Launch Window Diagrams

In 2018 I became interested in compact graphical representations of launch windows between various planets.

The first poster was inspired by the successful launch of Falcon Heavy. For many decades, steadily more ambitious robotic exploration missions have become less and less frequent, due in part to perceived cost and scarcity of launch options. For <5% of NASA's budget, the world's most powerful rocket could launch 10 times a year. A Falcon Heavy in every launch window to every planet. No payload too weird, too risky, too heavy. Multiple agencies, NASA centers, universities can join the train. And if you miss the launch window, there's another launch in a year or two.

The image (raw data here) shows the delta-v required to get to any given planet, which can be translated into a total payload mass too. There are, of course, numerous details that I had to elide to fit it in the graph. Missions that require orbital insertion prefer lower closing speeds, but fortunately those calculations are relatively trivial on a point design study. I would love to see a version of this with a few NEAs and main belt asteroids too. I also threw in return windows from Mars to show the possibility of sample return missions.

The second poster was inspired by SpaceX's efforts to develop the BFR - a human exploration rocket for settling Mars. Not much is known about the final form this rocket will take, although it will definitely be enormous. The design embodies the observation that "there isn't a problem in space exploration that can't be solved by building a bigger rocket."

This image (raw data here) is essentially identical to the one above, though it is focused on flights to Mars only, so the color bar is a bit more granular. I also factored the Earth to Mars launch windows by orbits that would return to Earth in the event of an aborted landing - which beats indefinite flight in space for a disappointed crew. The salient point of this diagram is that it's non trivial to fly a BFR to Mars and back in time for the next launch window. Almost certainly it will require solar electric propulsion, though this graph doesn't really show how low force propulsion would modify the windows. As more details of the BFR implementation are announced I may make future versions of the graph which translate, eg, fuel load and solar panel size to a total payload capacity as the graphed quantity, rather than delta-v.

Both these images, and the underlying data are licensed under CC-ASA and may be cited as:

Handmer, C J. Launch Window Diagrams. April 2018.

I performed the calculations with PyKep (slightly modified) and the plotting with Mathematica. If the graphs included the broken plane maneuver or other deep space maneuvers, they would look a *little* bit different, but the underlying requirements are set by how much delta-v is needed in the all-important trans-planetary injection burn.