# How would a weapon act if it negates the effects of gravity for itself?

A pretty major component of a lot of anime shows and other media is oversized weapons, like giant swords, hammers, the like. These types of weapons would be completely unfeasible in the real world, but it got me thinking of ways to make them easier to handle and use.

If you were able to negate the effects of gravity on a giant sword how would it handle? My assumption is it would be like handling it in micro-gravity, as in, it would be a similar situation if you took it up to the ISS and tried to swing it around, which may make you able to lift it and move it around, but it would still be ineffective as a weapon, is this assumption correct?

For the purposes of the question, assume the sword is 7 feet long and a foot wide. (Much like Cloud's buster sword from Final Fantasy VII)

If this is the case the real question becomes: What would be the best type of weapon to use if you could negate the gravity affecting the weapon.

Fantasy is fantasy, not realistic at all. Oversize swords are worse than a Klingon Bat'leth since you might be able to at least defend yourself with a Bat'leth.

The purpose of a weapon is to discourage, disable, or destroy. Attempting to wield a 7 foot steel blade with no weight, but 20 times the normal inertia is still a very, very bad idea. A swordsman using a standard long sword weighing 3.5 pounds (a little on the heavy side actually) will easily defeat you. Force = mass x acceleration. If you are wielding some with 20 times the mass (and 40 times the rotational inertia) you will always be way too slow as you struggle to move your sword around. A common sledgehammer is around 10 pounds, try swinging one of those around quickly and you will find it impossible. This is not because of its weight, but its inertial.

You want to be able to accelerate your weapon at about 10 gees. The weight of the sword is thus only about 10% of the resistance due to inertia. Found an article subtitled Observations on the force exerted by a sword in swing that mentions: On average the test swords swung with 10.54m/s velocity and 117.19m/s^2 acceleration; (11.95 gees) -- so a little higher than my memory, but the testing conditions appear a bit artificial so maybe 10 gees is a better number anyway.

Unless you can get inertial compensators, lose the over-sized blade and get something that will actually be much more effective as a weapon. Now, suppose you are super strong, 20 times human strength. You still don't want that oversize weapon, you don't need to cleave an armored man in two to be effective. Imagine what Hercules could do with a standard longsword. Perhaps a two-handed greatsword would be better for Hercules because of the greater reach. But a 70 pound sword would just make Hercules slower than necessary. Due to great strength and skill Hercules might well find a heavier weapon more optimal than that a normal man might choose, but since Hercules would still favor speed over overkill power, the heaviest weapon that preserves most of his speed is still his best choice. With his great strength any contact would be likely to kill or seriously wound any opponent.

Best weapon type depends upon type of combat. Mounted combat? Armored? Man on Man vs. Army vs. Army. One foe vs. multiple foes. No single weapon is ideal for all forms of combat or combat styles. If I had to select weapon without knowing combat type, I would probably select based on what works with my preferred combat style and experience and hope for the best.

Would anti-gravity help? A little - you don't have to lift the sword using your muscles so you would tire at a lower rate. How does antigravity work. Does it just means that Earth gravity is cancelled or does it cancel gravity from the sun, the rest of the galaxy, etc. Since these accelerations are multiple orders of magnitude less than 1 gee, you can ignore their effect and in fact do so every day.

How would an inertial compensator work. If it just cancels all or most of the inertia, your big sword now hits like a small sword because it has also lost momentum and kinetic energy. Thrusting attacks would still be mostly effective as they are less dependent on the inertial of the weapon. If your inertial compensator is smart enough to restore inertial just before impact or only compensate for inertial changes supplied via the hilt you would suddenly have a more effective weapon.

Adjustable inertial compensation would actually be pretty useful as you could set the mass of the sword based on combat conditions, and the extra reach would often be useful. You would not want to eliminate mass entirely as this would create a weapon with very poor balance, i.e., contact will tend to wrest it out of your hand.

Given the high tech levels required, one has to wonder why you would want to use a sword though. The only thing I could thing of beyond personal ego or fantasy role-playing was to assume you might be able to sneak in the tech in a setting similar to Ranks of Bronze by David Drake, the sequel the Excalibur Alternative by David Weber shares the tech level limited fighting scenario and may give you some other ideas.

• Thank you, ya, totally forgot about inertia in general until I actually wrote the question and mentioned the ISS. But at that point I decided to just submit the question anyway. – TaylorAllred Oct 17 '15 at 18:10
• Wow, I really really appreciate the edit you put in. It really pushed this answer over the top. Thank you for not only answering the question but also helping me potentially overcome the issues of the idea. That book looks pretty awesome, I'm going to have to check it out. – TaylorAllred Oct 18 '15 at 7:05
• Oh, also, I'm glad you basically asked what is the point of having such a weapon, that's definitely something to consider, I didn't think about why when I thought of it. – TaylorAllred Oct 18 '15 at 7:07
• LOL. Was upset to hear about a David Weber story I have not heard of, then noticed it is actually a David Drake book with a sequel by David Weber. (Have read the sequel, though. I guess it is the same for you since you attributed Weber?) – Ville Niemi Oct 18 '15 at 23:42
• Variable weight, variable inertia weapon sounds like Mjolnir. And could similarly be thrown, and used in something not wholly unlike flying. So ... you're Thor now. – Sean Boddy Oct 19 '15 at 5:40

Historically overweight weapons were used for training. The purpose was to make your sword arm stronger and more resistant to fatigue. If your arm gets too tired to fight effectively while the fight is still on you generally die.

The downside is that since overweight weapons have more inertia you do not learn to use the normal weight weapons with the speed and precision they are capable of. Because of this overweight weapons are not really used any more I think. Unless you expect the students to face a chaotic life or death melee of unknown duration training with the actual weapons simply works better.

Historically such combat was expected and it was often too chaotic and exhausting to use any "fancy stuff" anyway. Or more precisely after the fight got started exhaustion and confusion would handicap you anyway so training with overweight weapons wasn't a real problem.

Additionally more technical the skill, more teaching time per student would be required. When training an army it is better to train them to have strength and endurance with basic skill than any real technique and finesse. The economics work better.

But that is all about training, what about actual use in combat? Well, some exceptionally strong individuals did use overweight weapons in combat. Although it has always been rare since, like Gary Walker pointed out, it does usually compromise your ability to defend your self with the weapon.

So the first criteria should be that you do not need the weapon for defense. Heavy armor and shield (for one handed weapon) should be required. For your scenario, if everyone else is using guns, defensive aspects of swordplay might be irrelevant.

Second criteria should be that you can choose when to fight and when not to, so that you do not suffer from fatigue caused by the extra mass. A leader with body guard to watch his back, a guerilla fighting fast hit-and-run actions and so on.

Third, you have trained with the overweight weapon a lot and have little experience with normal weight weapons. Typically, this would be someone who wants to be strong and because of that trained obsessively with heavy weapons to get stronger. Actually learning to fight should have been an afterthought at best.

Fourth, there should be an actual benefit from using the overweight weapon. Usually this would have been psychological. If everybody knows you fight with a weapon too heavy for others, the effect on morale can outweigh anything you actually do with the weapon. You might be so strong that relying on your strength to overwhelm your opponents might be a reasonable tactic. In such case using a really heavy weapon might make sense since it would allow applying more strength to beat the opponents defences. You might simply not be confident in using anything other than your training weapon.

In conclusion:

Negating gravity does not seem to be anywhere in the criteria for using overweight or oversized weapons. As others have mentioned it is generally the inertia that matters.

The kind of weapon would depend entirely on the reason an overweight weapon is used. A sword or axe of some sort is generally used for psychological effect. A staff or mace might work for applying strength. And of course, if the reason is because you do not know how to use anything else, that, whatever it is, is what you use.

• Thank you for your in-depth answer, I really liked how you went over the defensive aspects of such a weapon, the fact that there really isn't any. – TaylorAllred Oct 18 '15 at 6:59
• @TaylorAllred Actually. there is. If you have initiative, it is harder for opponents to strike back and take the initiative from you. I didn't mention it because only an idiot would rely their survival on always having the initiative... Then again being insane would explain the huge weapon... – Ville Niemi Oct 18 '15 at 7:13
• An interesting fact is that it has now been shown scientifically that training with overweight tools will reduce performance in sports such as baseball or golf, since you're training to a tool with the wrong weight. – Monty Wild Oct 18 '15 at 22:38
• @MontyWild Sounds about what you'd expect. Training to do higher amount of inaccurate swings sounds like a good way to totally suck in either of those sports. – Ville Niemi Oct 18 '15 at 23:43

Gravity is not your only concern when wielding extra-large weapons. The inertia acts in all directions so that swinging that huge sword around would still be extremely difficult. Consider pushing a 20 kg weight laying on the ground to slide it on the floor. It's not easy, right? That's the case with ultra-large sized weapons too. Getting rid of weight of the object will not get rid of its inertia too.

That being answered, the best weapon in gravity-free environment would be a hammer. It is direct, simple and you don't cut yourself up if things go wrong swinging it. Just make sure the hammer head is at least 4 feet away from you. I suggest the hammer's head to be ~10 kg in weight.

• 10 kg is way too heavy for a hammer or sword. Few actual combat sword weighed over 4 pounds, swords over 6 pounds are quite rare. For a nice article on sword weight see thearma.org/essays/weights.htm – Gary Walker Oct 17 '15 at 8:03
• Of course it is super-heavy for our universe where gravity is a major concern. OP asked mass estimates for an environment where gravity is not present. Attached to a 3-4 ft thick shaft, a ~10 kg blunt mass can be used effectively by a muscular person in gravity-free environment. – Youstay Igo Oct 17 '15 at 8:06
• Actually, in the question, gravity is still present, it just doesn't affect the weapon. – TaylorAllred Oct 17 '15 at 18:00
• Exactly. And how different does it practically make the scenario? Other than that you cannot go around flying and swinging all around. – Youstay Igo Oct 17 '15 at 19:38

I'm aware this isn't really an answer to the question, but -

It seems like if most of the weight of the weapon (~90%) was fuel that fired a rocket, it could almost achieve what the user of your massive weapon wants - for very short durations.

The rocket would need to be multi-directional if you wanted to do anything more dextrous than chop wood. You'd want this to be handled automatically based on the user's thoughts or subtle hand movements ( like power steering ), as it would be pretty much impossible to handle a manual system of rocket adjustment with the speed required while fighting someone.

Assuming that all of that engineering is complete, the main limitation becomes the propellant and how long it will last, both during storage and active use. A weapon's worth of rocket fuel would probably have a burn duration well under a minute. Of course, if you're only fighting a single opponent, you should only have to hit them once!

• Interesting. Didn't even think of something like this, Reminds me of Pacific Rim when they use rocket engines to accelerate their fist to hit the creature. +1 for thinking outside the box. – TaylorAllred Oct 17 '15 at 18:03

If a weapon negates gravity, then any damage inured by it's weight is negated. Weapons that don't slash or pierce would be far less useful unless you used some superhuman strength to swing them.

Should a weapon be weightless, then a weapon that acts as an extension of your body would be ideal. Preferably one that slashes or pierces. Blunt objects could work, but it would be better to simply use a buckler or something to defend yourself, after all, if you can negate gravity then why not make a massive suit of armor that weighs nothing?

• "if you can negate gravity then why not make a massive suit of armor that weighs nothinf", well... I was planning on doing that too. lol – TaylorAllred Oct 17 '15 at 18:01
• A weightless weapon doesn't mean it would be mass-less too. You are mixing them up. A 1 kg brick hitting you in space at 60 km/h would do as much damage it does on Earth. Having no weight does not mean swinging the thing around would take any less effort than it did on Earth (well, slightly lesser, as the extra effort required to overcome gravity would be no more, but all the effort required to overcome inertia would still be required). – Youstay Igo Oct 18 '15 at 3:33
• Schlepping around 100 kg of weightless armor would still slow you down quite a bit, but you would certainly be a tank fighter. If they decided to run away you would never catch them. Compound longbows or crossbows might still be a problem as some of them can easily fly through a car door. – Gary Walker Oct 19 '15 at 18:05
• I know that individually array penetration would not be enough to cause significant damage. But as you continue to be hit, the armor is weakened and the arrow hits could add up. Medieval armor by contrast was up to about 25-30 kg and provided significant arrow protection, i.e., penetration occurs, but it is not deep enough to strike vital organs. – Gary Walker Oct 19 '15 at 18:16