You’ve seen Ironman’s booster rockets, right? They sit on the bottom of his feet and propel him straight up. In the movie, the writers try to offset the clear scientific issues by giving him stabilizing rocket with his hands, but that doesn’t completely nullify the issues with rocket boots in the first place. We’ve had rocket jumps in a number of video games, mostly third- and first-person shooters. But every single one of these games had similar issues that Tony Stark did in Ironman.
When I wrote the article about DOOM’s weapons, I thought that I had found a game that really considered the physics of the devices that it used in game. We examined the different weapons in DOOM, and for the most part, all the weapons and their general physics seemed plausible. The recoil on most of the weapons worked the way that recoil would work in real life, you know, assuming that we could have a weapon that fired plasma in little balls.
However, that bit of realism falls apart when we examine the rocket boots used for double jump. To find out why, we have to science the shit out of DOOM’s rocket boots.
Besides the obvious rocket, the design should include boots that are made from a non-flammable material. I am going to go ahead and assume that the main character’s suit in DOOM is already made out of flame resistant material. We know that too much heat will obviously damage the suit and kill the person inside, but considering that some of the battles take place in highly extreme locations, it’s safe to assume that a momentary burst of flame isn’t going to set the player’s ankles on fire.
Secondly, the location of the rocket is important. If the rocket is placed on the bottom of the player’s foot like many rocket boots, then there is no place for the exhaust to go. And a solitary thrust from the player’s ankle will cause other issues that we will talk about later. But primarily the placement of the rocket will have to allow for the venting. If not, the heat will be pushed into the boot itself, making it extremely dangerous for the wearer.
Next we need to look at a fuel source. Sustained flight like Ironman would take an incredible amount of fuel. And we all know that Tony has that. It’s not exact determined that the DOOM player has the same kind of fuel. Thankfully, the DOOM player only needs the rocket boost to do double jumps, which means that minimal fuel is required. The bursts from the rockets would be quick and sporadic.
Lastly, we’ll need stabilizing rockets. These are super important if the player hopes to actually land on his feet. If the rocket can only fire in one direction, then the person wearing the rocket boots would have to be extremely precise beyond human abilities to be able to not go flying off in an unintended direction. On top of that, landing would also be an issue without an ability to evenly land on a surface.
First, let's tackle some of the problems that aren’t an issue with the DOOM rocket boots before I explain why they just won’t work. If you look at the requirements above, the DOOM boots have all of them, mostly. Those requirements are just the start. To have ones that really work there are a few nuances that need to work in conjunction with the above.
The we discussed the fuel problem. Although there isn’t really a good place to store the fuel, I will give them that a double-jump rocket wouldn’t need as much fuel as a sustained rocket. Another thing that is missing is a way to cushion the fall. A human bone can take about 8600 kg of load before breaking. Since we aren’t talking about falling from any great height in DOOM, and the fact that the suit combined with the rocket themselves could help cushion the fall, there really isn’t a reason to have some sort of shock-absorber, but it would help solidify the effectiveness of the boots. If you’d like to see the math and a demonstration, Science Blogs has a great entry and a video of someone doing something very stupid.
The first problem that I see with the DOOM’s boots is the secondary rockets. In order to maintain balance the DOOM boots would have to have some sort of gyroscopic computer to make sure that the right amount of lift was given at the right interval. This is similar to the way that Segways work. Essentially, the rocket boots would be a Segway with rockets, but the problem is that you would need four rockets. The DOOM boots have two on each foot. And given the position of those rockets, I would venture to say that falling on your face or falling backward would happen all the time because there is no way to correct for those angles.
However, the biggest fault of the DOOM rocket boots is the lack of knee support. Why is this important? Although a human bone can take 8600 kg in pressure, the strongest man could only leg press 1229 kg. That means that it’s very likely that the player’s legs would buckle when the rockets were ignited causing him to flight completely off course and probably injure himself from the fall.
As always, science is about being proven wrong. If you have your theories about rocket boots, let me know what they are in the comments below, and also let me know what other gaming tropes you’d like to see me prove or disprove when I science the shit out video games again next week.