Another "What-If" Scenario - Guns for Jetpacks?

"Is it possible to build a jetpack using downward firing machine guns?" Yes. With enough money, just about anything can be built.

"Will my jetpack that uses downward firing machine guns lift me into the air?" No. Even a .50BMG would be insufficient reaction to lift itself off the ground for more than, perhaps, a few seconds, this complicated by the fact than ammunition (fuel in this case, I suppose) adds so much weight to the scenario.

I agree, the weight of the ammunition by itself would be too much. Furthermore, it wouldn't be cost effective. A couple rounds would be as much as a gallon of jet fuel.

In the early space program it was put on the table the idea of blasting several nuclear blasts under a huge plate of iron to launch a manned craft into space but shelved in place of other ideas. This idea had been theorized as conceivable by physicists and later used in a science fiction novel.

'.....In the early space program it was put on the table the idea of blasting several nuclear blasts under a huge plate of iron to launch a manned craft into space but shelved in place of other ideas....'

.

This went beyond theoretical.

In an early US nuclear test, either Pascal A or B, a roughly 2000 lb steel blast door was lauched at about 6 times escape velocity. This was pre-Sputnik, so it puts into question the 'first artificial earth satellite' record into question (no one makes the cleaim to emphatically though).

At six times the escape velocity I think it is safe to say that the remnants of this plate did escape Earth's gravitational pull and did not go into orbit. Sputnik still retains the prize for the first artificial satellite.

At 6 times escape velocity, I think there is a strong possibility that it did not stay together as one piece traveling throught the atmosphere.

I think it probably burned upin the atmosphere.

But if it didn't, how far around does it have to go, for you to conside it an artificial satellite?

It is really difficult to launch anything from earth and get it to orbit without corrections to trajectory once you have left the ground.....so unless the atmosphere made some hellacious corrections, none of that stuff was a satellite for long.

There was talk as well as experiments of using a upside down dish and shooting a laser into it.

The laser would heat up the air and moisture and propel it.

The had stablization problems. but when they put a spin on it that helped.

What really help was a guide rod running through the middle

"What really help was a guide rod running through the middle"

They stole that idea from the Estes model rocket launchers!

I saw a video clip of it.

A jet pack would need to go straight up and therefore thrust would have to exceed weight. With "real" ammo I doubt that the thrust could exceed the weight on anything that would resemble a usable platform.

I have heard of warthogs having a considerable decrease in forward speed when they get mad and express their anger. Thus, a tiny amount of support for the theory, but not enough to make it fly.

From the article:

But there's a problem: Ammunition.

An AK-47 clip holds 30 rounds. At ten per second, we'll get a measly three seconds of acceleration. We can improve this with a larger magazine-but only up to a point.

It turns out there's no advantage to carrying more than about 250 rounds of ammunition. The reason for this is a fundamental and central problem in rocket science: Fuel makes you heavier.

Each bullet weighs 8 grams, and the cartridge (the "whole bullet") weighs over 16 grams. If we add more than about 250 rounds, the AK-47 is too heavy to take off.

This suggests our optimal craft comprises a large number of AK-47s (a minimum of 25 but ideally at least 300) carrying 250 rounds of ammunition each. The largest versions of this craft could accelerate upward to vertical speeds approaching 100 meters per second, climbing over half a kilometer into the air.

XKCD has made another interesting and fun article.

However, I do think that an important point has been missed here. I'll overlook the error that by hurling bullets this is by definition not a gaseous jet and hence not a jet pack. The thrust control of a jet pack must be gradually adjustable to allow for a controlled landing. If the goal is to just launch a person or squirrel to their death then the normal operation of a gun will work much more efficiently.

The bullets don't need a projectile associated with them to give the same results.

Loaded AK-47 rifle 4.78 kg. Projectile 8 grams. Muzzle energy 2,460 J.

I come up with about 40 joules of recoil energy per shot fired, and this for a very short period of time.

It'll never fly.

Nevertheless, I do not want to be one of the journalists spectating.

Yosemite Sam says,

"Yer darn Tootin"

First, this is a ridiculous idea, but might aid slightly in thinning the gene pool.

The weight of sufficient ammunition to sustain rapid fire long enough to lift the vehicle

would be so large that this thing would never get off the ground.

Wait, let's use helium bullets.

Whoever would actually attempt making a jetpack out of guns would definitely be in line for some sort of Darwin award, that's for certain

The creator of the article claimed that the loaded AK-47 had a thrust-to-weight ratio of about 2. Wouldn't a large group of guns firing simultaneously be enough to cause lift-off?

Simply do it without the actual bullets (slugs) and you have a solid fuel rocket powered by small charges injected sequentially.
This technique has been tried before in the early days of rocketry by the likes of Clarence N Hickman who lost some fingers during such an experiment.
Del
(So if you find any fingers...)

Simply do it without the actual bullets (slugs) and you have a solid fuel rocket powered by small charges injected sequentially.

But the recoil has to do with moving the mass (bullet). And the recoil is use to discharge and reload.

This technique has been tried before in the early days of rocketry by the likes of Clarence N Hickman who lost some fingers during such an experiment.

I get the feeling that was no experiement, how old was he, 15-16?

Whoever he is, he helped create the Bazooka. The guy must've had a real fondness for explosions and loud noises (and a low fondness of keeping all of his limbs).

(and a low fondness of keeping all of his limbs).

I understand they just kept getting in the way anyways

Whoever he is?

This guy had quite a bio, that was a little diverse.

It reminds me, I worked with a guy that was with a company that was one of my clients, his background was that he was a Weapons Engineer for the then USSR.

He immigrated to this country back in the early 80's and because of the security risks, he could not get a job here in his field. So he's now a process engineer making cheese and butter. As he told me shaking his head.

I told him, yeah, I see the connection.

Take your criticism to NASA and try to convince them that the Atlas 5 rocket engine would work better with the addition of lead slugs...
Del
<slaps head with furry paw>

I didn't re-think, I'm not quite sure what you mean, but I thought about it.....

There are three types of systems

• Recoil Systems
• Blowback systems
• Gas mechanisms

But as far as the Atlas Rocket, now your talking more than a self contain small charges injected sequentially, aren't you.........

Cheezes,
I'm talking about the principle.
In order for it to work you need to get rid of the extraneous mass of the slugs and improve the combustion.
This effectively moves it towards becoming a solid fuel rocket, which is self evidently feasible.
I realise the whole thread is bonkers...
I was merely trying to illustrate that it's actually not too far from the development of the solid fuel rocket.
I think I'll give up and get back to my cat nap.
Del

I'm sure we are are familair with the basics physics of rocketry.

Yes, a nap may be over due.

I fully expect this thread to go at least a little off topic (maybe more, who can guess). The overall feasability of getting off the ground with a gun increases as you decrease the mass of the gun, so it's obviosuly the right idea. There are quite a few extraneous parts of a gun that are there for user operation that could also be eliminated, such as the barrel.

On another thread here, believe or not, we were talking about some things simular about the GAU-8/A Avenger Gatling gun on the A-10 Avenger, About it affecting it's flight.

Plus the couple of tons of shells it requires.......

I think Capt Moosie had some good input.

As long as we are down this path, we might as well add the C130 gunship to our consideration.

Firing 105mm, 40mm, and 20mm contiually out the port side certainly has an effect on position, though aside from the concussive jarring effect, I'm not sure if anyone other than the pilot, navigator and fire control (sorry for the guesses on the titles here) would have be able to quanify it.

Ok, here was the thread. It's called bunker busters, the thread started on post 262, my hyper link doesn't work on my iPad

http://cr4.globalspec.com/thread/80902?Pg=2

I'm in HOG heaven!

An A-10A Thunderbolt II (aka Warthog) from the Maryland ANG!!!

Buy an A-10 driver a beer, kill a terrorist! It's incentive!!! LOL thank you very much!

When the powder burns doesn't it provide equal force in both directions?

One of my buddies that saw the article went in a different direction. As a sci-fi enthusiast, he asked me if I thought some sort of high powered "photon laser" would be able to create propulsion. It's true that photons have momentum, but just how much energy do you think would have to be dissipated to create lift, or would there be no lift at all and just a massive hole in the ground?

[use your imagination]

The first need is to analyze and find out which machine guns have the strongest recoil. Strange as it may sound, some machine guns recoil "forwards", the old British .303 Bren for example.....

I found a reference to this strange turn of events here:-

Brengun.htm

Under the heading of:-

Firing the Bren

The sights on the Bren were offset to the left, giving the advantage to right-handed firers; the recoil of the weapon tended to pull the weapon forward, when firing on automatic it would "walk" away from the firer. Some Bren gunners found that a bulleted cartridge driven through a hole in the bipod could temporarily keep the Bren in place.

I once saw a 10 year old, trying out a Bren on an RN open day, get pulled up a small slope!!! (Yes we let kids fire weapons then!!)

Therefore, the design of the gun derives the direction of recoil, so I have to assume that it is possible to not only pick the direction of recoil with a suitable design, but also possible that some machine guns will have no effective recoil, just vibration........Not much use for taking off!!!!

Savage recoil, which is what is needed here, is not fun to shoot with though, even though it might help you to "take off "........

Thought for the day, " Is recoil the right word for a gun that 'recoils' forwards?" Perhaps "For-coil?"

Another thought, I wonder if the LMG, which was a later version of the Bren using NATO ammunition, had the same effects with the recoil......

Even more thoughts, the Bren was such an accurate weapon, the target that you could see and fire at, was marked very darkly and lightly offset from the lightly marked target where the hits were actually scored. The difference was the same as the distance between the gun barrel and the off set sights.........This accuracy was considered to be a hindrance in some actions, as bullets were not "scattered about" enough for some people.

I reckon that with a short 5 or 6 bullet burst, I could kill a terrorist/hit a target accurately at up to 1.5 miles distance........never got to actually kill a terrorist though.....

This is a bad idea on so many levels!

How in the hell would you aim AK's strapped to a jetpack? You can't, effectively that is. Having fired many an AK of all types at the ranges, it would be virtually impossible to get good solid kills.

AK's, especially AK-47 and AK-74, have one of the lousiest iron sights on a military assault rifle known to mankind! Damn sights are too close together.....it's basically 'spray and pray"!

To take a counterintuitive look, I have not fired an AK so I don't know if there is a kickback. I fired a Bren Gun when in the army, and that tried to walk away from the shooter. I also fired a 303 and that sucker did kick back but it is a rifle and not suitable for the rapid fire.

On the point of gun safety, an Australian General was interviewed in the USA I believe:-

For those that don't know him, Major General Peter Cosgrove is an Australian.

General Cosgrove was interviewed on the radio recently.

Read his reply to the lady who interviewed him concerning guns and children.

Regardless of how you feel about gun laws you have to love this! This is one of the best comeback lines of all time.

In a portion of an ABC radio interview between a female broadcaster and General Cosgrove who was about to sponsor a Boy Scout Troop visiting his military Headquarters.

FEMALE INTERVIEWER:
So, General Cosgrove, what things are you going to teach these young boys when they visit your base?

GENERAL COSGROVE:!
We're going to teach them climbing, canoeing, archery and shooting.

FEMALE INTERVIEWER:
Shooting! That's a bit irresponsible, isn't it?

GENERAL COSGROVE:
I don't see why, they'll be properly supervised on the rifle range.

FEMALE INTERVIEWER:
Don't you admit that this is a terribly dangerous activity to be teaching children?

GENERAL COSGROVE:
I don't see how. We will be teaching them proper rifle discipline before they even touch a firearm.

FEMALE INTERVIEWER:
But you're equipping them to become violent killers.

GENERAL COSGROVE:
Well, Ma'am, you're equipped to be a prostitute, but you're not one, are you?

The radio went silent for 46 seconds and when it returned, this interview was over.

Does WikiLeaks happen to have that 46 seconds by any chance? :)

Physics is a branch of science simple as that.

It's interesting to see possibilities using physics (as unrealistic / unpractical as the scenerios are).

This character comes to mind

Ground support personnel hard to replace after 1st flight.