraft. The advantages of NTP are that space flights would need to lift less fuel into space, and NTP engines would reduce trip times – cutting travel time to Mars by up to 25 per cent compared traditional chemical rockets. Reduced time in space also reduces astronauts’ exposure to cosmic radiation.


Nuclear electric propulsion (NEP), on the other hand, is an option in which the thrust is provided by converting the thermal energy from a nuclear reactor into electrical energy, eliminating the associated NTP needs and limitations of storing propellants onboard. In NEP, the thrust is lower but continuous, and the fuel efficiency far greater, resulting in a higher speed and potentially over 60 per cent reduction in transit time to Mars compared to traditional chemical rockets.

An NEP system being developed by Ad Astra Rocket Company, the Variable Specific Impulse Magnetoplasma Rocket (VASIMR), is a plasma rocket in which electric fields heat and accelerate a propellant, forming a plasma, and magnetic fields direct the plasma in the proper direction as it is ejected from the engine, creating thrust for the spacecraft. Unlike traditional NEP, the VASIMR design would enable the processing of large amounts of power while retaining the high fuel efficiency that characterizes electric rockets.[...]


[...]“In the near term, we envision the VASIMR engine supporting a wide array of high-power applications from solar electric in cislunar space, to nuclear-electric in interplanetary space,” said Franklin Chang Díaz, CEO of Ad Astra Rocket Company. “On a longer term, the VASIMR could be a precursor to future fusion rockets still in the conceptual stage,” he added.

 

[X-39]

DIU selects nuclear-powered spacecraft designs for 2027 demonstrations​

by Sandra Erwin — May 17, 2022

Artist rendering of Ultra Safe Nuclear spacecraft selected by the Defense Innovation Unit. Credit: DIU

DIU's small spacecraft demonstrations will complement the work being done by DARPA and NASA in nuclear propulsion for larger spacecraft

WASHINGTON – The Defense Innovation Unit announced May 17 it selected Ultra Safe Nuclear Corp. and Avalanche Energy to develop small nuclear-powered spacecraft for in-space demonstrations planned for 2027.

DIU, a Silicon Valley-based Pentagon organization that works with commercial industries and startups, awarded both companies “other transaction” contracts to demonstrate nuclear propulsion and power technology for future DoD space missions. OT contracts, increasingly used in military space projects, are negotiated faster than traditional defense procurements.

The selection of Ultra Safe Nuclear and Avalanche comes just seven months after DIU issued a solicitation for small nuclear-powered engines for space missions beyond Earth orbit.

Seattle-based Ultra Safe Nuclear will demonstrate a chargeable, encapsulated nuclear radioisotope battery called EmberCore.

Avalanche Energy, a venture-backed fusion energy startup also based in Seattle, developed a handheld micro-fusion reactor called Orbitron. “Compared to other fusion concepts, Orbitron devices are promising for space applications as they may be scaled down in size and enable their use as both a propulsion and power source,” said DIU.

Ultra Safe Nuclear last year won a contract from the Idaho National Laboratory to develop a nuclear thermal propulsion reactor concept for a NASA space exploration mission. The company also is a subcontractor to General Atomics and Blue Origin in the first phase of the Demonstration Rocket for Agile Cislunar Operations (DRACO) program overseen by the Defense Advanced Research Projects Agency.

DARPA plans to launch the DRACO nuclear thermal propulsion demonstration in 2025.

Air Force Maj. Ryan Weed, DIU’s program manager for nuclear advanced propulsion and power, said the two small spacecraft prototypes funded by DIU complement the work being done by DARPA and NASA on nuclear propulsion for larger spacecraft.

“DIU’s program is targeted at highly maneuverable, small spacecraft using fusion and radioisotopes,” Weed said. “Bottom line, chemical and solar-based systems won’t provide the power needed for future DoD missions.”

Nuclear technology has traditionally been government-developed and operated, Weed said, “but we have discovered a thriving ecosystem of commercial companies, including startups, innovating in space.”

DIU selects nuclear-powered spacecraft designs for 2027 demonstrations - SpaceNews

The Defense Innovation Unit announced May 17 it selected Ultra Safe Nuclear Corp. and Avalanche to develop small nuclear-powered spacecraft for in-space demonstrations planned for 2027.

spacenews.com

 

[Forest Green]

Wayback Machine

 

[NERVA]

http://ralph.open-aerospace.org/PDF/2003.01.23%20-%20MMO%20Final%20Report%20Summary.pdf

Link does not work for me. Getting a 'site can not be reached' message.

 

[Forest Green]

http://ralph.open-aerospace.org/PDF/2003.01.23%20-%20MMO%20Final%20Report%20Summary.pdf

Link does not work for me. Getting a 'site can not be reached' message.

Should work now.

 

[Forest Green]

https://ntrs.nasa.gov/api/citations/20170001817/downloads/20170001817.pdf

Pulsed Fission-Fusion
Specific
Impulse 20,000 sec
Exhaust
Velocity 196,000 m/s
Thrust 29,400 N
Thrust
Power 2.88 GW
Specific
Power 96 kW/kg
Fuel-
Propellant U-235 + D-T

 

[Forest Green]

https://www.nasa.gov/sites/default/files/atoms/files/niac_2011_phasei_werka_ffre_tagged.pdf

https://ntrs.nasa.gov/api/citations/20190018063/downloads/20190018063.pdf

 

[Archibald]

Fission reactor output is mostly fission fragments, plus prompt neutrons kinetic energy.

1-NTR like NERVA use fission fragments to heat LH2 fuel. They run into the 2nd law of thermodynamics and performance sucks. Unless unworkable GCNR. They have no use for the small percentage of energy related to prompt neutrons.

2-FFR : FISSION FRAGMENT ROCKET - Chapline, Werka, Rubbia.
No more LH2 to heat: fission fragments shoot through a nozzle. Specific impulse: 50 000 to 1 million seconds with some kg of thrust. https://en.wikipedia.org/wiki/Fission-fragment_rocket

3-PNTR PULSED NTR - Pr Arias, University of Catalonia
Pulse the reactor like a TRIGA. Lots of prompt neutrons with kinetic energy aplenty. Back to heating LH2, but at atomic level 2nd law of thermodynamics doesn't apply. End result: same as above but cleaner and with high thrust.

Pretty interesting to think 2 and 3 just rearrange 1 three basic elements
- LH2 fuel to heat
- fission fragments energy
- prompt neutron kinetic energy

Also interesting: FFR and PNTR have the same goal as GCNR, that is: busting solid core NTR limits. But they take a different path.

 

[Archibald]

Sometimes I wonder if a bimodal FFR / PNTR drive could be build. Problem: PNTR needs TRIGA pulses while FFR prefers Americium 241 to classic uranium or plutonium.
But imagine: FFR for low thrust cruises between planets; then PNTR for high thrust inside gravity wells. Both with 10000 to 1 million seconds specific impulse.
That would be the ultimate nuclear fission drive, better than Orion and beaten only by antimatter or fusion.

 

[Forest Green]

PNTR? (Pulsed Nuclear Thermal Rocket)??

 

[Archibald]

PNTR? (Pulsed Nuclear Thermal Rocket)??

Yes. I exchanged a few e-mails with Pr. Arias, who is a gentleman. He answered my questions with infinite patience, God bless his noble soul.
He has a very smart propulsion concept with PNTR.

 

[Forest Green]

Antiproton Annihilation Propulsion

Wayback Machine

 

[Archibald]

"Resistance is futile. Prepare to be anihilated."

 

[publiusr]

A nuclear Salt Water rocket would have a smoother ride than Pulse-Orion, but worse heating concerns.

 

[Forest Green]

A nuclear Salt Water rocket would have a smoother ride than Pulse-Orion, but worse heating concerns.

Mars in 3 days apparently with a 2% solution of 90% enriched Uranium Tetrabromide.

Engine List 2 - Atomic Rockets

www.projectrho.com

 

[publiusr]

Carlo Rubbia’s Americium 242 concept interests me

To Mars in Two Weeks?

www.scientificamerican.com

—a thin film…

This would lend itself to the recent hydrogen storage find.

Super-dense packing of hydrogen molecules on a surface

Hydrogen (H2) is currently discussed as an ideal energy carrier of renewable energies. Hydrogen has the highest gravimetric energy density of all chemical fuels (141 MJ/kg), which is three times higher than gasoline (46 MJ/kg). However, its low volumetric density restricts its widespread use in...

phys.org

 

[Forest Green]

This would lend itself to the recent hydrogen storage find.

Super-dense packing of hydrogen molecules on a surface

Hydrogen (H2) is currently discussed as an ideal energy carrier of renewable energies. Hydrogen has the highest gravimetric energy density of all chemical fuels (141 MJ/kg), which is three times higher than gasoline (46 MJ/kg). However, its low volumetric density restricts its widespread use in...

phys.org

This looks similar to the metallic hydrogen concept. Or at least it achieves the same ends.

Engine List 1 - Atomic Rockets

www.projectrho.com

Other futuristic chemical propellants include atomic hydrogen, free radical hydrogen and metastable helium (also on above link).

 

[Grey Havoc]

Via the Nuclear reddit:

Op-ed | It's Time for Congress to Order the Nuclear Option

Op-ed | It's Time for Congress to Order the Nuclear Option

spacenews.com

 

[Forest Green]

https://ntrs.nasa.gov/api/citations/20180006825/downloads/20180006825.pdf

https://www.nasa.gov/sites/default/files/atoms/files/niac_2016_phasei_thomas_fusiontopluto_tagged.pdf

 

[Forest Green]

Slough Fusion Drive Rocket

Wayback Machine

 

[Forest Green]

Nuclear DC-X

Wayback Machine

NTR - Nuclear Thermal Rocket using LH2 propellant
LA-NTR - LOx Augmented NTR (LOx serves as an afterburner)

 

[Cjc]

Missiles and Rockets 4 September 1961...

Do we have any idea how high the Saturn's V lift would have been with the nerva third stage?

 

[starviking]

Wayback Machine

Could this post be labled? Would make things easier for the search engine, and also if we lose the wayback machine (heavens forbid!) we’d have an idea of what was being shown.

 

[Forest Green]

Wayback Machine

Could this post be labled? Would make things easier for the search engine, and also if we lose the wayback machine (heavens forbid!) we’d have an idea of what was being shown.

Done.

 

[Forest Green]

Do we have any idea how high the Saturn's V lift would have been with the nerva third stage?

Curiously the Saturn V first stage produced twice the thrust of LANTR but it was using RP-1 fuel which is 11-14 times as dense as LH2 despite LH2 having a 50% higher specific impulse (Isp). An LANTR with RP-1 would be interesting thrust wise. It is also 6 times lighter than Saturn V.

The Isp of the NTR with LH2 only 1000s, which is ~4 times that of Saturn V and nearly 3 times that of LH2+LOx. With LANTR the Isp falls to 600s but thrust is tripled vs NTR.

Interestingly, with the Thin-Film Fission Fragment Heated NTR version, you can get an Isp of 4,000s with thrust similar to NTR but with a dirty exhaust.

 

[Forest Green]

Colloid Core NTR

https://ntrs.nasa.gov/api/citations/19710024150/downloads/19710024150.pdf

Gas Core NTR

https://ntrs.nasa.gov/api/citations/19680012569/downloads/19680012569.pdf

 

[publiusr]

The nuclear DC-X....that was the one Simberg dumped all over?

 

[Forest Green]

The nuclear DC-X....that was the one Simberg dumped all over?

Don't know, but a solid core NTR like DC-X looks like the most viable and currently achievable of the many nuclear rocket designs. The only problem is safety in the event that the rocket explodes or something. Not sure how you'd a design a pressure vessel that can withstand such an eventuality. But I guess if you build it on the moon, it's not so much of an issue. You would have to mine the Uranium there too though.

 

[RanulfC]

The nuclear DC-X....that was the one Simberg dumped all over?

Don't know, but a solid core NTR like DC-X looks like the most viable and currently achievable of the many nuclear rocket designs. The only problem is safety in the event that the rocket explodes or something. Not sure how you'd a design a pressure vessel that can withstand such an eventuality. But I guess if you build it on the moon, it's not so much of an issue. You would have to mine the Uranium there too though.

Nuclear rockets don't "explode" per-se, (getting one to do so takes careful design and construction which is how they actually got one TO explode for testing in the TNT test) they tend to just melt like any other reactor. Before it's gone 'live' it's relatively safe, once it's been run then it's highly radioactive of course.

The main issue with NTR's is thrust-to-weight and that's due to needing to shield the pile once its gone live. This is especially the case when (like the Nuclear DC-X) those reactors are surrounded by atmosphere and other materials that can easily reflect dangerous radiation past any 'shadow-shield' and therefore require a much more comprehensive (and heavier) shielding system.

Note that you can't use RP1 in an NTR due to the thermal disassociation that would occur at NTR temperatures. The 'carbon' in they hydrocarbon would precipitate out and onto the reactor causing it to overheat and melt which is why they 'prefered' reaction mass is pure hydrogen. (Ammonia and methane have been experimented with though)

Randy

 

[Forest Green]

Nuclear rockets don't "explode" per-se, (getting one to do so takes careful design and construction which is how they actually got one TO explode for testing in the TNT test) they tend to just melt like any other reactor. Before it's gone 'live' it's relatively safe, once it's been run then it's highly radioactive of course.

The main issue with NTR's is thrust-to-weight and that's due to needing to shield the pile once its gone live. This is especially the case when (like the Nuclear DC-X) those reactors are surrounded by atmosphere and other materials that can easily reflect dangerous radiation past any 'shadow-shield' and therefore require a much more comprehensive (and heavier) shielding system.

Note that you can't use RP1 in an NTR due to the thermal disassociation that would occur at NTR temperatures. The 'carbon' in they hydrocarbon would precipitate out and onto the reactor causing it to overheat and melt which is why they 'prefered' reaction mass is pure hydrogen. (Ammonia and methane have been experimented with though)

Randy

I'm not saying the nuclear part could explode, but the LH2 and LOx parts, in the case of LANTR, could explode, or it could develop some kind of malfunction and crash. How would you ensure that the pressure vessel is not going to be breached in such an incident? Sure, it doesn't happen a lot, but the potential consequences if it does are huge.

As regards the exhaust, the nuclear material is kept separate to the propellant, only the heat is transferred, as per a PWR-type system isn't it?

Fair enough, I didn't know that. Could the heat split hydrogen into atomic hydrogen? Ah, seems someone already thought of this, apparently above 3000K this is exactly what happens, unfortunately though it can cause heat flux in the reactor. There is however a workaround using a LPNTR (Low Pressure NTR). This yields Isp up to 1,350s but with reduced thrust due to reduced mass flow. it could be possible to vary the pressure to switch between high Isp and high thrust, or use LOx afterburner.

https://ntrs.nasa.gov/api/citations/19920001876/downloads/19920001876.pdf

Engine List 2 - Atomic Rockets

projectrho.com

The Hybrid MITEE also looks at a slightly different method.

Engine List 2 - Atomic Rockets

projectrho.com

 

[publiusr]

LOX afterburners we’re looked at by Borowski IIRC.

 

[RanulfC]

Nuclear rockets don't "explode" per-se, (getting one to do so takes careful design and construction which is how they actually got one TO explode for testing in the TNT test) they tend to just melt like any other reactor. Before it's gone 'live' it's relatively safe, once it's been run then it's highly radioactive of course.

The main issue with NTR's is thrust-to-weight and that's due to needing to shield the pile once its gone live. This is especially the case when (like the Nuclear DC-X) those reactors are surrounded by atmosphere and other materials that can easily reflect dangerous radiation past any 'shadow-shield' and therefore require a much more comprehensive (and heavier) shielding system.

Note that you can't use RP1 in an NTR due to the thermal disassociation that would occur at NTR temperatures. The 'carbon' in they hydrocarbon would precipitate out and onto the reactor causing it to overheat and melt which is why they 'prefered' reaction mass is pure hydrogen. (Ammonia and methane have been experimented with though)

Randy

I'm not saying the nuclear part could explode, but the LH2 and LOx parts, in the case of LANTR, could explode, or it could develop some kind of malfunction and crash. How would you ensure that the pressure vessel is not going to be breached in such an incident? Sure, it doesn't happen a lot, but the potential consequences if it does are huge.

Part of the reason you're unlikely to see an NTR used on Earth, on the other hand we do know what would happen as we've done the experiment. You really can't make an 'unbreachable' reactor vessel but you can take a lot of other measures to try and keep the damage to a minimum.

As regards the exhaust, the nuclear material is kept separate to the propellant, only the heat is transferred, as per a PWR-type system isn't it?

The reaction mass (propellant) has to come into contact with the reactor for this to work and there were issues early on with material transfer into the exhaust but they fixed it.

Fair enough, I didn't know that. Could the heat split hydrogen into atomic hydrogen? Ah, seems someone already thought of this, apparently above 3000K this is exactly what happens, unfortunately though it can cause heat flux in the reactor. There is however a workaround using a LPNTR (Low Pressure NTR). This yields Isp up to 1,350s but with reduced thrust due to reduced mass flow. it could be possible to vary the pressure to switch between high Isp and high thrust, or use LOx afterburner.

https://ntrs.nasa.gov/api/citations/19920001876/downloads/19920001876.pdf

Engine List 2 - Atomic Rockets

projectrho.com

The Hybrid MITEE also looks at a slightly different method.

Engine List 2 - Atomic Rockets

projectrho.com

Again your biggest issue is the mass of the reactor and shielding versus your thrust which for NTR's is pretty poor. ISP is great but there tends to be a inverse relation between ISP and thrust. LOX injection increases your thrust at the cost of ISP but it's not likely to be enough to make a surface launched NTR plausible.

Randy

 

[publiusr]

So help me—but my guess is that even if we had actual warp drive 10,000 years from now…it will still have to be lobbed up there with chemical rockets—being like NEP/ion engines…in space only.

Enterprise’s shuttlecraft are worse physics breakers than Enterprise itself.

NTR gives you good thrust and specific impulse depending on the LOX afterburner…pull the rods after you are thumped out of Earth-Moon so you won’t waste service life on a slow spiral out….unless you have, say—a solar tug push it out—unmanned…and once far enough out of the gravity well…send a Dragon atop Falcon Heavy as a fast taxi…then light it up to make it go farther.

 

[Forest Green]

Nuclear rockets don't "explode" per-se, (getting one to do so takes careful design and construction which is how they actually got one TO explode for testing in the TNT test) they tend to just melt like any other reactor. Before it's gone 'live' it's relatively safe, once it's been run then it's highly radioactive of course.

The main issue with NTR's is thrust-to-weight and that's due to needing to shield the pile once its gone live. This is especially the case when (like the Nuclear DC-X) those reactors are surrounded by atmosphere and other materials that can easily reflect dangerous radiation past any 'shadow-shield' and therefore require a much more comprehensive (and heavier) shielding system.

Note that you can't use RP1 in an NTR due to the thermal disassociation that would occur at NTR temperatures. The 'carbon' in they hydrocarbon would precipitate out and onto the reactor causing it to overheat and melt which is why they 'prefered' reaction mass is pure hydrogen. (Ammonia and methane have been experimented with though)

Randy

I'm not saying the nuclear part could explode, but the LH2 and LOx parts, in the case of LANTR, could explode, or it could develop some kind of malfunction and crash. How would you ensure that the pressure vessel is not going to be breached in such an incident? Sure, it doesn't happen a lot, but the potential consequences if it does are huge.

Part of the reason you're unlikely to see an NTR used on Earth, on the other hand we do know what would happen as we've done the experiment. You really can't make an 'unbreachable' reactor vessel but you can take a lot of other measures to try and keep the damage to a minimum.

As regards the exhaust, the nuclear material is kept separate to the propellant, only the heat is transferred, as per a PWR-type system isn't it?

The reaction mass (propellant) has to come into contact with the reactor for this to work and there were issues early on with material transfer into the exhaust but they fixed it.

Fair enough, I didn't know that. Could the heat split hydrogen into atomic hydrogen? Ah, seems someone already thought of this, apparently above 3000K this is exactly what happens, unfortunately though it can cause heat flux in the reactor. There is however a workaround using a LPNTR (Low Pressure NTR). This yields Isp up to 1,350s but with reduced thrust due to reduced mass flow. it could be possible to vary the pressure to switch between high Isp and high thrust, or use LOx afterburner.

https://ntrs.nasa.gov/api/citations/19920001876/downloads/19920001876.pdf

Engine List 2 - Atomic Rockets

projectrho.com

The Hybrid MITEE also looks at a slightly different method.

Engine List 2 - Atomic Rockets

projectrho.com

Again your biggest issue is the mass of the reactor and shielding versus your thrust which for NTR's is pretty poor. ISP is great but there tends to be a inverse relation between ISP and thrust. LOX injection increases your thrust at the cost of ISP but it's not likely to be enough to make a surface launched NTR plausible.

Randy

So, from what you're saying NTR is only really suitable for an intermediate stage in space, where exhaust contents are not such an issue. This 'dirty' stage could then be ejected before landing.

 

[Forest Green]

So help me—but my guess is that even if we had actual warp drive 10,000 years from now…it will still have to be lobbed up there with chemical rockets—being like NEP/ion engines…in space only.

Enterprise’s shuttlecraft are worse physics breakers than Enterprise itself.

NTR gives you good thrust and specific impulse depending on the LOX afterburner…pull the rods after you are thumped out of Earth-Moon so you won’t waste service life on a slow spiral out….unless you have, say—a solar tug push it out—unmanned…and once far enough out of the gravity well…send a Dragon atop Falcon Heavy as a fast taxi…then light it up to make it go farther.

Star Trek is honestly brain death in terms of the unrealistic/unscientific technology used. The Expanse is a lot better.

I'm not even sure about the long term consequences of polluting the solar system with radioactive gas. Sure, a few and it's sufficiently sparse not to make much difference, but people said there was plenty of space for satellites 30 years ago and now look.

 

[RanulfC]

So, from what you're saying NTR is only really suitable for an intermediate stage in space, where exhaust contents are not such an issue. This 'dirty' stage could then be ejected before landing.

It's not the exhaust but the reactor radiation which requires a lot of shielding if you're using it around people, and atmosphere or both

By using it away from both Earth or an atmosphere you avoid having to put lots of shielding on the reactor and you can get away with a lighter 'shadow' shield arrangement to protect the cargo/people on-board. The problem with things like the "Nuclear DC-X" is you have to fully shield the reactor to prevent stray radiation from bouncing off things like the interior materials, the exterior atmosphere and such and bouncing it's way right around your shielding and into your cargo/passengers. (Not to mention your entire 'engine bay' is being irradiated which 'activates' the materials of that bay making them radioactive too

As I said they pretty much solved that materials mitigation issues during the NERVA program (and you don't even have them with metal clad reactor elements) but you still have to worry about what happens if the core DOES melt and how to mitigate that. Easier to do in deep space than on the Earth's surface or atmosphere

Given its much higher ISP than chemical rockets an NTR makes sense for an intermediate or transfer stage but not so much for a lander or booster.

Randy

 

[RanulfC]

So help me—but my guess is that even if we had actual warp drive 10,000 years from now…it will still have to be lobbed up there with chemical rockets—being like NEP/ion engines…in space only.

"Technically" it depends on the type and species of "Warp Drive" really

If I understand it correctly the Alcubierre Warp Drive would tend to make any 'rocket' more efficient IF you can get it to work near a planet and/or in an atmosphere... In theory of course

Enterprise’s shuttlecraft are worse physics breakers than Enterprise itself.

Fictional story with fictional physics from the start so ya, that's kind of the point

NTR gives you good thrust and specific impulse depending on the LOX afterburner…pull the rods after you are thumped out of Earth-Moon so you won’t waste service life on a slow spiral out….unless you have, say—a solar tug push it out—unmanned…and once far enough out of the gravity well…send a Dragon atop Falcon Heavy as a fast taxi…then light it up to make it go farther.

Again though for getting off the Earth it's really not ideal or even really efficient given the restrictions you have to put on it to get it to work. A chemical rocket engine such as the RS-25 has a T/W of about 400/1, and GOOD NTR might see 40/1 but likely a lot less, (around 4/1 in some cases) all of which means you're using vastly more propellant AND emitting tons of radiation in every direction which in an atmosphere (where the radiation is being bounced back into your launch vehicle) isn't a good thing at all.

(Pathfinder from FAM? Ya the crew is dead the second they light up the reactor, the crew of the C5 carrier aircraft are dead as are all the people for about a hundred miles in any direct especially DOWN which will only be about 40,000ft away at best. Not a good thing at all )

Use as little shielding as possible from Earth orbit (or higher) to get that much better T/W of 40/1 and use the NTR as a transfer stage where it is most efficient. Does it rather 'suck' having to rely on "rockets" to get off Earth? Yes but it's so far the most efficient means we've found so far and there are dozens of 'tweaks' we still haven't used to make it better simply because the 'demand' for getting off Earth is so very low. (No "Starship" isn't the answer it's a hugely oversized rocket for any plausible 'market' we're going to have for the next several decades at least)

Falcon 9 could be a fully reusable TSTO system for getting people and payloads into LEO if SpaceX (Musk actually) cared about such thing but he doesn't so they don't, with only a few 'tweaks' to its design. Nothing big or Earth shattering even but that's not what the boss wants so we don't get it. Surface launched NTR just doesn't have the needed performance even if you could (or should) get past the regulatory and safety issues.

IIRC somewhere on here is a thread on the ASPEN space plane which had an NTR 'to-orbit' propulsion concept and even it had issues due to needing to get well above 100,000ft before lighting off the NTR. There have been other concepts as well, the problem is they don't really address the main issues of GTO (Ground to Orbit) transportation which are market and economics.

Rockets could be better but no one is actually interested in working on that at the moment, again because the market and economics are not there to support it.

Randy

 

[RanulfC]

So help me—but my guess is that even if we had actual warp drive 10,000 years from now…it will still have to be lobbed up there with chemical rockets—being like NEP/ion engines…in space only.

Enterprise’s shuttlecraft are worse physics breakers than Enterprise itself.

NTR gives you good thrust and specific impulse depending on the LOX afterburner…pull the rods after you are thumped out of Earth-Moon so you won’t waste service life on a slow spiral out….unless you have, say—a solar tug push it out—unmanned…and once far enough out of the gravity well…send a Dragon atop Falcon Heavy as a fast taxi…then light it up to make it go farther.

Star Trek is honestly brain death in terms of the unrealistic/unscientific technology used. The Expanse is a lot better.

I'm not even sure about the long term consequences of polluting the solar system with radioactive gas. Sure, a few and it's sufficiently sparse not to make much difference, but people said there was plenty of space for satellites 30 years ago and now look.

Gas no, but highly radioactive "spent" NTR's.... Well actually that's a "problem" I'd really like to have to deal with

Randy

 

[Forest Green]

Gas no, but highly radioactive "spent" NTR's.... Well actually that's a "problem" I'd really like to have to deal with

Randy

Well yeah, I guess you have to plan the ejection so that it won't get trapped in the orbit of anything, especially where you're going. I guess you would probably want to leave it in the orbit of say Mars, while you land, so you would have to be real careful about jettison on the way back. Eventually there would be like an accretion disk of NTRs around the Sun or something. The Sun itself would probably be the ideal disposal spot.

You still have the risk of the chemical stage of the rocket exploding on take-off and not knowing what is going to happen to the NTR in that event.

 

[RanulfC]

Gas no, but highly radioactive "spent" NTR's.... Well actually that's a "problem" I'd really like to have to deal with

Randy

Well yeah, I guess you have to plan the ejection so that it won't get trapped in the orbit of anything, especially where you're going. I guess you would probably want to leave it in the orbit of say Mars, while you land, so you would have to be real careful about jettison on the way back. Eventually there would be like an accretion disk of NTRs around the Sun or something. The Sun itself would probably be the ideal disposal spot.

You still have the risk of the chemical stage of the rocket exploding on take-off and not knowing what is going to happen to the NTR in that event.

Properly designed (and frankly there's no reason NOT to design these properly) the NTR should be fine. At this point even if it DOES crack or break nothing in it is really radioactive at this point.

Randy