外文翻译--太空电梯的经济学

Space elevator economics Space elevator economics compared and contrasted with the economics of alternatives, like rockets. 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 launch1 to about US$40,000/kg for a Pegasus launch (2004).23 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. 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: The first 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 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 elevators 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 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 Earths 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 Congress5 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, 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 - Vancouver, Canada. Retrieved on 2006-03-05. 7. 1 8. The Space Elevator - Chapter 7: Destinations. Retrieved on 2006-03-05. 太空电梯的经济学 太空电梯经济学 和火箭经济学的 对比 与比较。 目前（火箭）系统 的成本 使用完善的测试系统发射有效载荷的成本是很高的 ， 2004 年 其 价格范围 是从约 4300 美元每千克发射 一个质子 到 40,000 美元每千克发射一个 飞马座。 一些处于发展中的系统 ，如 长征系列的 新成员长征 CZ-2E， 其 提供 的价格 低至 5000美元每千克 ，但是 它 （目前）具有较高的失败率（ 2E 的失败率为 30 ）。各种被推荐的系统，有的甚至 提供更低 的价格 ，但 是 未能获得足够的资金 支持 （ 如roton ；海龙），仍然 处于 发展 之中 ，或更 为 普遍， 没 有财政 补助 （如太空 中的穿梭机 一样 ） 。像 shtil-3A 型火箭， 其 成本低至 400 美元每千克， 很少发射，但 其 有一个相对较小的有效载荷， 得到了 俄罗斯海军 的 部分资助， 他们将其用于发射演习。 地球同步轨道火箭发射技术 向 地球同步轨道提供 的有效载荷比向狮子宫提供的有效载荷小了两至 三倍，实现更高的轨道 所需要的 额外燃料，严重降低了有效载荷的大小。因此， 成本是按比例增大的，发射 天顶 -3SL 地球同步轨道火箭的批量 成本目前约 为 20,000 美元每千克 。 自 20 世纪 60 年代 以来， 火箭的 成本 改变 不大 ，但 火箭的 市场 需求却 一直很平稳 。然而， 我们可以作相当 合理的假设，火箭 的成本在将来将会更加 便宜， 尤其是市场对它们达需求增加时；同时，假定市场对火箭的需求也会增加亦是合理的，尤其是当火箭的成本变得更低的时候。 火箭的成本 受火箭固定部分生产量和发射场费用的影响显著。 凭直觉， 既然火箭 推进剂，是迄今为止 火箭 最大的一个组成部分， 那么 火箭推进剂的 成本 预计将 很高 ，但结果表明，与碳氢燃料 相比 ，这些费用 却在 50 美元 每公斤的有效载荷 之下 。 经过不断 研究表明， 一个火箭执行发射的次数越多，那么它将变得更加便宜 。规模经 济意味着 火箭的 大 批量 生产 ，将 大大降低 其 成本， 对于 任何 配件项目 制造 ，重复使用 火箭 也 可以 极大的降低其成本。 改进 制造火箭的 材料和实际施工技术 也可以对降低成本做出贡献； 更多地使用廉价劳工（全球化）和自动化，也能 减少人力 资源 成本。其他费用， 像 发射架上 的 成本，可以 通过频繁的火箭发射来减少其成本。 太空 电梯 的成本估算 太空 电梯 的 费用 依 不同设计 而变 。布拉德利爱德华兹博士，提出了太空电梯的设计， 他 表示： “ 首先，太空电梯 能够立即使 电梯费用 减少至 100 美元每 镑 ”即 （ 220 美元 /kg）。然而，这只不过是边际成本， 如果加上先前的航 天飞机成本， 实际成本 将 会 更 高。以实质计算， 其 开发成本可能相当于， 开发 穿梭 机 系统的成本 。边际或渐近的成本 不 仅仅 是由支撑太空电梯有效载荷所需要的电力成本构成， 维修 成本 和单向的设计（如爱德华兹） 亦 将增加电梯的成本。 处在 地球同步轨道 上的 任何物体 相对于 相对地球表面 所具有的引力势能， 约50 兆焦耳（ 15 千瓦时）每千克。 2008 至 2009 年 ， 使用的电力批发价格为（ 7.1美分，新西兰元每千瓦时），以及当前的 0.5的 工作 效率， 太空 电梯在电气成本 方面 将需要 220 美元 每千克，到太空 电梯建成 之时 ，博士爱德华兹预计技术进步， 将使其 工作效率提高至 2 。 此外 ，通过使用太空电梯来发电，或通过他们脱离 地球同步轨道 时所 产生的 大量 制动 ，也可以 恢复一些能量转移到每公斤 当中 ，因为他们 可以 制动 。 （ 20 世纪 80 年代弗里曼戴森 和 罗素庄士敦 在一次私人访谈中建议）。 太空电梯 能量转换的 效率 只 是其中一项限制 性 的问题 ， 提供给激光 的能源成本 亦是一个 限制性 问题。而陆基定位点在大多数地方 能够以 网格率 的形式使用能源 ， 这 对于远洋移动平台 来说， 不是一种选择。一个专门兴建和营运的电厂很可能是 比 较昂贵的 先前行动 ，比现有的 已存在的 一个 事物更加昂贵，在每一个飞船完成它们的行程之后， 飞船的设计都必须改变，一些返回舱的设计还必须能够携带足够的燃料，以使其能够返回地球，这是一种潜在的风险成本。 火箭与太空电梯 的比较 政府资助的火箭 在 历史上 并没有 偿还他们的资本成本 ， 部分的沉没成本是经常引用的一部分 发射成本 。因此 ，在 完全或部分消耗性火箭发射 的边际成本 和太空电梯的边际成本 之间作一比较，虽然 目前还不清楚 需要 多少人 来 建立，维持和运行 这一距离地球 10000 公里 的太空 电梯， 以及随后的太空电梯成本会增加多少，但 从目前的碳纳米管成本， 和 电梯电缆 成本推算 ，基本上是不可能 得到 准确的对比 。 太空电梯具有较高的资 本成本，但据推测 其 营运 成本比较低 ，所以他们作出比较 经济的意识， 即 在一个情况下，它们将被用于处理很多的有效载荷。目前 火箭 发射市场 还 不足够大 以至不能为太空电梯作出一个令人信服的理由。 但 随着发射材料价格的 急剧下降， 这将使得新类型的空间活动在经济上成为可行。 在这方 面，他们与其他交通基础设施项目，如公路或铁路 有着非常的类似 。此外， 随着配件从太空电梯中发运，并离开卫星发射，地球轨道之外的 探头和工艺 的