Attacking Darius:

tlb wrote:The point is that the drop-offs could have been performed by freighters on their way to the Manticore Junction, rather than at the limit of the net's detectability. That gives an enormous uncertainty in the amount of time that the weapons had to travel. In any case, while we know the method used; the authorities at Manticore and Grayson do not have a clue.

I think that what David is showing is that the RMN has made a series of very major mistakes. While these have not yet bitten them, they will in time. And due to these they won't be able to see what is missing from the MA planet they captured.

Alternately, the plot armor of the RMN is known by all the RMN leadership and is taken into account in their decision making process, so they make dumb decisions because it's easier that making smart decisions.

I really don't know.

I just can't see Spiders using any form of thrusters. Fusion thrusters should light up the heavens like a local fireworks display. Not that I can imagine fusion thrusters being also highly controllable, thus instantly variable. Talk about a process that absolutely has to create a lot of excess heat. How it is designed to be instantaneously variable to be practical eludes my imagination.

I assume that thrusters are necessary because a ship cannot operate wedges when close to other objects. Docking would be impossible. But anyone who played with Lunar Lander back in the day knows that you must have thrusters at all times. Fore and aft. Firing thrusters to slow forward progress when close to the space station should be dangerous to the station. Tugs probably tow warships to the station. But tugs need thrusters as well. More powerful thrusters at that.

At any rate, remember when I speculated about all of the systems on conventional ships that must need power. Well, add another.

I am beginning to think that the Spider will require much less power. Nowhere near as many reactors as a Fort or SD. Which translates into loads of surplus power. For weaponry!

ThinksMarkedly wrote:On the momentum transfer side, in one hour, that ship gained 900 billion kg m/s of momentum. If the hydrogen was expelled out at 0.1c relative, then the ship must have pushed out 30 tonnes in one hour. I suppose it can send 28 t of hydrogen and 2 tonnes of helium that is the product of fusion, so it keeps its bunkerage expenditure at 30 t/hour. Those are belieavable numbers.

Yeah, you're right, it's a mix of hydrogen and helium, not just hydrogen. Might as well use the waste helium from the reactor as reaction mass.

Loren Pechtel wrote:

ThinksMarkedly wrote:On the momentum transfer side, in one hour, that ship gained 900 billion kg m/s of momentum. If the hydrogen was expelled out at 0.1c relative, then the ship must have pushed out 30 tonnes in one hour. I suppose it can send 28 t of hydrogen and 2 tonnes of helium that is the product of fusion, so it keeps its bunkerage expenditure at 30 t/hour. Those are belieavable numbers.

Yeah, you're right, it's a mix of hydrogen and helium, not just hydrogen. Might as well use the waste helium from the reactor as reaction mass.

I suppose that would be a win win situation. Recycling waste hydrogen by finding a use for it. But hydrogen is very flammable, and the reactors of the large ships of the wall are buried deep inside the bowels of the ship, iinm. At any rate, you have very hot plasma coursing thru the veins of the ship, along with veins of hydrogen. I can't believe even a single hit from a graser head doesn't cause even an SD to flame like data. A pipe leading from the reactor's hydrogen containment to the thrusters on the hull of the ship sounds like a very long fuse on a huge stick of dynamite. HV ships should be more flammable than the Hindenburg. And I don't care how much armor an SD has, explosions emanating from the inside are much more fatal.

cthia wrote:I suppose that would be a win win situation. Recycling waste hydrogen by finding a use for it. But hydrogen is very flammable, and the reactors of the large ships of the wall are buried deep inside the bowels of the ship, iinm.

Reactors, yes. Bunkerage, not so much. If you have to carry so much hydrogen anyway, you might as well use it as radiation shielding, which hydrogen and water are actually pretty good at.

Yes, hydrogen is flammable, but it requires oxygen for combustion to happen. If there isn't some available, what is it going to do?

At any rate, you have very hot plasma coursing thru the veins of the ship, along with veins of hydrogen. I can't believe even a single hit from a graser head doesn't cause even an SD to flame like data. A pipe leading from the reactor's hydrogen containment to the thrusters on the hull of the ship sounds like a very long fuse on a huge stick of dynamite. HV ships should be more flammable than the Hindenburg. And I don't care how much armor an SD has, explosions emanating from the inside are much more fatal.

We don't know what forms the reactor intakes and exhausts are. It's possible the intake is cold hydrogen and that doesn't get heated up until the reactor by gravity. The exhaust is likely to be hot helium, though. But helium is far less reactive -- it's a noble gas, after all. It's hot and will exchange energy with everything (Thermodynamics), but it's not going to combust.

Flammability doesn't apply because there shouldn't be enough oxygen in the first place. With good carbon dioxide scrubbers, the oxygen is recycled, so you have basically a fixed amount of it inside the ship. The problem in our atmosphere is that there's 21% of it by volume, which is a lot.

The 50 million degree temp of the hydrogen at say 5000 atmospheres is probably more of an issue than a fire.

ThinksMarkedly wrote:

cthia wrote:I suppose that would be a win win situation. Recycling waste hydrogen by finding a use for it. But hydrogen is very flammable, and the reactors of the large ships of the wall are buried deep inside the bowels of the ship, iinm.

Reactors, yes. Bunkerage, not so much. If you have to carry so much hydrogen anyway, you might as well use it as radiation shielding, which hydrogen and water are actually pretty good at.

Yes, hydrogen is flammable, but it requires oxygen for combustion to happen. If there isn't some available, what is it going to do?

It's not going to do anything without a breach and a catalyst. The breach comes from a laser head. The catalyst (oxygen) comes from the pressurized crew compartments, living quarters, bridge and everywhere else that is fed by the environmental systems trying to keep the crew alive. Damaged ships have a habit of streaming atmosphere. And leaking plasma.

ThinksMarkedly wrote:

cthia wrote:At any rate, you have very hot plasma coursing thru the veins of the ship, along with veins of hydrogen. I can't believe even a single hit from a graser head doesn't cause even an SD to flame like data. A pipe leading from the reactor's hydrogen containment to the thrusters on the hull of the ship sounds like a very long fuse on a huge stick of dynamite. HV ships should be more flammable than the Hindenburg. And I don't care how much armor an SD has, explosions emanating from the inside are much more fatal.

We don't know what forms the reactor intakes and exhausts are. It's possible the intake is cold hydrogen and that doesn't get heated up until the reactor by gravity. The exhaust is likely to be hot helium, though. But helium is far less reactive -- it's a noble gas, after all. It's hot and will exchange energy with everything (Thermodynamics), but it's not going to combust.

Flammability doesn't apply because there shouldn't be enough oxygen in the first place. With good carbon dioxide scrubbers, the oxygen is recycled, so you have basically a fixed amount of it inside the ship. The problem in our atmosphere is that there's 21% of it by volume, which is a lot.

Yep, 21% by volume in our atmosphere. Overkill to fuel explosions. The % of oxygen aboard ship is underkill. The operative word in both is kill.

cthia wrote:Yep, 21% by volume in our atmosphere. Overkill to fuel explosions. The % of oxygen aboard ship is underkill. The operative word in both is kill.

Well, yes. But what else are you going to do?

If I were to design such a ship, I'd give it an outer and an inner armour, with the hydrogen bunkerage between the two. The inner hull armour encases the living spaces and pressurised compartments. What else gets in those is a matter for discussion, but not everything has to be armoured, for which there's a mass allocation coast.

A laserhead breach in the outer hull is going to cause hydrogen to spill out. Even the energy of the laserhead in the hydrogen isn't going to do much: it'll cause ionisation and thus it will be a plasma; at worst, it'll cause spontaneous fusion and thus a release of energy, but there's no chance this is a self-sustaining operation at the pressure levels that hydrogen is going to be kept.

A laserhead that breaches the inner hull is going to cause venting into or out of the pressurised areas. The direction is going to depend on the relative pressures. I suspect the pressure in the hydrogen bunkerage would be higher, so it would vent into the crew areas. It would be better if it were the other way around, of course, but that would limit your hydrogen mass. But maybe it's a good thing, in that the hair-thin hole in that armour is going to limit the flow of hydrogen into the ship, thus limiting the combustion too.

No, you’d store it as water. Liquid hydrogen is terrible. It’s a cryo fluid, it’s extremely low density. It it warms up it, to say 25 kelvin, it expands like 700 times. So now you have an expanding cloud of supercold gas that can penetrate virtually any seal turning your ship into a fragile glass carving.

The energy needed to disassociate water is trivial if you are feeding into a fusion reactor.

kzt wrote:No, you’d store it as water. Liquid hydrogen is terrible. It’s a cryo fluid, it’s extremely low density. It it warms up it, to say 25 kelvin, it expands like 700 times. So now you have an expanding cloud of supercold gas that can penetrate virtually any seal turning your ship into a fragile glass carving.

The energy needed to disassociate water is trivial if you are feeding into a fusion reactor.

You'd still need to keep a small supply of ready feedstock for the reactors, but only a couple % of the ship's total supply at most.