This fuel-saving orbital insertion approach could also be significantly helpful for exploring planets on the fringe of our photo voltaic system, together with the uncared for ice giants.
This diagram outlines the essential levels of the aerocapture approach. Credit score: Athulpg007/Wikimedia Commons
House businesses have carried out a blinding aerial feat at each Venus and Mars: they’ve dipped an incoming spacecraft into the planets’ atmospheres to sluggish it down with out squandering precious rocket gasoline.
However will this audacious aerocapture approach additionally work within the outer photo voltaic system? Athul Pradeepkumar Girija, who lately earned a PhD from Purdue College and now works for a personal house firm, appears to suppose so.
Detailed in a sequence of papers printed on arXiv.org, Girija explores utilizing aerocapture — a maneuver the place atmospheric drag is used to decelerate a spacecraft so it might extra simply enter orbit— throughout quite a lot of outer photo voltaic system worlds, together with Jupiter and Titan. However extra 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 approach 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 house.
However lately, the decadal survey — a 10-year survey the place planetary scientists and astronomers map out a future plan for the sphere — referred to as for a Uranus orbiter within the coming years. Whereas there’s no assure an precise mission will ever materialize, the first objectives outlined within the decadal survey do assist inform house businesses about what’s necessary to the scientific neighborhood.
“The ice giants are of explicit curiosity for aerocapture, as they’re fairly far-off,” Girija says. “And in the event you attempt to use the rocket to get to orbit, it takes a variety of propellant as a result of by the point you’re out within the outer photo voltaic system, you’re touring fairly quick.”
So, by as a substitute utilizing a planet’s environment to assist the spacecraft decelerate, you possibly can 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 essentially convey 50 to 60 p.c propellant with you,” Girija says. “You’ll want to convey a warmth protect with you, however typically that warmth protect is sort of much less large 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 way of the Uranus system. And the Mars Odyssey orbiter was solely going a fraction of that velocity 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 several other colleagues additionally published a paper on the subject in the identical journal.)
With better threat comes better reward
Not too long ago, Girija checked out two methods spacecraft might accomplish aerobraking within the outer photo voltaic system: by elevate 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 might be packed onboard.
Drag modulation depends on the truth that as a spacecraft speeds by way of the environment of a planet or moon, friction with air molecules helps to sluggish it down. Nonetheless, this drag methodology gives minimal management, and thus is just a little riskier.
Girija discovered that each approaches can work, and every comes with its personal advantages and downsides. However elevate modulation, he concluded, permits for a better preliminary entry velocity, which might help shave years off the whole mission time. Barreling by way of a planet’s environment is principally a free approach to considerably change the rate of a spacecraft, Girija mentioned. However doing so will also be a bit extra harmful than extra conventional, propulsion-based approaches. “So,” he added, it’s excessive threat, excessive reward.”
