Even with the many upheavals around the world, the news has been full of space stories lately. Some are in response to the Obama administration's desire to send people to an asteroid, where they have been talking about sending people by 2025.
Very recently, NASA released its Global Exploration Roadmap that has two options for the future -- concentrating on sending people to an asteroid and concentrating on sending people back to the moon. There have been many stories about an asteroid mission but most of the stories have made a difficult task seem far easier than it is. So let's look at a part of that process, and in future stories we will examine other facets.
First, what is so difficult about sending people to an asteroid? When you think of an asteroid, think of something that is far away and moving really fast. The orbits of a small number of known asteroids do bring them close to Earth, but they are traveling at extremely high speeds.
If you were to get close to one and match orbits, you are now in an orbit that takes you far from the Earth and does so rapidly. These are not good candidates for a visit -- you must grab and go, and your propulsion system had better be extremely reliable. Some asteroids are in orbits that do not take them farther from the Earth, but they are still far away from our planet.
Visitors to those asteroids would have to be able to live autonomously for years. For instance, the Japanese Hayabusa asteroid explorer was launched in May 2003, visited the asteroid Itokawa in 2005 and returned to Earth in June 2010. If that had been a mission with people on board, they would have had to survive without resupply for seven years. With the current technology for water reclamation, oxygen supply, etc. that we have seen on the International Space Station, the crew would have had to take a huge supply of those along to account for losses during the mission.
There are asteroids that pass "close" to Earth, one of them has the homey name of 1999 RQ36. It comes near our planet every six years, with a close approach in 1999 of 1.4 million miles. The next approach will be about 1.3 million miles. Compare that to our moon, which is about 240,000 miles away. The asteroid 1999 RQ36 is the destination of an exploration mission; called OSIRIS-Rex and a mission with people would fly a similar trajectory.
OSIRIS-Rex will launch in 2016, rendezvous in 2020, and return to Earth in 2023. So if people were included in that mission, people would have to bring along enough food, water, and air to survive for over seven years. Now potentially people would not have to stay as long as OSIRIS-Rex so let's assume they stay for a week and have a total six year mission. The International Space Station -- a huge, well-supplied facility, could not survive for six years without resupply.
Any asteroid mission would have to use an extremely reliable crew vehicle, one that had been proven in flight for several years. Since we can hope to have a deep space vehicle ready for test in 2018 or so, we will not have a proven craft (to take people to a destination that was enormously further than the moon) until 2030 or so.
In future stories we will look at the state of current technology and see if an asteroid mission can be done by 2025.
Charles Phillips has had a long career in the space field: he has worked in space operations since 1978, as an Air Force officer from 1978 until he retired in 2005 (working in space, communications, and maintenance), or as a NASA contractor, and he has been a writer all of that time. Now he finds the stories that people are interested in but might have been missed by other reporters.
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