A few weeks ago, when NASA's Orion returned to Earth, engineers made use of a guidance and control maneuver called a skip-entry – the first time a skip entry maneuver has been attempted for a human spacecraft.
While it’s not a perfect analogy, Orion will mimic a stone skipping across a pond by dipping into the Earth’s atmosphere, skipping out, then re-entering. Performed by the crew module, this maneuver gives Orion more space to travel before splashing down, allowing it to be more precise with where it lands.
“Skip entry gives us a consistent landing site that supports astronaut safety because it allows teams on the ground to better and faster coordinate recovery efforts,” said Joe Bomba, Lockheed Martin’s Orion Aerosciences Aerothermal Lead.
The first time I'd ever heard of this idea was in science fiction writer Robert Heinlein's classic Methuselah's Children, first serialized in Astounding Science Fiction in 1941. Heinlein expanded the three-part story into a full-length novel in 1958, which provides the quote used below.
In the story, the Howard Families are attempting to escape the Solar System in a vast generation ship, the New Frontiers. They are aided in their efforts by Slayton Ford, the chief executive of Earth's government. Ford is forced to go with them, joining them in orbit:
One figure emerged. Lazarus saw that it was Ford, pressed the switch again to close the port, kicked the blind latch into place, while never taking his blaster off his visitor. “Now what the hell?” he demanded. “What are you doing here? And who else is here? Patrol?”
“I want to go with you . . . if you’ll have me.”
Lazarus looked at him and did not answer. Then he went back to the bull’s-eye and inspected all that he could see. Ford appeared to be telling the truth, for no one else was in sight. But that was not what held Lazarus’ eye.
Why the ship wasn’t a proper deep-space craft at all. It did not have an air1ock but merely a seal to let it fasten to a larger ship; Lazarus was staring right into the body of the craft. It looked like-yes, it was a “Joy-boat Junior,” a little private strato-yacht, suitable only for point-to-point trajectory, or at the most for rendezvous with a satellite provided the satellite could refuel it for the return leg.
There was no fuel for it here. A lightning pilot possibly could land that tin toy without power and still walk away from it provided he had the skill to play Skip-to-M’Lou in and out of the atmosphere while nursing his skin temperatures-but Lazarus wouldn’t want to try it. No, sir! He turned to Ford. “Suppose we turned you down. How did you figure on getting back?”
“I didn’t figure on it,” Ford answered simply.
Heinlein didn't originate the idea. The skip-glide concept was originated in the WWII era as a way to extend the range of bombers and missiles; the technique was used by the Soviet Zond series of circumlunar spacecraft (1964-70), which used one skip before landing. In this case a true skip was required in order to allow the spacecraft to reach the higher-latitude landing areas. Zond 6, Zond 7 and Zond 8 made successful skip entries.
Update 15-Jan-2023: Fans of Raymond Z. Gallun will not be surprised to find that he had included this idea in his wonderful 1961 story The Planet Strappers - see the entry for skip-glide.
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