[Spaceships] Ram-Rockets and Air-Rams

[Diomedes]

In Spaceships, nuclear and antimatter rockets can be built with an air-ram for atmospheric maneuvering, for ×5 to cost. How much thrust should such a ram have, and what cost should be appropriate for a pure air ram?

[SCAR]

I'd assume that the Engines have their normal listed performance when running in Air-Ram mode, they simply don't use fuel.
I'm not sure what the cost of a pure Air-Ram would be.

[Diomedes]

Originally Posted by SCAR

I'd assume that the Engines have their normal listed performance when running in Air-Ram mode, they simply don't use fuel.
I'm not sure what the cost of a pure Air-Ram would be.

That could be problematic for engines with the high-thrust and water remass options, which I can't see making a difference to the ram-rocket.

[SCAR]

Originally Posted by Diomedes

That could be problematic for engines with the high-thrust and water remass options, which I can't see making a difference to the ram-rocket.

I'd assumed that the use of Water instead of Hydrogen didn't change the engine itself, just the fuel use. High-Thrust is a different matter.
If it seems wrong, then just use the base stats for the engine in air-ram mode, and ignore any water or high thrust options.

[malloyd]

Originally Posted by SCAR

I'd assumed that the use of Water instead of Hydrogen didn't change the engine itself, just the fuel use. High-Thrust is a different matter.
If it seems wrong, then just use the base stats for the engine in air-ram mode, and ignore any water or high thrust options.

That's probably the best option for the water option, high thrust is definitely an engine reconfiguration and probably should apply to the air ram too.

Realistically I suppose you should recompute the engine performance using whatever the composition of the air is as reaction mass, which for most atmospheres will give you a thrust increase just like going to water reaction mass. That would also increase the reaction mass use, but you don't care about that in an air ram. Except that the additional hardware needed to deliver it will depend on it, and hence the atmospheric composition, and how big a compressor pump you need will vary with atmospheric pressure. And of course it lowers you exhaust velocity, which since you are now operating with a fuel that's not moving with your vehicle matters has become a speed limit. And... You could make this quite a complex engineering challenge if you really wanted, but why?

[Agemegos]

Originally Posted by Diomedes

In Spaceships, nuclear and antimatter rockets can be built with an air-ram for atmospheric maneuvering, for ×5 to cost. How much thrust should such a ram have, and what cost should be appropriate for a pure air ram?

Going by the rules alone there is no effect on thrust. But really the thrust ought to be multiplied by SQRT {(average molecular mass of atmosphere) / 2} for the same reason that thrust is multiplied by 3 when using water. Earth's atmosphere has an average molecular mass of 28.8, so thrust ought to be multiplied by 3.8.

In my opinion the cost of ram-rockets is way too high. It tends to imply that air air intake and compressor cost more than an entire shuttlecraft, despite the fact that a shuttlecraft with a jet engine has to include these things and is much cheaper.

[Diomedes]

Originally Posted by Brett

Going by the rules alone there is no effect on thrust. But really the thrust ought to be multiplied by SQRT {(average molecular mass of atmosphere) / 2} for the same reason that thrust is multiplied by 3 when using water. Earth's atmosphere has an average molecular mass of 28.8, so thrust ought to be multiplied by 3.8.

In my opinion the cost of ram-rockets is way too high. It tends to imply that air air intake and compressor cost more than an entire shuttlecraft, despite the fact that a shuttlecraft with a jet engine has to include these things and is much cheaper.

My solution was to apply the ×5 cost modifier to the fusion reactor system, declare thrust to be 1G and call it a day.

[martinl]

Originally Posted by Brett

In my opinion the cost of ram-rockets is way too high. It tends to imply that air air intake and compressor cost more than an entire shuttlecraft, despite the fact that a shuttlecraft with a jet engine has to include these things and is much cheaper.

It may be possible that Mr. Pulver was implying a complete redesign of the engine, to tough dual-use specifications, was required.

[davester65]

Originally Posted by martinl

It may be possible that Mr. Pulver was implying a complete redesign of the engine, to tough dual-use specifications, was required.

X5 is awfully high though. Especially where some of these engines are pretty pricey to begin with. I can see x2, but x5 seems too much.