ESCAPADE’s path through space, relative to the Earth, has the peculiar shape of a kidney bean. In the world of astrodynamics, this is called a staging, or libration, orbit. It’s a way to keep the spacecraft on a stable trajectory to wait for the opportunity to go to Mars late next year.

“ESCAPADE has identified that this is the way that we want to fly, so we launch from Earth onto this kidney bean-shaped orbit,” said Jeff Parker, a mission designer from the Colorado-based company Advanced Space. “So, we can launch on virtually any day. What happens is that kidney bean just grows and shrinks based on how much time you need to spend in that orbit. So, we traverse that kidney bean and at the very end there’s a final little loop-the-loop that brings us down to Earth.”

That’s when the two ESCAPADE spacecraft, known as Blue and Gold, will pass a few hundred miles above our planet. At the right moment, on November 7 and 9 of next year, the satellites will fire their engines to set off for Mars.

An illustration of ESCAPADE’s trajectory to wait for the opportunity to go to Mars. Credit: UC-Berkeley
There are some tradeoffs with this unique staging orbit. It is riskier than the original plan of sending ESCAPADE straight to Mars. The satellites will be exposed to more radiation and will consume more of their fuel just to get to the red planet, eating into reserves originally set aside for science observations.

The satellites were built by Rocket Lab, which designed them with extra propulsion capacity in order to accommodate launches on a variety of different rockets. In the end, NASA “judged that the risk for the mission was acceptable, but it certainly is higher risk,” said Richard French, Rocket Lab’s vice president of business development and strategy.

The upside of the tradeoff is that it will demonstrate an “exciting and flexible way to get to Mars,” Lillis said. “In the future, if we’d like to send hundreds of spacecraft to Mars at once, it will be difficult to do that from just the launch pads we have on Earth within that month [of the interplanetary launch window]. We could potentially queue up spacecraft using the approach that ESCAPADE is pioneering.”