Re: [Spaceships] TL10 Space RV
 

Sticking to SS instead of 3e Vehicles, there aren't too many options that can boost a ship by at least 0.18G, provide at least half of Mercury's escape velocity, and not use up too much of the ship's mass. In fact, I've only found two:

- "Mini-Mag Orion": 1 system divvied into 3 smaller systems, one External Pulse Propulsion, one Fuel Tank, and one Magsail. $62k for hardware, $37.5k for fuel, +0.6G, 2.6 mps
- "AM Is Your Friend": 2 systems, one Antimatter Thermal, one Fuel Tank. $56k for hardware, $10k for fuel, +0.2G, 1.8 mps.

(A Laser Rocket or HEDM rocket come close, but either one needs at least 3 systems just for enough fuel.)

The current spec's chemical-rocket JATO unit uses 2 smaller systems, which I can get rid of; and I can try doubling the cost of the Fuel Tank to turn it into a reconfigurable system that doubles as a cargo bay. So with the Mini-Mag, I wouldn't lose any cargo space, while with the AM I'd only lose a third of a space of cargo; and the AM costs a lot less per landing or take-off, so that's what I'm leaning towards, despite the inherent coolness factor of any Orion-derived drive design. :)


I don't know what "diamondoid" is made of, but THS:ITWp71 includes the line, "If the device has nanocomposite or diamondoid armor (advanced laminate from TL9 or above, in GURPS Vehicles terms), acid-proofing is free." For strength, p70 has a formula for what's needed, in terms of size, frame-strength and DR. For a SS spaceship, which can be assumed to have a 'medium' frame, the dDR required on every section is (67*SizeMod)-1... kind of hard to manage on anything smaller than SM+12 (with $18B of diamondoid).

Re: [Spaceships] TL10 Space RV
 

In THS:DBp154, there's a formula for figuring out the crush depth of a vehicle, which seems to agree with the one from VX1p30. For a spaceship with DR 30, medium frame, boxy hull, and SM+4, that works out to getting crushed at 30 yards (and a test-depth of 15 yards).

I've just noticed that on the next page of Deep Beyond, the note on translating crush-depth to atmospheres of pressure seems... wildly over-optimistic. It says to multiply the depth by 11.3; that is, from 30 yards to 339 atmospheres, and from 15 yards to 169.5 atmospheres. But if you actually take a craft down 30 yards in an Earthly ocean, it's only experiencing around 4 atmospheres of pressure. If 4 atmospheres of pressure would crush a vehicle underwater, why would 40 atmospheres in a gas giant be more survivable?

Am I misinterpreting something? Should I ignore the 11.3 figure? Should I take the seeming weirdness as written?

Re: [Spaceships] TL10 Space RV
 

Carbon mostly. That's why it's "diamond-like".

I'd have to say that any acid-proofing is some sort of external coating. Carbon is fairly reactive.

Re: [Spaceships] TL10 Space RV
 

There's an alternate equation for crush depth in the alternate spaceship rules from Pyramid 34.

(crush depth in yards) = dDR*150/(hull length in feet)

It also has a different equation for converting from crush depth to atmosphere. It's (depth in feet)/33, which seems to imply that the equation you saw had the right number, just it should have been divided rather than multiplied.

EDIT: I just looked it up, and apparently that equation is off by a factor of 100 and should be 15000, not 150.

Re: [Spaceships] TL10 Space RV
 

There are other, more detailled formula in THS: Under Pressure (as well as detailled formula to calculate crush depth for aquatic vehicle, depending on frame, shape, dr, ...)

It gives
Pressure at x depth (in atmospheres) = Pressure in Atmospheres above liquid + (Depth in feet / K)

With K = 33.2 for Earth sea water, and varies for other worlds. (THS UP p 48)
K is a number equal to 34 / (the gravity of the world in Gs * the density of the liquid relative to fresh water).

So I think the "multiply by 11.3" should be "divide".

edit : the confusion isn't helped by having some equations assume depth in feet, others in yards, with the odd one in miles ... I won't resume a lost battle, but there has been spaceships lost because of that sort of mess ...

Re: [Spaceships] TL10 Space RV
 

Thank you, that clarifies everything. :)

Say, is SJG still accepting errata for In the Well? Who would I submit it to?


(Unrelatedly, I've just realized that with proper design, the Space RV doesn't need a JATO unit to kick its ground-speed up to its stall speed. I've got enough 3e Vehicles stats to work out the numbers to give the craft "variable-sweep wings", which can effectively halve the stall speed down to 110 mph, well within what it can accelerate to within a kicker.)

Re: [Spaceships] TL10 Space RV
 

Latest silliness: Pondering how much coolant tankage it would make sense to throw in as another layer of backup, in case the radiator wings get shot off.

By mixing and somewhat abusing SS's somewhat scant rules on coolant tanks with THS's rules on cooling, it looks like a tank of 100 lbs of coolant would be enough to let the reactor run for an extra 180 seconds as the coolant vents; venting 100 lbs of water instead would get 90 seconds; and melting 100 lbs of ice into water would provide all of 11.25 seconds of reactor time. All of which is after the reactor spends 30 minutes without radiator wings building up heat, and the only thing on the ship requiring full reactor power is the 0.2G main drive, so we're already dealing with a situation where the drive's been running without radiator-wings for at least half-an-hour, which already puts us into at least quaternary-level backup territory. (I've already jotted down the existence of a 20-lb, 36,000 kJ battery, which can power the main drive without the reactor for 30 seconds; and there's a secondary reactor that can push the main drive at 0.02G, and there's a tertiary reactor that can power a backup 0.001G drive.) So it looks like 20 lbs of coolant could keep the ship moving at 0.2G for 6 seconds longer than 20 lbs of battery - and coolant can only be used once, while a battery can be recharged.

The closest I can think of to getting some use out of the idea is that water is often useful for all sorts of things on a spaceship*, so if I throw in a 100-lb tank of ice/water for miscellaneous purposes, then I might as well run a heat-sink into it (plus a valve for venting outside the ship) just on the bizarrely-rare circumstance that a few extra seconds of reactor-power might be useful.

Also related, treating the fusion plant as THS's 'New Fusion', then 1.2 MW of generation requires all of 75 square feet of radiator area. I've already worked out the craft has 475 sf area; checking THS for surface features, I could dedicate 100 sf to the lasers, 224 sf for 14-tons of external-clamp capacity, and still have 151 sf for two separate surface-mounted radiators, either of which would handle the generator's heat all by itself. Meaning I wouldn't need any radiator-wings at all, unless I wanted to spend (by THS's numbers) 750 lbs on 0.075 ksf of folding radiator wing.


(*: Edited to add: Like a hot-tub. :) )


I've also been thinking of micrometeor protection, in hopes of shaving off some of the mass currently dedicated to standard armour. Here in TL8, we use Whipple shields, one or more thin layers held outside a spacecraft's main body, which break up high-velocity impactors into rapidly-dispersing plasma before they touch the craft's real surface. According to table 6 of this paper, it looks like one example of such a shield is 0.230 grams/cm^2, which works out to 224 lbs to cover 475 sf. And the graph here suggests that a simple whipple shield can handle a 3mm micrometer travelling at 3 km/second (0.12 inch, 1.86 mps), and seemingly oddly, larger or smaller projectiles travelling even faster. Up to 0.33" at 4.3 mps, which at average impact speeds, THS:HFp33 suggests would do an average of 145 damage. (I think that would be 14.5 dDmg in 4e SS terms, but I have to re-read a couple of rules to be sure.)

As it happens, 3e Vehicles suggests that over 475 sf, 150 DR of TL10 open-frame advanced ablative armour would weigh 171 lbs and cost $1,368, which seems plausible for a higher-tech version of a couple of thin layers of aluminium. Technically, open-frame armour is supposed to protect against "collisions, falls, rolls, or swinging melee attacks" and only has a 1/3 chance to protect against "thrusting attacks ... bullets, or other small missiles"... but I think I could make a case for an alternative version of open-frame armor, that only protects against objects below 8.5mm/0.33" moving at least 0.5 mps (1800 mph).

Or maybe someone has a better idea; anyone else want to try mathing out a TL10 whipple shield? :)

Re: [Spaceships] TL10 Space RV
 

OMG, 400cf of internal space is tiny!

That’s 7 ft high, ~5.75 ft wide, and 10 ft long (is that even as big as a solitary confinement prison cell?), and has to include 2 fold-away bunks, a combo all-in-one bathroom (probably with fold-away sink and toilet), tiny “efficiency” kitchen (probably just a hot plate and microwave, a pilot station / desk, and all the cargo space tucked into every available nook and cranny.

Better hope that you can get decent exercise with jumping jacks (with everything folded away) and maybe a few resistance pulleys.

There are few UT gear options mentioned down thread that I would not allow in a space that small.

I think at this size, you’re picking and choosing rulesets to get the best of both worlds.
Try working the whole thing up in Vehicles.