Krdytkyu

Your martial artists will need 3 things; speed, flexibility and upper body strength.

The real issue with fighting in zero G is purchase. When Chuck Norris stands his ground against an attacker, he does exactly that; The purchase he gets from his legs on the ground means that when he strikes, the momentum he's building with his fist, foot, shoulder etc. is projected into the other person, not pushed back onto him. Most martial arts are based on the idea of strikes intended to catch your opponent wrong-footed or off guard, hitting them where they're weakest with all of your strength rooted so as to deliver maximum effect.

In space, you have to assume you won't be able to do that.

You might have the option of standing your ground wearing velcro shoes or something similar, but there won't be any spinning leaps et al. The reason is that once you're off the ground, it's all about momentum. Unlike on Earth, where you're going to land again, in this case you'll bounce off the roof, the opposite wall, your opponent, etc. once you get there, meaning that if your opponent weighs what you do, then there's a good chance that any momentum for strikes is going to be halved, with half going to your opponent as intended and the other half pushing you in another direction. This also means that your opponent isn't likely to be disabled because the energy will just push them back, especially if they are also off the walls or deck.

So; what you're going to have to focus on are holds. Not just any holds, but holds where ALL the strength comes from your muscles and don't rely on gravity assists. You can't use an opponent's 'weight' against them in space, you can only use the strength of your muscles and perhaps a wall (bearing in mind that there's nothing holding them to the ground or the wall which brings us back to your own strength).

You'll need speed to get your opponent into these holds, and avoid theirs. You'll need flexibility because in this environment, your legs aren't anchors so much grappling hooks and will be a major part of any hold you try out. And of course, upper body strength because you'll be holding someone against their own desire to get out, and without gravity assisted moves, the strongest muscles will tend to win.

I'd start by looking at something like Judo rather than Tai Kwondo because you want to start with the holds and then reverse engineer out the differences gravity makes to some of the holds and how you'd compensate. A good working knowledge of kinematics will certainly help you build up your own zero G variations to the holds and blocks you need to avoid being captured by your enemy. Speed is a factor, especially in terms of disabling people with guns, but that speed will be more along the lines of dexterity than single line of motion speed. In other words, how quickly can you wrap yourself around a gun laden hand? How quickly can you convince it to let go?

Training in this environment would use something similar to the wooden training poles that are used in many Asian martial arts, where you have a pole that you learn to wrap yourself around quickly and strongly. As for muscle strength, you'd find that any form of exercise will help with that but ideally there would be an additional focus on flexibility in that training. I don't know how Pilates would work in Zero G (I'm guessing it wouldn't because many of the moves are designed to take advantage of bodyweight) but it would be very useful in this regard because it wouldn't sacrifice flexibility for strength, especially if coupled with some form of Zero G yoga.

As a bonus suggestion, also take a look at Greco-Roman wrestling as many of the moves in that sport also require strong upper body strength and are tests of the ability of the participants to hold their opponent in check.

Nice question!
First of all, if you want to do martial arts in space, then the entire basis of martial arts would have to change. Instead of focusing on using gravity against the opponent, you would have to use momentum and power sources to power your punches.

This would mean extensive training. First, I'm assuming there is a floor. Meaning, you're not fighting when flying around in space. So... on a spaceship. That would mean a person would be able to push off the ground. That would be the main factor in a fight. A person would have to know which angle to push off of to launch herself (or himself) towards the attacker. Also, the person needs to be comfortable with changing his source of "gravity", or his floor. For example, he or she can push off a wall if that's more convenient. (Note: Ender's Game by O. S. Card might be helpful here).

Next, to be able to effectively pack a punch, there would need to be boosters on the suit. Like.. mini "rocket launcher" like things that let you punch something at a fast speed. Sharp objects wouldn't make much of a difference because the opponent will very likely have a suit on. An object that can smash the visor or break some important tube in the suit, on the other hand, would be immensely useful. Like... a hammer! (That has weight in space, of course.)

Now, for the suit, it would be important to have a light and flexible suit with strong headgear. Also, if there were some high-tech gravity bases that let the user stay still in a fight. Something like a very heavy "thing" that works "kind" of like gravity. For example, if the spaceship has a magnetic inside, then magnetics that move based on the users movements would be immensely useful.
Now, the moves: I'm not some expert here, but the moves would be different, but some of the fundamentals would stay the same. For example, you would still need to move with grace and such because... in space... changing direction is hard. Fast moves would be very hard to do, so those would require lots of skill. Charging someone and making a flurry of attacks would be useful as well. If the opponent, for some reason, doesn't have a suit, then attacking pressure points (Kyusho-Jitsu) would be great. The bloodflow is even less strong and attacking the blood vessels would be even more effected. BUT... this can be lethal... so it really depends on your world.

Let's see... if there anything I missed? Maybe... training? All of the discipline involved in martial arts on earth would apply, like respect and fairness. If you want to prevent the use of guns, you might want to have magnets or bulletproof suits that can either attract the guns or repel the gunshots. (Obviously, no one without suicidal intent will shoot a gun).

Good luck, Claire

@Tim B II above raises very good point about lack of support from legs. Moreover, wrestling might be more viable than striking arts even here on earth. But it is not nearly as spectacular. So here are a few ideas (I do assume you are fighting inside a ship or station):

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  Leaping of the walls will be limited to moving into/out of the fight, and ambushing unsuspecting opponent. Even in Earthly martial arts, getting both feet of the ground is frowned upon, as it limits your contol puts you on a predictable trajectory for the duration of the leap. that the enemy can exploit. In space, rather than engaging in aerial joustling, it seems wiser to wait on the wall till your opponent flies close, and kick them where it hurts (while they cannot dodge), or attack them as they prepare for safe landing.

  
  
  
  
  
  • Leaping will likely involve a somersault, since you want to push off with the legs for max speed, and then land on the legs to absorb the shock. There will be some highly cinematic acrobatics, but it will leave you open to attack.
  
  
  
  


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  Main technique will be clinging to walls, and trying to hit opponent with hands or feet. I am not sure which approach is more viable: hit with legs for more strenth and reach and safety of the head, or hit with hands for better control and visibility. Imho, sitting in a narrow tunnel and kicking everything that comes into it seems like a viable defensive strategy.

  
  
  
  
  
  • Note that zero-G ship or station will have handholds everywhere, and will likely have very limited space between walls (just look at ISS)
  
  
  
  


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  Melee weapons will surely come handy. Both edged and pointy seem viable. blunt might not have room to swing; but offer best stopping power. Polearms are limited by small space, but can completely close a choke point like a narrow corridor.

  
  
  
  
  
  • Thrown objects are viable, since zero makes aiming easier. I doubt you can throw them hard enough to kill, but they will still work as a distraction.
  
  
  
  


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  To train in 1G:

  
  
  
  
  
  • suspend fighters on ropes (I think Circe de Soleil had such a performance), - train in the water (no gravity, and resistance helps build strength)
  
  
  
  

It's been mentioned in a couple answers here, but the key thing to understand is in zero-g you don't have the purchase to do many of the kinds of moves seen in typical martial arts so you have to make/modify a martial art that creates purchase as part of each move or uses purchase created by your opponent or surroundings as part of the move. For example, throwing a punch or a kick while suspended mid-air in zero-g would be underpowered because the momentum transfer in the hit would split between you and your opponent and would send you flying away. To resolve that issue would require the combination of a grapple and a hit. For example, you could combine a leg grapple with upper body strikes, an upper body grapple with leg strikes, or a purchase grapple combined with a twist or submission grapple.

The real complexity in the martial arts would be in acquiring a superior grapple position on an opponent that would allow you to strike while blocking your opponent from striking. For example, locking up your opponent's arm to immobilize him would allow you to strike with your remaining limbs, but your opponent would be able to strike you just as easily. However, if you were to land say a half nelson on your opponent you would be behind him/her and would be able to land some vicious strikes without your opponent being able to respond in kind. In a real fight, you might see an initial hold grapple, followed by crawling/maneuvering over your opponent to reach a superior grapple with opportunity hits thrown whenever they are created by either side.

I can imagine a group of space marines practicing these moves in an Olympic sized pool while on earth using protective headgear with rebreathers attached and a weighted suit to keep them suspended in the water. In space, they could practice the moves with a suit designed to add resistance to their movements to also get a decent aerobic exercise.

The current answers on martial arts are all very good, but just because guns are ruled out doesn't mean you can't have any weapons.

If you are going far future you can just go down the standard phaser/stun gun route, if you want to keep it more current tech level, there is no reason that the current police 'less lethal' gear would not work, things like tasers and bean bag rounds.

If you want something more visually pleasing then rope based weapons would work very well, a knife or hook attached to a rope can be thrown at the enemy and pulled back if you miss to be used again, if you do embed it in them then you can pull them free from the walls so they have no surface to push against

Clothing and weaponry that can be used to redirect and focus acceleration, such can still use the mass of the body as a focal point.

We have an instinctual understanding of momentum that expands with experience such that for day to day activities thought not need be applied, a significant part of martial arts training is teaching a body and a mind to more efficiently recognize, shift and exploit 'centres of gravity' of course, centres of gravity are misnamed, but the principle of consciously altering acceleration around preferred focal points is intrinsic to all combat, armed or unarmed.

In other words perhaps, martial arts training would not need to change much at all, and people are far more capable of comprehending altered states of acceleration than the question seems to imply. Every mammal attempts to make mass judgements of things it interacts with in order to understand how it's own applied forces will interact with the forces already interacting with the object, one of the reasons kittens and puppies are so ridiculous is because their instincts have not yet been informed by experience, one is not born with a knowledge of the mass and acceleration of objects, but rather the tools with which to judge and store those judgements.

Zero G 'melee' combat would obviously(?) depend on the environment more than when under terrestrial conditions for most species.

Being able to extend and/or reshape ones' surface area would be 'pivotal,' indeed the lack of gravity as a counterpoint 'resisting' any application of force means that almost any application and/or ability to apply that force gains scope and utility.

We often see scifi 'space suits' ejecting gas for instance against space to provide alterations in momentum, massively inefficient when one considers that if the intention is to change orientation the force can be applied from one part of a contiguous body to another part of the same.

There are various methods to shift mass in a body by using the external environment aside from gravity, but it would seem silly for anybody wanting to win to rely on factors that may be outside of their control at the point of conflict.. Gyroscopes, magnetic shifts and etc can be used to impart not just angular momentum, but 'regular' momentum also.

For low-tech or contemporary scenarios, consider that recoil-less rifles were invented a long time ago, and could 'easily' be engineered to redirect any residual recoil to maintain a relatively static position. Whip-like devices, hollow devices with variable-resistance interior mass could be utilized to magnify force around selected points of motion which would be hard or impossible for opponents to predict with precision allowing for skill-based combat.

You didn't really specify what kind of enviroment the fight takes place on - if on the surface of a moon, inside a low-G training room/arena or just plain old space.

Regardless, I think the ultimate fighting technique for low/zero-gravity is one that focuses mainly on submission - so I would say the answer for this question is something in the likes of Brazilian Jiu-Jitsu.

It meets all the criteria:

A practical martial art, for real world use, not a sport or display martial art.

This martial art is basically focused on getting your opponent on the ground in order for you to get in a position capable of breaking an arm/leg or simply choking him senseless. This makes a lot of sense if you think that these fights could take place in plain old space, where there is no ground or walls to get a hold on. A good Jiu-Jitsu fighter will hold onto his enemy like a tick that will not let go until he is done.

Primarily unarmed. Firing a gun on board a spaceship is a suicidally stupid thing to do, so one of the goals of such a martial art would be to disarm somebody before they can punch a hole in the hull and kill everyone.

This one really depends on the situation at hand. If a reaction is possible, all the fighter needs to do is tackle his foe - which is also part of this martial art. They're taught techniques to get an opponent to the ground so they can start going for the immobilization/submission.

The techniques would need to be ones you could learn and practice in a different gravity environment, so that somebody living in space can practice the ground-based techniques and visa versa.

Aside from the knowhow, which generally comes from a master (but you could make changes in order for the master to be just a series of videos, for example), all you need is another person to continuously train with and a space large enough to do so.

Anybody living in a low gravity environment long term risks muscle and bone loss unless they spend hours every day exercising. Techniques that can serve as part of that exercise would be more practical.

I've never practiced Jiu-Jitsu but I've been to a gym where I practiced Muay-Thai and we used to kind of share this enormous space with the Jiu-Jitsu students. Even though the martial arts are very different, the warmup execises we did had a lot in common -
functional exercises like running, squats, pushups, etc. Assuming the facility the training takes place has space that can allow for this kind of training, this should be covered.

The practicing of the art itself has a lot of grabbing and using your own bodyweight in your favor, so jiu-jitsu might look a little tedious for an observer, but a fighter has to put in A LOT of strength until he finds an opening to finish his opponent.

Realistically? I wouldn't bother training any space person in martial arts. I would instead focus on deescalation techniques and how to read a situation.

Guns are dangerous, and there is no way to disarm a ranged opponent without having them pull the trigger on you or anything around you unless you have a huge element of surprise. No martial arts technique will allow you to beat a gun, unless the person holding the gun is high inexperienced and easily manipulated. A determined assailant will just shoot you or threaten to shoot something if you approach them and keep their distance.

An inexperienced shooter can be coerced with words, to stand down. That things will improve and get better. That they can have a new life or a voice and be heard. This falls under deescalation techniques which will play a more vital role in allowing you to close the distance and disarm the shooter than yelling, jumping and kicking would ever achieve.