Could a nuclear powered rocket be safely launched from Earth?

[Nabir14]

TL;DR Summary

I found a video online showing a theoretical nuclear powered spacecraft propulsion concept that was discontinued due to high chances of danger.

My question is if we don't use the nuclear module of the rocket to launch from Earth but instead launch it using normal methods then use the nuclear module to move in space. Would it be possible and safer?

I was scrolling through YouTube and saw this video:


The video showcases the Project Orion rocket. Project Orion was a theoretical spacecraft propulsion concept which uses nuclear explosions to propel a rocket. Opening the comment I further learned that it was discontinued due to Nuclear Test Ban Treaty in 1963 and being dangerous to launch from Earth.

I still had a question. What if we didn't use the nuclear module to launch from Earth. Instead if we used a normal method to launch from Earth and then used the nuclear method to move in space.

Would it be possible and safe?

 

[FactChecker]

Any nuclear explosions in space would probably open a can of worms related to nuclear weapons in space.

 

[Andrew Mason]

TL;DR Summary: I found a video online showing a theoretical nuclear powered spacecraft propulsion concept that was discontinued due to high chances of danger.

My question is if we don't use the nuclear module of the rocket to launch from Earth but instead launch it using normal methods then use the nuclear module to move in space. Would it be possible and safer?

The video showcases the Project Orion rocket. Project Orion was a theoretical spacecraft propulsion concept which uses nuclear explosions to propel a rocket. Opening the comment I further learned that it was discontinued due to Nuclear Test Ban Treaty in 1963 and being dangerous to launch from Earth.

I still had a question. What if we didn't use the nuclear module to launch from Earth. Instead if we used a normal method to launch from Earth and then used the nuclear method to move in space.

Would it be possible and safe?

The 1950's were a bit wild. I would have thought that the metre thick lead shielding in the large blast shield needed to protect the crew from the intense radiation of the nuclear explosion would make it a non-starter for a space craft.

Nuclear rocket propulsion using thermal nuclear power using hydrogen propellant has been suggested for interplanetary missions. The idea is to have a nuclear reactor that raises the hydrogen propellant to a very high temperature (and, therefore, its H2 molecules to a very high speed) before ejecting them through the nozzle to provide thrust.

AM

 

[Nabir14]

Any nuclear explosions in space would probably open a can of worms related to nuclear weapons in space.

I hope they don't

 

[Vanadium 50]

Any nuclear explosions in space would probably open a can of worms related to nuclear weapons in space.

These aren't bombs over your cities. They are..um..interplanetary gas stations.

 

[DaveC426913]

I still had a question. What if we didn't use the nuclear module to launch from Earth. Instead if we used a normal method to launch from Earth and then used the nuclear method to move in space.

Would it be possible and safe?

Setting aside the issues mentioned by others about not liking bombs in space over our heads, the issue of safety still has not gone away.

Even if we didn't deliberately drop our nuclear payloads on people's homes, they can still fall on them inadvertently - whether that be a malfunction during launch or a malfunction in orbit.

 

[glappkaeft]

Another issue is that the 500-1000 nuclear bombs the different Orion concepts used would be a new kind of expensive. The concept as based on the availability of small cheap fusion bombs without a fission starter that would soon be invented. 60 years later they still don't exist.

 

[FactChecker]

Even if we didn't deliberately drop our nuclear payloads on people's homes, they can still fall on them inadvertently - whether that be a malfunction during launch or a malfunction in orbit.

Good point. During the Cold War the possibility of nuclear-powered airplanes was investigated. An airplane flew with a nuclear reactor on board (not actively powering the plane, just there for proof of concept). When it flew, bulldozers were kept on alert so any crash could be buried as fast as possible.

 

[berkeman]

bulldozers were kept on alert so any crash could be buried as fast as possible.

Did they pay time and a half for that bulldozer duty?

 

[Flyboy]

I still had a question. What if we didn't use the nuclear module to launch from Earth. Instead if we used a normal method to launch from Earth and then used the nuclear method to move in space.

Would it be possible and safe?

Possible? From a technical perspective, yes, and such an approach was actually considered in the designs.

https://projectrho.com/public_html/...n--USAF_10_Meter_Orion--10_Meter_Mars_Mission

"Single Launch Mission Capacity

The reference missions assume multiple Saturn V launches to loft the components into orbit, where they are assembled. There is a way to use just one Saturn V launch. Unfortunately it involves using the Orion drive. In Terra's atmosphere.

The Orion is used as the top stage, starting at an altitude of 93 kilometers. The savings are substantial, the risks are manageable. But the thought of detonating *Two* *Hundred* *Nuclear* *Bombs* per launch will cause any nukeophobic person to scream in your face at the top of their lungs. Especially if you are a politician and they are one of your constituents.

The reference mission has one Saturn V launch to loft the Orion propulsion module, one launch for operational payload (personnel accomodations unit, remaining vehicle structure, some supplies), one launch for the Mars excursion modules, and a couple of launches carrying nuclear pulse units and miscellaneous small payloads."

Keep in mind this study was in 1963/4, and some of the design elements were proven outdated in a few years. But the gist of it still stands.

Practically... It'd be extremely difficult today just from the technical aspects alone.

• The sequential EMPs generated by the pulse units in the upper atmosphere and low orbit would cause significant damage to pretty much anything that wasn't specifically designed to withstand that. Which... isn't much anymore.
• As others have pointed out, there's the whole safety angle for the pulse units. That is a lot of energy onboard the vehicle, especially if it's an all-up launch, and if one goes wrong... well, it gets messy for everyone, very, very quickly.
• What exactly would be the need for such a vehicle? There's no pressing missions that would require an Orion-type system at present, unless you're planning a flags and footprints mission to Mars via Brachistochrone trajectories. And tbh, that would be a massive waste, but that's a topic for another day.

And there's the political angle of it, as has been pointed out from the very beginning of the idea. In the words of the study used in the above concept... "The report says the problem "rather obviously, stems from the fact that nuclear pulse propulsion uses in small scale the same energy source used for nuclear weapons"."

Let that sink in. The study authors, in 1964, said that it was politically challenging. Nuke-happy era folks, saying it's a problem that can't be addressed by engineering. If that doesn't drive home the point, I don't know what will.

 

[mfb]

What's the application?

Exploding nuclear weapons in the lower atmosphere is really bad for anything nearby, and exploding them in the upper atmosphere (that includes common low Earth orbits) is really bad for satellites. So you probably want to limit the use to interplanetary missions after leaving low Earth orbit.

Nuclear weapons don't scale well. You can make a conventional rocket engine with half the mass and half the thrust, but you can't do that with nuclear weapons. Same problem with shielding. Everything smaller than 100 tonnes yield propelling a few thousand tonnes of ship mass is having a horrible efficiency.

That means our mission profile asks for tens of launches of our largest conventional rockets to assemble a massive spacecraft in Earth orbit. By the time we are done with that, a conventional spacecraft would have reached its destination already. And without the cost and political problems of sending hundreds of nuclear weapons to space.

If we want to send probes to nearby stars then we might see this happening at some point.

 

[Flyboy]

If we want to send probes to nearby stars then we might see this happening at some point.

Y’know, that’s a fair point. Orion is the only technology that has a reasonable readiness level for that kind of mission.

Downside is that it still takes several generations to reach the target. It would be, what, a century or so to Proxima Centauri? And there’s no real reason to send a probe there. So the mission would be even longer than that.

What’s the nearest star system that would warrant such a mission?

 

[Nabir14]

What's the application?

Exploding nuclear weapons in the lower atmosphere is really bad for anything nearby, and exploding them in the upper atmosphere (that includes common low Earth orbits) is really bad for satellites. So you probably want to limit the use to interplanetary missions after leaving low Earth orbit.

Nuclear weapons don't scale well. You can make a conventional rocket engine with half the mass and half the thrust, but you can't do that with nuclear weapons. Same problem with shielding. Everything smaller than 100 tonnes yield propelling a few thousand tonnes of ship mass is having a horrible efficiency.

That means our mission profile asks for tens of launches of our largest conventional rockets to assemble a massive spacecraft in Earth orbit. By the time we are done with that, a conventional spacecraft would have reached its destination already. And without the cost and political problems of sending hundreds of nuclear weapons to space.

If we want to send probes to nearby stars then we might see this happening at some point.

Yeah I was talking about moving in space not launching. Like after the launch to go to a very far planet or star we use it?

 

[mfb]

If you want to launch a big spacecraft to a nearby star and need to launch that within 20 years for whatever reason then it's our best option. Otherwise: Probably not.

 

[DaveC426913]

Yeah I was talking about moving in space not launching. Like after the launch to go to a very far planet or star we use it?

A nuclear pile, when it is hovering over your head, is still dangerous, even when not in use.

Not until we can build our spaceships away from Earth orbit will we be safe from having radioactive debris from fallnig on our heads.

 

[berkeman]

BTW, how does one steer a nuclear rocket? I'm not able to see any mention of that on the Wikipedia page for Orion. It seems like just being a little bit off center with an explosion would induce a pretty big yaw force...

 

[Astronuc]

Orion is the only technology that has a reasonable readiness level for that kind of mission.

What is the basis of such a statement/opinion?

To my knowledge, no prototype has been demonstrated.

BTW, how does one steer a nuclear rocket? I'm not able to see any mention of that on the Wikipedia page for Orion. It seems like just being a little bit off center with an explosion would induce a pretty big yaw force...

One of many challenges.

I've had discussions over the past 4 decades with different folks. Using a nuclear detonation is rather inefficient, and highly dependent on the distance from (and solid angle with respect to) the 'pusher plate' to the detonation. One concept to improve efficiency was to coat the 'pusher plate' with an ablative material. However, one then needs a mass of ablative material (and storage) and an application system to coat the 'pusher plate' between detonations. That ablative material would also, in theory, reduce the erosion of the 'pusher plate' material, which would complicate the propulsion.

Regarding efficiency, if the 'pusher plate' is flat, even if the detonation is at the surface, then half the explosive energy is dispersed to space. As the detonation site is place further away from the plate, it becomes less efficient. So, one could try a cone of some kind, and it would have to have a high melting point, strength at temperature, and be resistant to erosion and catastrophic failure.

The size of the 'pusher plate' was another matter. Ostensibly, it is made of a material with a high melting point, e.g., tungsten. One can play around with numbers related to size (thickness and diameter) and consider the density of tungsten (19300 kg/m³).

How about storage of the nuclear devices? How large a bomb bay?

I don't know of anyone in the nuclear-aerospace community who would seriously consider Orion in any form.

 

[glappkaeft]

To my knowledge, no prototype has been demonstrated.

Only this prototype that was build by General Atomics and tested in 1959 using conventional explosives.
https://airandspace.si.edu/collecti...-test-vehicle-project-orion/nasm_A19721008000

 

[DaveC426913]

I don't know of anyone in the nuclear-aerospace community who would seriously consider Orion in any form.

Yeah, Think part of the reason it's still given at least some consideration is that it is less a physics problem than an engineering problem. i.e. ostensibly, there is no new science required to do it. We can do it with current science, it's "just"* a matter of how.

*(Stephen King, in his book "On Writing", recounts innumerable friends and family who fancied themselves authors and wanted to partner with him 50/50: "I've got a great idea for a story in my head, all you have to do is "just" write the words". )

 

[gmax137]

there is video of test flights in the other (2022) thread

https://www.physicsforums.com/threa...e-future-of-space-travel.1013336/post-6612136

 

[Vanadium 50]

Greetings, beings of Earth! Do not worry about the thousands of nuclear warheads in orbit overhead. This is merely our star drive.

Although, this just occured to us - our empire is looking for new junior members. Would now be a good time to talk about it?

 

[DaveC426913]

Greetings, beings of Earth!

In an interesting counter-example, in Niven's Footfall, the first thing the Fithp did upon arriving in Sol System was detach and drop their Stardrive into the Sun, just in case those pesky monkeys got uppity.