Adam Hibberd
Conceptually the problem of a rendezvous with Halley’s comet, i.e. the requirement for the vehicle to apply thrust to match its velocity to that of the comet’s, is largely a problem of matching orbital plane. Once this is done, a significant proportion of the work has been performed.
Of course the challenge with Halley is that its orbit is quite significantly inclined to the ecliptic plane ( 𝑖 ∼ 162◦) – to such an extent, in fact, that it has a strongly retrogade orbit in comparison to those of all the (prograde) solar system planets.
However, when one restates the problem into one of a plane-match, one can begin to imagine solutions, specifically involving the gas giant Jupiter, which may help in this regard.
To this end a very useful serendipity presents itself in that Jupiter crosses Halley’s orbital plane in January of 2060, just one year before Halley’s perihelion. Can this coincidence be exploited in some way?
It turns out launching from Earth in 2059 and performing (a) a passive gravity assist (PGA) of Jupiter, (b) a retrograde orbit matching the plane of Halley’s after the PGA, (c) a return back to the inner solar system, and (d) a velocity match with Halley; is asking far too much from one Jupiter encounter.
Instead as a more measured strategy, this workload can be distributed across 3 consecutive Jupiter encounters by arriving at Jupiter one orbital period before this orbital sweet-spot, to the equivalent alignment 11.9 years earlier. This 3-Jupiter sequence can be summarised as follows:
1. Travel to Jupiter and execute a PGA
2. Transfer to retrograde motion at approximately Halley’s inclination
3. After a DSM ABOVE the ecliptic plane, return to Jupiter again
4. Match Halley’s plane almost precisely and travel to the next DSM, which is this time BELOW the ecliptic
5. Return to Jupiter and conduct another PGA to return inwards to the inner solar system
6. Arrive and rendezvous Halley with minimum ΔV
