太空电梯的经济学外文文献翻译、中英文翻译、外文翻译

英文文献翻译

Space elevator

economics

of alternatives, like rockets

.

Space elevator economics compared and contrasted with the economics

Costs of current systems (rockets)

The costs of using a well-tested system to launch payloads are high. Prices

range from about $$4,300/kg for a Proton launch

[1]

to about US$$40,000/kg for a

Pegasus launch (2004).

[2][3]

Some systems under development, such as new

members of the Long March CZ-2E, offer rates as low as $$5,000/kg, but

(currently) have high failure rates (30% in the case of the 2E). Various systems

that have been proposed have offered even lower rates, but have failed to get

sufficient funding (Roton; Sea Dragon), remain under development, or more

commonly, have financially underperformed (as in the case of the Space

Shuttle). (Rockets such as the Shtil-3a, which offers costs as low as $$400/kg

rarely launch but has a comparatively small payload, and is partially subsidised

by the Russian navy as part of launch exercises.)

Geosynchronous rocket launch technologies deliver two to three times smaller

payloads to geosynchronous orbit than to LEO. The additional fuel required to

achieve higher orbit severely reduces the payload size. Hence, the cost is

proportionately greater. Bulk costs to geosynchronous orbit are currently about

$$20,000/kg for a Zenit-3SL launch.

Rocket costs have changed relatively little since the 1960s, but the market has

been very flat.

[3]

It is, however, quite reasonable to assume that rockets will be

cheaper in the future; particularly if the market for them increases. At the same

time, it is quite reasonable to assume the market will increase, particularly if

rockets will become cheaper.

英文文献翻译

Rocket costs are significantly affected by production volumes of the solid parts

of the rocket, and by launch site costs. Intuitively, since propellant is by far the

largest part of a rocket, propellant costs would be expected to be significant,

but it turns out that with hydrocarbon fuel these costs can be under $$50 per kg

of payload. Study after study has shown that the more launches a system

performs the cheaper it becomes. Economies of scale mean that large

production runs of rockets greatly reduce costs, as with any manufactured item,

and reuseable rockets may also help to do so. Improving material and practical

construction techniques for building rockets could also contribute to this.

Greater use of cheap labour (globalisation) and automation is practically

guaranteed to reduce manpower costs. Other costs, such as launch pad costs,

can be reduced with very frequent launches.

Cost estimates for a space elevator

For a space elevator, the cost varies according to the design. Dr. Bradley

Edwards, who has put forth a space elevator design, has stated that:

space elevator would reduce lift costs immediately to $$100 per pound

($$220/kg).

[4]

However, as with the initial claims for the space shuttle, this is only

the marginal cost, and the actual costs would be higher. Development costs

might be roughly equivalent, in real terms, to the cost of developing the shuttle

system. The marginal or asymptotic cost of a trip would not solely consist of

the electricity required to lift the elevator payload. Maintenance, and one-way

designs (such as Edwards') will add to the cost of the elevators.

The gravitational potential energy of any object in geosynchronous orbit (GEO),

relative to the surface of the earth, is about 50 MJ (15 kWh) of energy per

kilogram (see geosynchronous orbit for details). Using wholesale electricity

prices for 2008 to 2009 (7.1 NZ cents per kWh) and the current 0.5% efficiency

of power beaming, a space elevator would require USD 220/kg just in electrical

英文文献翻译

costs. By the time the space elevator is built, Dr. Edwards expects technical

advances to increase the efficiency to 2% (see power beaming for details). It

may additionally be possible to recover some of the energy transferred to each

lifted kilogram by using descending elevators to generate electricity as they

brake (suggested in some proposals), or generated by masses braking as they

travel outward from geosynchronous orbit (a suggestion by Freeman Dyson in a

private communication to Russell Johnston in the 1980s).

For the space elevator, the efficiency of power transfer is just one limiting issue.

The cost of the power provided to the laser is also an issue. While a land-based

anchor point in most places can use power at the grid rate, this is not an option

for a mobile ocean-going platform. A specially built and operated power plant

is likely to be more expensive up-front than existing capacity in a pre-existing

plant. Up-only climber designs must replace each climber in its entirety after

each trip. Some designs of return climbers must carry up enough fuel to return

it to earth, a potentially costly venture.

Contrasting rockets with the space elevator

Government funded rockets have not historically repaid their capital costs.

Some of the sunk cost is often quoted as part of the launch price. A comparison

can therefore be made between the marginal costs of fully or partially

expendable rocket launches and space elevator marginal costs. It is unclear at

present how many people would be required to build, maintain and run a

100,000 km space elevator and consequently how much that would increase

the elevator's cost. Extrapolating from the current cost of carbon nanotubes to

the cost of elevator cable is essentially impossible to do accurately.

Space elevators have high capital cost but presumably low operating expenses,

so they make the most economic sense in a situation where they would be

used to handle many payloads. The current launch market may not be large

英文文献翻译

enough to make a compelling case for a space elevator, but a dramatic drop in

the price of launching material to orbit would likely result in new types of space

activities becoming economically feasible. In this regard they share similarities

with other transportation infrastructure projects such as highways or railroads.

In addition, launch costs for probes and craft outside Earth's orbit would be

reduced, as the components could be shipped up the elevator and launched

outward from the counterweight satellite. This would cost less in both funding

and payload, since most probes do not land anywhere. Also, almost all the

probes that do land somewhere have no need to carry fuel for launch away

from their destination. Most probes are on a one-way journey.

Funding of capital costs

Note that governments generally have not historically even tried to repay

the capital costs of new launch systems from the launch costs. Several cases

have been presented (space shuttle, ariane, etc), documenting this. Russian

space tourism does partially fund ISS development obligations, however.

It has been suggested that governments are not usually willing to pay the

capital costs of a

new

replacement launch system. Any proposed new system

must provide, or appear to provide, a way to reduce overall projected launch

costs. This was the nominal impetus behind the Space Shuttle program.

Governments tend to prefer to cut costs in many cases. Spending more money

is something they are usually loath to do.

Alternatively, according to a paper presented at the 55th International

Astronautical Congress

[5]

in Vancouver in October 2004, the space elevator can

be considered a prestige megaproject and the current estimated cost of

building it (US$$6.2 billion) is rather favourable when compared to the costs of

constructing bridges, pipelines, tunnels, tall towers, high speed rail links,

英文文献翻译

maglevs and the like. It is also not entirely unfavourable when compared to the

costs of other aerospace systems as well as launch vehicles.

[6]

Total cost of a privately funded Edwards' Space Elevator

A space elevator built according to the Edwards proposal is estimated to

cost $$20 billion ($$40B with a 100% contingency)

[7]

. This includes all operating

and maintenance costs for one cable. If this is to be financed privately, a 15%

return would be required ($$6 billion annually). Subsequent elevators would

cost $$9.3B and would justify a much lower contingency ($$14.3B total). The

space elevator would lift 2 million kg per year per elevator and the cost per

kilogram becomes $$3,000 for one elevator, $$1,900 for two elevators, $$1,600 for

three elevators.

For comparison, in potentially the same time frame as the elevator, the Skylon,

12,000 kg cargo capacity spaceplane (not a conventional rocket) is estimated to

have an R&D and production cost of about $$15 billion. The vehicle has about

the same $$3,000/kg price tag. Skylon would be suitable to launch cargo

and

particularly

people to low/medium Earth orbit. An early space elevator can

move only cargo although it can do so to a much wider range of destinations.

[8]

References

1

.

^Space Transportation Costs: Trends in Price Per Pound to Orbit

1990-2000 (PDF). Retrieved on 2006-03-05.

2. ^Pegasus. Encyclopedia Astronautica. Retrieved on 2006-03-05.

3. ^The economics of interface transportation (2003). Retrieved on 2006-03-05.

4. ^What is the Space Elevator?. Institute for Scientific Research, Inc.. Retrieved

on 2006-03-05.

5. ^55th International Astronautical Congress. Institute for Scientific Research,

Inc.. Retrieved on 2006-03-05.

6. ^ Raitt, David; Bradley Edwards. THE SPACE ELEVATOR: ECONOMICS AND

APPLICATIONS (PDF). 55th International Astronautical Congress 2004 -