The explosive guillotine in the Lunar Module

You: “Did you say ‘guillotine’?”
Me [approximating John Cleese]: “Explosive guillotine, yes.”

LM guillotine

In missions past and present, explosive devices feature in pretty much every spacecraft because they’re a safe, reliable way to ensure that processes start, items such as antennas are deployed, and connected assemblies that need to come apart are quickly and cleanly separated.

On the Apollo missions, over 210 pyrotechnic devices were in the Saturn V stack and the Command, Service, and Lunar Modules, used for everything from extending the LM landing gear to deploying drogue and main parachutes to ensuring fuel was at the correct side of a tank – for which the word ullage (in French, ouillage) was borrowed from vintners, to whom it means the headspace between the top of the wine and the container it’s in, whether a cask or a bottle.

The Lunar Module had several devices on board:

ED Locations

Control over them was through the Explosive Devices Control Panel:

ED Control Panel

All of these devices were essential, but particularly key were the devices set off to initiate separation of the ascent and descent stages of the LM when the astronauts departed the lunar surface. This was a three-stage process that took place in the tenths of seconds before the ascent engine was lit:

  • First, fire circuit interrupters to cut off electrical signals between the stages
  • Second, fire and shear the four explosive nut and bolt assemblies that affix the ascent stage to the descent stage
  • Third, using the explosive guillotine, slice through a thick bundle of umbilical cables and wires and a water supply line that run between the two stages

Though these devices were known to be generally reliable, a certain level of trepidation about them is understandable. Blowing up some high explosives to drive a big blade through wires doesn’t exactly sound like the most controlled process even though it actually was.

“Did you know when that unit was up on the moon, and the ascent stage was going to take off, they had all those wires – fourteen miles of them – running from the ascent stage into the descent stage, and it all had to be disconnected before you took off, or you didn’t take off? That’s all there was to it. You couldn’t use wire couplings that just pulled out when you gave it a good, hard yank. Do you want to trust a wire coupling to hold through a Saturn V liftoff and all that g-force and vibration? Uh-uh. Try flying a ship with a few loose wires. So, it was all solid connections, which is why we put a guillotine inside the descent stage: to cut all the wires. Everything had to be timed just right. The explosives had to trigger the guillotine and the blade had to cut through some pretty thick cables, and at the same time, the ascent rocket engine, which was never run before, had to start.”
– Bob Ekenstierna, LM descent stage construction supervisor at Grumman

In Chariots for Apollo by Pellegrino and Stoff, a somewhat sensationalist telling of the building of the Lunar Module at Grumman*, they speak of Joe Kingfield, the director of quality control. I won’t quote them directly since they went over the top with their narrative, but Kingfield had frequent nightmares about the liftoff from the moon that involved the guillotine and one or more of the explosive bolts failing. In his dreams, the ascent stage lifted off, but, still connected by miles of wire, dragged the descent stage along the ground and eventually crashed back into the surface. In later years, Kingfield still could not bring himself to watch the footage of the lunar liftoffs taken by the Mission Control-directed TV cameras on the Lunar Roving Vehicles of Apollo 15, 16, and 17.

*Not to be confused with the unimpeachable NASA volume of the same name by Brooks, Grimwood, and Swenson; web and epub links at the link.

Charlie Duke, Lunar Module Pilot of the Apollo 16 Orion (the LM pictured in the Finley Quality Network banner above), said that the pyrotechnics for the ascent stage separation gave him brief pause just before he and Commander John Young lifted off from the moon. When the circuit interrupters fired, then the four interstage bolts at the corners were sheared, and finally the guillotine sliced through the umbilical and water lines, the entire ascent stage suddenly dropped an inch or so. Duke thought, “Oh, sh…” but did not have time to finish that thought as the ascent engine fired and abruptly took them away from the surface back toward Ken Mattingly awaiting their return aboard the Casper Command and Service Module in lunar orbit.

You can see a fair amount of the thermal protection fly off the ascent stage as it lifts off, which happened to all of the ascent stages to some extent. In addition, panels on the rear that provided thermal protection for the Aft Equipment Bay were damaged during the liftoff, but they had done their job already. Mattingly took this photograph of the Orion before docking:

AS16-122-19535

Apollo deniers like to point to this and other photographs of the Orion damage as ineluctable proof of chicanery, but what it really means is that they prefer extending and enhancing their apparently quite enjoyable fantasies to, say, reading the post-mission report (9th link in the background material):

At lunar lift-off, four vertical thermal shields (fig. 14-26) on the aft equipment rack were torn loose from the lower standoffs and remained attached only at the upper standoffs. This occurrence was observed from the lunar-based television.

The most probable cause of the failure was ascent engine exhaust entering the cavity behind these thermal shields. A cross section of the lower edge of the shields is shown in figure 14-27. Analysis shows that the thermal shield which extends below the support tube allows a pressure buildup on the closure shield which exceeds its capability. Once the closure shield failed, the exhaust entered the cavity behind the shield, resulting in a pressure buildup exceeding the capability of the vertical thermal shields.

In the lunar surface photographs taken prior to lift-off, some of the shields appear to have come loose from the center standoff (fig. 14-28). Excessive gaps between some of the panels are evident. Both conditions could be caused by excessive pressure in the thermal blanket due to insufficient venting during boost.

The corrective action will include a redesign of the thermal shield to eliminate the projection below the support tube, as shown in figure 14-27, and to provide additional venting to the blankets as well as additional standoffs.

This anomaly is closed.

Not one problem was detected in any of the pyrotechnics during any Apollo mission. The device designs used in Apollo were later adopted by the Shuttle program, with, for instance, the Single-Bridgewire Apollo Standard Initiator (SBASI) becoming the NASA Standard Initiator (NSI).

Tindallgrams

An introduction to Tindallgrams from one of the documents linked below:

The enclosed collection of memoranda were written by Howard W. “Bill” Tindall, Jr., the former Director of Flight Operations at NASA’s Manned Spacecraft Center in Houston. They document key technical decisions made between 1966 and early 1970 for all unmanned and manned flights through Apollo 13, and became widely know as “Tindallgrams.” Astronauts, flight controllers, and engineers took part in this planning, and many have lamented that they had lost track of their copies, so we have bound this set together for them. As Buzz Aldrin remembered, “Bill had a brilliant way of analyzing things and the leadership that gathered diverse points of view with the utmost fairness.”

In 1966, Apollo Spacecraft Program Manager George Low made Tindall responsible for all guidance and navigation computer software development by the Massachusetts Institute of Technology. Bill quickly grasped the key issues and clearly characterized the associated pros and cons, sometimes painfully for us, but his humor, friendliness, and ever-constructive manner endeared him to all of us.

In 1967, Low put Tindall in charge of a group called Mission Techniques, which was designed to bring together hardware development, flight crew procedures, mission roles, and spacecraft and control center computer programming. According to former MSC Director Christopher Kraft, “Those meetings were the hardened core of Apollo as far as operations planning was concerned. That’s where the famous Tindallgrams came from.” He continued, “It would be difficult for me to find anyone who contributed more individually to the success of Apollo than Bill Tindall.”

Those of us who took part in those meetings and other interactions with Bill will always appreciate another aspect of his contribution…he made it a lot of fun!

I’ve read hundreds of Tindallgrams. The one below is my all-time favourite, so I’ve cleaned it up considerably from the microfiche photocopy I got from the Kennedy Space Center years ago. These days, you don’t have to write to NASA and then wait eight or ten weeks before being pleasantly surprised by a ten-pound box in the mail. You can find PDFs with scans of many Tindallgrams here on CollectSpace, all completely weightless through the marvel of modern technology – much of which is the indirect result of Apollo, come to think of it.

LM2 cockpit

In this photo of the LM2 cockpit at the National Air & Space Museum, I’ve placed an arrow pointing to the panel and highlighted in the inset the DES QTY light being discussed:

LM2 Controls

By the way, they made the fix as Tindall had hoped – the DES QTY light did come on during landings, but did not trigger the master alarm.

You develop an instant global consciousness, a people orientation, an intense dissatisfaction with the state of the world, and a compulsion to do something about it. From out there on the moon, international politics looks so petty. You want to grab a politician by the scruff of the neck and drag him a quarter of a million miles out and say, “Look at that, you son of a bitch.”

Ed Mitchell, Lunar Module Antares pilot, Apollo 14

The moon

If the moon is mesmerising to me on an everyday basis, like this evening when I paused to take this photograph, how transfixing must it have been for the last forty-five years to the men who once walked on it?

P1010198

Why, she’s a lovely model

Something new for my office desk arrived in the mail this week. It’s a pre-built Apollo 11 “Lunar Approach” display by Dragon Models. Sure, I could have built, painted, and finished the less expensive kit version myself, but a) I’m no longer a teenager with that sort of idle time on his hands, and b) these days, when I spend hours crafting something, I like to be able to see it disappear as I eat it shortly afterwards. This would be far too crunchy.

Dragon Models DRW-50375 “Apollo 11 Lunar Approach”

Dragon Models DRW-50375 “Apollo 11 Lunar Approach”

I had my doubts about ordering because, as it turns out, this right here is the only decent photograph of the pre-assembled version on the entire web as far as I can tell. The other photos I found before ordering — on eBay at a bargain price — are small, fuzzy, and do no justice to it, and that includes Dragon’s catalogue and box cover photographs. Tsk. Here at the FQN we do things right, or at least emphatically say that we do.

When I opened the box and had a look, I immediately approved. For a model of about ten inches in length, it’s pretty accurate and incredibly detailed, even down to the crinkly thermal blankets in three colours.

P1010160 s

Though the Lunar Module did have Mylar in the superinsulation blankets behind the outside shielding, what you saw on the outside was not Mylar, but aluminized Kapton polyimide film, in multiple 0.5, 2, and 5 mil layers.