Ballistic capture
Ballistic capture is a method of achieving orbit around a planet or moon - a spacecraft moving at a lower orbital velocity than the target celestial body is inserted into a similar orbit, allowing the planet or moon to move toward it and gravitationally snag it into orbit around the celestial body with no need for an insertion burn.[1][2]
It was first used by Japanese scientists in 1991 as a method to get to the Moon.[3]
It is predicted to be
- safer, as there is no time critical insertion burn.
- can launch at almost any time, rather than having to wait for a narrow window of opportunity
- would be more fuel efficient for some missions.
Hohmann transfer orbit
The conventional method is a Hohmann transfer orbit.
Ballistic Capture
Low energy transfer was proposed in 2014, although it built off concepts invented over the past 30 years. The spacecraft is launched into a transfer orbit that places it ahead of the target planet's orbital path. As the planet approaches the spacecraft, the planet's gravity draws the craft into a high circular orbit eliminating the need for an insertion burn. This orbit is a temporary one, eventually the spacecraft would leave it again - but then it uses low power thrusters to get into a lower orbit. It can use the much more efficient ion thrusters at this stage as there is no need for a high level of thrust.
With some target orbits the total fuel is less than for Hohmann transfer. Hohmann transfer is more fuel efficient if you target an orbit closer to Mars, but can only be done at particular times. Ballistic capture has the advantage that you can use it at any time.
References
- ↑ Hadhazy, Adam (22 December 2014). "A New Way to Reach Mars Safely, Anytime and on the Cheap". Scientific American. Retrieved 25 December 2014.
- ↑ http://arxiv.org/abs/1410.8856, http://www.universetoday.com/117615/making-the-trip-to-mars-cheaper-and-easier-the-case-for-ballistic-capture/
- ↑ http://www.scientificamerican.com/article/a-new-way-to-reach-mars-safely-anytime-and-on-the-cheap/