Figure 1: Orbits of the best 10 asteroids for human missions (Source: ESA ACT).
The Advanced Concepts Team (ACT) of the European Space Agency (ESA) has been looking at potential asteroids to visit. From their news release...
Human missions to asteroids (as recently announced by US President Obama* on April 15 at the Kennedy Space Centre) are in several aspects different from those to Mars or to the Moon, among others because of the wide choice: there are millions of them in the Asteroid belt between the orbits of Jupiter and Mars and thousands in the Near Earth vicinity (NEAs). Not all of these are equally easy and safe to reach – and return from.
The team has taken up the challenge of filtering the good ones out finding possible return trajectories to all known asteroids.
For a first human mission to an asteroid after 2020, one can assume some basic requirements in order to help downselecting a list of interesting asteroids:
- The asteroid should be not too small in order to be able to eventually land and take samples;
- A minimum stay on the asteroid should be guaranteed to allow for a useful scientific return.
- The trajectory should allow for a safe way to return rapidly to Earth in case of problems up to half way to the target asteroid.
- The overall mission duration should not be too long in order to keep the journey bearable for astronauts.
- No new revolutionary propulsion system by 2020 - thus delta V values within the range of current capabilities.
- A maximum hyberbolic excess velocity relative to Earth of 4.5 km/s for the return leg so as to allow for a safe landing of the return capsule.
The technical parameters used for the selection are:
Table 1: Baseline for asteroid selection
|Apparent magnitude (corresponding to roughly 200m)||H ≤ 22|
|Time of flight||< 1.5 years|
|Stay time on the asteroid||> 5 days|
|Relative velocity at Reentry||4.5 km/s|
|Propulsion||Chemical, with 1 deep space manoeuvre per leg|
|Launch V infinity||6 km/s|
Table 2 lists those asteroids considered as the prime candidates for such a mission.
Table 2: Preliminary list of best suited asteroids for a human mission
|Id||Designation||Nominal deltaV |
|Nominal return time of flight |
return time of flight (days)
|Asteroid orbit's semi major axis a |
|Asteroid orbit's eccentricity |
|1365||207945 (1991 JW)||6.937||414||70||3.167||1.03||0.12|
|209||65717 (1993 BX3)||8.505||248||120||1.808||1.39||0.28|
|468||10302 (1989 ML)||7.701||351||165||3.622||1.27||0.14|
Link: ACT News Item