[Spaceships] Can't find the right propulsion system

[Michael Thayne]

I was hesitant to suggest "smaller systems" because the OP mentioned "little work pods", which might imply SM+4. It made me think of the Kobold from Spaceships 6 (an SM+4 design that uses nuclear thermal rockets as I've suggested). But smaller systems is definitely a valid choice for SM+5 designs.

Re: the danger of antimatter, antimatter-catalyzed fuel (as opposed to antimatter boosted) fuel is not listed on p. 62 of Spaceships as a volatile fuel type. This surprised me when it was first pointed out to me, but it's true, and a major reason I suggested antimatter thermal rockets.

[Anthony]

Originally Posted by Michael Thayne

Re: the danger of antimatter, antimatter-catalyzed fuel (as opposed to antimatter boosted) fuel is not listed on p. 62 of Spaceships as a volatile fuel type. This surprised me when it was first pointed out to me, but it's true, and a major reason I suggested antimatter thermal rockets.

The volatile systems section is rather generous; rocket fuel and antimatter-catalyzed hydrogen or water should be added to the volatile list, and antimatter-boosted or matter/antimatter should be noted as hilariously explosive (the maximum REF of volatile fuel is roughly 124 * (mps/tank)^2; Nuclear Saltwater will probably go subcritical after destroying the ship, limiting the destruction, but other volatile fuels will probably manage at least a pretty high fraction of that max).

[RyanW]

Originally Posted by Michael Thayne

I was hesitant to suggest "smaller systems" because the OP mentioned "little work pods", which might imply SM+4. It made me think of the Kobold from Spaceships 6 (an SM+4 design that uses nuclear thermal rockets as I've suggested). But smaller systems is definitely a valid choice for SM+5 designs.

Since many systems are easy enough to extrapolate, I'm perfectly happy to allow smaller modules even on SM+4 vehicles. And there are certainly tiny rockets. Capsules use SM+0 or smaller chemical rockets for attitude control.

[acrosome]

Originally Posted by Kale

You can use Smaller Systems to convert a single system into three systems of one size (SM) smaller: You can replace a 3G chemical rocket with a 1G rocket and two small fuel tanks, all one SM smaller than the ship. This gives 2/3rds the capacity of a full SM sized fuel tank. If you want to go really small, you can convert down by two SM levels and get 10 systems at SM-2 for a single full sized slot. Each rocket would provide 0.3G of thrust at that level.

This looks like the answer I was seeking.

But, yes, I'm making a lot of little SM+4 pods. But I see no reason I can't still do this. Right?

Yes, initially I designed the pods with antimatter thermal rockets. They were pretty perfect. Except for the spewing radioactive death thing.

Thanks, all.

[Kale]

Originally Posted by acrosome

This looks like the answer I was seeking.
But, yes, I'm making a lot of little SM+4 pods. But I see no reason I can't still do this. Right?

I've actually done this with small "Work Bee" yard ships. They are SM4 and have SM2 smaller systems to represent tiny thrusters and some tools and other equipment. Given that you can make palm-sized chemical rockets, SM2 is still downright large. Here are some fan rules for tiny systems: http://gsuc.roto.nu/doku.php?id=sm_3

[Johnny1A.2]

Originally Posted by acrosome

Hi, all. I'm trying to find an appropriate propulsion system for little work pods and inter-ship lighters, for in the space near stations, in work areas, etc. These are not long-range vehicles so they don't need massive delta-V. But they probably do need acceleration measured in something larger than milligees, if only for time management concerns, so Ion and VASMIR drives are out.

In this setting (TL10) there is a limited superscience switch that makes antimatter extremely cheap and things like the antimatter plasma torch possible. But for small craft like this such systems wouldn't be used since every Tom, Dick, and Harry welder or taxi pilot can't be trusted with a drive that spews radioactive death.

So for the life of me the only option I seem to be able to find is a chemical rocket. But this seems like overkill at 3G acceleration. What I really need is just some sort of OMS, y'know? Have I missed some other option?

For the mission you describe, 3G sounds like more acceleration than you'd likely want anyway. Why do work pods and intership taxi vehicles need that kind of acceleration?

[Say, it isn't that bad!]

Where are the rules for using smaller systems on larger craft?

[Ulzgoroth]

Originally Posted by Say, it isn't that bad!

Where are the rules for using smaller systems on larger craft?

Spaceships 7, p4-5.

Also, if you have guesses about how it works, they're probably right. It's not very complicated or tricky.

[acrosome]

Originally Posted by Johnny1A.2

For the mission you describe, 3G sounds like more acceleration than you'd likely want anyway. Why do work pods and intership taxi vehicles need that kind of acceleration?

Because they don't; you failed your Reading check. :) I said that 3G rockets were overkill. You're thinking that I said the exact opposite of what I actually said.

Originally Posted by Ulzgoroth

Spaceships 7, p4-5.

Also, if you have guesses about how it works, they're probably right. It's not very complicated or tricky.

Thank you.

[Kale]

I find the 3G rocket systems are handy for Tug designs that might end up having to clamp to and move a larger vessel. For small ships that just have to go to a nearby location in a shipyard though, an SM-2 system at 0.3G is plenty. Just remember if you need to drag around a big hull plate or something the extra mass might actually justify the full 3G. For instance an SM5 tug can shove around an SM6 ship at 0.75G if the tug has a full 3G rocket system installed. Just make sure not to use the rocket at full thrust when the tug isn't actually pulling anything.