[Spaceships] Designers' Championship I: ground to LEO

[thtraveller]

I am guessing that a 6G laser launcher (5G effective) with 13 fuel tanks and 2 passenger seating will be the one to beat.

Is there a limit on the G force we can apply to passengers?

Do we need to worry about the real G Force felt with nearly empty tanks?

[Chansith]

Originally Posted by thtraveller

I am guessing that a 6G laser launcher (5G effective)

With a laser launch system I guess you have to stay over the launcher, which is a bit of a pest. With a 6 g rocket you would pitch down to a flight path with a 9.6° angle of climb, and enjoy an effective acceleration of 5.9g. But that gets you over the horizon pretty quickly. (The advantage of an inclined flight-path is more significant with lower acceleration: at 2 gee it means a difference of 70% in your available delta-v).

with 13 fuel tanks and 2 passenger seating will be the one to beat.

I have some sort of hopes for air-breathing fusion engines at the higher TLs, maybe even air-breathing AM engines at the lower ones.

Is there a limit on the G force we can apply to passengers?

Crushing the passengers to death is counter-indicated. And there are brownie points to be had for getting them into orbit without their blacking out. But trying to figure an appropriate cash bonus for an easy ride is too difficult and fiddly for this, which is supposed to be a simple exercise.

Do we need to worry about the real G Force felt with nearly empty tanks?

I don't think so. All the rocket types we have on hand can be throttled back to allow for the changing mass.

[thtraveller]

Originally Posted by Chansith

I have some sort of hopes for air-breathing fusion engines at the higher TLs, maybe even air-breathing AM engines at the lower ones.

Then I think we need conversions for the fission/fusion air rams from TS.

I got as far as outline design for a laser launch vehicle before deciding that the base station cost is going to be very expensive. Even for a 4G size 5 craft you are looking at M$360+ for the base station.

I now quite like the look of the Nuclear thermal rocket at TL9+. Though not sure if its exhaust is allowed?

[thtraveller]

TL9+ Orbital Lighter (Spaceplane) v1 "Alida"

Alida class spaceplanes are cheap reusable single stage orbital lighters that can take off and land at a normal airport.

Using a jet engine to take off it clears local population centres before going supersonic and accelerating to maximum air speed. It then engages the Nuclear Thermal rocket drive and climbs into orbit in under 7 minutes. Having docked and exchanged passengers it reenters atmosphere and then makes a slow descent back to Earth. On final approach it powers up its jet engine and lands at an airport. It can comfortably make the return journey once every two orbits or every 180 minutes. (It could probably make the journey every 1.5 orbits by constantly switching between landing sites in two hemispheres).

Front
1 Armor (Advanced Laminate)
2-3 Passenger Seating (4 seats)
4-6 Fuel Tank (Hydrogen)
0 Control Room

Central
1-6 Fuel Tank (Hydrogen)
0 Fuel Tank (1 hours Jet Fuel)

Rear
1-5 Nuclear Thermal Rocket (2.5G)
6 Jet Engine (1G)

dST/dHP 20, Hnd 4 atmo/0 space, SR 4/5, HT 12, Move 1G/2500 mph/0.69 mps, 2.5G/5.67 mps, LWt 30, Load 0.5, SM +5, Occ 1+4 SV, dDR 3, Cost M$ 1.44, TL9, Streamlined, Winged, Length 15 yards

DeltaV 6.36mps (ample reserve)
-Jet Engine 2500mph = 0.69mps
-9 Hydrogen Fuel Tanks = 9*0.45*1.4 (9 tank adjustment) = 5.67 mps

Draft economics:

1 flight every 3 hours operating for 7200 hours pa= 2400 flights per year
4 passenger seats at 75% loading = 3 passengers per trip
= 7,200 passengers per year

Variable cost per trip:
Insurance = M$1.44/1000 = K$1.44
Servicing = M$1.44/100 = K$14.4
Fuel: 13.5 tons Hydrogen (K$27) + 1.5 tons Jet Fuel (K$6) = K$33

Total Variable = 1.44+14.4+33 = K$48.84

Annual Costs to Amortise:
Requires 4 pilots at $7200 pm TL9 Comfortable salary each = K$345.6 pa
Other economics = Insurance+Depreciation+RoI = 10% = K$ 144

Total Fixed = K$ 489.6

Divided over 2400 trips = $204 per trip

Return Ticket price = K$49 / 3 passengers = $16,350 (4.5 months income for an average TL9 job)

I don't see a significant difference between TLs other than the pilots wages increase, which adds about $30 per TL to the ticket price.

On backwoods world you only employ one pilot part time so annual costs are K$34.56 + K$144 = K$178.56 / 240 trips = $744 per trip

So ticket price per passenger increases by $250 to $16,600 on backwoods worlds

As most of the ticket cost is variable cost the ticket price should scale with ship size fairly linearly.

[Chansith]

Originally Posted by thtraveller

TL9+ Orbital Lighter (Spaceplane) v1 "Alida"

Inaugural champion designer (div'n I, ground to LEO):

thtraveller

for the "Alida" class orbital lighter (spaceplane)

[Chansith]

Originally Posted by thtraveller

Then I think we need conversions for the fission/fusion air rams from TS.

Will the "Ram-Rockets" rules on p. 30 do the job?

I now quite like the look of the Nuclear thermal rocket at TL9+. Though not sure if its exhaust is allowed?

I would guess so. In the NERVA design the nuclear fuel retained in the core. The propellant should not pick up significant radioactivity as it passes through as coolant: indeed, hydrogen cannot.

[thtraveller]

Originally Posted by Chansith

Inaugural champion designer

Shouldn't we wait and see if others post a design?

Originally Posted by Chansith

Will the "Ram-Rockets" rules on p. 30 do the job?

Oops missed that option. In which case the Alida does not need a Jet Engine and Jet fuel and can now operate from any airport in the world (not just those near the equator).

Just convert the Jet Engine to a NT Ram-rocket, lose the jet fuel tank, add a passenger seat module (+2 seats). Cost is now M$ 1.89. Return Ticket Price is now $10,640 (3 months basic income). Now has 3G drive to orbit, Top Air Speed 1800 mph (0.5 mps).

[thtraveller]

TL9+ Orbital Lighter (Spaceplane) v2 "Alida"

Alida class spaceplanes are cheap reusable single stage orbital lighters that can take off and land at a normal airport anywhere in the world.

Using a Nuclear Thermal Rocket in fuel-less air-ram mode to take off it clears local population centres before going supersonic and accelerating to maximum air speed in an easterly direction. It then engages the other normal Nuclear Thermal rockets and climbs into orbit in under 6 minutes. Having docked and exchanged passengers it re-enters atmosphere and then makes a rapid descent back to Earth. Again using its air-ram engine it lands at an airport. It can comfortably make the return journey once every two orbits or every 180 minutes. (It could probably make the journey every 1.5 orbits by constantly switching between landing sites in two hemispheres).

Edit: The excess delta-V (6.17 mps versus the 4.6 mps required) allows for losses due to air-resistance and gravity. It also includes an emergency reserve (e.g. single engine failure in flight). The 3G thrust allows it to get it into orbit quickly to reduce gravitational losses.

Edit: The excess delta-V also allows for the spaceplane to enter orbit from higher latitudes rather than on the equator (e.g. Europe) and hence not have the full benefit of 0.25 mps from equatorial spin. It also allows it to enter slightly higher orbits and also satisfies the G:Spaceships 5.6 mps orbital velocity requirement.

Front
1 Armor (Advanced Laminate)
2-4 Passenger Seating (6 seats)
5-6 Fuel Tank (Hydrogen)
0 Control Room

Central
1-0 Fuel Tank (Hydrogen)

Rear
1-5 Nuclear Thermal Rocket (2.5G)
6 Nuclear Thermal Ram-Rocket (0.5G)

dST/dHP 20, Hnd 4 atmo/0 space, SR 4/5, HT 12, Move Fly 0.5G/1800 mph/0.5 mps, Boost 3G/5.67 mps, LWt 30, Load 0.7, SM +5, Occ 1+6 SV, dDR 3, Cost M$ 1.89, TL9, Streamlined, Winged, Length 15 yards

DeltaV 6.17mps (ample reserve)
-Ram Rocket 1800mph = 0.5 mps
-9 Hydrogen Fuel Tanks = 9*0.45*1.4 (9 tank adjustment) = 5.67 mps

Economics:

1 flight every 3 hours operating for 7200 hours pa= 2400 flights per year
6 passenger seats at 75% loading = 4.5 passengers per trip
= 10,800 passengers per year

Variable cost per trip:
Insurance = M$1.89/1000 = K$1.89
Servicing = M$1.89/100 = K$18.9
Fuel: 13.5 tons Hydrogen (K$27)

Total Variable Cost = 1.89+18.9+27 = K$47.79

Annual Costs to Amortise:
Requires 4 pilots at $7200 pm TL9 Comfortable salary each = K$345.6 pa
Other economics = Insurance+Depreciation+RoI = 10% = K$ 189

Total Fixed Cost = K$ 534.6

Divided over 2400 trips = $223 per trip

Return Ticket price = K$48 / 4.5 passengers = $10,640 (3 months income for an average TL9 job)

I don't see a significant difference between TLs other than the pilots wages increase, which adds about $30 per TL to the ticket price.

On a backwoods world you only employ one pilot part time so annual costs are K$34.56 + K$189 = K$223.56 / 240 trips = $932 per trip

So ticket price per passenger increases by $210 to $10,850 on backwoods worlds

As most of the ticket cost is variable cost the ticket price should scale with ship size fairly linearly.

[thtraveller]

Originally Posted by Chansith

Ground rules:
14. In the case of a vehicle that is not winged, it will be assumed that supporting the vehicle against gravity will reduce available delta-v from V to V' = V * square root of (A-squared - 1), where A is the acceleration of the vehicle.

Is that meant to be all divided by A? Otherwise Delta-V increases significantly when you take the wings off.

[Chansith]

Originally Posted by thtraveller

Shouldn't we wait and see if others post a design?

I reckon that you can be acknowledged champ until someone posts a better design (if anyone does).