This fuel-saving orbital insertion method could also be notably helpful for exploring planets on the fringe of our solar system, together with the uncared for ice giants.
This diagram outlines the essential levels of the aerocapture method. Credit score: Athulpg007/Wikimedia Commons
House companies have carried out a stunning aerial feat at each Venus and Mars: they’ve dipped an incoming spacecraft into the planets’ atmospheres to gradual it down with out wasting your rocket gasoline.
However will this audacious aerocapture method additionally work within the outer solar system? Athul Pradeepkumar Girija, who just lately earned a PhD from Purdue College and now works for a personal space firm, appears to assume so.
Detailed in a collection of papers printed on arXiv.org, Girija explores utilizing aerocapture — a maneuver the place atmospheric drag is used to decelerate a spacecraft so it could actually extra simply enter orbit— throughout a wide range of outer solar system worlds, together with Jupiter and Titan. However extra just lately, he’s turned his consideration to the ice giants, Uranus and Neptune, as outlined in each arXiv.org papers and a peer-reviewed examine in Acta Astronautica.
A greater strategy to discover the neglected ice giants
Humanity has solely visited every of the ice giants, Uranus and Neptune, as soon as. NASA’s Voyager 2 probe had fleeting encounters with Uranus in 1986 and Neptune 1989, earlier than setting sail for interstellar space.
However just lately, the decadal survey — a 10-year survey the place planetary scientists and astronomers map out a future plan for the sector — known as for a Uranus orbiter within the coming years. Whereas there’s no assure an precise mission will ever materialize, the first targets outlined within the decadal survey do assist inform space companies about what’s essential to the scientific group.
“The ice giants are of specific curiosity for aerocapture, as they’re fairly distant,” Girija says. “And for those who attempt to use the rocket to get to orbit, it takes a number of propellant as a result of by the point you’re out within the outer solar system, you’re touring fairly quick.”
So, by as a substitute utilizing a planet’s environment to assist the spacecraft decelerate, you may notably scale back the quantity of propellant required for the journey.
“The rewards are fairly excessive as a result of now you don’t want to actually deliver 50 to 60 % propellant with you,” Girija says. “You should deliver a warmth defend with you, however usually that warmth defend is sort of much less huge in comparison with propellant.”
All of it sounds fairly wild. In any case, Voyager 2 was touring at 39,000 mph (24,000 km/h) when it flew by the Uranus system. And the Mars Odyssey orbiter was solely going a fraction of that pace when it used aerobraking at Mars in 2001.
Nonetheless, papers, together with two printed by JPL personnel within the Journal of Spaceflight and Rockets, again up the feasibility and advantages of aerocapture. (Girija and a number of other colleagues additionally published a paper on the subject in the identical journal.)
With higher threat comes higher reward
Just lately, Girija checked out two methods spacecraft might accomplish aerobraking within the outer solar system: by carry and drag modulation.
Elevate modulation permits a level of management, however requires propellant to decelerate, growing the mass of the spacecraft, which cuts into what number of devices will be packed onboard.
Drag modulation depends on the truth that as a spacecraft speeds by the environment of a planet or moon, friction with air molecules helps to gradual it down. Nonetheless, this drag methodology provides minimal management, and thus is a bit riskier.
Girija discovered that each approaches can work, and every comes with its personal advantages and disadvantages. However carry modulation, he concluded, permits for the next preliminary entry pace, which might help shave years off the total mission time. Barreling by a planet’s environment is principally a free strategy to considerably change the speed of a spacecraft, Girija mentioned. However doing so can be a bit extra harmful than extra conventional, propulsion-based approaches. “So,” he added, it’s excessive threat, excessive reward.”
