外文翻譯--太空電梯的經(jīng)濟學

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. 太空電梯的經(jīng)濟學 太空電梯經(jīng)濟學 和火箭經(jīng)濟學的 對比 與比較。 目前（火箭）系統(tǒng) 的成本 使用完善的測試系統(tǒng)發(fā)射有效載荷的成本是很高的 ， 2004 年 其 價格范圍 是從約 4300 美元每千克發(fā)射 一個質(zhì)子 到 40,000 美元每千克發(fā)射一個 飛馬座。 一些處于發(fā)展中的系統(tǒng) ，如 長征系列的 新成員長征 CZ-2E， 其 提供 的價格 低至 5000美元每千克 ，但是 它 （目前）具有較高的失敗率（ 2E 的失敗率為 30 ）。各種被推薦的系統(tǒng)，有的甚至 提供更低 的價格 ，但 是 未能獲得足夠的資金 支持 （ 如roton ；海龍），仍然 處于 發(fā)展 之中 ，或更 為 普遍， 沒 有財政 補助 （如太空 中的穿梭機 一樣 ） 。像 shtil-3A 型火箭， 其 成本低至 400 美元每千克， 很少發(fā)射，但 其 有一個相對較小的有效載荷， 得到了 俄羅斯海軍 的 部分資助， 他們將其用于發(fā)射演習。 地球同步軌道火箭發(fā)射技術 向 地球同步軌道提供 的有效載荷比向獅子宮提供的有效載荷小了兩至 三倍，實現(xiàn)更高的軌道 所需要的 額外燃料，嚴重降低了有效載荷的大小。因此， 成本是按比例增大的，發(fā)射 天頂 -3SL 地球同步軌道火箭的批量 成本目前約 為 20,000 美元每千克 。 自 20 世紀 60 年代 以來， 火箭的 成本 改變 不大 ，但 火箭的 市場 需求卻 一直很平穩(wěn) 。然而， 我們可以作相當 合理的假設，火箭 的成本在將來將會更加 便宜， 尤其是市場對它們達需求增加時；同時，假定市場對火箭的需求也會增加亦是合理的，尤其是當火箭的成本變得更低的時候。 火箭的成本 受火箭固定部分生產(chǎn)量和發(fā)射場費用的影響顯著。 憑直覺， 既然火箭 推進劑，是迄今為止 火箭 最大的一個組成部分， 那么 火箭推進劑的 成本 預計將 很高 ，但結果表明，與碳氫燃料 相比 ，這些費用 卻在 50 美元 每公斤的有效載荷 之下 。 經(jīng)過不斷 研究表明， 一個火箭執(zhí)行發(fā)射的次數(shù)越多，那么它將變得更加便宜 。規(guī)模經(jīng) 濟意味著 火箭的 大 批量 生產(chǎn) ，將 大大降低 其 成本， 對于 任何 配件項目 制造 ，重復使用 火箭 也 可以 極大的降低其成本。 改進 制造火箭的 材料和實際施工技術 也可以對降低成本做出貢獻； 更多地使用廉價勞工（全球化）和自動化，也能 減少人力 資源 成本。其他費用， 像 發(fā)射架上 的 成本，可以 通過頻繁的火箭發(fā)射來減少其成本。 太空 電梯 的成本估算 太空 電梯 的 費用 依 不同設計 而變 。布拉德利愛德華茲博士，提出了太空電梯的設計， 他 表示： “ 首先，太空電梯 能夠立即使 電梯費用 減少至 100 美元每 鎊 ”即 （ 220 美元 /kg）。然而，這只不過是邊際成本， 如果加上先前的航 天飛機成本， 實際成本 將 會 更 高。以實質(zhì)計算， 其 開發(fā)成本可能相當于， 開發(fā) 穿梭 機 系統(tǒng)的成本 。邊際或漸近的成本 不 僅僅 是由支撐太空電梯有效載荷所需要的電力成本構成， 維修 成本 和單向的設計（如愛德華茲） 亦 將增加電梯的成本。 處在 地球同步軌道 上的 任何物體 相對于 相對地球表面 所具有的引力勢能， 約50 兆焦耳（ 15 千瓦時）每千克。 2008 至 2009 年 ， 使用的電力批發(fā)價格為（ 7.1美分，新西蘭元每千瓦時），以及當前的 0.5的 工作 效率， 太空 電梯在電氣成本 方面 將需要 220 美元 每千克，到太空 電梯建成 之時 ，博士愛德華茲預計技術進步， 將使其 工作效率提高至 2 。 此外 ，通過使用太空電梯來發(fā)電，或通過他們脫離 地球同步軌道 時所 產(chǎn)生的 大量 制動 ，也可以 恢復一些能量轉移到每公斤 當中 ，因為他們 可以 制動 。 （ 20 世紀 80 年代弗里曼戴森 和 羅素莊士敦 在一次私人訪談中建議）。 太空電梯 能量轉換的 效率 只 是其中一項限制 性 的問題 ， 提供給激光 的能源成本 亦是一個 限制性 問題。而陸基定位點在大多數(shù)地方 能夠以 網(wǎng)格率 的形式使用能源 ， 這 對于遠洋移動平臺 來說， 不是一種選擇。一個專門興建和營運的電廠很可能是 比 較昂貴的 先前行動 ，比現(xiàn)有的 已存在的 一個 事物更加昂貴，在每一個飛船完成它們的行程之后， 飛船的設計都必須改變，一些返回艙的設計還必須能夠攜帶足夠的燃料，以使其能夠返回地球，這是一種潛在的風險成本。 火箭與太空電梯 的比較 政府資助的火箭 在 歷史上 并沒有 償還他們的資本成本 ， 部分的沉沒成本是經(jīng)常引用的一部分 發(fā)射成本 。因此 ，在 完全或部分消耗性火箭發(fā)射 的邊際成本 和太空電梯的邊際成本 之間作一比較，雖然 目前還不清楚 需要 多少人 來 建立，維持和運行 這一距離地球 10000 公里 的太空 電梯， 以及隨后的太空電梯成本會增加多少，但 從目前的碳納米管成本， 和 電梯電纜 成本推算 ，基本上是不可能 得到 準確的對比 。 太空電梯具有較高的資 本成本，但據(jù)推測 其 營運 成本比較低 ，所以他們作出比較 經(jīng)濟的意識， 即 在一個情況下，它們將被用于處理很多的有效載荷。目前 火箭 發(fā)射市場 還 不足夠大 以至不能為太空電梯作出一個令人信服的理由。 但 隨著發(fā)射材料價格的 急劇下降， 這將使得新類型的空間活動在經(jīng)濟上成為可行。 在這方 面，他們與其他交通基礎設施項目，如公路或鐵路 有著非常的類似 。此外， 隨著配件從太空電梯中發(fā)運，并離開衛(wèi)星發(fā)射，地球軌道之外的 探頭和工藝 的