Will SpaceX ever go nuclear propulsion?

[Patchouli]

If Musk wants to see a colony of thousands of people something faster then chemical propulsion will be a must.

But will it be nuclear I'm not sure it would have to depend on solar electric propulsion being good enough.

OT I do suspect to eventually see some sorta partnership between Spacex and a company that manufacture high ISP propulsion like Ad Astra.

As for on Mars a small reactor would be the ideal power source probably the best possible for early on but solar might be easier politically.
It might be possible to use some of the ISRU propellant in fuel cells for back up power during dust storms.
But this would require more mass and setup work and it will be do or die for the first crew unless it can be done using robots.

[Robotbeat]

Would solar really require more mass? That's not obvious. What sort of figures of merit are Mars surface fission reactors?

Also, abundant chemical is a pretty fast way to get around, as fast as regular old NTR.

[Patchouli]

The solar panels must be deployed,the fuel generator needs setup,there needs to be fuel storage for the fuel cells, and all the hoses connected.
Enough fuel to last though the first dust storm must be made before it happens.

For nuclear all that's needed the reactor the cart drives off a safe distance and deploys it radiators and starts up.

As for chemical vs nuclear a NTR rocket does double the effective payload since the mass fraction for a nuclear mission is 40% vs 17% for a chemical mission.
This means half the number of flights needed to refuel the vehicle.

Though if a fusion rocket if built it'll be a total game changer.

[Robotbeat]

Don't use fuel cells. Too inefficient. Lithium Sulfur batteries are way better. You'd probably want some anyway even with nuclear to help load following.

A fuel cell for emergency use might make sense to convert the methane/LOx propellant, but only in an emergency.

[Robotbeat]

Also, solar DOES produce significant power in a dust storm.

And, nuclear thermal doesn't necessarily double payload since it's own dry mass is so great. Also, remember that a NTR running on hydrogen makes ISRU more difficult since you're throwing away a bunch of propellant and only using hydrogen from H2O.

[luinil]

What about solar thermal on Mars?
How does that compares to nuclear thermal and photovoltaic ?

But this subject is on propulsion, so this might not be the best place to talk about it.

[raketa]

Elon is not against nuclear energy, but I think if he is planing to use it for on Mars surface purpose. To avoid political troubles I think that nuclear reactor could be delivered to Mars empty and rods of fuels could be deliver to LEO  and to Mars by dragon, in case of failure, nuclear rods will be safely bring back to earth like astronauts.

[guckyfan]

Elon is not against nuclear energy, but I think if he is planing to use it for on Mars surface purpose. To avoid political troubles I think that nuclear reactor could be delivered to Mars empty and rods of fuels could be deliver to LEO  and to Mars by dragon, in case of failure, nuclear rods will be safely bring back to earth like astronauts.

One major obstacle is that small reactors need highly enriched weapons grade fuel. Very hard to get permission for even if safety is assured because the material can be abused. But this has been discussed before and is not for this thread to continue on.

[hellofu]

every one is focused on nuclear reactors but what about nuclear batteries. they provide a simple stopgap/safety net. you also have to remember that solar power only work during the day so you need to store power when the your not facing the sun. nuclear batteries help that problem but also solve the problem as a backup to nuclear reactors.

nuclear batteries also help to your power your craft on the trip to mars in stead of having to deploy a large solar array and worry about stresses on them from the propulsion system. they would make a great start to a solar powered colony as well given a easy and predictable drop off in power output allowing a steady ramp up of solar power production and installation.

[Patchouli]

Elon is not against nuclear energy, but I think if he is planing to use it for on Mars surface purpose. To avoid political troubles I think that nuclear reactor could be delivered to Mars empty and rods of fuels could be deliver to LEO  and to Mars by dragon, in case of failure, nuclear rods will be safely bring back to earth like astronauts.

One major obstacle is that small reactors need highly enriched weapons grade fuel. Very hard to get permission for even if safety is assured because the material can be abused. But this has been discussed before and is not for this thread to continue on.

Don't use U235 or plutonium instead make use of U233 which can be made from thorium.

U233 does give off Gama rays so it will have to ride by it's self.

Just dedicate a few Red Dragons for the fuel load or put the entire reactor on a cart that is deployed and drives away trailing power cables.

[docmordrid]

Elon is not against nuclear energy, but I think if he is planing to use it for on Mars surface purpose. To avoid political troubles I think that nuclear reactor could be delivered to Mars empty and rods of fuels could be deliver to LEO  and to Mars by dragon, in case of failure, nuclear rods will be safely bring back to earth like astronauts.

One major obstacle is that small reactors need highly enriched weapons grade fuel. Very hard to get permission for even if safety is assured because the material can be abused. But this has been discussed before and is not for this thread to continue on.

Don't use U235 or plutonium instead make use of U233 which can be made from thorium.

U233 does give off Gama rays so it will have to ride by it's self.

Just dedicate a few Red Dragons for the fuel load or put the entire reactor on a cart that is deployed and drives away trailing power cables.

In spite of what you may have read, U233 can be used in nuclear weapons. The trick is removing the residual U232, which is the source of the gamma output and the presence of which makes assembling the pit dangerous. Oak Ridge developed a process for doing this.  In 1998 India's Shakti V test was a subkiloton U233 device.

[Jet Black]

You don't need a lot of Delta-v capability to operate in the asteroid belt. Dawn is doing Vesta to Ceres with solar electric propulsion in about 2 years. If all you are doing is shipping manufactured goods around, you don't have to worry too much about a 2 year journey. Escape velocity on Ceres, the biggest object in the main belt, is about 500 m/s. Escape velocity is so low that some rifle or tank rounds fired would actually escape. I would concentrate the colony there and mine asteroids that pass by. We don't know much about it, but we will learn a lot more in just a few months time including about potential nuclear resources(Uranium).

Yes, I am aware of that. But it does mean that any groups of humans would  be very isolated from any other group of humans. Each location will need to be very nearly self sufficient. Very hard to do if not impossible unless each group is very large. A big problem for mining locations unless you assume it is all fully automated?

I think self sufficiency will be a requirement, an inevitability and ultimately an ideal. The less opportunity for planets holding distant colonies to ransom the better, really. Centralised power over distant colonies never works.

[kfsorensen]

In spite of what you may have read, U233 can be used in nuclear weapons. The trick is removing the residual U232, which is the source of the ga output and the presence of which makes assembling the pit dangerous. Oak Ridge developed a process for doing this.

Impossible. No one knows how to do this, including Oak Ridge.

[macpacheco]

every one is focused on nuclear reactors but what about nuclear batteries. they provide a simple stopgap/safety net. you also have to remember that solar power only work during the day so you need to store power when the your not facing the sun. nuclear batteries help that problem but also solve the problem as a backup to nuclear reactors.

nuclear batteries also help to your power your craft on the trip to mars in stead of having to deploy a large solar array and worry about stresses on them from the propulsion system. they would make a great start to a solar powered colony as well given a easy and predictable drop off in power output allowing a steady ramp up of solar power production and installation.

Nuclear batteries are unsuited for such usage. No way to turn on/off/tune the power output. And low power density. It uses natural decay of radionuclides like Pu-238. Nuclear fission can be turned off (secondary heat generation from natural decay like that of nuclear batteries stay for a while). Nuclear fission is extremely powerful. One ton of U233/U235/Pu239 fission is over 2 GWyear of thermal power or 1GWyear of electric power. A Mars base would need something in the order of 200MWt, so one ton of actual fission would provide about 10 years worth of power. Of course a reactor never fully consumes the nuclear material inside it, you must maintain a certain fairly high inventory of fissile material.

[nadreck]

Taking from the concept of a high power to weight ratio reactor like the molten salt ones, and bringing the conversation back to propulsion, how about a molten salt reactor that powers a low thrust high ISP monatomic hydrogen engine that, at highest thrust (still to low for anything except a space only stage), lowest ISP (where 100% of the power generated is used to produce monatomic hydrogen and maybe even a little lox is added to increase thrust) without the lox, ISP would be about 800 to 900, however you could get a much higher ISP if you took a couple of percent of the power to make monatomic hydrogen and feed it into an MHD drive using the rest of the available power. There you could theoretically get performance at or beyond what VASIMR provides.

The advantage in this process though in a Mars colonization effort only a couple of the reactors need to be left behind to provide electric power while the rest continue to ply the space between Mars and Earth (or later be adapted to cruise the 'roids, Trojans, Jovian moons).

[hellofu]

every one is focused on nuclear reactors but what about nuclear batteries. they provide a simple stopgap/safety net. you also have to remember that solar power only work during the day so you need to store power when the your not facing the sun. nuclear batteries help that problem but also solve the problem as a backup to nuclear reactors.

nuclear batteries also help to your power your craft on the trip to mars in stead of having to deploy a large solar array and worry about stresses on them from the propulsion system. they would make a great start to a solar powered colony as well given a easy and predictable drop off in power output allowing a steady ramp up of solar power production and installation.

Nuclear batteries are unsuited for such usage. No way to turn on/off/tune the power output. And low power density. It uses natural decay of radionuclides like Pu-238. Nuclear fission can be turned off (secondary heat generation from natural decay like that of nuclear batteries stay for a while). Nuclear fission is extremely powerful. One ton of U233/U235/Pu239 fission is over 2 GWyear of thermal power or 1GWyear of electric power. A Mars base would need something in the order of 200MWt, so one ton of actual fission would provide about 10 years worth of power. Of course a reactor never fully consumes the nuclear material inside it, you must maintain a certain fairly high inventory of fissile material.

my suggestion is not to simple use nuclear batteries for all power but to use it where it excels. it can work as a perfect uninterrupted power supply for solar power or nuclear reactor if it scrams.

it can serve as a much safer power supply in transit to mars form earth. this way you would avoid the trouble of land a running nuclear reactor on mars.

[macpacheco]

There was a single MSR design that actually ran for a year, and that was in the late 60s, early 70s.
Right now we have a bunch of paper reactors, some at the cusp of having its designs actually finalized.
First we need operational, full scale, stationary MSRs to prove the NRC, NASA, DoD that they are up to snuff for stationary applications, within safety margins, predicted performance.

Then it might be possible to design a more weight efficient reactor for space propulsion.

Its much like trying to say that F9R reusability will happen without a single change or with a boatload of changes, even SpaceX people with in depth knowledge don't know for sure.

But MSR reactors offer the highest power density, simplest design of nuclear reactors. Due to the chemical characteristics of salts in general.

Until we convince the public at large that MSR nuclear is another class of nuclear, and people accept that as a sure thing, operational nuclear reactors even for 2nd stage rockets just aint gonna happen. Politicians literally consider nuclear subjects, hu, radioactive (pun intended). Launch abort scenario: a ton of radionuclides shower over the atmosphere, it will disperse, but it doesn't burn like chemical fuels.

[macpacheco]

my suggestion is not to simple use nuclear batteries for all power but to use it where it excels. it can work as a perfect uninterrupted power supply for solar power or nuclear reactor if it scrams.

it can serve as a much safer power supply in transit to mars form earth. this way you would avoid the trouble of land a running nuclear reactor on mars.

1 - MSRs don't need active cooling upon shutdown. Since the coolant and the nuclear fuel is one and the same, the core materials are drained into the drain tank which is designed to maximize thermal radiation and has no neutron moderating materials and has some neutron absorbers, so criticality stops immediately

2 - I still don't see how a nuclear battery would help. Its the opposite of a UPS, it never shuts down. Its usage is exactly when you need a small scale power source, using the heat differential to generate electricity and to warm things up. Chemical batteries + some solar panels is a far more logical emergency power supply in that case.

[Joffan]

I think SpaceX will never use nuclear propulsion.

1. I don't expect SpaceX to last forever. For the purpose of discussion, let's assume that the company will last for 60 years - a rather generous allowance.

2. Elon has set the company up to focus on cost-effective access to space. They continue to use non-bleeding-edge technology wherever they can and avoid getting sucked into "the best possible" technical arguments.

3. Nuclear propulsion scores in the availability of large quantities of power, allowing rapid transit times under some designs, but loses on maturity, complexity and bureaucracy - especially the latter.

4. SpaceX will never see a requirement for space transport such that the development, licensing and production of fission-powered propulsion will be a cost-effective proposition.

----------------------

I'd still like to see nuclear reactors in space though. I think they could have a strong role to play but the road to get there is very murky. My answer to "where could nuclear propulsion tests take place?" is two-fold: the Moon, and a high-orbit fabrication facility.  One is good for constrained tests, the other is ideal for testing zero-g response.

[nadreck]

I think SpaceX will never use nuclear propulsion.

1. I don't expect SpaceX to last forever. For the purpose of discussion, let's assume that the company will last for 60 years - a rather generous allowance.

Seriously if SpaceX lasts to the point of a Mars settlement being established (settlement to me is the point at which there is less personnel return capacity than people living there), then they will probably have looked at a variety of more exotic propulsion technologies than we have now and nuclear fission will be among them. However, they may initially be only involved in enabling spaced based testing of the technologies on behalf of others until such time as the technology is more mature. By thirty years from now many of the technologies we have discussed here and on other threads(and many we haven't thought of) will have been tested in space, I am sure a few will be going into new craft at that time.

Just as a bromide here, don't bet against another period of rapid development of space technologies like we had between 1945 and 1965. Just bet against it being for military purposes. I can see several potential scenarios where a lot of activity and development happen, however the key to most of these, is cheaper access to space.

4. SpaceX will never see a requirement for space transport such that the development, licensing and production of fission-powered propulsion will be a cost-effective proposition.

I would agree here with the combination of all three, but one of three might happen

----------------------

I'd still like to see nuclear reactors in space though. I think they could have a strong role to play but the road to get there is very murky. My answer to "where could nuclear propulsion tests take place?" is two-fold: the Moon, and a high-orbit fabrication facility.  One is good for constrained tests, the other is ideal for testing zero-g response.

I see a lot of potential for GEO stations in this.