Antimatter Catalyzed (triggered) fission Air Augmented SSTO

[Spacescifi]

How would such an SSTO look?

My guesses are:

1. Provided antimatter safe storage and effcient production is possible, we need..

Air intakes, likely some sort of turbo-ramjet with a shock cone during ramjet speed. Big main engine nozzles handle heat better, so forget tiny ones, as we need not worry about combustion as we are using nuclear power.

Result? A large oblong fuselage body with big engine nacelles with shock cones and large nozzles behind it.

Aerospikes may not be practical, since they use tiny nozzles to spray exhaust onto tge aerospike.... which dealing with nuclear energies they may overheat and melt.

Takeoff: Like a plane. Lands like one too.

 

So ultimately, the easiest practical SSTO we can make is belly lander that takes off and lands like a plane.

And we could also augment it to land on the ocean instead.

May even be preferable if it uses water as propellant.

The engine: Uses FIFTY mini antimatter catalyzed nuclear reactors to power the rocket propellant thrust.

How much thrust would I get with water as propellant and using StarshipX as a model?

Augmented to land on the ocean.

[K^2]

Lets start with how you're planning to use antimatter to catalyze nuclear fission. Best I can tell, absolutely all references to antimatter "catalyzed" nuclear pulse propulsion go back to a single team in Pennsylvania State that managed to achieve microfusion by bombarding targets with antiprotons. Naturally, there is nothing like actual catalysis going on. The bombardment simply heated a region in the target to fusion temperatures. An experiment to achieve fission in subcritical targets is referenced, but I was not able to find any results from that, so that doesn't sound promising. In either case, you need to be very near criticality for it to work even in principle. I see no references to successful microfission experiment anywhere.

If you're merely subcritical on fission NPP, we're talking about pulses in kT ranges. That is absolutely not something you want to ignite in atmo of a planet you plan to continue living on. And there is no way to make that closed cycle.

The antiproton "catalyzed" fusion looks better on the surface, because it is, indeed, microfusion, but a considerable fraction of energy is coming from antimatter in this scenario. If you can produce antimatter in required quantities, there are better ways to ignite a fuel pellet. That's on top of open cycle NPP used for getting out of atmosphere of inhabited planet being a very iffy proposition either way, even if you're just burning hydrogen in micropulses.

Best I can tell, the only serious proposals on using this mechanisms have had to do with reducing fissile mass in NPP fuel pellets well bellow criticality for safer storage. That certainly has advantages if you're trying to build a practical interplanetary craft, but that's about it.

[Spacescifi]

6 hours ago, K^2 said:

Lets start with how you're planning to use antimatter to catalyze nuclear fission. Best I can tell, absolutely all references to antimatter "catalyzed" nuclear pulse propulsion go back to a single team in Pennsylvania State that managed to achieve microfusion by bombarding targets with antiprotons. Naturally, there is nothing like actual catalysis going on. The bombardment simply heated a region in the target to fusion temperatures. An experiment to achieve fission in subcritical targets is referenced, but I was not able to find any results from that, so that doesn't sound promising. In either case, you need to be very near criticality for it to work even in principle. I see no references to successful microfission experiment anywhere.

If you're merely subcritical on fission NPP, we're talking about pulses in kT ranges. That is absolutely not something you want to ignite in atmo of a planet you plan to continue living on. And there is no way to make that closed cycle.

The antiproton "catalyzed" fusion looks better on the surface, because it is, indeed, microfusion, but a considerable fraction of energy is coming from antimatter in this scenario. If you can produce antimatter in required quantities, there are better ways to ignite a fuel pellet. That's on top of open cycle NPP used for getting out of atmosphere of inhabited planet being a very iffy proposition either way, even if you're just burning hydrogen in micropulses.

Best I can tell, the only serious proposals on using this mechanisms have had to do with reducing fissile mass in NPP fuel pellets well bellow criticality for safer storage. That certainly has advantages if you're trying to build a practical interplanetary craft, but that's about it.

 

Interesting.

So you are saying that trying to induce antimatter triggered nuclear reaction is just an expensive way to kill the self and everything around three kilometers out and maybe a bit further?

It's a bomb?

 

No record os fission reactions?

Too bad...I had hoped that we could make mini reactors ALA Ironman.

Jury of experiments is still out though... since absent data to disprove it we can still experiment.

And modernt tech may yield somewhat better results?

Or not?

[K^2]

You might be able to do microfusion (not fission!) reactors this way. But I kind of question efficiency gained over, say, just boiling water with antimatter beam. It might, ultimately, make economical sense to do it this way, if price point of antimatter falls into just the right sort of region where you could build a pure antimatter drive, but it's expensive enough that you go to trouble to do triggered fusion instead to reduce the amount of antimatter needed. But being able to build practical antimatter reactors and produce enough fuel for them at reasonable price is a pre-requisite.

If you really, really want to stretch it thin, maybe an antiproton-triggered microfusion reactor powering a closed cycle NTR with some really cheap and environmentally friendly propellant, like water, might make sense for an SSTO. Again, if cost of antimatter falls into just the right sort of range. But the tech involved is gnarly, and I'm reasonably confident that there are much, much better options for an SSTO if you are at that level of tech.

[Spacescifi]

3 hours ago, K^2 said:

You might be able to do microfusion (not fission!) reactors this way. But I kind of question efficiency gained over, say, just boiling water with antimatter beam. It might, ultimately, make economical sense to do it this way, if price point of antimatter falls into just the right sort of region where you could build a pure antimatter drive, but it's expensive enough that you go to trouble to do triggered fusion instead to reduce the amount of antimatter needed. But being able to build practical antimatter reactors and produce enough fuel for them at reasonable price is a pre-requisite.

If you really, really want to stretch it thin, maybe an antiproton-triggered microfusion reactor powering a closed cycle NTR with some really cheap and environmentally friendly propellant, like water, might make sense for an SSTO. Again, if cost of antimatter falls into just the right sort of range. But the tech involved is gnarly, and I'm reasonably confident that there are much, much better options for an SSTO if you are at that level of tech.

What other options?

Generally... keeping the amount of antimatter low is a good thing when launching from a planet or even landing due to safety concerns.

Also... how would the exhaust plume look?

My instincts say steam... lots of it.

But I don't know why but having flamey plumes come from water reacting with AM seems odd.

Yet for all I know it would probably be a flamey bluish plume with a lot of steam exhaust.

Am I even close?

[K^2]

Oh, no, no, no. You wouldn't use any of that for exhaust directly. Again, we're not trying to irradiate the planet. The only way to use this safely is as a part of a closed loop thermal rocket. This won't be any different from any NTR out there, you're just swapping out the fuel. The exhaust would look very similar to that of an LH2 rocket either way. That is, mostly invisible, but with a slight blueish glow if you you have it against dark background.

As for options, if we're going for the rocket, good, efficient use of chemical fuels might still win out. If not, it's probably going to be a thermal rocket of some kind. There are several NTR options and we can also move the power source completely out of the ship, placing it on the ground or in orbit and beaming energy via laser or microwave beam. In that case, the propellant is still probably going to be water because it is abundant and cheap, but you don't have to bring a reactor of any kind.

My favorite speculative option for a power source is nuclear isomer battery. Less specific energy than a fission reactor, but still plenty for a thermal rocket, no waste, reasonably safe, as they emit only gamma radiation and at lower energies than antimatter, and they might even be rechargeable. Having a rechargeable source of gamma rays boiling water is probably about as close to a sci-fi shuttle as you'll get without getting into realm of totally made up things.

But that's just pure rockets. If we're serious about space exploration, we can't rely on just rockets. Even if we figure out much more efficient propulsion, sending cargo and passengers to space in quantity will require a different solution. Some variation on a launch loop is probably a best option. Accelerate the craft by magrail, let go of it at 30+km altitude, and then it can use on-board propulsion to make it to orbit from there. At that point, orbital propulsion can be either an NTR or some form of an ion drive as you will only need a few km/s of delta-v and thrust isn't as critical.

[Spacescifi]

11 hours ago, K^2 said:

Oh, no, no, no. You wouldn't use any of that for exhaust directly. Again, we're not trying to irradiate the planet. The only way to use this safely is as a part of a closed loop thermal rocket. This won't be any different from any NTR out there, you're just swapping out the fuel. The exhaust would look very similar to that of an LH2 rocket either way. That is, mostly invisible, but with a slight blueish glow if you you have it against dark background.

As for options, if we're going for the rocket, good, efficient use of chemical fuels might still win out. If not, it's probably going to be a thermal rocket of some kind. There are several NTR options and we can also move the power source completely out of the ship, placing it on the ground or in orbit and beaming energy via laser or microwave beam. In that case, the propellant is still probably going to be water because it is abundant and cheap, but you don't have to bring a reactor of any kind.

My favorite speculative option for a power source is nuclear isomer battery. Less specific energy than a fission reactor, but still plenty for a thermal rocket, no waste, reasonably safe, as they emit only gamma radiation and at lower energies than antimatter, and they might even be rechargeable. Having a rechargeable source of gamma rays boiling water is probably about as close to a sci-fi shuttle as you'll get without getting into realm of totally made up things.

But that's just pure rockets. If we're serious about space exploration, we can't rely on just rockets. Even if we figure out much more efficient propulsion, sending cargo and passengers to space in quantity will require a different solution. Some variation on a launch loop is probably a best option. Accelerate the craft by magrail, let go of it at 30+km altitude, and then it can use on-board propulsion to make it to orbit from there. At that point, orbital propulsion can be either an NTR or some form of an ion drive as you will only need a few km/s of delta-v and thrust isn't as critical.

 

Is building a magnetic rail 30 kilometers high practical?

I mean... it might be plausible, but such a feat limits how heavy you can launch.... leading to time consuming launch a piece, rendezvous in orbit assembly.

Edited July 26, 2020 by Spacescifi

[kerbiloid]

On 7/25/2020 at 12:55 AM, Spacescifi said:

The engine: Uses FIFTY mini antimatter catalyzed nuclear reactors

A rather wise and realistic redundancy.

If one got chernobylled, there are fourty nine more onboard.