[Spaceships] TL10 Space RV

[Michael Thayne]

Originally Posted by ericthered

I've got some concerns about the play between air resistance, lift, velocity, and heating. You need to be in atmosphere to generate lift until you reach orbital velocity. atmosphere is going to slow you down as long as you're in it, and eventually create massive heating around your ship, not to mention drag. You can reduce drag by flying higher, but that also reduces your lift.

Yeah, I don't think there's any way you can make it to orbit with 0.1G thrust. Even doing it with 1G would be tricky. If you want a rigorous answer though you'd need to play around with a program like Orbiter or perhaps a heavily modded Kerbal Space Program.

[Fred Brackin]

Originally Posted by DataPacRat

The setting is approximately THS, roughly TL10 with only a couple of pieces of superscience: a low-thrust reactionless drive (call it around the stats of Spaceships' Rotary Reactionless Drive, 0.1G per space) and as a spinoff of that tech, what's effectively a vacuum-energy power plant (though it uses completely different technobabble; call it SS7's Perpetual Motion Machine, 1 PP per space).)

Do you have Transhuman Space's DNA Repair nano? They get it 1 TL earlier (at the cost of the Extended lifespan) than the same-named item from Bio-tech. This is absolutely esential to keep people from getting lethal doses of cosmic radiation in small, thin-hulled spacecraft.

Thrash is right about the take-off run and that applies to climbing to altitude and even breaking loose rom Earth Orbit. You won't be able to jsut point your nose where you want to go. Any time you're ina gravity well you're going to have to spiral outward while you build up speed.

I'd go to at least .2 Gs so I could land on the moon and get closer to commercial aircraft rates of speed and acceleration.

If you stay at 0,1G a rule of thumb is that after you reach escape velocity it will take you 9 days of accel/decel to go 1 AU. The good news is that longer distances get multiplied by the square root of the increase factor. So if you've got a 9 AU trip to Saturn(Titan) that's 27 days plus orbital maneuvering and takeoff/landing. Put a hibernation pod in the thing and sleep the trip away. That cuts way down on your habitat requirements.

[DataPacRat]

Originally Posted by Ulzgoroth

I can't follow the equations without a lot of digging into the book, but it looks like you're still getting a ground acceleration of more than double your vessel's actual thrust.

I've triple-checked Vehicles' formulas, and I think I'm following them properly now. I don't know what to say, other than that it seems like Vehicles thinks that applying thrusters to a wheeled vehicle on the ground has different effects than applying them when it's in the air.

Originally Posted by Fred Brackin

Do you have Transhuman Space's DNA Repair nano? They get it 1 TL earlier (at the cost of the Extended lifespan) than the same-named item from Bio-tech. This is absolutely esential to keep people from getting lethal doses of cosmic radiation in small, thin-hulled spacecraft.

Yes, definitely; I'd even forgotten the BioTech version was at a higher TL.

Originally Posted by Fred Brackin

Thrash is right about the take-off run and that applies to climbing to altitude and even breaking loose rom Earth Orbit. You won't be able to jsut point your nose where you want to go. Any time you're ina gravity well you're going to have to spiral outward while you build up speed.

Just taking an orbital speed of 17,800 mph, and an acceleration of 0.1G, it takes around 2.25 hours to get up to speed, and travelling 32,300 km. That's over three-quarters of the way around the Earth, which I'd say is a fairly good spiral.

Originally Posted by Fred Brackin

I'd go to at least .2 Gs so I could land on the moon and get closer to commercial aircraft rates of speed and acceleration.

With the bunks dropped from 10 spaces to 5, there's actually enough room for that, now.


Since there's been a few changes, here's the latest draft of the Space RV. (For the takeoff run, it seems that the craft would accelerate up to 200 mph with the reactionless thruster, then kick in the booster for just under a second for the other 20 mph needed to get up to stall speed.)

Quickie design sketch: SM+4, streamlined, TL10 (mostly non-superscience).
- Design switches: Advanced Computers (as TL11), Exposed Radiators, Slower Industrial Systems
- Winged: $50k
- 2 spc: Armor, diamondoid, dDR 10 (4/3/3), $200k
- 5 1/3 spcs: Cargo Holds, 2.666 tons
. Food, 1 ton: 500 man-days, $1k
- 1 spc: Control Room, $20k
- 1 spc: External Clamp, $1k
- 1/3 spc: SM+3 Fuel Tank in SM+4 craft, 0.05 mps delta-v (8.2 seconds, +180 mph, good for 9 takeoffs), $1k. 0.15 tons fuel, $120 for fuel.
- 5 spcs: Habitat: 0.5 SM+6 spaces: bunkroom for 2: $50k
- 2 spcs: Power Plant, Fission Reactor, 2 PP, 75 years: $60k
- 1/3 spc: SM+3 Reaction Engine in SM+4 craft, Chemical Rocket: 1G accel, $6k.
- 2 spcs: Reactionless Drive, rotary, accel 0.2 G, req 2 PPs, $100k
- 1 spc: Weapon, central turret, improved laser, very rapid fire: Major SM+4 battery (30 kJ, dDmg 1d-2, RoF 200/20s, rng C or 150/500 mi), req 1 PP: $100k
-- Total cost: $588k
-- LMass 10 tons, length 10 yards, dST/HP 15, HT 12, Hnd/SR -1/4, dDR 4/3/3, Occ 2ASV.
-- Air performance: 1,120 mph. Hnd/SR 3/5.

. 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.
. aDrag = 24, aSpeed = 1,120 mph, aAccel 4 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 1,136 yards + 6 yards (0.65 miles)
. floatation rating 34,800 lbs (17.4 tons), draft 22 inches, wDrag 737, wSpeed 11 mph, wAccel 4 mph/s, wMR 0.75, wSR 6, wDecel 10 mph/s.
. gSpeed: 200 mph, gAccel 8.8 mph/s, gDecel 10 mph/s, gMR 0.25, gSR 4.

[Ulzgoroth]

Originally Posted by DataPacRat

I've triple-checked Vehicles' formulas, and I think I'm following them properly now. I don't know what to say, other than that it seems like Vehicles thinks that applying thrusters to a wheeled vehicle on the ground has different effects than applying them when it's in the air.

I suspect it's that thrusters are bolted on to the calculation and thruster-only builds interface poorly with the expectation that ground acceleration is a factor of the square root of drive train power/weight.

[DataPacRat]

Originally Posted by Ulzgoroth

I suspect it's that thrusters are bolted on to the calculation and thruster-only builds interface poorly with the expectation that ground acceleration is a factor of the square root of drive train power/weight.

Well, if I cap gAccel at sAccel, that'd be 2.2 mph/s for just the thruster, and 24.1 mph/s with the booster. So that'd be a takeoff run of 4,545 yards to get up to 200 mph, then another 5 yards for the final boosted push to stall speed (total 2.6 miles). Or, 182 yards to get up to 40 mph, plus 336 yards to use up all the booster's fuel for the remaining 180 mph (total 0.3 miles).

[AlexanderHowl]

An alternative version that I think would work better at TL10^ would be a SM+6 spaceship with the following: 1 control room, 1 engine room, 1 fusion reactor, 2 external clamps, 2 hot reactionless engines, 3 steel armor, 4 habitats, 6 hanger bays. The spacecraft would possess four double occupancy cabins (two crew and two passenger), allowing for a total of eight people. The 6 hanger bays would allow for unloaded cargo without decompressing the entire ship and would allow for 18 tons of cargo. The two external clamps would allow for additional cargo transfer, as the 2g acceleration of the spacecraft would allow it to take two SM+5 cargo barges into orbit at 1.25g. With artificial gravity and winged, it would cost $2.97M.

Now, this is not as cheap as the SM+4, but it is a mighty workhorse due to its high acceleration. While towing two SM+5 barges, it is capable of making Earth to Saturn in 8 days (maximum velocity a hair over 1.4% c). Of course, it would likely cater to clientele who did not want to go with the regularly scheduled cargo ships (usually smugglers), but that would be part of the excitement. It would tow SM+5 barges for legitimate purposes while the illicit cargo (and passengers) would be hidden within the hanger bays and cabins.