[Spaceships] Designers' Championship I: ground to LEO

[Chansith]

Using the spaceship design rules in GURPS Spaceships, without superscience, what is the cheapest way to provide a shuttle service between the ground and low Earth orbit, at TL 9? At TL 10? At TL 11?

Ground rules:

1. Orbital lighters must not release highly-radioactive exhaust into Earth's atmosphere.
2. Lighters must carry their passengers from a spaceport on Earth's surface to a ship or space station in a ninety-minute prograde equatorial orbit (ie. at an altitude of 170 miles, heading east at circular orbit velocity), and then return to a spaceport on Earth's equator. For simplicity, treat the circular orbit velocity at LEO as 4.85 miles per second, and the rotation of the Earth as providing 0.25 miles per second, requiring the engines to provide 4.6 miles per second of delta-v to do the job.
3. Earth may be assumed to have no more than two suitable spaceports, one in Ecuador at an altitude of 15,000 feet and possibly one on Sumatra at 9,000 feet. Headway on the service must therefore be an integer multiple of 45 minutes.
4. Embarkation and disembarkation may be assumed to require ten minutes each, and refuelling (if necessary) may be assumed to be completed within twenty minutes, so that the lighter must spend 20 minutes docked to the ship and twenty minutes on the ground in each duty cycle.
5. A lighter may be assumed be in service for 7 300 hours per year.
6. Lighter crew work 1,920 hours per year, of which 5% is administrative overhead, so the flight crew wage bill for the operation is wages for four crews.
7. Lighter crew is a comfortable job.
8. Lighters work at an average load factor of 75% (ie. on average, quarter of the seats are empty).
9. The commercial real return on capital is 5% per annum.
10. Depreciation on an orbital lighter is 4% per annum, straight-line (for accounting convenience).
11. Basic insurance of an orbital lighter is 1% per annum. Operational insurance is 0.001% per round trip to orbit, times 3 if the lighter's Hnd is +3, times six for Hnd +2, times ten for Hnd +1, times 15 for Hnd +0.
12. The servicing cost on an orbital lighter is 0.01% of the cost of engine and fuel tanks, per round trip.
13. Fuel costs are as given on Spaceships p. 46.
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)} / A, where A is the acceleration of the vehicle.

What is the most cost-effective ground-to-orbit lighter you can build at each TL, without superscience?

How are things different on a backwoods colony planet where there is only a liner in orbit 10% of the time, and where there is only one spaceport?

[Chansith]

By the way: is there any comment on the ground rules as set out?

How do wings affect Hnd?

[alimantando]

What about a space lift?
Is that super science?

[AstralRunner]

Space lifts are easily TL 9, given an adequately motivated and organized civilization.

A launch loop might be even cheaper than that, though.

[Chansith]

Originally Posted by alimantando

What about a space lift?

• There are no rules for them in GURPS Spaceships, so they don't provide a suitable basis for a design championship.

• Space lifts are no good for getting to LEO: you can't get off below GEO. And it takes a long time to get to GEO, which might make space lifts unattractive to passengers. Rotorvators, bolo space stations, and even space fountains sound more practical to me.

• Space lifts eat up an awful lot of valuable territory in orbit, besides which they are mind-bogglingly capital-intense, and a very considerable engineering challenge. A beanstalk is equivalent to a suspension bridge with a 24,000-mile span. There might be a long wait before we get one built. We are much closer to building an orbital lighter. It is not clear to me that a space lift will ever be economic: operating costs are much lower than shuttles, but amortisation is through the roof, and there might be prohibitive rental costs on orbital territory.

• Until we design the most cost-effective orbital lighter we don't know what price the space lift will have to compete with. I won't be surprised if at higher TLs lighters (perhaps fusion powered) provide a trip to LEO that is cheaper than a space lift ticket to GEO.

• This design exercise will give us a basic approach to the more general problem of building lighters for trips from ground to low orbit on habitable planets. This will be important in the case of comparatively low-population colony worlds, which don't generate enough traffic to amortise a minimum-scale beanstalk.

[Crakkerjakk]

Laser Launch system is the most cost effective(at low TLs), I believe, but that was in THS, not Spaceships.

Also, by highly radioactiv,e do you mean no orion drives, or no saltwater nuke drives? Orion drives are not that hazardous in terms of fall-out

[Chansith]

Originally Posted by Crakkerjakk

Laser Launch system is the most cost effective(at low TLs), I believe, but that was in THS, not Spaceships.

Also, by highly radioactiv,e do you mean no orion drives, or no saltwater nuke drives? Orion drives are not that hazardous in terms of fall-out

I was particularly thinking of NSWR. Old Bang-Bang hadn't even crossed my mind. I think Orion is currently outlawed by the CTBT, but I might entertain a case that the law might be reformed if the emissions were likely to be negligible.

I am, obviously, considering commercial operations: thousands of passengers per day. Regulators would be concerned with cumulative emissions over myriads of launches, plus of course the possible use of the bombs as bombs.

Have you thought about Daedalus?

[thtraveller]

Originally Posted by Chansith

By the way: is there any comment on the ground rules as set out?

What do you mean by "cost effective"?

I would normally calculate Return on Investment. So build cost may be only a small consideration.

What ticket price can we charge? (what will the market bear?)

[Chansith]

Originally Posted by thtraveller

What do you mean by "cost effective"?

I mean "having a high ratio of effect achieved to cost borne", or, which is the same thing, a low ratio of cost to effect.

What is (at each TL) the shuttle that has the lowest ratio of total cost (ie. operating costs plus amortisation of investment) to the number of trips to orbit that it provides?

I would normally calculate Return on Investment. So build cost may be only a small consideration.

Include operating costs, such as maintenance, fuel, and wages.

What ticket price can we charge? (what will the market bear?)

Assume that you are in a competitive industry that is in long-run equilibrium. You cannot charge a higher price than your competitors, and they cannot charge a price lower than their costs including amortisation. Ticket price will be equal to cost at the stated price of capital.

[thtraveller]

Originally Posted by Chansith

How are things different on a backwoods colony planet where there is only a liner in orbit 10% of the time, and where there is only one spaceport?

Do you mean a backwoods planet with exactly the same stats as Earth? Or did you have a particular planet in mind, like the trace atmosphere and low gravity planet Mars? Or can we make up a planet to best fit our designs?

Hmm, this seems like two different competitions.