This area will cover relevant news of the threat to the planet from Near Earth Objects (NEOs) including concepts and designs for mitigation. All opinions are those of the author.

25 May 2010

ESA Advanced Concepts Team (ACT) Analysis of Potential Asteroids to Visit

 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.
Furthermore, it is reasonable to assume some further human-related constraints, such as:
  • 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.
As well as some technical constraints such as:
  • 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
(km/s)
Nominal return time of flight
(days)
Emergency
return time of flight (days)
Emergency
return deltaV
(km/s)
Asteroid orbit's semi major axis a
(AU)
Asteroid orbit's eccentricity
e
323 2000 EA14 6.590 405 195 6.022 1.11 0.2
1365 207945 (1991 JW) 6.937 414 70 3.167 1.03 0.12
1109 2002 TD60 8.776 365 110 5.107 1.20 0.08
434 998 HG49 7.141 405 80 2.654 1.20 0.11
853 2001 QC34 7.428 379 85 2.349 1.12 0.19
1000 2002 OA22 8.675 389 90 2.803 0.94 0.24
1595 2000 OK8 8.931 500 90 4.043 0.98 0.22
515 2006 YF 8.217 448 195 6.677 1.11 0.19
1109 2002 TD60 8.776 365 110 5.107 1.20 0.08
209 65717 (1993 BX3) 8.505 248 120 1.808 1.39 0.28
1527 2006 HR29 9.187 500 120 3.613 0.98 0.26
173 2006 SU49 7.197 230 170 1.019 1.41 0.31
1491 2006 KL21 8.015 373 170 1.836 1.2 0.12
222 2004 KE1 8.561 320 130 2.256 1.30 0.18
66 25143 Itokawa 7.274 261 140 1.945 1.32 0.28
304 2006 QQ23 8.155 249 145 6.167 0.80 0.29
1685 1999 RA32 7.959 369 175 2.160 1.03 0.09
122 2002 TC70 8.714 405 150 2.839 1.37 0.20
1444 2007 SQ6 7.428 369 180 6.629 1.04 0.14
468 10302 (1989 ML) 7.701 351 165 3.622 1.27 0.14

Link: ACT News Item

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