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  Mercury and Gemini splashdown impacts

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Author Topic:   Mercury and Gemini splashdown impacts
Explorer1
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Posts: 208
From: Los Angeles, CA, USA
Registered: Apr 2019

posted 04-25-2020 04:41 AM     Click Here to See the Profile for Explorer1     Edit/Delete Message   Reply w/Quote
I am curious to know the splashdown experience was for astronauts who landed in a Mercury capsule and then in a Gemini capsule.

The Mercury capsule used a landing bag to absorb some of the impact load of landing in the water and this of course made for a softer landing. No such provisions were made for the Gemini capsule and of course, the astronauts had the unusual difference of landing seated upright.

Which one was the more comfortable landing? Also, what were the landing speeds for the Mercury and Gemini spacecraft?

Mike Dixon
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From: Kew, Victoria, Australia
Registered: May 2003

posted 04-25-2020 05:11 AM     Click Here to See the Profile for Mike Dixon   Click Here to Email Mike Dixon     Edit/Delete Message   Reply w/Quote
Gemini Parachute Development Diary.

Negligible difference I'd have thought.

oly
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From: Perth, Western Australia
Registered: Apr 2015

posted 04-25-2020 10:40 AM     Click Here to See the Profile for oly   Click Here to Email oly     Edit/Delete Message   Reply w/Quote
The decent speeds for the spacecraft below inflated parachutes only make up part of the "speed of landing," there is also wind speed and ocean conditions. In calm conditions, the spacecraft theoretically descends vertically, as the wind speed increases, the spacecraft moves relative to the sea surface.

Combined with an ocean swell height, where the spacecraft could touch down at the peak or trough of a wave, but could also impact the wave as it was going down or coming up to meet the descending spacecraft.

For these reasons there is no answer to your question, because each landing occurred under different conditions.

As for comfort, I would imagine that the moment of touchdown would be considered as a THUD, followed by expedited checklist verifications and looking about the spacecraft for leaks. After having just experienced spaceflight, re-entry, freefall, confirmation that the parachute(s) deployed, inflated, and reefed correctly prior to splashdown, I doubt gauging the comfort level was high on their priority list.

Robert Pearlman
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From: Houston, TX
Registered: Nov 1999

posted 04-25-2020 11:58 PM     Click Here to See the Profile for Robert Pearlman   Click Here to Email Robert Pearlman     Edit/Delete Message   Reply w/Quote
quote:
Originally posted by Explorer1:
Also, what were the landing speeds for the Mercury and Gemini spacecraft?
As Pete (Oly) explained, each landing was different based on number of factors. As one example, Gordon Cooper described his Mercury splashdown in NASA SP-45, Results of the Fourth Manned Orbital Flight:
Landing at a rate of 30 fps with the landing bag down is a good solid jolt, but certainly tolerable. In fact, one does not really have to be in an ideal position and braced tightly to be able to take this momentary shock in good shape.
Decades later, he wrote about the same experience in his memoirs, "Leap of Faith," as follows:
Even with the huge chute, I was dropping at 32 feet per second, or approximately 22 miles per hour. Upon impact with the ocean, the force of the spacecraft drove it a good 10 to 12 feet underwater before it popped back up to the surface.
Cooper described his and Pete Conrad's splashdown in the Gemini 5 Technical Debriefing:
Impact was very, very soft. We just hit. We hit very easy. We didn't go underwater at all. We didn't change attitude one bit from the time we hit the water. We went bloop.
You might be able to find similar comparative descriptions from Gus Grissom and Wally Schirra in their respective Mercury and Gemini technical debriefings and/or their memoirs ("Gemini" and "Schirra's Space").

oly
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From: Perth, Western Australia
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posted 04-26-2020 02:32 AM     Click Here to See the Profile for oly   Click Here to Email oly     Edit/Delete Message   Reply w/Quote
For the MR-3 Post Launch Report, Shepard described the landing to be a "moderate shock."

Later in the report "The landing bag performed satisfactorily and, although there was no instrumentation provided to record landing accelerations, the pilot reported that the landing impact was moderate. He compared the acceleration to that of an aircraft catapult launch."

Shepard reported during descent, "Main chute is good, rate of descent is reading about 35 ft/sec."

In the MR-4 Post Launch Report, Gus Grissom described his Mercury landing.

The spacecraft landing in the water was a mild jolt; not hard enough to cause discomfort or disorientation. The spacecraft recovery section went under the water and I had the feeling that I was on my left side and slightly head down. The window was covered completely with water and there was a disconcerting gurgling noise. A quick check showed no water was entering the spacecraft. The spacecraft started to slowly right itself; as soon as I was sure the recovery section was out of the water; I ejected the reserve parachute by actuating the recovery aid switch. The spacecraft then righted itself rapidly.
As can be seen from these two reports, a comparison between landing "comfort" is subjective, with Shepard's comparison to an aircraft catapult launch and a moderate shock (others have compared a catapult launch to being shot out of a cannon).

The landing bag arrangement adequately attenuated the landing deceleration loads to approximately 15g.

Mercury and Gemini: These manned spacecraft were omnilanders with preferred orientation, designed for injection into Earth orbit, followed by entry and landing. Each spacecraft was designed primarily for water landing, with a reduced-performance capability for land landings. The Mercury and Gemini spacecraft carried one and two men, respectively; their respective nominal vertical velocities before impact were 28 fps (8.5 m/sec) and 30 fps (9.1 m/sec).

Jim Behling
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Posts: 1502
From: Cape Canaveral, FL
Registered: Mar 2010

posted 04-26-2020 08:08 AM     Click Here to See the Profile for Jim Behling   Click Here to Email Jim Behling     Edit/Delete Message   Reply w/Quote
quote:
Originally posted by Explorer1:
...the astronauts had the unusual difference of landing seated upright.
They weren't seated upright, they were at a 45 degree angle.

Explorer1
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From: Los Angeles, CA, USA
Registered: Apr 2019

posted 04-27-2020 10:39 PM     Click Here to See the Profile for Explorer1     Edit/Delete Message   Reply w/Quote
Thank you for pointing out the angle.

Philip
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From: Brussels, Belgium
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posted 04-28-2020 01:55 AM     Click Here to See the Profile for Philip   Click Here to Email Philip     Edit/Delete Message   Reply w/Quote
On Gemini III, Gus Grissom broke the glass of his helmet, so that must have been a "bang"?

LM-12
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From: Ontario, Canada
Registered: Oct 2010

posted 04-28-2020 08:09 AM     Click Here to See the Profile for LM-12     Edit/Delete Message   Reply w/Quote
Grissom broke his helmet faceplate during the descent on the main chute when the spacecraft went to the three-point landing attitude, not at splashdown.

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