Molten Ferrometal as a Penetrator in Space Combat?

[Sea Skimmer]

You might some day be able to make a safe nuclear salt water rocket by mixing in neutron absorber into the fuel. This would then be either filtered out, tricky to do that part safely, or overwhelmed via an external neutron generator surrounding the engine nozzle. Then the ship doesn't blow up if enemy fire pierces a fuel tank.

Its also not unlikely that STL ships could end up with multiple engine systems, a high impulse one, and a high efficiency one. This might be done even if total specific impulse suffers, because of factors like reliability restarting the high thrust engine many times, or the need for more combinations of power settings. A very high thrust engine may simply be incapable of reasonable operations at low power. It is of course also useful to have more then one engine as a backup, particularly if the main engine requires a large exposed nozzle.

Many tricks are likely to be employed to extend cruising range. Tankers are the easiest, and highly likely in all circumstances, multiple tankers per warship even. One could also employ unarmored external tanks, likely, given how crazy it is to armor an entire spaceship to any really useful degree, I think fuel will be most of the armor. Material and fuel technology allowing, they might not be cylinders or spheres, and could instead be conformal and wrap around a large portion of the hull. Large numbers of overlapping spheres would also work though, if you need such a shape for strength.

Initial departure from a major base could also employ a tug that gives the ship its initial cruise acceleration, then goes back home to help another ship depart. This would be extra useful if you have practical issues with peak acceleration. Such as we have special couches for the crew that allow us to do 20 G, but can never put 20 G worth of engine on the ship. So only use them for departure to get the mission going faster.

[Guardsman Bass]

I read a proposal for something like that "tug" system. You'd have spacecraft continually orbiting the Earth (or another planet) is highly elliptical orbits, using gravity assists during the close approach to accelerate ships that launched from the planet and rendezvoused with them into interplanetary space.

[Beowulf]

You might some day be able to make a safe nuclear salt water rocket by mixing in neutron absorber into the fuel. This would then be either filtered out, tricky to do that part safely, or overwhelmed via an external neutron generator surrounding the engine nozzle. Then the ship doesn't blow up if enemy fire pierces a fuel tank.

Rather than mixing it into the fuel, you could have the absorber in the spaces around the fuel tubes, such that if the fuel tank gets pierced, it ends up mixing with the fuel.

[Dominarch's Hope]

What if it had engines all over the ship, with mild thrust vectoring, say at six points, and when they needed a weapon, they just used the engines and focused the thrust from a widespread outward thrust to a much more fouzed and precise area.

Like using the reaction engines as highly radioactive particle weapons.

[Sea Skimmer]

Rather than mixing it into the fuel, you could have the absorber in the spaces around the fuel tubes, such that if the fuel tank gets pierced, it ends up mixing with the fuel.

Then you have to have the mass and volume for the existing fixed absorber inside the tank, and this external absorber jacket and all the structure to hold that together. That's going to be a serious increase when the ship may well have tens of thousands of tons of fuel. If the absorber is mixed then the fixed absorption system goes away, saving weight and volume inside the tank, and the fuel can be much more safely handled outside of the tanks as well. Some weight, space and power would be needed for neutron generators or filters, or some combination, of course

Your idea also becomes highly dependent on the size of the hole, and the violence of the impact that causes it, just like a self sealing fuel tank. Holes from even lasers may not be very small at all, and since this is space we acceleration can come from any direction, greatly affecting leakage-drainage and mixing rates. You need good mixing as a critical mass will form from only 20-30kg of this fuel, that's going to be something like 5-8 gallons, not that big a leak.

These numbers could go down you used more highly enriched fuel, proposals I've looked at before used 20% enriched fuel. Assuming you can use higher enrichment levels, I don't know if it will work or cause new problems, it would be very highly desirable to do so for increased energy density. You might end up with only a few gallons being a dangerous leak.

If the fuel is all external to the ships armor, and serious armor is actually possible, then its possible a critically accident outside the ship won't be crippling due to the radiation shielding effect, but I wouldn't want to bet on that, nor that fuel could not leak into the interior of the ship from say, damage to the fuel piping to the engine. My idea would reduce this dangerous length to an utter minimal, the engine nozzle itself if neutron generators could work alone. This area could then be heavily armored, and we just hope nothing shoot us from dead astern.

[MrDakka]

What if it had engines all over the ship, with mild thrust vectoring, say at six points, and when they needed a weapon, they just used the engines and focused the thrust from a widespread outward thrust to a much more fouzed and precise area.

Like using the reaction engines as highly radioactive particle weapons.

Weaponized exhaust a la Kzinti lesson?

[Simon_Jester]

As a weapon it leaves a lot to be desired because it's almost automatically going to be pretty short ranged- the exhaust disperses widely.

[Dominarch's Hope]

Which is why when you would use it as a weapon, you narrow the cone down to what would effectively be a particle beam.

Its just a concept though and there are hilarious problems with it.

[Simon_Jester]

Taking a widely scattered stream of ionized particles (they DO have to be ionized, you know that right?) and forcing them to come out narrow is... really not easy. Google the phrase 'emittance particle beam.'

[Dominarch's Hope]

So not physically impossible? No, the real stupidity is the ineffeciency of having all of those thrusting modules all over in the first place. But it could be done?

[Simon_Jester]

Since I'm not going to sit down and spend several years doing design work:

It might be physically possible, but I guarantee you you'd be better off using the mass and hull space for real weapons, or missile launchers, or almost anything at all instead of bizarro inefficient 'rocket-exhaust-sprayer' weapons.

[Sea Skimmer]

Yes use your main exhaust as a weapon, so that by definition you have to turn and run directly away from the enemy in ordered to engage him. This concept is not brilliant.

[Dominarch's Hope]

Actually it is. If your goal is survival, hurting your enemy while trying to escape is brilliant.

But not particularly bright as a turret concept.

[Simon_Jester]

If your goal is survival, retreating out of the effective range of your own weapons whenever you fire the weapon is... impressively dumb.

The enemy is probably armed with something that shoots farther than your exhaust plume.

[Sky Captain]

If you are trying to escape a missile spam turning the back towards it and going pedal to the metal could be a viable tactic. Missiles have to get fairly close to do some damage if they don't have bomb pumped laser warheads. At few km distance radiation and plasma from large nuclear engine could be more than enough to burn out electronics in missile rendering it useless. Besides running away from incoming missiles will increase the time missiles have to stay within point defense range.

[Guardsman Bass]

Your missiles might have fuel enough to do maneuvers to get them in close enough to hit (particularly if they actually have to hit the target, instead of just going off nearby with bomb-pumped or non-bomb-pumped nukes). Constantly maneuvering your ship so that the missiles risk running into the exhaust isn't going to be easy on the fuel supply.

[Simon_Jester]

If you are trying to escape a missile spam turning the back towards it and going pedal to the metal could be a viable tactic. Missiles have to get fairly close to do some damage if they don't have bomb pumped laser warheads. At few km distance radiation and plasma from large nuclear engine could be more than enough to burn out electronics in missile rendering it useless. Besides running away from incoming missiles will increase the time missiles have to stay within point defense range.

OK, now that is a good point. On the other hand, that's a dedicated missile defense tactic: "what to do if being pelted by missile barrages from beyond your own effective range." And it works nearly as well without bizarre mutant 'weapon-engines,' especially if you have a bit of thrust vectoring aboard your ship.

Your missiles might have fuel enough to do maneuvers to get them in close enough to hit (particularly if they actually have to hit the target, instead of just going off nearby with bomb-pumped or non-bomb-pumped nukes). Constantly maneuvering your ship so that the missiles risk running into the exhaust isn't going to be easy on the fuel supply.

Depends on context. Sometimes we imagine spacecraft with very limited delta-v (i.e. an hour or less of engine burn time). Any prolonged combat occurs while coasting from one place to another. Is this "realistic?" Yes, in the sense of "a lot like the experience of 20th century spacecraft." But it's not the only answer in keeping with the laws of nature.

If your engine burn time is larger (an hour or more), expending a few minutes of it to increase your chances of survival against a missile attack might be worth it. If it's very long (a day or more), doing so is a no-brainer.

On the other hand, if you do this enemy missiles will be most likely to plow into your engine compartment. If your ship is durable enough to withstand multiple hits, you're putting yourself at a disadvantage this way.