Onwards to Uranus and Neptune! Options

[SFJCody]

As soon as MESSENGER gets to Mercury, the most poorly explored planets in the solar system will be Uranus and Neptune. Could this lead to a revival of interest in the ice giants and their retinue, in the same way that the existence of New Horizons is perhaps partly due to the Pluto stamp*?







*via Pluto Fast Flyby and later Pluto Kuiper Express

[nprev]

Again, this is why I wish that there was a 'library' of outer-planet launch opportunities. Seems like trajectory calcs only happen when there is a viable mission proposal like NH in the pipeline; might have the cause & effect relationship backwards here.

If we knew that there were favorable launch opportunities for Uranus & Neptune (even with inner-system gravitational assists) in, say, the late 2020s, then draft mission proposals could start development now. With that much lead time, it's even conceivable that Frontier-class missions would be feasible given assumed technology advances.

[mchan]

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There may or may not be such a library, but there are usually a couple or more papers each year at the AIAA/AAS Astrodynamics conference that discuss trajectories for future missions to places all over the solar system. Probably >95% of these come to naught but some folks are having fun cranking out the plots.

Not sure what is gained by a stretched development cycle. There is the risk that product of earlier development efforts be obsolete or difficult to support when launch date comes around.

[ugordan]

There really is no need for a launch opportunity library for the outer solar system if you want to go from A to C via B. As long as B and C are on the "same side" of the solar system there'll probably be an extended gravity assist trajectory with a varying efficiency over a couple of years. Jupiter would typically be your B body and from then on tweaking the launch date is a piece of cake if you have constraints on launch energy, launch date and/or arrival velocity. These sorts of calculations can be done on demand in a matter of minutes I figure.

More complex slingshot trajectories (involving say Jupiter AND Saturn) to get to Uranus or Neptune will occur rare enough that it's probably no use predicting them that far into the future. Furthermore, they usually impose bigger trajectory constraints which then constrain the slingshot gains. It might prove more efficient to use just an aggressive Jupiter flyby to catapult yourself outward than trying to fly by both J and S for what can turn out to be a weaker boost in the end.

[kwp]

As long as B and C are on the "same side" of the solar system there'll probably be an extended gravity assist trajectory with a varying efficiency over a couple of years. Jupiter would typically be your B body and from then on tweaking the launch date is a piece of cake if you have constraints on launch energy, launch date and/or arrival velocity. These sorts of calculations can be done on demand in a matter of minutes I figure.

Since this is a three body problem (spacecraft, Jupiter, Sun), I believe there is no closed, analytical solution to the problem of finding the best trajectory. I have thus assumed that it is done via Monte Carlo simulations. Alternatively, while there is no analytical solution, there might be good approximations. I'm hoping one of our resident experts will weight in and tell me how slingshot trajectories are calculated, and how computationally intensive the process is.

-Kevin

[ugordan]

I believe trajectory search and optimization software nowadays uses Keplerian orbits and patched conics to find plausible/optimum trajectories (and things like impact parameter or miss distance during flybys) and then when a "conceptual" trajectory is selected, it's precisely worked out by numerical integration and taking into accounts other factors such as solar light pressure, etc. That last part might be iterative and computationally more expensive, but it's all within reach of modern computers.