This afternoon at 12:40 PM Eastern, so 9:40 AM local (Pacific time), the uncrewed Orion capsule splashed down uneventfully off the west coast of Mexico's Baja Peninsula. I wondered why they had chosen 25-1/2 days as the mission duration for Artemis I considering all the light green days on the program's calendar were marked as 26-28 days, but the way they announced the splashdown tells all. The end of Artemis I comes 50 years to the day that Apollo 17 landed on the moon for the start of their operations there. In fact, 50 years back from the time I'm writing this, the first Apollo 17 moon walk was starting.
"Splashdown! From Tranquility Base to Taurus-Littrow to the tranquil waters of the Pacific, the latest chapter of NASA's journey to the moon comes to a close: Orion back on Earth," NASA spokesperson Rob Navias said during the agency's livestream of the event on Sunday.
Of course, Tranquility
Base was the name Apollo 11 gave to their landing site and Taurus-Littrow was the area that Apollo 17 explored. These two bookends marked the first and last Apollo moon landings. Invoking a tie to the Apollo program shows up nearly everywhere in Artemis literature.
NASA's Orion Spacecraft descends toward the Pacific this morning, local time. NASA Photo.
I don't think I need to talk about the difficulties the program had getting to liftoff; we followed those in real time from last summer until November 16th's launch. While they have tons of data to go over that will undoubtedly take months to process, and it seems unlikely we'll see Artemis II until late '24 or early '25, everything I've been able to keep up with has shown that things went very well, and the problems that did arise were minor.
There were novelties and records set during the mission, although those are secondary to the fact that they did what they needed to do to prove out their hardware and mission profiles. The mission seems to have been a resounding success. Something I don't quite grasp, probably because I've never heard of it and could use to see some pictures, was a difference in the way they re-entered the atmosphere.
Shortly after entering Earth's atmosphere, Orion left again, bouncing off the upper layers of air like a rock skipping off the surface of a pond. This "skip maneuver," which no human-rated spacecraft had ever performed before, allows the capsule to cover greater distances and land more precisely during reentry, NASA officials have said.
My vague memories of reading about Apollo re-entries from over 50 years ago all seem to be that "bouncing off the upper layers of the atmosphere" was to be considered a Bad Thing, and if an Apollo capsule did skip off the atmosphere, it wasn't likely to come back into the atmosphere. Since I really doubt the physics of reentry have changed, our understanding of that physics and how to use it to best advantage must have.
Well, it's a good day for congratulating the various teams spread across the globe that made this happen. Good summaries at Space.com and Ars Technica.
Thanks for the update
ReplyDeleteTo the best of my memory, Arthur C Clarke mentioned this type of reentry in a fictional story (not 2010: Odyssey Two) sometime in the 70s. You might remember in that story the Leonov used an inflatable ballute for braking to enter Jupiter orbit. Clarke DID mention - somewhere - about essentially double tapping the atmosphere in his story for the reentry of a crewed vehicle. Well before that was considered a more or less fatal oops using the techniques available then.
ReplyDeleteGreat piece, thanks SiG.
An inflatable ballute was designed in '66 or '67 as a way to recover the engine portion of the Saturn V 1st stage. Previously an inflatable ballute was designed as a one-man lifeboat for the Apollo program, where the astronaut would ride inside the shield as it reentered, and was equipped with parachutes, inflatable raft, survival kit and radio/radio transpoder.
DeleteVery not new, even by the 70's.
Apollo adjusted it's attitude during reentry using it's thrusters. It didn't do a full skip back out of the atmosphere, but it did regain some altitude on purpose during reentry to let some of the heat dissipate. Since it wasn't planned for, a full skip back out could have had dire consequences.
ReplyDeleteGlad it worked, but I'm a bit skeptical that Artemis will ever put folks on the Moon. I hope I'm wrong.
ReplyDeleteWant to start a pool on whether Artemis gets to the moon or the US collapses first? Too close for me to call!
DeleteNo idea, but hope springs eternal; I ordered a rotating Mars globe with the thought that my grandkid might be inspired.
DeleteI would suspect that we didn't have the precise trajectory control then that we do now, as the reason that skipping is feasible this time. Nor the automation in action during the loss of telemetry.
ReplyDeleteDo they use thrusters to change the angle and skip back out? Seems they'd have to, but I don't have a feel for how big a control surface would need to be.
DeleteI don't have any more specific insight on it than you do, just my experience as an engineer. As you say, using the attitude thrusters to change the angle of the dished heatshield is the only real control they have. But I do know that this is a VERY tight "window" to achieve the right trajectory, and I cannot but believe that our guidance system and thruster control is far superior to what we had in Apollo.
DeleteAnd we most certainly have better aero simulations around which to design control strategies. We couldn't do good hydrodynamic sims in the 70s.
It appears that the "degree of skip" depends on the amount of velocity lost on the first dive.
ReplyDeleteIn the 1930's in Germany, Doc Sanger did the Math for an Intercontinental Rocket Bomber, that Launched out of Germany, could Hit a West (U.S.) Coast Target, Skip, and Land at a Base in Japan, then be Turned Around to Bomb the East Coast and return to a Luftwaffle Base. (this, well before the War started.)
ReplyDeleteThe BETTER Space Shuttle (designed by German Rocket Scientists, before the bureaucracy Ruined the Project) was a pair of true Rocket-Planes, one a Carrier and the other an Orbiter, that would perform this Maneuver to Launch, Recover the Carrier, and then the Orbiter. This design built on the Work of the X-15 and other Experimental Planes. They would have been Constructed of Nickel Alloys and Titanium, and the Orbiter had Hinged Wings for Low-Speed Landings.
Instead we got the Aluminum Tub with Bathroom Tiles glued on with Bathtub Sealer, and Shot into Orbit with Fireworks.
"Place on Ground, Light Fuse, Get Away." All sorts of convoluted bureaucratic conniptions were done to justify Solid- Fuel Rockets as Manned-Vehicle Primary Propulsion - where up until then, Fireworks were Only used for Emergency Systems, or in a few cases, as Boosters for specific Military Aircraft. we all saw how well that worked.
I find it funny that it took 50 years for the Hidden Figures cast to put a duplicate empty capsule around the moon and skip atmosphere for the first time ever after forgetting all the manufacturing and engineering of that time just because.
ReplyDeleteAlmost as funny as the competition to make the most realistic phallic lift platform. That is a slap in the face, the landing is a teabag.
Have you seen the video making the rounds of the Artemis launch synched up to Freebird? Can not stop smiling watching it.
ReplyDeleteBack to the topic a fitting day indeed.
Somehow, they haven't offered me that one yet. Now I gotta go find it!
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