Thread by @aerohistorian

1/ 54 years ago today, #Gemini 9 #astronaut Gene Cernan was in trouble.
In space.
Alone.
In the dark.
No one could hear him.
His heart raced at 180 beats per minute.
His breathing labored.
His skin so flushed that he looked sunburnt...
@AFResearchLab @pilliarscreatio

2/ Sweat poured down his face & into his eyes.
His visor fogged over so badly that he couldn't see anyway.
His back was even hotter than the rest of him, meaning only one thing: his space suit was badly torn.

Cernan called it the “spacewalk from hell.”

3/ What was Cernan doing?
Trying to test the @AFResearchLab Air Force's Astronaut Maneuvering Unit (AMU), the first "jet pack" in space. Thanks to overconfidence, ignorance, & bad luck it ended up as the biggest missed opportunity of the Gemini program.
This is its story.

4/ Let's rewind.
The Air Force @AFResearchLab explored spaceflight techs throughout the 1950s, only to have Ike hand over initial human spaceflight responsibility to the nascent NASA in 1958. Still, AF saw a role for military men in space, tho the rationale often changed.

5/ Tho Mercury went to NASA, AF continued programs like Dyna-Soar & space station concepts. All eventually involved extravehicular activity (EVA or space walks) for astronauts. Why? Repairs, take pics, recover satellites, or even disable enemy ones. (pic credit: Mark Wade)

6/ To do those, you need to get from Point A to B.
SciFi long had space jet packs, but we start in '59.
The cast:
-Air Force Aero Propulsion Lab (AFAPL) & Flight Accessories Lab @AFResearchLab @WrightPattAFB (pic)
-Aerospace company Ling-Temco-Vought (LTV, orig. Chance Vought)

7/ in '59 LTV "studied extravehicular propulsion & stabilization" & sent proposal to AF Propulsion Lab (AFAPL) which was working same stuff. Results in continued studies & contracts, & partnership w/Flight Accessories Lab. Looked at other options, like this Marquardt Space Sled

8/ Initially called "self-maneuvering units," the packs required research & lots of tests esp for stability & control systems, & human interface. Tried: integrated vs separate life support, backpack vs belt type, single vs multiple controls; #/location of nozzles etc.

9/ 1st tests in USAF KC-135 Vomit Comet in 1962. AMU proved difficult to test b/c short duration & flight profile of 0G parabolas & AMU start/stop procedures (didn't want test subject crushed when planes hits 2.5G pullup) left only 15-20 secs of flight time. Remember that.

10/ AMU dev wasn't hard, just tech choice. Used hydrogen peroxide thrusters as best combo of power/reliability/size, but produced hot gas & was caustic. Note the thruster location between the legs! Used gyros for stability. Hand controllers was single central unit.

11/ Now Gemini. Program didn't initially plan for EVA, as space EVA (vs lunar) wasn't needed on Apollo (they later added it), so minimal accommodation for that. The space suit cooling system (blown air) was sized for low levels of activity, sitting in capsule, maybe floating EVA

12/ In 1963, NASA & DoD meet to discuss military participation in program, set up DoD Experimental program for Gemini astronauts to conduct on-orbit tests, from photos to radiation to EVA, eventually includes D-12, the Astronaut Maneuvering Unit.

13/ Aero Propulsion Lab contracts with LTV in May 1964. Ed Givens is AF manager for D-12 at MSC, Pete Van Schaik at WPAFB. System tests hit one big snag: H2O2 hot gas thrusters impinge on suit legs & can melt the material. 1st fix was nozzle extension

14/ For 2nd fix, AFAPL looked over to AF Materials Lab (also @AFResearchLab), were researching high temp woven metal fabrics for aerodynamic decelerators (parachutes, ballutes, paraglider) for reentry vehicles & inflatable space structures @ParachuteMuseum @LaboPotvin

15/ Hoskins Mfg Co developed Nickel-Chromium alloy called Chromel, w/Chromel-R as high temp superalloy. AF Materials Lab sponsored Fabric Research Labs to improve mfg process for many thin filaments & soft, tight weave fabric. Withstands >1500 deg, minimal stretch, very flexible.

16/ AF reduces Chromel-R fabric cost by 1/5.
AMU assigned to Gemini 9 w/Cernan as spacewalker.

Team makes 11-layer pants for Cernan's suit, alternating insulation & Chromel-R, Gives distinct "iron pants" look. Also added to his gloves in smaller amount.

17/ Cernan trained frequently, some in KC-135, but mostly on the ground due to the difficulties noted earlier. An air bearing rig at MSC (1st pic) was typical. Also did ground trainer at LTV facility (2nd pic). Good for familiaization w/control, but utterly inadequate for 0G sim

18/ Backup Buzz Aldrin also trained. Pic shows the AMU located at the back of the Gemini Adapter Module. Astronaut would guide himself from open cockpit, along side of craft, to the back, pull open AMU arms, activate, hook himself up w/tethers & umbilical. Easy? Nope.

19/ Prior to GT-9, only US EVA experience was Ed White 36-min mostly floating on GT-4. No one appreciated at the time that any activity he did (installing a camera, closing the hatch) was HARD, sweated, visor started to fog. Almost exactly 1 year between EVAs (6/3/65-6/5/66)

20/ But little had changed in EVA procedures & training. Added some handholds to capsule & even velcro (Cernan was enamored w/stainless steel velcro until Chuck Matthews literally used it to shred his pants in a meeting to demo its hazards) but what worked there didn't in space

21/ Gemini 9 launched on 6 Jun 1966. The AMU was mounted weeks earlier & fluids filled. Because mission was scrubbed once, AMU batteries were changed out. Otherwise system was nominal. Mission wasn't. Agena target didn't open correctly (angry alligator). Inauspicious.

22/ AMU EVA went on 5 Jun 66, day later than planned because of Agena. Cernan left the cabin 50hrs into mission (MET). He found pressure suit stiffer than expected, handholds harder to use, umbilical uncontrollable. Returned to cabin to rest before AMU.

23/ Cernan made his way to the back, struggling for handholds & body control the entire time. Bars to help him hadn't deployed, flexible handholds didn't help, light on back wasn't on, & had to use penlights. Found 2-hand tasks that worked on ground were impossible in space.

24/ Cernan had particular difficulty hooking up tethers. Began to burn on his back because he had ripped his suit on a protrusion at some point. Maxed out cooling flow in suit. Didn't help much. Visor constantly fogged.

25/Geno could hear his commander Tom Stafford talking, but couldn't talk back, only 1 click yes, 2 clicks no. Kept at it. Unstowed control arms, opened valves, backed himself into position, all done at night. But visor completely fogged now. After 1 hour, Stafford called no-go.

26/ NASA learned it needed to improve EVA training & in-space equipment. Langley was already working on underwater training & Cernan actually watched them sim his EVA just over a month after he got back. Resulted in better EVAs, esp on XII.

27/ The AMU never flew again, as the Air Force was getting into the Manned Orbiting Lab program and the Aero Propulsion Lab phased out its space tool/vehicle program by 1969. NASA tested similar ones on Skylab & the shuttle flew with the Manned Maneuvering Unit. /END

I probably should’ve tagged @TheRealBuzz since that’s him in the picture & he had an important role in figuring out how to train for & do EVAs

These nozzle extensions contributed to Geno’s problems. He had to extend them (effort) but found one wasn’t oriented correctly. Couldn’t fly til it was fixed but couldn’t see thru visor to adjust it. Was one of the last straws.

I bet @mikeheil and @DrMikeGregg recognize a few facilities in that photo. Several of the Aerospace Systems ones are no longer there, like the wind tunnel & rotor test stands.