美國宇航局揭開太空發射系統遠景

美國宇航局揭開太空發射系統遠景
Nasa unveils Space Launch System vision
By Jonathan Amos
BBC News
14 September 2011
Translation by Autumnson Blog

Nasa's top official, General Charles Bolden, hails the start of a new era
美國宇航局的頂級官員查爾斯博爾登將軍，歡呼一個新時代的開始

The design for a huge rocket to take humans to asteroids and Mars has been unveiled by the US space agency Nasa.
對於一枝巨大的火箭將人類帶往小行星和火星的設計，已由美國航空航天局公佈。

The Space Launch System (SLS), as it is currently known, will be the most powerful launcher ever built - more powerful even than the Saturn V rockets that put men on the Moon.
該目前已知的航天發射系統（SLS），將是有史以來建成最強大的發射器 - 甚至比擺人上月球的土星五號火箭更強大。
On top of the SLS, Nasa plans to put its Orion astronaut capsule, which is already in development.
在航天發射系統之上，美國宇航局計劃將它的獵戶座太空艙擺上，那已經是在發展中。
The agency says the first launch should occur towards the end of 2017.
機構說第一次發射應該在2017年底實現。
This will be an uncrewed test flight, and it is estimated the project will have cost $18bn (£11.4bn) by that stage.
這將是一次沒機員的試飛，據估計項目在那階段將耗資180億美元（£11.4bn）。
"The next chapter of America's space exploration story is being written today," said Nasa's top official, General Charles Bolden.
“美國太空探索故事的下一章正在今天寫出，”美國宇航局的頂級官員查爾斯博爾登將軍說。
"President Obama has challenged us to be bold and dream big, and that's exactly what we do.
“奧巴馬總統已挑戰我們要大膽和發春秋大夢，而這正是我們所做的。
"While I was proud to fly in the space shuttle, tomorrow's explorers will dream of one day walking on Mars."

演進的設計
Evolved design
The SLS will borrow many technologies developed for the recently retired space shuttle programme. These include the shuttle orbiter's main engines.

But whereas the reusable spaceplane had three such power units on its aft, the SLS main core stage in its full-up configuration will have five.

A further stage on top will provide additional muscle, as will shuttle-like strap-on boosters. Although, again, these will be bigger than those used on the shuttle.

The initial design calls for the SLS to be able to put 70 tonnes in a low-Earth orbit (LEO), the altitude of the space station. Some 130 tonnes is the eventual target.

By comparison, today's biggest commercial launch vehicles, such as the Ariane 5 or the Delta IV Heavy, can put just over 20 tonnes in LEO.

The immense lift capability is necessary to put all the equipment in orbit that is needed to undertake a deep-space mission. This would consist of not only the Orion capsule but perhaps a habitation module and a landing craft to go down to the surface of another planetary body.

In the case of a Mars mission, several SLS launches would probably be needed.

目標“路線圖”
Destination 'roadmap'
Wednesday's announcement is the culmination of months of study on the part of Nasa engineers, and sometimes fractious argument with the US Congress which felt the agency was not moving fast enough on the project it initiated in a piece of legislation called the Nasa Authorisation Act 2010.

"We have been frustrated by the time delays," said Senator Kay Bailey Hutchison, a Texas Republican who serves on a Nasa oversight committee and who joined Charles Bolden on Capitol Hill to make the SLS announcment..

"The numbers are within the authorization levels; we are now moving forward as a team for America," she added. "Sometimes the making of the sausage isn't pretty but we are at the right end, we hope."

Since the retirement of the shuttle in July, America has no means of getting its own astronauts into orbit; it must rely on Russian Soyuz rockets to do that job.

Nasa has invited the private sector to sell it transportation services to the space station, but these commercially operated rockets and capsules will not be ready for flight until the middle of the decade. And, in any case, none of them will have the power or the life-support systems capable of taking astronauts beyond LEO.

In leaving routine LEO operations to the commercial sector, Nasa hopes it will have sufficient funds available to develop the SLS and Orion in time for the 2017 inaugural launch.

There is no "roadmap" yet for where the SLS and Orion might take humans, and when. President Obama has talked only about getting astronauts to an asteroid in the 2025 timeframe, and to Mars at some unspecified future date.

Other targets might include missions to geostationary orbit to fix broken, high-value telecommunications satellites that sit 36,000km (22,370 miles) above the Earth.

"We've talked conceptually about multiple destinations," said Bill Gerstenmaier, Nasa's Human exploration and operations associate administrator. "We need to get some more details on the actual rocket performance, put that together with these concepts and then start talking to people about specifics.

"We can do pretty exciting missions with the capability we've got, even in the 70-metric-tonne range."

To send a manned mission to Mars, even just to circle it, would require a lot of support equipment
要發送載人任務往火星，甚至衹是為了環繞它，將要求大量的輔助設備

The Space Launch System (SLS)
航天發射系統（SLS）

Nasa's intention is to lean on as much space shuttle heritage as possible
Its central tank's width is 8.4m - same as the space shuttle's famous orange tank

Design calls for two liquid-fuelled (cryogenic hydrogen and oxygen) stages
Core stage has three to five RS-25D/E engines - the units used on the orbiter (above)

Upper stage will use the J-2X engine that has been in development for some years

SLS will incorporate solid-fuelled side boosters, although this may change over time

At 2017, the SLS should be able to lift 70 tonnes to LEO. It must evolve to 130 tonnes eventually


http://www.bbc.co.uk/news/science-environment-14915725

太空穿梭機計劃停止另有隱情？