NASA plans to send manned expeditions to near-Earth asteroids in order to discover more about their formation and structure
Asteroids can tell us a great deal about the formation of our Solar System and could be stepping stones to the long-term colonisation A of the Moon and interplanetary trips to Mars and beyond. They might well contain water and air that could be used to support deep-space manned missions, and there’s the possibility of mining them for their precious metals. They certainly have the potential to enhance human existence, yet there are at least 1,000 dangerous asteroids that pose a risk to Earth.
In April 2010, former president Barack Obama announced that NASA should send a manned mission to an asteroid by 2025. Though this target doesn’t look likely, one of NASA’s future plans is to use an unmanned spacecraft to capture a 500-tonne, seven-metre (23- foot) diameter asteroid and send it into a high lunar orbit. Here, unmanned spacecraft and manned crews using Orion spacecraft could easily visit and study it in detail. An asteroid capture and return spacecraft would take about four years to reach a suitable asteroid, 90 days to deploy a large capture bag and a further two to six years to take it to the Moon.
A more advanced plan is to use a combination of Orion spacecraft and a Deep Space Habitat (DSH) to go beyond Earth orbit. The habitat would consist of a four-person habitation module and would be suitable for 60-day missions. With an additional Multi-Purpose Logistics Module (MPLM) linked via a utility tunnel and docking module to the habitation module, it could operate for 500 days. These modules would be based on existing and functional International Space Station designs and technology. Either option would be propelled using a cryogenic propulsion stage using liquid hydrogen-liquid oxygen engines, and possibly in future by more advanced ion engines.
The DSH would also carry a small two-person Multi-Mission Space Exploration Vehicle (MMSEV). This would take the astronauts from the DSH to a nearby asteroid to obtain geological samples and carry out science experiments. Testing of a prototype has already been conducted at Johnson Space Center, which involved two astronauts spending three days and two nights living inside it. Using virtual-reality headsets and a rig to suspend the astronauts to reproduce weightlessness, they evaluated simulated extravehicular activities (EVAs) on the surface of an asteroid. Other training projects are dealing with living in deep space for long periods of time.
