Re: [Spaceships] TL10 Space RV
 

An option to reduce cost, and perhaps make streamlining more feasible, would be to cut the habitat in half (5 systems), giving it the same amount of living space but removing the total life support. That drops price by $50k, and you can stock the additional 5 systems (which you can set as cargo holds) with enough food to last the pilot over 3 years. Indeed, the $50k you save is enough to keep you stocked with food for somewhere around 68 years (more if you invest it somewhere with a decent rate of return), so long as you're able to stop at a store every couple of years or so.

I considered an option to replace the reactor with a fuel cell and sacrifice some of those cargo holds for fuel tanks to power it, but that doesn't make for much savings at the start, and you only get a few months of use out of it before fuel replacement makes it cost more than the fission reactor did.

Is it strictly necessary that the ship be capable of interfacing? A pure spaceship would be a lot easier, and at least a bit cheaper, to design, although at SM+4 it's not got any space for an interface craft (it would need to dock with an orbital station so the owner could rent/hire a shuttle to go planetside).

Re: [Spaceships] TL10 Space RV
 

I'm a little curious why you're so set on having cheap spaceships in your setting. If you're trying to do the Han Solo / Mal Reynolds thing of having lots of people who somehow own spaceships in spite of being hard up for cash, my first suggestion is not thinking about it too hard. If the PCs want to be that sort of person, you can represent that as Wealth with a -20% limitation for Conditional Ownership meaning you "cannot or will not resell" the asset (see Spaceships 2, p. 27). Alternatively, there was an article in Pyramid #3/71 that suggested treating the ship itself as a Patron. The article has a fair amount of detail but the basic idea is to replace "patron's net worth" with "value of the ship" in the Patron rules. So for example, a constantly available patron with resources of 1000x campaign starting wealth is 40 points, there owning a spaceship worth 1000x campaign starting wealth while inexplicably being hard up for cash otherwise is also worth 40 points.

If you want to justify this sort of thing in-setting somehow, maybe there are legal restrictions on buying and selling of spaceships that make it difficult to convert spaceship ownership into cash. This could be as simple as exorbitant taxes on the buying and selling of spaceships, or something bizarre like early 19th century entailment laws applied to spaceships, or prohibitions on a certain class of people owning non-spaceship capital. But it's not necessarily wrong to just have that as an area where suspension of disbelief is called for.

Re: [Spaceships] TL10 Space RV
 

This is true, but it's eliding a key difference between air-breathing aircraft and this vessel:

The reactionless thruster produces the same 0.1g at all speeds and altitudes. That's the main limiter on real high-altitude airplane operation. Air-breathing engines lose performance (or outright stop working) in thin, fast airstreams. (Even if you're using a non-combustion air-breather like a nuclear ramjet.) No problem with that here.

Without that problem, I think things look good. Drag and lift both tend to scale with air density and the square of airspeed, AFAICT, so if you can get above the surface effect at sea level with 0.1g you should be able to sustain flight an any altitude with 0.1g, and that means you can insert into low orbit for sure.

Re: [Spaceships] TL10 Space RV
 

A spaceship as a Patron is also not a bad idea for something like Rogue Trader, where the spaceship belong to your family (and small starships are SM+15).

Re: [Spaceships] TL10 Space RV
 

<Does algebra>

Oh huh, you're right. At higher altitudes, you can cancel out having less lift due to lower pressure by going faster, which you can do because the lower pressure means less drag. So it al works out.

EDIT: This actually upends a lot of assumptions I and other seem to have historically made about world-building futuristic settings. Kinda wanna test out a low-thrust spaceplane concept in a simulator like Orbiter. But I'm going to resist the urge to get too deep into this in the near-future.

Re: [Spaceships] TL10 Space RV
 

Wouldn't gravity drag be an issue with only 0.1g acceleration? For a 3g acceleration, you end up losing around 0.5 km/s when attempting to reach orbital velocity (meaning gravity drag is around 0.15g). In effect, the spaceship should not be able to fly, much less leave the atmosphere, as gravity drag would negate its acceleration.

Re: [Spaceships] TL10 Space RV
 

Note that at 0.1g, this implies a takeoff run of 7,000 to 28,000 feet, assuming your ship can even manage those speeds as a ground vehicle. I echo ericthered's comment and recommend you increase this to 0.3g, despite the added cost.

Re: [Spaceships] TL10 Space RV
 

'Gravity drag' only exists when you're thrusting against gravity. You basically don't ever do that at all with this type of craft.

Gravity drag is also a somewhat misleading name, and describing it as an acceleration suggests you have in fact been mislead...

Re: [Spaceships] TL10 Space RV
 

Maybe a small rocket for take-off assist? You could probably get that into just a few smaller systems. A water NTR would be pretty easy to refuel on most bodies that you'd have any chance of leaving...

Re: [Spaceships] TL10 Space RV
 

Al/right/y, then. That nicely solves the bit of math that I hadn't been able to figure out; thank you kindly. :)


A fair point; I can work with that.


I'm already invested in the particular technobabble in play, but I'm still doing a bit of setting-creation, working out further consequences of the basic setting assumptions (ie, the existence of the superscience drive and power plant). The fact that, for the price of a good-sized house, somebody can buy a two-person craft capable of booting around the whole Solar system while going for a couple of years without resupply, leads to a variety of knock-on effects compared to the original THS setting. It would have been easier to move the mass from Luna into L4 and L5 to create O'Neill Cylinder colonies; there's much less incentive to save launch costs by building a beanstalk; there's no need for He3 mining in gas giants; it's that much easier to found an asteroid settlement; and so on. As long as I keep the consistent world-building at least one step further than the freelance Vacuum Cleaner PCs, I should be good. :)

(Next on my to-do list: check SS5's table of near-c ablation damage, to check for the feasibility of sub-trillion-dollar STL colonization attempts.)


I've just finished back-engineering a few numbers to get a full set of 3e Vehicles stats:

. SM+4: excellent streamlining, external volume 540 cf (internal volume 400 cf), area 400 sf; wings 8.4+8.4 cf, area (25+25)*1.5=75 sf; wing hp 38 ea.
. gSpeed: 250 mph, gAccel 10 mph/s, gDecel 10 mph/s, gMR 0.25, gSR 4.
. aDrag = 24, aSpeed = 790 mph, aAccel 2 mph/s, aMR 1.5, aSR 5, aDecel 6 mph/s, aStall = 220 mph, ceiling 9.4 km; terminal speed 2500 mph, top glide speed 1,000 mph, glide ratio 20:1; takeoff/landing run 1,210 yards (0.7 miles)
. floatation rating 34,800 lbs (17.4 tons), draft 22 inches, wDrag 737, wSpeed 8 mph, wAccel 2 mph/s, wMR 0.75, wSR 6, wDecel 10 mph/s.

... which is a takeoff run of only 3,630 feet, which seems reasonably reasonable.