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  About the Mercury hatch release mechanism

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Author Topic:   About the Mercury hatch release mechanism
moorouge
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From: U.K.
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posted 01-05-2011 02:00 PM     Click Here to See the Profile for moorouge   Click Here to Email moorouge     Edit/Delete Message   Reply w/Quote
Researching another topic I came across this about the 'blown hatch' on Grissom's Mercury flight. This extract is taken from an interview given by Wayne Koons, Flight Range Coordinator under the Flight Operations Division at the time of the flight -
On that hatch there was a safety pin. It's kind of like the safety pin on a hand grenade. You know, you slip it out to enable the control to move. There was also, I think, a cover over the button that you used to explode the hatch. The hatch had this initiator in there, but what actually separated the hatch was a ring of Primacord that went all the way around the hatch. Then it was secured with a bunch of bolts that had been weakened by being [necked] down. The Primacord caused the bolts to fail, and so the hatch was really bolted in place and sealed. Then when you exploded the primer, which set off the Primacord, it blew the hatch off. There’d been some tests done, and the thing came off, a big bang, and it really blew the hatch a good distance.

So anyway, he had taken the cover off and pulled the safety pin preparatory to getting out. But there’s still, the way that thing’s configured, there’s a ring around that button, and it just doesn’t seem possible that he made contact with that. Certainly, based on his debrief, he certainly didn’t do it deliberately, and it’s hard to see how he could have possibly done it accidentally, because the way that button is down inside a ring, a cylindrical protector, you have to be very deliberate about it to make that thing go off.

Lou Chinal
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posted 01-05-2011 09:43 PM     Click Here to See the Profile for Lou Chinal   Click Here to Email Lou Chinal     Edit/Delete Message   Reply w/Quote
Like the Kennedy assassination the question of Grissom's hatch will never be resolved to everyone's satisfaction.

There was a way of releasing the hatch from the outside.

To quote "The Project Mercury Familiarization Manual" section 2 page 7. "An exterior hatch release control is also provided to enable ground personnel to explode the hatch in the event the Astronaut is unable to do so."

It is my belief the line from the dyemarker snagged this external handle.

To also quote from the "Results of the Second U.S. Manned Suborbital Space Flight July 21,1961" page 55, "After I was in the water and away from the spacecraft, I noticed a line from the dyemarker can over my shoulder. The spacecraft was obviously sinking and I was concerned that I might be pulled down with it". - Virgil Grissom (Pilot's Flight Report).

Weather it was the line from the dyemarker canister, a strap from the landing bag or a parachute suspension line, we will never know.

Grissom had no cut on his knuckles.

ejectr
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posted 01-06-2011 08:39 PM     Click Here to See the Profile for ejectr   Click Here to Email ejectr     Edit/Delete Message   Reply w/Quote
I often think of how physically fit Grissom must have been to get out of that thing as quick as he did.

You see the pictures of all the help they needed getting in and the ones getting out on the carrier deck (Schirra and Cooper) and you wonder how the heck he managed to get out of there so fast.

ilbasso
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posted 01-07-2011 06:14 AM     Click Here to See the Profile for ilbasso   Click Here to Email ilbasso     Edit/Delete Message   Reply w/Quote
I guess that coming out, they didn't need to worry about which switches and buttons they kicked!

I'm also amazed that they could get out through the "nose" by crawling under the control panel. That seems physically impossible to me, but I've seen photos of them doing it.

space1
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posted 01-07-2011 06:40 AM     Click Here to See the Profile for space1   Click Here to Email space1     Edit/Delete Message   Reply w/Quote
Keep in mind that the section of the control panel to the right of the periscope could be removed (by pulling a lever). This allowed easier exiting through the side or nose hatches.

moorouge
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posted 01-07-2011 08:28 AM     Click Here to See the Profile for moorouge   Click Here to Email moorouge     Edit/Delete Message   Reply w/Quote
Further to my previous post and as a matter of interest there is this from the Mission Report for MR-4 -
The explosively actuated side hatch was used for the first time on the MR-4 flight. The mechanically operated side hatch on the MR-3 spacecraft was in the same location and of the same size but was considerably heavier (69 pounds rather than 23 pounds). The explosively actuated hatch utilizes an explosive charge to fracture the attaching bolts and thus separate the hatch from the spacecraft. Seventy 1/4-inch titanium bolts secure the hatch to the doorsill. A 0.06-inch diameter hole is drilled in each bolt to provide a weak point. A mild detonating fuse (MDF) is installed in a channel between an inner and outer seal around the periphery of the hatch. When the MDF is ignited, the resulting gas pressure between the inner and outer seal causes the bolts to fail in tension. The MDF is ignited by a manually operated igniter that requires an actuation force of around 5 pounds, after the removal of a safety pin. The igniter can be operated externally by an attached lanyard, in which case a force of at least 40 pounds is required in order to shear the safety pin.
Note the last sentence. This explains this as posted earlier in this thread -
There was a way of releasing the hatch from the outside. To quote "The Project Mercury Familiarization Manual" section 2 page 7. "An exterior hatch release control is also provided to enable ground personnel to explode the hatch in the event the Astronaut is unable to do so."

moorouge
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posted 01-07-2011 09:46 AM     Click Here to See the Profile for moorouge   Click Here to Email moorouge     Edit/Delete Message   Reply w/Quote
quote:
Originally posted by space1:
Keep in mind that the section of the control panel to the right of the periscope could be removed (by pulling a lever). This allowed easier exiting through the side or nose hatches.

It wasn't quite that simple. The pilot also had to remove the forward pressure bulkhead and the parachute container.

gleopold
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From: Reston, VA, USA
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posted 01-07-2011 05:10 PM     Click Here to See the Profile for gleopold   Click Here to Email gleopold     Edit/Delete Message   Reply w/Quote
Could a tangled lanyard have generated the 40 pounds of pressure required to explode the MR-4 hatch from outside the spacecraft, as has been posited above, by Guenter Wendt and perhaps by others?

moorouge
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posted 01-08-2011 08:48 AM     Click Here to See the Profile for moorouge   Click Here to Email moorouge     Edit/Delete Message   Reply w/Quote
A further thought. The description of an external release of the hatch says - "The igniter can be operated externally by an attached lanyard ...".

Does this mean that the lanyard was already attached or does it mean the recovery crew had to attach it?

If the latter and remembering that Wayne Koons said that the hatch went a fair distance, how close was the person that yanked the lanyard?

Were those blown hatches ever recovered?

gleopold
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posted 01-11-2011 12:24 PM     Click Here to See the Profile for gleopold   Click Here to Email gleopold     Edit/Delete Message   Reply w/Quote
quote:
Originally posted by moorouge:
Were those blown hatches ever recovered?
If you are referring to the MR-4 hatch, no. Curt Newport was unable to retrieve it when he recovered Liberty Bell 7.

Paul78zephyr
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posted 03-29-2012 03:04 PM     Click Here to See the Profile for Paul78zephyr     Edit/Delete Message   Reply w/Quote
I have seen interviews with both John Glenn and Wally Schirra where they state that when they operated the 'button' to blow the hatch the button had a 'recoil' that injured their hands. Schirra stated that since Grissom had no such injury that was proof that he did not actuate the button.

I do not doubt at all what Glenn and Schirra stated. My question is why would there need to be designed into a switch that was to be used perhaps in an emergency something that could potentially cause an injury (minor or not) to the astronaut? I've never understood why the switch would have this 'recoil'. It does not make sense to me. Does anyone know why?

CurtMR4
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posted 03-29-2012 05:18 PM     Click Here to See the Profile for CurtMR4     Edit/Delete Message   Reply w/Quote
The hatch actuation plunger recoiled due to the gases generated by the MDF fuse when ignited. The external lanyard was always in place and not put there by the rescue team. However, a small panel had to be removed to expose this exterior lanyard and handle and it took considerably more force to fire the hatch without the internal safety pin removed.

C. Newport

Jay Chladek
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posted 03-29-2012 05:34 PM     Click Here to See the Profile for Jay Chladek   Click Here to Email Jay Chladek     Edit/Delete Message   Reply w/Quote
The thing to keep in mind about such a system is sure one could design it to be a button of some sort on a panel. But then you add a layer of complexity and of course a point of failure. Plus, you add weight as well. So having an actuation lever directly connected to the system makes sense. That way, when an astronaut hits the switch, he knows he is hitting THE SWITCH and not some system connected to the real switch.

Escape systems are typically like that in aircraft, be they canopy jettison switches or the ejection seat handles. When they have to work the first time, cutting down the equipment to the bare minimum means the chances of success go up. Besides, a bruise and cuts on knuckles are tame compared to the potential alternative (which is one reason why Apollo's hatch was redesigned after Apollo 1, since they didn't have that direct escape method).

As for Grissom's speed in getting out, if you are a guy normally used to being on land when you AREN'T flying and a wall of your spacecraft just came off unexpectedly, adrenaline alone would add speed to your escape and you don't care WHAT you hit on the way out because you want OUT.

Rusty B
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posted 03-29-2012 08:55 PM     Click Here to See the Profile for Rusty B   Click Here to Email Rusty B     Edit/Delete Message   Reply w/Quote
Here's a theory about how the hatch blew. It's only a theory, no way to prove it.

On page 55 of the of Results Of The Second U.S. Manned A Suborbital Space Flight July 21, 1961" - Pilot's Flight Report Grissom said he removed a survival knife from the hatch and removed the protective cap and safety pin from the hatch detonator.

The survival knife appears to be nearly one-foot long in pictures from the recovered Liberty Bell 7. See Figures 6a and 6b Page 7 here.

Grissom mentions the knife twice in the pilot's flight report. Once when he said he removed the knife from the hatch and stowed it in the survival kit. A second time when he said he thought about carrying the knife out with him as a souvenir.

And here's a diagram from the 1961 edition of the Mercury Familiarization Manual, PDF page 18. This shows where the survival knife and hatch release initiator are located on interior of the side hatch. Right next to each other.

Is it possible, in trying to maneuver this large knife in the confined capsule, tossing in the sea, he accidentally bumped the hatch detonator with the knife? Setting off the detonator in this manner would leave no mark on his hand like later Mercury astronauts received.

The knife was found loose in the bottom of the capsule. If it happened this way, maybe Grissom was too embarrassed to admit the hatch blew because of a souvenir.

Just a theory. No way to prove it one way or the other.

MCroft04
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posted 03-29-2012 09:14 PM     Click Here to See the Profile for MCroft04   Click Here to Email MCroft04     Edit/Delete Message   Reply w/Quote
Gus would have called it the way it happened.

alanh_7
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posted 03-29-2012 09:32 PM     Click Here to See the Profile for alanh_7   Click Here to Email alanh_7     Edit/Delete Message   Reply w/Quote
It could have happened that way, but I agree with Mel. Everything I read about Gus says he was a strait shooter, and the professional test pilot in him would not have allowed the speculation over the hatch to continue had he made a mistake.

moorouge
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posted 03-30-2012 02:36 AM     Click Here to See the Profile for moorouge   Click Here to Email moorouge     Edit/Delete Message   Reply w/Quote
The problem about getting old is that the memory starts to forget the detail. However, I can remember that a NASA engineer came up with two possible scenarios as to why the hatch blew without any input from the astronaut.

Perhaps a younger brain than mine can remember and post the details.

alanh_7
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posted 03-30-2012 05:30 AM     Click Here to See the Profile for alanh_7   Click Here to Email alanh_7     Edit/Delete Message   Reply w/Quote
If my memory is correct I think Guenter Wendt had an idea about the external panel that divers had access to could have opened and waves blew the lanyard to the hatch. But I cannot remember the details. I may be wrong and it may not have been Guenter's theory.

Rusty B
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From: Sacramento, CA
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posted 03-30-2012 06:11 AM     Click Here to See the Profile for Rusty B   Click Here to Email Rusty B     Edit/Delete Message   Reply w/Quote
Here's a color video showing a test of the Project Mercury explosive hatch.

There was another video, no longer on YouTube, showing a Mercury hatch test and also showing close-ups of the hatch interior. Here's a NASA Spaceflight page with screen captures from the video. You can clearly see the detonator cover, plunger, arming pin and to the right the survival knife holder.

moorouge
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posted 03-30-2012 06:12 AM     Click Here to See the Profile for moorouge   Click Here to Email moorouge     Edit/Delete Message   Reply w/Quote
An interesting video. Any idea who the astronaut(?) was?

Rusty B
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posted 03-30-2012 12:47 PM     Click Here to See the Profile for Rusty B   Click Here to Email Rusty B     Edit/Delete Message   Reply w/Quote
I found the video through a Google search, so I have no info about the astronaut. To me it looks kind of like Wally Schirra exiting the capsule after the test, but it may be a test engineer and not an astronaut.

Lou Chinal
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posted 12-07-2012 05:58 PM     Click Here to See the Profile for Lou Chinal   Click Here to Email Lou Chinal     Edit/Delete Message   Reply w/Quote
Yeah, I think it's Schirra also.

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