Most see a greater role for the private sector in launching astronauts to low-Earth orbit.
The other study would look at new low-Earth orbit applications for an ATV-derived vehicle.
No longer will it own the vehicles it uses to go to low-Earth orbit.
This meant relying on unproven and complex technology and launching dozens of satellites into low-earth orbit.
The rocket was attempting to carry a 19.5kg satellite to a low-Earth orbit of 450km.
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The Long March 5 will be capable of putting more than 20 tonnes in a low-Earth orbit.
But it remains to be seen how useful an acoustic sensor placed in a low-Earth orbit might be.
They were most concerned with low-Earth orbit (that is, below 2, 000km in altitude).
Reed warns that if space junk is not removed it could mean that low-earth orbit might eventually become unusable.
For the most part, though, their proposals call for activating nuclear reactors only after the vehicles have reached low-Earth orbit.
Thagard, the former NASA astronaut, said he was exposed to 120 millisieverts during his 115 days in low-Earth orbit aboard Mir.
Its most striking feature is to delegate the humdrum task of ferrying people and equipment to low-Earth orbit to the private sector.
But even if NASA does not venture beyond low-Earth orbit, others might.
Nasa astronaut Stan Love knows first-hand the difficulties with technology that his colleagues have experienced on the International Space Station in low-Earth orbit.
Virgina-based Iridium is almost halfway through a multi-year plan to replace its low-earth orbit network of communication satellites with a powerful new generation.
"We need to get NASA out of the business of getting crew" to low-earth orbit, she told The Wall Street Journal at the time.
Nasa's new Space Launch System (SLS) is a multi-billion-dollar venture to take humans beyond the International Space Station (ISS) and the confines of low-Earth orbit.
Beyond low-Earth orbit, astronauts are bombarded with harmful cosmic rays, which can boost the risk of certain diseases such as cancer and neurological damage.
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It should be noted also that the 2017 maiden test flight will use a "lite" variant, one capable of lifting about 70 tonnes to low-Earth orbit.
But until the commercial astronaut taxis are ready to go, the nation will be dependent on Russian Soyuz spacecraft to launch its crews to low-Earth orbit.
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However, he said in due course this revised vessel would also serve as the "technological foundation" for much more capable vehicles to take astronauts beyond low-Earth orbit.
The Space Launch System, or SLS for short, is NASA's go-to rocket to carry NASA's planned Orion capsule and possibly other future payloads beyond low-Earth orbit.
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The intention was to give the US a crew-carrier and rocket technology that could go beyond low-Earth orbit to more distant targets, back to the Moon and further.
The President and the NASA Administrator both believe that we have to be forward thinking and aggressive in our pursuit of new technologies to take us beyond low-Earth orbit.
Nasa is attempting to offload routine human spaceflight operations in low-Earth orbit to commercial industry in a way similar to how some large organisations contract out their IT or payroll.
Designed to be flexible for launching spacecraft for crew and cargo missions, SLS and Orion will expand human presence beyond low-Earth orbit and enable new missions of exploration in the solar system.
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Geosynchronous satellites are so distant that their images aren't sharp, while low-earth orbit satellites, which fly as low as 100 miles, can feed information only when they pass over an area of interest.
"This will be one step in the long road to human expansion off of the planet into low-Earth orbit and beyond, " NASA astronaut Donald Pettit, one of Burbank's crewmates aboard the station, said Friday.
One part, space tourism, is a luxury service that is, in any case, unlikely to go beyond low-Earth orbit at best (the cost of getting even as far as the moon would reduce the number of potential clients to a handful).
At least some of the incoming Republican panel chairmen and other senior GOP lawmakers, these officials said, may view the proposed test flight as circumventing congressional language to quickly develop a new heavy-lift NASA rocket able to transport astronauts past low-earth orbit.
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