A key scene in 2001 occurs when astronaut Dave Bowman blows the “explosive bolts” embedded in his space pod’s door in order to effect an emergency exit. There are a number of things about the whole explosive bolt concept and execution which are sort of interesting.
Blowing the door off is not something you want to do lightly. So there’s a complicated series of steps involved, to avoid the risk of accidental bolt detonation. These unlatching and button press steps are required to trigger first the arming stage and then the final firing stage.
Bowman is seen reaching for an anodized green device, which is mounted to the starboard back wall of the pod. He unclips a metal cover from it.
The device is one of the few found objects in the pod design – it was a Martin-Baker PEC (personal equipment connector) from a military aircraft ejection seat. This is a device used on the pilot’s seat, and through it oxygen and communications data flow. The device has two halves – one on the seat and one in the cockpit – which separate instantaneously if the explosives used to fire the ejection seat go off.
In the movie Bowman is seen pressing a series of three hemispherical buttons to arm the bolts. But these aren’t actually buttons – they’re the oxygen cutoff valves on the PEC, being used as pretend buttons. The click sound effects as he presses the buttons were added in afterwards – the real PEC has spring-loaded valves that bottom out and don't click.
The cover he removes, incidentally, has a machined aluminium plate with circular recesses, attached to an anodized green cover. The bare aluminium plate appears to have been custom-machined for the film. The green piece is a Martin-Baker part: a protective stowage cover for the PEC.
Once Bowman has removed the metal cover he then has this thing loose in his hand. This seems to be a bad idea for a zero-G vehicle, since you really don't want random junk like heavy metal objects floating around the interior of the cabin! For safety you'd think the cover would be on a hinge or cable or something like that.
Anyway, in the film you see Bowman lowering the cover out of frame. You then, if you watch carefully, see him flip down a black lid.
This shows he was supposed to have flipped open a storage compartment to the starboard side of his armrest prior to unlatching the PEC cover. He then stowed the cover safely inside the compartment, and flipped the lid of the compartment shut.
This compartment is not shown in the film; only part of each lid top can just be seen. However, three behind the scenes photos show more detail. One of the three photos shows the actual shape of each lid - they weren't square or rectangular, but had an angled back end.
After Dave has stowed the cover plate and pressed the pushbuttons on the green panel, a low electronic farting sound begins and a red light starts flashing on the rear starboard console. This light is labelled DISCON in behind the scenes photos, but for filming they changed the text to ARMED, which makes more sense.
Incidentally, this is one of the few times you see a blinky light on a 2001 set, which avoided such things except in cases like this, where an emergency situation warrants a flashing attention light.
They also changed the text on the red rectangular sticker beneath the light to read SEQ ACT 3 SEC INT in the final film. Perhaps “sequence activation (at) 3 second intervals”, maybe? Prior to this change it read something like “PROC. 1 ACTIVATION DEACTIVATION”, but the text is partially obscured by the top of the handle.
The EVA pod is the only spacecraft in the film without any form of seatbelts. You don't see them in the film, and you don't see them in any behind the scenes photo of the pod interior.
However, when Bowman turns around in the seat to prepare for egress he reaches down to his waist, out of camera frame. He appears to unclip each side in turn, and you hear three clicking sounds. These are presumably the unseen seatbelts of the craft. Though perhaps there were supposedly tie-downs attached directly to his suit, maybe to the diagonal grey straps running from waist to crotch, rather than to a separate waist belt.
But the film shows no fasteners or belts. And no photos exist showing either seatbelts or the area of the seat where belts should exist. Maybe they were added for filming, after the high-resolution photos of the interior were taken, or maybe actor Keir Dullea simply mimed the action of unfastening the belts.
As noted, this lack of EVA pod seatbelts is an anomaly. The sets for all the other vehicles in the film (Orion, moonbus, Discovery) had visible four-point seatbelts – belts which run from either side of the waist, plus two over the shoulders, like the kind used by flight attendants on commercial aircraft. They don't seem to have five-point belts used by military pilots, race car drivers, and infants in child seats. (the fifth point is the belt that goes between the legs) Even Heywood Floyd is strapped in with a four-point belt as he dozes off on the Orion. The one exception is the elevator of Space Station V, which had waist belts only.
If the EVA pod was supposed to have clips at the waist only, that does seem like an odd omission. It's true that the EVA pod was mostly seen tootling around the Discovery at relatively low speeds. But it also had a large rocket bell on the bottom, and control panels on the pod interior set are clearly marked indicating that it was supposed to be able to do exploratory missions to Jovian moons. Given all that you'd think that the craft would have: a) proper seatbelts, and b) a back and neck rest to avoid the astronauts getting whiplash injuries! Even at really low speeds you'd need some form of restraint to keep yourself from floating around the cockpit, crashing into things.
The upper part of the door has a printed panel with text, much like the outside of the door. It lists the first three “maintenance and replacement instructions”, versus the four lines printed on the outside. All text is, as usual for the film, in Futura Bold.
CAUTION
MAINTENANCE AND REPLACEMENT INSTRUCTIONS
(1) SELF TEST EXPLOSIVE BOLTS PER INST 14 PARA 3 SEC 6D
AFTER EACH EVA.
(2) REPLACE DEFECTIVE BOLTS BY OOL UNITS ONLY INV
CONT Nº 2D 496.
(3) BOLTS SUBJECTED TO TYPE 2 ENVIRONMENTAL CONDITIONS
MUST UNDERGO STANDARD SIMULATED IGNITION TESTS.
EXPLOSIVE BOLTS
Incidentally the fourth line, seen only on the outside of the door, reads
(4) PERFORM ACT - DEACT CONTROL TESTS AND CFM CLEANING UNDER
EXTERNAL POWER CONDITIONS ONLY.
People often put lights behind this door panel in their models, but we don't see that in the film. The real panel was not lit internally, but was illuminated by a spotlight, kept out of frame behind the camera, for the scene in which Bowman bends forward in preparation for the emergency egress. You can tell it wasn't backlit because the red panel is of the same brightness as the circular red stickers on the door, which weren't lit either. Also, since the stickers are red, versus the darker oxblood/brick red of the door in general, they obviously look brighter.
Beneath that, in the middle of the door interior, is a small yellow and red panel with a tiny screen. At least, by time of filming it bore a sign – the area was blank in the pre-filming photographs, such as the one published in the Making of Stanley Kubrick's 2001: a Space Odyssey by Piers Bizony. The finished panel has some oddly formatted text that doesn’t properly fit the space – it’s got rather weird word spacing and line spacing. Certain key words are also printed in larger type.
Only the first two heading lines are readable in the film, but there is a continuity Polaroid stored in the Kubrick Archives, and which was published on social media, which reveals the actual contents of the body text. It matches what we see in the final film, and is as follows:
WARNING
10 SECOND DELAY
FOR USE ONLY IN EMERGENCY
CONDITION AS DESCRIBED IN U.S.A.A
MANUAL (D35 AND A2) AMENDED (PRIOR
SEC 3) PARA (6-8)
ACTIVATE CLEAR (PRESS CONTROL)
AND ACTIVATE DISCHARGE TO EXPOSE
FIRING BUTTON FIRE GRASP
HANDLES DURING FINAL 10 SECOND
COUNTDOWN
As I've noted elsewhere for other bits of 2001 text, this panel has somewhat idiosyncratic phrasing for English. Additionally there's a very small readout panel in the top red section of the panel. This was illuminated with a numeric countdown – the continuity Polaroid shows a test of the 16mm rear-projection film used to show the digits. (the glowing numeral 7, probably in Futura Bold, is shown) However, no illuminated digits were shown in the film. Kubrick instead elected to focus on Dullea's strained face as he prepares himself to be blown out the hatch.
Incidentally, Bowman takes in a deep breath while waiting. This would seem to make sense from an oxygen in the blood point of view, but in fact later research indicates that you should probably hyperventilate and then exhale, or at least not take in a deep breath, before entering a vacuum environment. This is because air in the lungs will expand in a vacuum, rupturing fragile lung tissues.
At the top of the door is a rectangular control panel with two pushbuttons and a metal flap. It’s sheet aluminium in pre-production photos, but painted black in the film. Unusually for 2001, which has stuff with concealed fastenings much of the time, it’s got visible screw heads in the corners. (you can't really see the screwheads in the film because of the black paint)
The two red buttons are marked CLEAR and DISCHARGE, thus matching the instructions on the panel below. They are never illuminated in the film.
The metal flap must have been intended to conceal the unseen FIRE button mentioned in the instructions on the small sign. This third button and the interior of the flap are never seen in the film or in any known photo. However, Bowman is seen reaching up to the out of shot panel to activate the time-delayed firing of the door's explosive bolts, now that the system has been armed.
Above the metal flap is the text CHARGE ACTIVATOR with a red arrow pointing down to the flap. People sometimes have added text below the flap, but that's incorrect. What appears to be a pair of narrow bright areas to either side of the bottom of the flap are actually parts of the flap corners. The flap had an angled recess at the bottom, presumably where the hinge was located.
Having pressed the first button, the farting of the “armed” status is then accompanied by a more rapid high-frequency yelping sound, indicating the 10 second countdown for the actual firing of the bolts. Bowman then presses the last two buttons and braces for impact.
If you look at the back of the pod you'll see a rectangular shape inset into the door, outlined by the ten red squares that mark the explosive bolts. Each bolt is depicted as a machined aluminium cylinder cap. The idea was that the door would stay shut, but that its inner section, a kind of hatch, would get blown out, or at least detached, by the bolts. The bolts weren't supposed to cause the door to rotate open or something.
Incidentally, the position of these bolts on the outside of the door does not match the position of the raised squares on the inside of the door. These interior door squares, which are blank in behind the scenes photos, but in the film have round red stickers with the word CAUTION printed on them in white text, are meant to be the interior locations of the explosive bolts. But because the exteriors of the pods and the interior set were separate sets with different sizes, they don't really match.
Interestingly, there's evidence that at least one of the full sized pods was built with a removable hatch within the door. Behind-the-scenes photos exist in the Kubrick Archives, and published on social media, featuring this partially closed door with the hatch removed! They're casual photos, on a contact sheet of pictures taken by photography Dmitri Kessel, showing actors Dullea and Lockwood relaxing on the set between takes. Dullea is holding a small battery-powered fan, no doubt owing to the rather overheated film set, which was lit by tungsten and carbon arc lamps.
The film, however, does not show this hatch blowing out. Indeed, the airlock entry sequence doesn't show the back door operating in a fashion you'd expect at all, indicating a certain continuity error or change in plan.
Also, complicating this blow-out hatch idea, is that the interior of the door does have a recess that could presumably blow out. But the recess traces a shape that's on the inside of the door interior's squares. On the outside of the pod the recess traces a shape that's on the outside of the door exterior's squares.
This is a question. Given the risk to the pilot of having actual explosions, with gas and shrapnel flying around unhindered by air or atmospheric gravity, it seems unlikely that you'd want to fire a whole bunch of explosive devices that would propel the removable hatch forward. On top of that you'd also have this big heavy door hatch flying around.
Instead, the hatch was presumably held in place by pyrotechnic fasteners – small explosive charges within a bolt which, when fired electrically, would simply cause the bolt to break in two at a specific weakened point. These explosive bolts are commonly used in space vehicles, such as allowing rocket stage separations and so on. When triggered, the hatch would safely detach, permitting the pilot to push it away and exit.
However, in the film we see a big explosive burst of gas as the bolts are fired.
I'm no physicist or space scientist. But I understand that the airlock scene in 2001 is not accurate, given current understanding of the matter. In the 1960s it was probably thought of as realistic, though.
There would obviously be some air inside the EVA pod, and it would be under a certain amount of pressure. With the hatch gone this air would exit from pod interior, owing to the lack of pressure in space. However I understand that it would not have occurred in a massive explosion like we see in the film, but in a more gentle fashion.
The recent TV show the Expanse features scenes with people in airlocks being brutally murdered by sending them out into open space. In this show they sort of drift out slowly, suffering horrible skin burns (unfiltered sunlight unmitigated by atmosphere) and burst capillaries and so on before succumbing to the loss of oxygen in their blood. This is, I understand, apparently a more realistic fate for someone in this sort of situation.
I'm not sure what the deal is with the handles. The door has, on the interior side, two deep rectangular recesses containing a pair of vertical black handles. These have a series of parallel ridges in them, for antislip properties when an astronaut with gloved hands holds them, I guess. The handles have the same surface treatment as the handles on the cylindrical remote arm (waldo) controllers slung under the dash.
The instructions on the door interior, reproduced above, tell the astronaut to “grasp handles” when the bolts are blown. But that doesn't make much sense, since the handles are on the panel that presumably would get blown out! Is the astronaut supposed to go shooting out into space, clinging to the panel? Or, as fellow 2001 enthusiast Karl Tate suggests, perhaps they mean the handles on the sides of the door - the ones in the recesses in the padded vestibule/entry area? Who knows?