Posts: 169
From: Ledignan, Gard (30), France
Registered: Mar 2009

posted 02-22-2022 11:48 AM               

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By reading the document entitled "Technical Memorandum 33-425 Proceedings of the 4th Aerospace Mechanisms Symposium May 22-23, 1969," the part of the document concerning the Apollo unified crew hatch, I am still puzzled by a passage that I have trouble understanding. Here it is:

The sequence of hatch operations at launch:

1. Pressurize the cylinder (ground crew).
   
2. Board the spacecraft (flight crew).
   
3. Force command module hatch closed against the cylinder pressure (ground crew).
   
4. Close the command module hatch latches (flight crew).
   
5. Set the gearbox control knobs to the "open latches" position (flight crew).
   
6. close and latch the boost protective cover hatch (ground crew).

I have a problem with number 4. How is this possible?

Is it not the ground staff that closes and locks the hatch (and therefore the latches)?

Posts: 908
From: Danville, Ohio
Registered: Dec 2002

Posts: 169
From: Ledignan, Gard (30), France
Registered: Mar 2009

Posts: 908
From: Danville, Ohio
Registered: Dec 2002

Posts: 169
From: Ledignan, Gard (30), France
Registered: Mar 2009

Posts: 540
From: Italy
Registered: Dec 2010

posted 02-23-2022 09:23 PM               

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From "Technical Memorandum 33-425 Proceedings of the 4th Aerospace Mechanisms Symposium":

A manually operated spool valve controls the GN, flow from the bottles to a power cylinder and piston. A control cylinder is mounted axially inline with the power cylinder and houses a piston and orifice to regulate the flow of Freon which controls the hatch opening velocity.

Photo from my personal collection:

Pressurized cylinder for charging the side hatch opening actuator, called the counterbalance. Originally pressurized with gaseous nitrogen at 5,000 psi. Enabled a fully suited astronaut inside the Command Module to open the 350 pound weight of the combined side hatch and outer cover in 3 seconds.

Posts: 169
From: Ledignan, Gard (30), France
Registered: Mar 2009

posted 02-24-2022 07:04 AM               

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No... but I know that! I have the same document "Technical Memorandum 33-425 Proceedings of the 4th Aerospace Mechanisms Symposium May 22-23, 1969 (first message).

It is precisely in another extract of this one that I do not understand the procedure described which is just below the description you (Charlie16) give...

The sequence of hatch operations at launch:

1. Pressurize the cylinder (ground crew).
   
2. Board the spacecraft (flight crew).
   
3. Force command module hatch closed against the cylinder pressure (ground crew).
   
4. Close the command module hatch latches (flight crew).
   
5. Set the gearbox control knobs to the "open latches" position (flight crew).
   
6. close and latch the boost protective cover hatch (ground crew).

I have a problem with number 4. How is this possible?

Everyone is talking to me about how to "blow" the hatch, but I ask how the astronauts close the hatch (number 4) while they are harnessed on their couch? Is it not the ground staff that closes and locks the hatch? (Sorry for my poor English.)

Posts: 908
From: Danville, Ohio
Registered: Dec 2002

posted 02-24-2022 09:29 AM               

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That Apollo 13 movie sequence takes some liberties with the actual procedure. Note that no one is pressing against the hatch to close it against the pressure of the counterbalance. (Somewhere) I have seen video of this procedure, with more than one technician (2 or 3) pushing against the hatch with all their strength to close it against the pressurized counterbalance. And it is really a simple task for a crewmember to crank the hatch gearbox once the hatch is closed.

I did not realize that the right seat astronaut would open the hatch in an emergency. Apparently the gearbox handle is within reach for either the center or right astronaut.

Posts: 169
From: Ledignan, Gard (30), France
Registered: Mar 2009

posted 02-24-2022 10:06 AM               

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I'm agree with you the movie takes some liberties with the procedure, but I was convinced that it was the ground crew that locked the hatch with a special tool.

So if I understand well the way, the technicians push the hatch and it is one of the astronauts who locks it from the inside

Concerning the closing of the hatch (the real one) here it is (end of vidéo) (they are four technician pushing against the hatch):

EDIT : YES, I've found... (I will go to bed less stupid tonight)

From Apollo operations handbook Block II spacecraft volume 1

"The hatch is normally latched and unlatched manually from the inside by an actuating handle permanently attached to the gear box
(figure 1-23). Prior to handle actuation, the two control levers are positioned to the LATCH or UNLATCH positions as shown in view E and G, Both selectors are placed in identical positions when operating the latches. Next, the shear pin release lever is placed in
the UNLOCK position. This will extend the orange-yellow shear pin permitting free rotation of the gear box. When the latches are fully
engaged, or the release lever is placed in the LOCKED position, the orange-yellow pin will retract, locking the gear box. The shear pin may be sheared during an emergency opening of the hatch. A sheared condition is indicated by the protruding red pin, within the
orange-yellow pin, as indicated in view E. After the preceding steps have been performed, the handle is unstowed. This is accomplished by gripping the handle (which depresses the trip bar) and pumping approximately five 60-degree strokes. This will fully engage or disengage the latches.