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Wikipedia's Yuri Gagarin says:

At about 23,000 feet (7,000 m), Gagarin ejected from the descending capsule as planned and landed using a parachute.

and the section Vostok_programme; Vostok 3KA says:

After one orbit, the descent module successfully re-entered the atmosphere, the mannequin was safely ejected, and the dog and other specimens landed separately in the descent module by parachute.

and this answer references Wikipedia explaining that the "ejection seat" of Vostok was removed in Voskhod.

Question: How did the Vostok ejection seat safely eject an astronaut from a sealed space capsule?

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    $\begingroup$ what else could it mean? After all, fighter pilots had been ejecting from sealed airplanes for quite a while before 1961. en.wikipedia.org/wiki/Ejection_seat $\endgroup$
    – RonJohn
    Jun 17, 2019 at 17:01
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    $\begingroup$ @RonJohn sealed ≠ welded & space capsule ≠ airplane & atmospheric reentry at 8 km/sec ≠ flying an airplane. It's a very different engineering challenge, these are not equivalent scenarios. $\endgroup$
    – uhoh
    Jun 17, 2019 at 23:19
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    $\begingroup$ "atmospheric reentry at 8 km/sec ≠ flying an airplane" #1 The capsule isn't travelling at 8 km/sec through the atmosphere. #2. No one in his right mind would put the capsule hatch facing the wind. $\endgroup$
    – RonJohn
    Jun 17, 2019 at 23:30
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    $\begingroup$ @RonJohn the capsule is built to meet all of the demands of spaceflight, an airplane is not. They are not the same objects and do not present the same engineering challenges. It's a false equivalence. $\endgroup$
    – uhoh
    Jun 17, 2019 at 23:39
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    $\begingroup$ @RonJohn there's nothing in the question to that effect. I think you are reacting to something that isn't there. $\endgroup$
    – uhoh
    Jun 17, 2019 at 23:52

3 Answers 3

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According to this NASA page someone was killed when his space suit was ripped during a test of the ejection system.

Korolyovs [Korolevs] reaction to Dolgov's death was to take a number of urgent and clever measures. First he had the exit hatch made larger. Secondly, he increased to two seconds the interval between shooting off the hatch and the operation of the ejector mechanism.

But blowing off the hatch and ejecting the seat with the cosmonaut was not all.

The Vostok capsule was pressurized with nitrogen and oxygen to about 1 bar. The air pressure at 7000 m height is about 0.41 bar. To avoid injuries caused by the explosive decompression, a pressurized suit with closed helmet and gloves were worn. There is too little oxygen at 7000 m for a human without altitude adaption. When ejecting the seat, the suit was disconnected from the life support system of the capsule and sealed to retain pressure.

Cables for medical telemetry and for voice communication (microphone and earphones) were disconnected too.

The pressure difference from inside the suit to outside at 7000 m was about 0.59 bar, the suit was not very flexible but only for few minutes. The air inside the suit was breathable for the short time of fast descent from 7000 m to about 2500 m without oxygen supply or carbon dioxide removal.

At a height of 2500 m and an air pressure of about 0.75 bar, the cosmonaut could open his helmet to breathe fresh air with an oxygen partial pressure of 0.16 bar. The pressurized cabins of passenger airplanes are operated at about 0.75 bar.

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    $\begingroup$ Sounds quite exciting all by itself, maybe the scariest part of the whole mission! $\endgroup$
    – uhoh
    Jun 17, 2019 at 10:17
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    $\begingroup$ @David Richerby thanks for editing, looks much better now! $\endgroup$
    – Uwe
    Jun 17, 2019 at 14:46
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    $\begingroup$ I wonder if there was an automatic suit ventilation below 2500 m. If an unconscious cosmonaut failed to open his helmet, he would fade away due to low oxygen and high carbon dioxide in the suit. $\endgroup$
    – Uwe
    Jun 17, 2019 at 14:52
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    $\begingroup$ @uhoh But these problems were very similar to an U-2 pilot wearing a pressurized suit using the ejection seat in a height above 7000 m. $\endgroup$
    – Uwe
    Jun 17, 2019 at 17:09
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The hatch blew off and the pilot was ejected in a seat.

enter image description here

He then separated from the seat and descended on a parachute.

This was all kept quiet because of the contemporary FAI rules about manned spacecraft.

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    $\begingroup$ Note that fighter aircraft from that era were already using rocket-powered ejection seats to escape from a sealed pressurized cabin in a hurry, just as they are today; it was pretty typical for an explosive charge to eject the canopy a fraction of a second before igniting the seat motor. $\endgroup$
    – Russell Borogove
    Jun 17, 2019 at 0:54
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    $\begingroup$ Canopy breakers seem to be typical on planes designed for low-level attack operations, where the brief delay after blowing the canopy might make a life-or-death difference. $\endgroup$
    – Russell Borogove
    Jun 17, 2019 at 1:00
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    $\begingroup$ My favorite ejection seat story is harrowing, but everyone survives: gallagherstory.com/ejection_seat $\endgroup$
    – Russell Borogove
    Jun 17, 2019 at 1:19
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    $\begingroup$ @uhoh I do not know. The source I used just said "jettisoned", perhaps I was assuming too much when I said "blew off". $\endgroup$
    – Organic Marble
    Jun 18, 2019 at 0:49
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    $\begingroup$ This personal narrative says "blew off" but it's translated. spaceflight.nasa.gov/outreach/SignificantIncidents/assets/… $\endgroup$
    – Organic Marble
    Jun 18, 2019 at 0:55
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In addition to previous answers: This source (in Russian) http://epizodsspace.airbase.ru/bibl/i_tsk/zv-reis.html

contains Gagarin's post-flight debriefing. His exact words regarding ejection were:

"Жду катапультирования. В это время приблизительно на высоте 7 тысяч метров происходит отстрел крышки люка № 1. Хлопок, и крышка люка ушла. Я сижу и думаю, не я ли это катапультировался? Так, тихонько голову кверху повернул. В этот момент произошел выстрел, и я катапультировался. Произошло это быстро, хорошо, мягко. Ничем я не стукнулся, ничего не ушиб, все нормально. Вылетел я с креслом. Дальше стрельнула пушка, и ввелся в действие стабилизирующий парашют."

Translation:

"Waiting for ejection. In the meantime, at an altitude of approximately 7 thousand meters, shoot off (fire off) of the hatch cover No. 1 has happened. [Then I heard] the slam [or bang, meaning sharp sound], and the hatch cover was gone. I am sitting and thinking: was it me already catapulted [ejected]? [Then I] quietly (in a slow pace) turned my head up. At that moment, a shot occurred, and I ejected. It happened quickly, well [meaning satisfactorily], softly. I didn’t hit anything, didn’t bruise anything, everything was fine. I flew out with the chair. Then the gun (mortar) fired, and a stabilizing parachute (drogue chute) deployed."

I'm not 100% sure I translated in the best way his words "отстрел крышки люка" as "shoot off of the hatch cover", but I'm sure (as a native speaker) in Russian that word is tightly associated with some kind of explosive charge (whether it's gunpowder in a bullet or a TNT charge, I.e. something that rapidly blows off).

Also this web page (in Russian) http://www.astronaut.ru/bookcase/books/spacecrash/text/08.htm shows a sketch of the ejection (not sure, though, how authentic that is):

enter image description here

There are few more pictures on the web: enter image description here

enter image description here

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    $\begingroup$ This is great! Thank you for rounding up these sources and excellent graphics! $\endgroup$
    – uhoh
    Nov 28, 2019 at 8:29
  • $\begingroup$ There’s no needed for a mechanism to actively eject the hatch. With that pressure difference, the issue is holding it in place until you want it gone, then getting a clean release of the retention mechanism. The ‘blow off’ then naturally comes from the air pushing the hatch off and decompressing. Explode the resting bolts and the hatch will accelerate away at many G’s. $\endgroup$
    – Bob Jacobsen
    Nov 28, 2019 at 17:19

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