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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Essentially, deliver an asteroid into Earth orbit and drop a wire down from it.
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From there, it could be shipped to Earth orbit for refueling commercial satellites or spacecraft.
The Long March 5 will be capable of putting more than 20 tonnes in a low-Earth orbit.
In fact China is, at the moment, the only entity that can launch astronauts into low earth orbit.
But it remains to be seen how useful an acoustic sensor placed in a low-Earth orbit might be.
The risks and burdens of developing transport to low Earth orbit will thus fall to the private sector.
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ICO's ten satellites fly about 9, 000 kilometres higher in medium-earth orbit and have a life-span of 12 years.
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.
The commercial efforts to low Earth orbit, which SpaceX achieved, are only a piece of the U.S. space program.
Instead of putting the probe on a course for Phobos, the probe is now trapped in low Earth orbit.
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Despite the warm words of the nation's leaders, America's manned space-flight programme has been becalmed in Earth orbit for decades.
For the most part, though, their proposals call for activating nuclear reactors only after the vehicles have reached low-Earth orbit.
It became stuck in Earth orbit after its launch in November and will probably fall back to Earth next month.
Thagard, the former NASA astronaut, said he was exposed to 120 millisieverts during his 115 days in low-Earth orbit aboard Mir.
The eventual aim would be commercial-stage passenger travel market with hundreds of thousands to millions of people flying in earth orbit.
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It was also keen on a proposal to use Virgin's White Knight launch system to put satellites into low Earth orbit.
The shuttle was a big bus -- a reusable vehicle that could carry both cargo and people to low Earth orbit.
The most recent Russian probe, which was launched to the Mars moon Phobos last November, never made it out of Earth orbit.
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.
This marks a big step forward for the commercial space company, which aims to build inexpensive commercial space stations for low Earth orbit.
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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.
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