“I’m Sorry.”
Is this a realistic depiction of explosive decompression in a spaceship? Spoilers: No. Does Halo do a better job depicting decompression in games, books, and other media? Keep reading to find out.
Well before I started writing this blog or even started helping out at Podcast Evolved, I would occasionally write in to the Halo Conversationalists podcast when they were discussing a specific science topic that would come up during an episode. Way back in April 2017, on Episode 11, they discussed the book The Cole Protocol, and had a heated discussion about how accurate to reality one of the scenes in the book was to physics. I wrote in saying it was actually probably close enough given the small detail provided, but promised to write up a more in-depth look at explosive decompression in the Halo universe in the future. Two and a half years later, I think I have finally procrastinated enough to the point where this article is entirely irrelevant and no one cares, but I am committed to writing it, so here we go.
Related Media
While minor, the following article makes reference to and could potentially contain spoilers for Halo Wars, Halo: The Fall of Reach, Halo: Ghosts of Onyx, and the short story The Impossible Life and the Possible Death of Preston J. Cole from the anthology Halo: Evolutions.
The Question JUMP TO CONCLUSION ▶
How does explosive decompression actually work in space, and is its portrayal in the halo universe accurate to physics or just a bunch of science fantasy?
The Answer
UPDATE: Following a comment by Incredible Canemian, I realized I missed a significant portion of the description of the Spartan Training Station Bombing (example 6). I have since included the missing part and have updated my analysis.
Similar to my previous article on the gravity assist maneuver, I am going to start with a brief discussion on the realities of explosive decompression, what it is, how it works, and whether it happens in real life. From there I will go into the major examples of explosive decompression in the Halo media and see how they stack up against cold, hard vacuum (which just so happens to be one of those engineering/operations terms that I really love). As with the gravity assist maneuver, if I missed a major example of decompression in Halo, let me know and I will try to update this article and include that one as well.
What is Uncontrolled Decompression?
I have thus-far used the term “explosive decompression” because I think it is more well-known than some of the other decompression-related terms, but in reality the “explosive” part of that term is only a small subset of a broader range of phenomena referred to as uncontrolled decompression. This refers to any form of loss of pressure in a sealed vessel, be it a slow leak or an instantaneous loss of pressure. The United States Federal Aviation Administration (FAA) divides decompression into three distinct categories based on the speed of decompression, though it is a sliding scale so there is no hard divider between the phenomena in real life. For our purposes it doesn’t really matter what we call it since it is the conditions and how they are portrayed that we are concerned with, but I will briefly describe each one and what are some of the defining factors.
Gradual Decompression
Gradual decompression is an event that happens very slowly, or at least slowly enough that it would not be readily noticeable by people inside the chamber. This would be something like a small leak through a pinhole that causes air to be lost slowly, something that has happened in real life, and while not immediately dangerous, can still lead to death if not recognized and remedied. When the International Space Station started losing pressure in August 2018 recently due to a small hole, the crew didn’t feel the pressure change. Instruments detected a loss in pressure and alerted the crew. This is important, because if pressure is reduced very gradually, your body will adjust quickly enough so that you wouldn’t notice pressure reaching dangerous levels until you are ready to pass out. What it won’t do is get sucked out into space through a tiny hole like in the clip from Alien Resurrection above.
Rapid Decompression
Rapid Decompression is described as occurring quickly enough to be noticeable, but slowly enough that physical lung damage is not likely to occur. In an airplane this means the flight crew only has a few seconds to get oxygen masks on before they lose consciousness, at which point they would reduce altitude enough to raise cabin pressure sufficiently and make an emergency landing. In a spacecraft, if you didn’t already have a pressure suit on, you likely wouldn’t have enough time to get one on before you passed out and died from hypoxia and other trauma from a total loss of pressure (more on that later). A rapid decompression event occurred in April 2018 on Southwest Flight 1380 when the left engine failed catastrophically, ejecting engine parts in all directions, including into a main cabin window. While the crew reacted promptly and safely, one passenger died when they were partially sucked out of the plane before eventually being pulled back in.
Explosive Decompression
This is the event that most people associate with the decompression of a spacecraft or airplane, and while it is the most dangerous and absolutely can and has happened, it is not how most uncontrolled decompression events occur. This is particularly common in the movies when any sized hole seemingly causes all the air in the cabin to escape instantaneously, or keeps escaping endlessly at full pressure, as is there is some invisible source of air being resupplied into the cabin to make the situation as dire as humanly possible (more thoughts on this later). The defining factor that separates a rapid decompression from an explosive decompression is the rate, the latter of which is fast enough that you cannot exhale air out of your lungs fast enough to compensate, risking damage to organs including burst lungs. There has even been a recent example of explosive decompression in the news, when Sichuan Airlines Flight 8633 lost its windshield at 30,000 feet (9,000 m), resulting in an emergency landing and injuries to the first officer who was blown partially out of the aircraft, though no casualties were reported.
The Mythbusters test what would happen during an explosive decompression in a modern airliner at 35,000 feet.
Effects of a Decompression Event on the Body
Now that we have established the basics of what an uncontrolled decompression is, we need to look into what can happen during one, so we have a baseline to compare against when looking at the examples below. The two major concerns with an uncontrolled decompression are the physical effects to your body and the structural concerns with the air or spacecraft you are in. To put the latter out of the way quickly, unless we are dealing with severe structural damage outside of just the hole itself, even an explosive decompression wouldn’t rip the craft apart. As has been evidenced in the real-world examples above, holes of many sizes have occurred in both airplanes and spacecraft, and the structural integrity remained. Granted, the pressure change at cruising altitude isn’t as severe as in a true vacuum, but pressure at 30,000 to 40,000 feet (9,000 - 12,000 m) is still 70-80% of the way to a vacuum, meaning the structural effects of a sudden pressure drop are substantially similar at 40,000 feet to the same event at the International Space Station.
A chart of pressure versus altitude. Beyond around 18 km up, pressure reaches the Armstrong Limit, so low water at body temperature begins to boil. (Original image by Cmglee. Created under Creative Commons license. Image colors adjusted for site formatting.)
As for the effects on the human body, they are wide ranging depending on the rate and magnitude, but they all happen to some degree or another during an uncontrolled decompression. The most dangerous is hypoxia, or a deprivation of oxygen to the bloodstream. Causes of hypoxia are numerous, but in a decompression event, the lower pressure results in less oxygen available in the same volume of air and less oxygen getting to your blood. This happens very quickly in a rapid or explosive decompression, but also happens in a gradual decompression over time, and can occur so slowly that crew might not notice until they are about to pass out. Hypoxia can be treated if a fresh supply of oxygen is given, but if the whole crew is passed out from the same event, there is no one left to help and suffocation would result.
The other major danger during an uncontrolled decompression is barotrauma, or damage to the body due to a change in pressure. The organs that interface with the atmosphere are the most at risk, including lungs, skin, and eardrums. We have all experienced our ears popping from a small change in pressure before, so we know eardrums are particularly sensitive. A rapid decompression can rupture eardrums, resulting in severe pain and temporary loss of hearing. Blood vessels in the skin can burst, and if the event is severe enough, severe lung damage can occur as well. Probably the worst symptoms come from Altitude Decompression Sickness (DCS), or a build-up of nitrogen bubbles in your body. The most well-known of these is the bends, or buildup of nitrogen bubbles in the joints, but air bubbles can build up in many places in the body, including the brain, spinal column, and lungs. While most symptoms are just pain, more severe symptoms include difficulty breathing, memory loss, and seizures.
For brevity I won’t go into the other symptoms of decompression since they are mostly long-term effects or indirectly related, but additional possible injury can occur from frostbite and hypothermia due to exposure to cold temperatures, as well as physical trauma from projectiles loosed during explosive decompression events. Unless specifically referenced, these aren’t going to be easily analyzed, and in the case of exposure-related injury, are generally long-term effects that aren’t covered in the source material.
Comparing to Deep-Sea Diving
Before We get to the examples, I wanted to briefly compare what we are talking about to something people might be more familiar with, or at least something that is similar to a decompression event in space, though with important differences. Most of the symptoms we have been talking about can also be found in deep-sea divers who don’t adequately decompress on the way back up, so you might want to use that as a direct comparison, but it isn’t exactly the same. For one, divers actually experience a greater pressure change than does someone blown out into space. Pressure increases by one atmosphere, or the difference between sea level and complete vacuum, every 33 feet (10 m) you go underwater. Divers who dive to 100 feet (30 m) and come back up experience 3 times the pressure change than someone who goes from the inside of a spacecraft to complete vacuum. In terms of the potential effects due to the change in pressure alone, divers are at higher risk of injury than an astronaut. The real issue comes in the time following the decompression. While a diver with the bends is still able so sit and breathe at a normal atmospheric pressure, an astronaut in deep space doesn’t have that luxury. Even if they survive the initial decompression, there is no comfy atmosphere to breathe in, and they quickly succumb to the elements, or lack thereof.
Surviving at Low Pressure
While we usually talk about the actual decompression event as the cause of injury or death, it isn’t the worst part, particularly out in space, where the real problem comes from trying to survive in a decompressed environment. Without a pressurized space suit, no amount of luck is going to save you if there is no air in the ship. For one thing, even trying to breathe with an oxygen mask won’t work without pressure to supply it. And if the event was severe enough to cause lung damage, it may be more difficult to breathe at all. The bottom line is if you aren’t in a pressurized suit before your ship loses pressure, you will very quickly lose consciousness and die unless you are rescued within a minute, maybe a few minutes if you can get pressurized oxygen.
The other really interesting thing that happens at very low pressure is that the pressure drops enough that water starts to boil at normal atmospheric temperatures. We all know that water boils at 212°F (100°C) at sea level, but without all that atmosphere creating a bubble of pressurized gas around you, water will boil at a normal body temperature of 98°F (37°C). The altitude at which this happens on Earth is known as the Armstrong Limit, and occurs at around 60,000 feet (18 km) above sea level. Beyond this point, which space is certainly well beyond, any exposed fluids in your body quickly boil off, including saliva and the wetting fluids in your lungs that help with oxygen transfer. Without an oxygen supply you have maybe a minute to live, and with it maybe a couple more. That is, of course, assuming there is someone there to help you, since you will have likely passed out in the first few seconds.
A decompression test for aspiring U-2 pilots. Notice that once pressure inside the chamber gets low enough, water begins to boil, indicating that he has reached the Armstrong limit. At about 3:30 a explosive decompression test is performed, causing the pressure suit to inflate rapidly and the humidity in the room to condense into a fog.
The Force of Decompression
The other huge factor that we haven’t discussed yet is the actual force of the decompression itself. We know from actual events that punching a hole in the side of an aircraft can and has sucked people and objects out. While the one fatality on Southwest Flight 1380 did get pulled back into the plane, there have been other accidents where people did get sucked out of an airplane entirely. So we know it can happen, but what is the force a person might expect to experience during an uncontrolled decompression? Normal atmospheric pressure is 14.7 psi (101 kPa), or literally 14.7 pounds for every square inch of spacecraft skin. The pressure pushing back is a vacuum, so 0 psi. To figure out how much force there would be, you only need to know the size of the hole in square inches and multiply that by 14.7.
This is of course making a few assumptions. First, the force calculated is going to be at the hole itself. The further you get from it the larger the affected area is and the lower the force is on the body. If you were to take a cylinder and cut off the entire end, the force felt would be basically identical everywhere, but for most situations, a crew member would feel less force.
Second, the force calculated is only valid for the instant the hole appears. As soon as the air starts leaking out, the pressure goes down and the force does as well. For simplicity, however, we will only talk about the worst case scenario, understanding that after the initial hole is made, the situation improves, at least in terms of the force.
I won’t get too in-depth in this part since we can calculate the force for each example below as we get to them, but just for reference, We can look at a few scenarios and see what kind of force is produced. Knowing one atmosphere is 14.7 psi, I will make the math simple and keep it to full square inches. Just off the top of my head, I have made up the following few scenarios:
HOLE AREA
DIMENSIONS
FORCE
1 inch2
1 x 1 inch
14.7 lbs
9 inches2
3 x 3 inches
132 lbs
36 inches2
6 x 6 inches
529 lbs
144 inches2
12 x 12 inches
2,117 lbs
So from this it is pretty apparent that a small hole isn’t that big a deal from a rip-you-out-of-the-spaceship perspective, but the force rapidly becomes strong enough to pull people, objects, and even Spartans in full Mjolnir straight into space. A 6 x 6 inch hole is more than enough to suck out someone unsecured who happens to be nearby, and just a 1 x 1 foot hole is more than enough to suck someone out and launch them well beyond the range of a ship for the 60 seconds or less they have to live.
Time to Unconsciousness
The other factor we need to consider is how long would someone have before they fall unconscious. In an explosive decompression event, as we said earlier, if you aren’t already in a space suit when it happens, it was nice knowing you. Without supplemental oxygen, you have maybe a minute before the lack of breathable air, coupled with your fluids beginning to boil within your body, take the ultimate toll. But you would fall unconscious far before that, in a matter of seconds at best. Survivability time is more important in the scenarios where you are losing pressure slowly enough that you might have several minutes or hours to react before the pressure drops sufficiently to cause you to lose consciousness. And then perhaps several more before you fully succumb to hypoxia. So determining how fast the air is escaping is quite important.
A chart of atmospheric pressure versus oxygen concentration. As pressure in a sealed compartment like a spacecraft starts dropping (assuming normal starting conditions), pressure falls along the red line. Once it exits the safe zone, people start passing out and, if not assisted promptly, die.
As we discussed above, the largest concern when dealing with an uncontrolled decompression is hypoxia, or loss of sufficient breathable oxygen. While the body can acclimate to lower oxygen environments to a point, that has to be done over the course of days, not minutes. So assuming the leak is fast enough that the body can’t acclimate, the bottom limit for air pressure that someone can stay conscious is around 8.5 psi. That is about 58% of standard pressure at sea level.
Now knowing the pressure we start at (14.7 psi) and the pressure a person will fall unconscious (8.5 psi), we know pressure has to drop 6.2 psi through a hole. As I mentioned above, flow rate will decrease as pressure drops inside the spacecraft, so figuring out the time isn’t a linear plot. Cheating a bit for brevity, I am using the work done by GeofferyLandis.com to determine the equation for figuring out time to passing out boils down to:
Time = 0.005 x ( Volume / Area ) x Ln( Initial Pressure / Final Pressure )
Since we already know our pressures, the equation gets even simpler:
Time = 0.00274 x ( Volume / Area)
This is the point where we have to make another assumption. How big is our spaceship? We will have to figure this out for each scenario below, but just for an example, lets assume it is the size of a small house in the US or the average size in the UK. That means around 1,000 square feet, or 93 square meters Using an average room height of 8 feet or 2.44 meters. This makes the total volume of air to be 227 cubic meters. Using the same example hole sizes from above and the calculation we just determined, the times to unconsciousness for each hole size are as follows:
HOLE AREA
DIMENSIONS
TIME
0.00065 m2
1 x 1 inch
16 minutes
0.00581 m2
3 x 3 inches
107 seconds
0.02323 m2
6 x 6 inches
26 seconds
0.09290 m2
12 x 12 inches
6.7 seconds
So just like when determining the force of the air flowing out of the hole, the time to unconsciousness reduces exponentially with hole size. With a small puncture, there is hopefully time to suit up, find the hole, and plug it if you can. Time gets tight quick as the hole gets bigger, though, with only 26 seconds of time with a hole half a foot on each end, and less than 7 seconds if it is a foot on a side. Obviously these times would increase if the area were larger, but since we will have to calculate the times for each scenario below anyway, I am not going to go into more examples here.
Okay, so I think we have covered all the effects and concerns when it comes to uncontrolled decompression. There will likely be more to cover as we explore the examples below, but hopefully you at least have a solid foundation to try and understand what is happening in each one. With all this in mind, lets finally dive into some Halo and see whether decompression is handled well or if it is all just a bunch of fantasy.
“He unbuckled himself and moved to each checking for vitals—finding only Lieutenant Jorgenson still breathing, and quickly tying a tourniquet above her bleeding calf.
He tapped the comm station, cleared his voice, and said, ―”Any medical personnel, any fire teams on decks four, five, or six—report to the bridge.” He looked about once more, taking the carnage in, and then added, ―”Any crewmen who can get up here, do so immediately.”
From the flickering weapons station a shrill alarm sounded, confirming missile lock on the Las Vegas.
Cole yelled into the comm, "All hands brace for impact! All crew brace—"
The bridge shuddered.
For a split second the air condensed into fog, then explosive decompression blasted out the atmosphere.”
- Halo: Evolutions
The Impossible Life and the Possible Death of Preston J. Cole
Section Four
There isn’t much given here to argue against, so since my policy is to default to the source material unless there is a blatant violation of physics, I am immediately leaning towards this being science. The only information we are given is that while everyone is already dead or incapacitated prior to the bridge experiencing an explosive decompression, Cole is still alive and conscious enough to give out orders. Then a missile strike apparently punches a hole in the UNSC Las Vegas, presumably on or very near the bridge, and all or most of the atmosphere on the bridge is lost violently. Based on the log in the book, the explosive decompression occurs at 0332 hours, and the next scene picks up with Cole, presumably on the bridge still, 16 minutes later at 0348. We don’t have a lot to work with in terms of the events that take place in these 16 minutes, but we are provided with the events on the bridge starting at 0348:
“Captain Lewis and Commander Rinkishale are dead. The rest of the bridge crew are either incapacitated or dead.
I, Second Lieutenant Cole, Preston J. (UNSC Service Number: 00814-13094-BQ), do hereby assume command of the UNSC destroyer Las Vegas and responsibility for the actions detailed henceforth.
Emergency bulkheads are in place on the bridge and the additional breaches on decks one through eight and eleven through fourteen have been contained. Decks sixteen and seventeen remain evacuated and cannot be repaired.”
- Halo: Evolutions
The Impossible Life and the Possible Death of Preston J. Cole
Section Four
From this we can deduce a few things in regards to the events that took place during and immediately after the decompression. The event was obviously very violent and the hole would have had to have been very large to explosively decompress the entire bridge. Cole was unbuckled when the bridge decompressed, so he could have been sucked towards the hole, but we aren’t given enough information as to where he was in relation to it to say for sure. Since we know Cole survived, and potentially others on the bridge as well, the emergency bulkheads would have had to have closed very quickly, and the bridge recompressed to at least a livable pressure within a minute. Recompression means an emergency supply of pressurized air to refill the bridge rapidly, so the ship has some capacity to seal and repressurize compartments in the event of attack or just mechanical failure. This makes sense, since otherwise a ship could rapidly be incapacitated by venting atmosphere with no ability to recover in time.
The one interesting bit of this scene which we didn’t mention yet is the line “For a split second the air condensed into fog…” This is something we can definitely analyze, as it is just about the only direct description of the event. So is this really a thing? As it turns out, yes. For those unaware, cloud or fog formation is dependent on the relative humidity, which is itself dependent on the temperature and pressure of the air. If you have ever noticed it getting foggy outside when the weather rapidly changes from warm and humid to much cooler, that is because while the total amount of moisture in the air remains mostly constant, the ability for the air to hold that moisture drops as temperature drops. Once the temperature lowers enough to reach the dew point, water vapor will begin to condense in the air, forming dew and/or fog.
In the case of a explosive decompression, the same effect is happening, but it is the pressure that is causing the atmosphere to reach the dew point. Pressure and temperature are directly related, so in a fixed volume like the bridge of the UNSC Las Vegas, lowering pressure means lowering temperature. If you have ever used a can of compressed air before and noticed how the can gets cold as you release air from the nozzle, this is exactly what is happening, but at a larger scale. So in the case of explosive decompression, the air would basically get to the dew point instantaneously, and the humidity would condense into a fog for a brief moment before getting ejected from the ship entirely. It appears that in this first example, as far as we know given the little bits of information we have, this is science.
The great thing about analyzing video clips is that there is a lot of information that has to be given, just because of the nature of the medium. This can also be to the detriment of the storyteller too, though, since the general flow of the scene is what they are focused on, but picky fans like me come by and break down every frame to find faults. That being said, I still plan on dissecting this scene for all its worth, but I will start out by saying sorry for ruining anyone’s suspension of disbelief.
The two parts of this I plan on looking at are the initial impact of Blue Team through the pane of glass and the physics behind the elites getting sucked out of the hole. I wanted to see whether the very act of four people, clad in MJOLNIR or not, could reasonably plow through a wall of air like that, but decided against it since there are just too many variables at play, many of which we would have to guess at. I’ll just say that I am somewhat skeptical of the ease in which they seemed to fly through the glass and outflow of air from the hole, but considering they are half a ton of person and armor in a pressurized suit with some sort of computer-aided system to control their exact flight path and help maintain balance and trajectory while firing projectile weapons in a vacuum, unsupported, I’m willing to accept it.
The next part will be fun (at least for me), and while we are going to have to make a couple assumptions, I think we can calculate a pretty decent approximation of what kind of force would be pulling the elites through the hole. To determine my rough numbers for size of the hole and size of the room, I will be using two frame from the above scene, shown here:
Blue Team enter the Argent Moon in style during Operation: BIRD IN HAND, October 23, 2558.
Sangheili members of Jul ‘Mdama’s Covenant are taken by surprise at the onset of Operation: BIRD IN HAND, October 23, 2558.
Using the upper frame for reference and assuming a height of around 7 feet for a Spartan (John is 7’2” in armor), I am going to guess the window is maybe 30 feet across and a little less than that tall. Since it isn’t a perfect rectangle either, I will shave a little off the height and assume a rectangle for simplicity of calculating, so lets say 28 feet tall. That means the hole, which opens up pretty much instantaneously, is 840 square feet, or 120,960 square inches. Using the math from earlier (14.7 psi x hole size in square inches), we get the following:
HOLE AREA
DIMENSIONS
FORCE
120,960 inches2
28 x 30 feet
1,778,112 lbs
That is an incredible amount of force from just airflow, but we also need to consider a coupe more things. First, the room the Elites are in is much larger than the hole, so the force felt will be spread over a larger area. The first two would likely get the full brunt of it, but those further back are going to feel less pressure pushing them out. Getting more rough numbers for the size of the room based on the second image (and I know the room is more complex in the game), I am going to assume it is about 3 windows-width across and maybe 35 feet tall, so around 90 x 35 feet in total. This calculates out to be around 3,150 square feet or 453,600 square inches. with the hole dimensions assumed to be 120,960, the force felt by the Elites would be 453,600 / 120,960 times less, or 3.75 times less. Keeping the force of 1,778,112 pounds constant, the new pressure drop for the entire room is as follows:
ROOM AREA
DIMENSIONS
PRESSURE
453,600 inches2
35 x 90 feet
3.92 psi
We now have a somewhat meaningless number for pressure though, because we know the room pressure is still 14.7 psi. What this means, though, is that we have a new pressure drop to use to calculate for the force on an Elite. It should also be considered that until now, the holes we looked at were all smaller than a person, so translating that force to what is felt by the person was assumed to be one to one. When dealing with a hole much larger than the subject, the actual dimensions of the subject need to be considered. What I mean is, the actual force felt by an individual is proportional to their surface area perpendicular to the airflow. If you were to imagine the same scene but the Elites were all holding large sails, the force pulling them out would be greater. In other words, the only thing feeling the entire 1.8 million pounds of force is a flat sheet the exact dimensions of the room. An Elite takes up much less area, so we need to estimate their surface area in order to figure out how hard the air is pushing them out the window.
This is going to require a bit of estimating, since each Elite is a different size and I don’t want to do complex calculations of the surface area of an armored Sangheili. Instead, I will assume an Elite is a series of five rectangles, two for arms, two for legs, and one torso/head. The average Elite is about 8 feet tall and maybe half that wide. Based on that, I get the following rough dimensions:
BODY PART
DIMENSIONS
AREA
Torso/Head
48 x 30 in
1,440 in2 (0.929 m2)
Arm (x2)
48 x 6 in
576 in2 (0.372 m2)
Leg (x2)
48 x 9 in
864 in2 (0.557 m2)
TOTAL
2,880 in2 (1.86 m2)
Now that we have an estimate for the dimensions of an Elite, we can calculate the force on their body. There are a couple ways to do this from here, but since we know the area of the room they are in and the force felt for the entire room, I will determine the area difference between the two and divide the force of the room by the difference in size. The room is 453,600 square inches, and the Elite is 2,880 square inches, so the difference in the two areas is 157.5 times. Taking the force in the room and dividing it by this scaling, we get the following:
ELITE SIZE
TOTAL FORCE
FORCE ON ELITE
2,880 inches2
1,778,112 lbs
11,289 lbs*
So is that enough force to suck an elite out of the hole? Definitely. An Elite weighs around 300-400 pounds, so this is significantly more than enough to vacate the entire room of every hostile. Even assuming I was off by an order of magnitude and the force felt is only 1,100 pounds, it is still easily strong enough to suck out an Elite. Given that the force would diminish a bit over time as pressure dropped, I think there is comfortably enough margin here to call this science.
*NOTE: I later reanalyzed this problem slightly differently because I was unsure of the method I used. Instead of using the pressure directly to calculate force, I used wind speed to determine the force. Using this calculator, I conservatively estimated the wind speed to be 300 m/s (decompression happens a little slower than the speed of sound of 344 m/s, see paragraph below), and the air pressure to be a little lower than normal atmospheric at 1.0 kg/m³. By using these numbers and the area we calculated above of 2,880 in² (1.86 m²), we get a little over 5,000 pounds of force after correcting for the change in area between the hole and room. This is less than half of what we calculated using the pressure method, but is still several times the weight of an Elite. Based on this, I am sufficiently convinced that our numbers are at least reasonable and that the conclusion that this portion is science is justified, even assuming the lower number of 5,000 pounds of force.
There is one last thing I wanted to consider here before we moved on though. One thing that always bothered me was that it seems like there is a delay between when the window breaks and when the Elites start feeling the force. Because we are literally talking about the motion of a pressure wave as the atmosphere decompresses, it will behave just like sound, which as a pressure wave itself, does. This means that the propagation of the force we calculated above will move at the speed of sound, or 761 mph (344 m/s). Given the speed of sound goes down as pressure lowers and we are talking about a complex change in pressure, the actual average speed will be slightly lower, but for simplicity’s sake I will assume the speed of sound at sea level.
From rewatching the scene, it takes around 5 seconds for the furthest Elite to feel the full effects of the decompression, and the 6 seconds for those closer to the window. Yes, they are running, but remember we are talking between 5,000 and 11,000 pounds of force. Even assuming 5 seconds, it takes way too long for the Elites to get sucked out. Based on the speed of sound, the Elites closest to the window, who were maybe 3 meters away, would have started getting sucked out in less than 0.01 seconds. The one furthest, who is perhaps 15 meters back from the window, would have started getting sucked out in less than 0.05 seconds. I know it is artistic license and all, and I am not faulting 343 for using it to build their scene, but I am pointing out it isn’t strictly following physics. The glass, for example, gets broken and manages to get launched all the way to the floor before finally turning around and getting flung back into space. In reality it would only make it a few inches at most before getting sucked back out, and then only the glass directly impacted by Blue Team. Again, I am not judging the artist’s creative license, but I personally prefer when they try to stick as close as possible to physics, even for minor stuff like this. Based on the Elites getting sucked out being science, but the actual speed and behavior of things getting sucked out being fiction, I am going to have to give this scene as a whole a partly science.
“Sir, request permission to leave the station.”
“For what purpose, Master Chief?”
“To give the Covenant Back their bomb.”“…Permission granted.”
- Halo 2
Cairo Station end-mission cutscene
This is an example I nearly skipped because on initial analysis I didn’t think it added anything substantial to the discussion, but I reconsidered because it is one of the most iconic scenes in Halo and its exclusion would be heresy. In many ways this is similar to the previous example of Operation: BIRD IN HAND, both in type of decompression and size. It primarily differs in that it only really provides one or two things we can analyze, whereas the previous example had much more happening, at least in terms of the decompression itself. The two things we really need to look at here are the size of the hole and the mass of the objects being propelled. So long as the hole is sufficiently large and the mass is low enough that the decompression will be able to force the bomb along with Master Chief out of Cairo Station, this one will be science.
First, the hole. We already showed how the force, while dependent on the hole size, really becomes dependent on object size once the hole gets big enough. In this case I think it is pretty apparent that the hole is significantly larger than either Master Chief or the Covenant bomb, so this analysis is going to come down to whether the force from the decompression is larger than the weight of the bomb and Master Chief put together. Without going too deep into analyzing the total surface area of Chief facing the hole, I’m just going to use the numbers we got above from the Elite and back it off a little since Chief is shorter, but also a bit less aerodynamic, if not actually wider. The Elite was 2,880 in² (1,86 m²), so estimating his size using the same method from above, we get the following:
BODY PART
DIMENSIONS
AREA
Head
9 x 9 inches
81 in2 (0.052 m2)
Torso
36 x 24 inches
864 in2 (0.557 m2)
Arm (x2)
36 x 6 inches
432 in2 (0.279 m2)
Leg (x2)
36 x 9 inches
648 in2 (0.418 m2)
TOTAL
2,025 in2 (1.3 m2)
As for the bomb, it is really hard to say since it is mostly round, not flat, but has those weird spikes on all sides. While it is definitely larger than Chief, it is probably more aerodynamic overall, so I will assume its about the same, 2,025 in² (1.3 m²). Remember, we are just approximating to see if the numbers could work, so as long as we aren’t off by an order of magnitude in either direction (0.13 m² or 13 m²), we should be close enough to perform an educated analysis.
The second part needed for this is the mass of the bomb and John. We know from the lore that Chief is about half a ton in armor (995 lbs), so I will just assume an even 1,000 lbs. As for the bomb, we really don’t know for sure how much it weighs, but based on how difficult it is for John to pull it, and knowing he can bench press upwards of a ton or possibly much more, it is safe to assume the bomb weighs much more than John does. It should also be noted that in this cutscene, Chief grabs onto the bomb as it is sliding out of the bay and it seemingly has almost no reaction to the added weight. So this also supports the idea that the bomb is much heavier than Chief. How heavy is hard to say, but assuming it is ten times the weight of Chief, or 10,000 pounds, seems like a reasonable assumption. So together, Chief and the bomb weigh perhaps 11,000 pounds. Since John only grabs on at the last second after the bomb is already on its way out the door, combining the masses from the start should give us a conservative estimate for whether the decompression could suck out the bomb.
Using the same method from the previous example for determining force on the bomb, we are going to assume the force applied to the bomb is just the pressure drop (14.7 psi) multiplied by the surface area of the bomb perpendicular to the airflow. Using the assumed 2,025 in² surface area and the pressure drop, the maximum force on the bomb would be 29,767 pounds. This would only be valid when the door is full open, but even so it seems high. When the door starts to open, it would be a percentage of that value based on the room to hols size ratio. At 20% open, that would be more like 6,000 pounds.
The Cairo Station bay doors, in the process of opening, at approximately 20% open.
Using the wind velocity method I later used for example two, assuming the same basic parameters (300 m/s wind velocity, 1.0 kg/m³), and using 1.3 m² as the surface area, we instead get a maximum force of 13,151 pounds with the door full open. As this is the more conservative of the two methods, I will use this instead to ensure we aren’t being too generous to the fiction.
METHOD
RESULT
Pressure Drop
29,767 lbs
Wind Velocity
13,151 lbs
Assuming the maximum force on the bomb is 13,151 pounds, and the weight of the bomb along with Chief is 11,000 pounds, it seems like this scene is feasible. Even if the door was in the ceiling, the force is enough to suck the bomb straight up. The one thing I didn’t consider last time, however, is the actual friction force between the object and the bulkhead. Depending on what the coefficient of friction is, the force that friction is pulling back against the decompression force could be much less or much greater. We don’t know exactly what the bulkhead or the bomb are made out of though, so we will have to make an educated guess. It is safe to assume that both are some type of metal, so looking at a table of friction forces, the value could be anywhere from 0.5 to 1.0. To stay conservative and make our numbers easy, I’ll assume 1.0, meaning if the bomb weighs 11,000 pounds, the friction force is 11,000 pounds. If the coefficient of friction were lower, the frictional force would be lower as well.
So even considering the actual friction force, and using the lower value for the force due to the decompression, the bomb and chief would get sucked out of Cairo Station in some manner. It is hard to say with certainty that what is shown in the cutscene in terms of the motion of the bomb is totally accurate, but I am comfortable enough with what we have looked at to call this portion science.
Master Chief and the Covenant bomb getting sucked out of Cairo Station after a manually-initiated explosive decompression.
The only issue I still have with this scene is the fact that the room appears to be an enclosed space and the bomb takes a few seconds to get fully sucked out. If the room were sealed, the entire air volume would be sucked out in a fraction of a second. Based on what is shown, that chamber must not be airtight, and with sufficient additional air volume elsewhere that the decompression lasts several seconds. In addition, there has to be enough capacity to supply that air from wherever else it is to that room. Based on what we can see, which covers just about the entire room, I find it very questionable whether this is a feasible scenario. Without hard data, and defaulting to the fiction whenever possible, however, I have to conclude that it at least isn’t impossible. Because of this, I have to give this portion a rating of partly science.
“Canfield’s helmet twisted and Keyes heard the crackle of his radio in his earpiece. “Okay, Helljumpers, move out, Oedant—”
Keyes didn’t hear the rest of Canfield’s orders. The container they stood next to exploded, throwing Keyes clear and smacking his head against the deck.
The scene of Helljumpers scrambling for cover faded away as a thick cloud of smoke and unconsciousness rolled over Keyes...
Four more explosions rocked the inside of the cargo bay. Debris flew through the air and clattered off the walls, then rained down to the floor. A thick haze of smoke filled the air, making it nearly impossible to breathe. Keyes lay on his side, blinking away the blood trickling down his forehead into his eyes…
The loud roaring in the cargo bay had grown a bit more noticeable. Keyes looked at the soldier checking the wounded over and ignored Faison’s disdain for a more immediate concern. “Son, where are we losing air from?”
“Everywhere. The explosives punched holes all over this little tub,” came a response.”
- Halo: The Cole Protocol
Chapters Four & Five
This is the bit of fiction that kicked off this whole idea. The Halo Conversationalist guys seemed unconvinced, at least Shadow was, that the ship could have survived the blast at all given the holes ripped in the hull and that anyone inside would have been able to survive given the loss of pressure. As we looked at earlier, the force of decompression is directly proportional to the size of the hole or holes. What definitely does NOT happen is the clip I posted in the intro of the Newborn Xenomorph getting sucked out, bit by bit, through a hole about the width of a large finger. The ship also won’t rip itself apart like a balloon because it is a rigid structure, not a flexible one like a blimp. What will happen is the room will depressurize at a rate proportional to the net size of the holes and the size of the room.
Only problem is, we don’t know the size of the room or the size of the holes. Finnegan’s Wake is a cargo ship, and the hold they were in was obviously large enough to land a Pelican and deploy maybe a dozen ODSTs, along with Captain Keyes and also hold four crew of the Finnegan’s Wake. So we are looking at nearly twenty people, plus a Pelican, plus an unknown number of cargo containers. It is really hard to say with any certainty how large the airspace in this room was, but it wouldn’t be outside of the canon to say it was fairly large. Its of course filled with things other than air, so those will take up some space, but even so there would probably be a decent about of air within the hold.
We don’t know the size of the leak either, but from the exchange between Keyes and the injured ODST it sounds like it is fairly large. Following the explosion, Keyes almost immediately redirects the ODSTs to verify who sent out the emergency beacon. After confirming with every living ODST and verifying via helmet-cam footage that one of the dead ones sent it, we get this line:
“Keyes took a deep breath and another wave of dizziness hit him. They were losing too much air from the cargo bay.”
- Halo: The Cole Protocol
Chapter Five
So in what is, a little more than three minutes or so (based on estimated timing from the start of Chapter Five to the above quote), the air pressure drops enough to start feeling its effects. On Earth, we would call this altitude sickness, or symptoms from the loss of air pressure and oxygen. Based on the sources I read, that starts around 8,000 feet, so assuming the air pressure in the cabin has dropped to a level equivalent to that, pressure would be around 10.9 psi. We still don’t have a good number for size of the hole or the size of the room, but we do have a ballpark number for the rate of pressure loss. Since we already know the rate, we can use the equation from earlier for decompression time.
Time = 0.005 x ( Volume / Area ) x Ln( Initial Pressure / Final Pressure )
Initial Pressure = 14.7 psi
Final Pressure = 10.9 psi
Time = 200 seconds
Knowing all this, we can simplify the equation to the following:
Volume / Area = 133,741
or Volume = 133,741 x Area
This means we at least have a relationship between volume and area, so if we assume one we can calculate the other. This is all predicated on the initial assumption of 200 seconds for time, so if you change that number, the relationship changes. But for now, I am going to move ahead with that assumption since I think it is a fairly reasonable one.
So knowing the ratio of volume to area, we can now establish some reasonable ranges for the hole size and the room volume. The comment from the ODST states that they are losing air from “everywhere” and “The explosives punched holes all over…”. So knowing that, but not knowing the size of each hole, it isn’t going to be easy to pin down a total area, but it is safe to assume the total area of all the holes put together is not insignificant. Let’s start by assuming the holes that managed to punch through the hull were a between and equivalent 6 x 6 inch to 12 x 12 inch hole. Could be larger, but lets see how large of a room we would need assuming a total hole area of 0.02323 and 0.09290 square meters.
HOLE SIZE
AIR VOLUME
ROOM AREA (8FT HIGH)
0.02323 m2
3,107 m3
1,323 m2
0.09290 m2
12,425 m3
5,095 m2
So even with a 6 x 6 inch hole, you would need a pretty large room to support the information we are given. I could probably mess around with the numbers a little to make the room smaller and still fit within canon, such as shortening the time between explosion and Keyes noticing getting dizzy, lowering the pressure before Keyes notices, or just make the hole smaller, but lets just stick with what we have now, and say the cargo hold is the equivalent of a 1,500 square meter room with 8 foot (2.44 m) high ceilings. For Americans, that is a 16,000 square foot room. It seems massive when compared to the average house, but what about something more relatable to a freighter, say a modern container ship. As of this writing, the largest container ship is the MSC Gülsün at 400 meters long and 62 meters long. If you were to make a cargo hold that size, it would be 24,800 square meters. Making that into a room that was only an average ceiling height (2.44 m), the room would be 60,400 cubic meters. Based on the table above, that is significantly larger than the required size for a 12 x 12 inch hole, so assuming the ship is the size of a container ship, I think there is plenty of margin to consider this completely feasible.
Of course one of the biggest unknowns in this entire example is just how big is this ship. In my research I didn’t find anything that gave us an idea of how large Finnegan’s Wake was, or when it was built, so I am basing my analysis on a decent amount of guessing based on the small amount of data available. While a spacecraft the size of a container ship would be impossible today, in the Halo universe it seems completely within reason. Consider that the UNSC In Amber Clad was 478 meters long and 152 wide, and is one of the smallest, if not the smallest, UNSC warships ever built in the 26th century. Also, the UNSC Spirit of Fire, built in 2473, over sixty years before the Finnegan’s Wake Incident, was 2,500 meters long and 800 meters wide. So imagining that Finnegan’s Wake was large enough to support the events described above is well within the available data, and base on that I am considering that portion of the event science.
NOTE: There is an additional part of this scene regarding their escape from the ship that I really want to look into the feasibility of, but because it isn’t decompression related, I am going to leave it for another article. To be honest, I am skeptical of the realities of the escape as it is presented, but for now I will leave it to the mysteries of science fiction and save the truth for another fiction science.
“Right then, Veronica opened fire on the observation deck’s windows. She brought the Condor low and gimbaled the gun up at a high angle, shooting at the panes opposite the captured people inside the complex. She wasn’t going to hit any humans that way—nor any of the Forerunner soldiers, but that wasn’t part of the plan anyhow.
The moment her first blasts shattered a window, explosive decompression blew every one of the Forerunner soldiers right outside onto the moon’s airless surface. A few tried to latch onto something anchored inside, but they couldn’t manage to hold on. One by one, they went flying out through the giant hole in the dome, and they probably shot straight into space.
Man, I hoped so.
Despite my warning, a few of the people in the room started skidding backward toward the gap as well. The roaring wind was strong enough to lift them off their feet and haul them toward the chilly terror of the lunar terrain.”
- Halo: Bad Blood
Chapter Seven
This one is fairly straight-forward. There isn’t a lot of information given, and the information that we are provided is through the voice of Edward Buck, who is definitely an unreliable narrator, providing a lot of leeway with the information presented. Similar to Blue Team during Operation: BIRD IN HAND, Dare fired the Condor’s main gun at a large window of the Daedalus complex, blowing a huge hole in the station, and sucking out all the Forerunner Soldiers. As we already looked at, this kind of event is definitely plausible based on the size of the hole Blue Team made on the Argent Moon, so since we don’t have much of anything to go on for this event, I will have to assume it is science. As for the details of the event, that the Soldiers got sucked out but Buck and the rest of the group didn’t, I again am going to assume it plausible since we have basically no information regarding they layout of the room, the size, or the location of the people in the room. The only information we really have is that the Soldiers are close to the window, while Buck and the group were further away.
The only bit I am slightly hung up on is the comment “…and they probably shot straight into space.” My assumption from this is that Buck thought the Soldiers would literally leave the moon based on the force of the decompression, which is definitely not true. Like I mentioned in example two, the decompression is a pressure wave, which moves at the speed of sound through that medium. In this case, that would be an initial velocity of the speed of sound at sea level, or 761 mph (340 m/s). Since the escape velocity (the speed required to completely escape the gravity of a large object) of the Moon is 2,380 m/s, the Soldiers would be travelling far less than the required speed. They may have been launched a good distance from the station depending on the specifics of the event, but they should have remained somewhere on the moon’s surface, potentially unharmed. However, as I said at the start of this example, Buck is an unreliable narrator, and that comment is his thoughts on the events, not the actual events that transpired. So based on this, I will mostly ignore this part since it doesn’t actually describe what happened and declare the event, as presented, science.
“The viewport looked out from the rec room into the airless space through which the space station swung on its orbit around its dark dwarf planet. When it gave way, the room decompressed violently. Anyone and anything in the room at the time got sucked straight out into the raw vacuum, which tugged at every exposed part of the station.
The air in the hallway became a howling wind, pulling us toward the rec room as if a giant were sucking us through a straw...
Just in time, the emergency shutter slammed closed, sealing us off from the damaged room. That didn’t stop my momentum, though, and I smacked into it hard.”
- Halo: New Blood
Chapter Fifteen
“They weren’t even halfway down the corridor when Tom felt the telltale pop in his ears that signified massive explosive decompression from somewhere in the station. The air began to haul Tom and Lucy forward, hard. She managed to snag a grip on a door handle as she went past it, but Tom couldn’t find purchase...
Tom found a foothold on a nearby doorway, which relieved much of the strain. An instant later, the door at the end of the hallway slammed shut, sealing it off from whatever catastrophe had suddenly decompressed the station.”
- Halo: Fractures
Lessons Learned
The last example I am going to look at for this analysis is really interesting because it is the only decompression event in which we see it from two separate points of view from two different books completely. Granted, they were both written by Matt Forbeck, so one can hope that a consistency would exist between the two, but whenever you cover the same event from two separate viewpoints, there is the risk that contradictions will arise and the entire thing will be given the ‘fiction’ label.
The first description of this event from Edward Buck in New Blood gives the most detailed information, but, honestly, there still isn’t a whole lot to analyze. We know there was an explosion, a window of some significant size was destroyed, and the station decompressed violently, sending people and objects flying, including two people straight out of the station entirely. Based on what we already know now, this is a totally plausible scenario depending on the specifics of the station design, and since we don’t have those specifics, This seems completely reasonable and therefore science.
In the short story Lessons Learned from Halo: Fractures, the same event is described from the viewpoint of Spartans Tom-B292 and Lucy-B091. In this scene, the same thing happens to them, albeit from further away than Buck was. They also got thrown by the force of the decompression, and were forced to hold on until emergency bulkheads sealed the station off. We aren’t given any more details regarding the event specifics, so again, this portion of the scene is still science.
There is a bit more to this event, though. Continuing on directly from the New Blood quote above, Buck continues:
“If I hadn’t been a Spartan, the impact might have splattered me as if I’d leaped off a skyscraper. It still hurt like hell, but my reinforced bones kept me from becoming a pancake.
And then Captain O’Day—who must have torn free from whatever she’d been caught on—landed on me. I saw her coming at me, and I did my best to cushion her. Because she’d passed out, though, she had no means of helping herself. Little did I realize that she landed at a terrible angle, and died instantly.”
- Halo: New Blood
Chapter Fifteen
So is it possible the force was great enough to kill someone. That is really hard to say without getting more specifics, but it is certainly possible. Captain O’Day would have been propelled by a force potentially over 6,500 lbs (29,000 Newtons) using the wind speed method, and assuming she weighed 150 lbs (68 kg), the equation to determine her acceleration would be:
Force = Mass x Acceleration
29,000 = 68 x Acceleration
Acceleration = 29,000 / 68
Acceleration = 426 m/s² (43.5 times gravity)
This is an incredible amount of acceleration, and while it is a worst-case scenario, it isn’t out of the realm of possibilities that the acceleration would still be very high under ideal circumstances. The highest g-forces a person has ever survived in a lab setting is 46.2 Gs, and while that is likely not the absolute limit for an instantaneous acceleration, it would be deadly long-term. O’Day could easily have been moving quite fast when she impacted Buck, and death seems like it isn’t unreasonable given the right circumstances. I am going to give this portion of the event a rating of science as well.
There is one last part of this scene that needs to be addressed. In the aftermath of the decompression, Musa and Buck discuss what transpired between Jun-A266 and the terrorist Rudolf Schein.
“The explosion—along with the lack of gravitation reinforcement—compromised the viewport in the rec room. While he was struggling with the terrorist, they smacked into it, and it gave way. I managed to find a handhold and pull myself to safety, but Jun and our traitor were pulled out into space. Jun is currently in our infirmary, recovering from his exposure to raw vacuum…”
“But even people like that are only good for a few minutes at best,” I said. “How’d we get him back into the station so quick? Wouldn’t the decompression have shot him out into space?”
Musa nodded. “Once Jun was clear of the station and the air escaping from it, he planted his feet on the traitor’s chest and kicked off as hard as he could. That propelled him back toward the station, and we were able to recover him in time. He’ll be on the mend for a while, but he should do so completely.”
- Halo: New Blood
Chapter Fifteen
In addition, the scene is portrayed in real-time in great detail in Lessons Learned:
“Two men struggled with each other out there, exposed to raw space but too intent on murder to worry about it. One of them was a blond-haired Spartan recruit Tom remembered hollering at just a few days ago. Schein, he thought…
Neither was wearing a protective suit.
Jun broke free from Schein’s desperate grip and planted both feet on the recruit’s chest. Then he kicked off as hard as he could, sending Schein somersaulting deeper into the vacuum. The recoil shoved Jun back toward the station…
Lucy smacked a button somewhere behind him, and the air blasted out of the lock. His ears painfully popped, and Tom felt like he was being dragged into a deep, dark ocean determined to freeze-dry him in a flash. His lungs collapsed, and he fought against the urge to try to breathe.
Tom had performed exercises like this before—just like every Spartan had—but always under controlled circumstances. He’d only had to expose himself to raw vacuum for up to ten seconds at a time, and even then he’d hated every instant of it. With his augmented body, Tom could survive in space like this for up to a minute…
As Tom sailed through the station’s shadow and emerged into the light from the distant sun, he knew he’d made a critical mistake. Jun hadn’t been moving as fast as he’d thought.
Without anything to grab onto, Tom immediately overshot Jun’s path. He flailed his arms as he went, hoping to find some purchase on the lost Spartan, but Tom never made contact…
Tom looked off to his left and saw Jun coming his way. He couldn’t tell if the man had spotted him yet, but from the way Jun kept flailing about, he seemed to still be conscious…
But the bald-headed Spartan managed to get his arm tangled in the line. At that point, the man must have finally blacked out, as he stopped struggling entirely.
Tom yanked himself down the tether even faster, hand over hand, praying that he wouldn’t dislodge Jun from his precarious position. When he reached the Spartan, Tom looped his arms around Jun’s waist and held tight…
Just as Tom’s vision had narrowed so far that it felt like he was staring down twinned rifle scopes, he bumped into the side of the station. It almost jarred Jun loose from his grip, but Tom managed to hold on. He shoved the man through the hatch before him, and Lucy guided his unconscious body inside.
Then Tom’s vision went black.”
- Halo: Fractures
Lessons Learned
This part of the entire event is by far the hardest to believe. We’ve looked at several examples, including this same one just two paragraphs ago, where the force of the decompression was enough to launch people with a large enough force to kill them or send them off uncontrollably. And yet, while Captain O’Day was killed due to the high speed she flew into Buck due to the decompression, Jun manages to push off Schein’s body and get back to the station, or at least close enough to be recovered in time. There is just no way Jun could have pushed Schein with enough force to launch him in any meaningful way back to the station, Spartan or not. Assuming Jun managed that in the first few seconds before he lost consciousness, he would have had to slow himself down from incredible speeds. That would have to be one hell of a push too. Like we saw in the portion above regarding Captain O’Day, the force from the decompression is enough to propel a person from full stop to deadly speeds in a matter of less than a second. Even assuming Jun was at a standstill when the glass broke, he would have been launched out the window with a mass of air pushing him very far from the station very quickly. Any actions Jun could have taken would basically be useless considering the very short time he had to react before losing consciousness.
But how fast was he going? Without knowing the dimensions of the broken glass it is hard to say for sure, but when I picture it I imagine a window similar in size to the one Blue Team broke in Operation: BIRD IN HAND (example 2). Assuming this size of 30 x 28 feet, or 120,960 square inches (78 m²), and the entire window failing at the same time, the total force of the decompression would be 1,778,112 pounds (7,909,436 N). Assuming unarmored Jun is a bit smaller from a surface area than Master Chief calculated in example 3, and that him and Schein are sufficiently intertwined that the force felt is basically the same as it would be by one person, I’ll assume a total surface area of 1 m², or 1/78th the size of the window, meaning the force felt by Jun and Schein together is 22,800 pounds (101,419 N).
As we found before, however, I am unsure how accurate this method is, so I will use the more conservative wind velocity method. Using that, and assuming the same values from earlier, I get a force of 45,000 N (10,000 pounds). Because that number is more conservative, I am going to go with that.
So now to figure out the acceleration on Jun-Schein like we did for Captain O’day. We only looked at whether O’day’s death was feasible before, but now that we want to get an actual number for Jun’s velocity, we need to estimate the actual acceleration. Using the same equations, we find the following:
Force = Mass x Acceleration
45,000 = 222 kg (Jun x2) x Acceleration
Acceleration = 45,000 / 222
Acceleration = 203 m/s² (20.7 times gravity)
That’s pretty intense. But to know velocity, we have to know the time Jun-Schein felt that acceleration. To know this we would need to know the total air released in the ship prior to the airlocks engaging, which we just don’t know at all. It was a short period for sure, so to be conservative, I will assume 0.25 seconds, which seems reasonably low enough given the event as described seems to take several seconds. So this means the equation for velocity is:
Velocity = Acceleration x Time
Velocity = 203 m/s² x 0.25 seconds
Velocity = 50.75 m/s (114 mph, 183 kph)
Yeah, so assuming what I feel are pretty conservative values, Jun and Schein are travelling away from the station at over 100 mph. That is seemingly impossible to counter with a push. But how hard can someone jump (which is basically what Jun is doing)? Using a few different sources including Quora and this paper, the average human jump force is between 1,000 and 2,000 N. Since Jun is a Spartan, I will assume his strength is between 3 and 5 times a normal human without armor. Using 5 times, that means Jun could theoretically jump with a force of 10,000 N. Using the equation for impulse (Force x Time) and assuming Jun’s jump force is applied for a full 0.5 seconds (a normal jump is less than half a second and not a constant force), the total change in velocity of Jun would be calculated using the following:
Impulse = Force x Time = Mass x Velocity
10,000 x 0.5 seconds = 111 kg x Velocity
Velocity = 5,000 Ns / 111 kg
Velocity = 45 m/s
So even in the very best scenario win regards to the decompression force and Jun’s strength, He would still be flying away from the station at 5 m/s. I think I was very generous to the fiction here, and I just can’t make the numbers work out in regards to Jun’ recovery. This is in addition to the entire scene with Tom recovering Jun, which seems to take place over nearly a minute. Forbeck does correctly point out that survival in a vacuum is limited to about a minute, but the amount of time both Jun and Tom spend in total vacuum conscious and actually performing difficult tasks is incredibly hard to imagine. The thing is, the fluids in your body boiling off and the force of air pressure in your internal organs including your brain pushing out will cause immediate disorientation and unconsciousness almost immediately. I was willing to accept this scene when it was just a floating Jun briefly pushing Schein before losing consciousness, but Lessons Learned makes it clear they spend several seconds fighting in space, then Jun pushes off Schein, then he grabs onto Tom’s tether. It is just too big a fiction pill for me to swallow.
For both because of the inability for Jun to actually make it back to the station and the extended scene in space, I have no choice but to give this portion of the example a rating of fiction.
Conclusion
So what is the big takeaway from looking at some examples of decompression in the Halo universe. I think overall it is handled fairly well, at least when compared to a lot of other science fiction (see example from Alien Resurrection at the top). There are definitely discrepancies between science and the fiction, and the two examples I used that were an actual video rather than just text only got a ‘partly science' and ‘mostly science’ rating due to the unrealistic behavior of the Elites getting sucked out of the Argent Moon and questionable amount of air in the room Chief uses to exit Cairo Station, but overall nothing in that I found seemed entirely absurd. Out of the six examples I covered, three were rated ‘science’, one ‘mostly science’, and two ‘partly science’. Frankly, I think that is a decent outcome, and I expected it to be a bit worse once I got into the meat of the fiction.
The other huge conclusion everyone should get from this is that installing large, breakable panes of glass on the outside hull of a space ship, particularly a military vessel, is an incredibly terrible idea. It is apparent that transparent aluminum has not yet been discovered in the Halo universe, and until it is, the UNSC should avoid ship designs that boast their ‘large scenic views’ and instead focus on things like not launching the entire crew into deep space because the captain slipped and hit his head. I never bothered mentioning the likelihood of humans designing such obviously flawed warships when they had no reason to, but doing that would have opened a whole can of worms regarding why Halo ships are the way they are in the first place, so I am just going to leave that be.
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Want to join the Podcast Evolved community? We have a Facebook Group and a Discord Server we use to talk with our members and fans. Podcast Evolved is always open to new members, and welcome every Halo fan to join, whether they are podcast listeners or not. We hope to see you soon!
Pledge Your Support
Podcast Evolved now has a Patreon! We aren't here to make money, just cover some of our operating costs and keep everything clean and ad-free. Whether or not you wish to pledge your support, you are still just as valuable a community member as ever. If you do want to help, however, head over to our Patreon page and become a patron.
Visit Our Store
Want to show your friends and family what your favorite podcast is and support the show as well? Take a stop in our new merch store, where you can pick up Podcast Evolved-themed shirts, hats, coffee mugs, and more! All proceeds go towards helping pay for operating costs, and any additional funds are returned to to community via giveaways and special events.