The article directly refers to Munroe's What-If article, and Munroe is pretty clear that he relies heavily on Wolfram Alpha for his calculations (see end of "Falling With Helium" [1])
So it's rather amusing to me that things are coming full circle, and that Worlfram's guys are now using Munroe's topic to demonstrate SystemModeler, another Wolfram product.
The page you linked says that he normally uses Mathematica, and fell back to Wolfram|Alpha for that piece when it started locking up.
While researching this article, I managed to lock up my copy of Mathematica several times on balloon-related differential equations, and subsequently got my IP address banned from Wolfram|Alpha for making too many requests.
Oh, suuuuuure, some kind of magic mathematics company run by a reclusive genius who got a Ph.D. from Cal Tech when he was twenty, and/or college dropout and/or megalomanaic bald silicon valley mogul.
answer for those following along: all of the above :)
"In 1982, Larry Walters flew across Los Angeles in a lawn chair lifted by weather balloons, eventually reaching several miles in altitude. After passing through LAX airspace, he descended by shooting some of the balloons with a pellet gun."
In Brazil, a priest doing a gimmick to raise some funds to his church went on flying with helium balloons. He was drifted to the ocean by the wind and didn't know how to return. He did took a phone and a GPS device. But he didn't know how to use the GPS he took to tell people his location. He died.
Trivia: the rifle's momentum comes not only from (M_bullet x V_bullet), but also significantly from (M_gunpowder x V_gunpowder). The burnt gunpowder is often 1/3 to 1/2 the weight of the bullet, and traveling faster than the bullet.
I've just realized that it's curious how the cop pulled him over. Pretty sure tanks aren't fast enough or durable enough to make pursuit, and unless he stops firing while changing lanes, he likely strafed the cop getting off the road.
Frankly, I think the scenario is just too unbelievable. Perhaps a souped-up SWAT van clad with ablative plating and 12 inch thick laminated windshields, but definitely not just some ordinary cruiser.
I dunno. The gun is not aimed downwards, and i suspect the bullet drop is fairly limited for some distance, allowing for the cruiser to potentially pull in underneath the stream. Whoever is driving said cruiser will have some big metal balls to pull it off.
Checking Wikipedia it seems the round drops 1 meter pr 400 meters of travel.
From inside the ship you wouldn't really know that you were being propelled using nuclear bombs. Between the pusher plate and the ship are extensive shocks that would be designed to smooth out the pulsing power of the bombs into a smooth acceleration. Anything else wouldn't work very well and induce loads of stresses up the ship.
My first thought was a space propulsion drive based on machine guns, much like ion propulsion. If humanity decided to get rid of all firearms (ha!), we could probably send them to space and drive a few spacecraft cheaply, easily and for a very long time (there are a lot more bullets than nuclear weapons)
Thermonuclear propulsion, as cool as it is, would be very powerful but uncontrolled acceleration, whereas a firearms-based drive could be controlled a lot more.
It would be fun if someone did a comparison on how long, fast and far nuclear versus bullet drives would get us in space.
Most bullet cases are made out of brass. I'm no rocket scientist, but brass cases would make a horrible rocket engine material.
The only reason cases don't catastrophically fail when you fire a gun is because of the bolt/chamber providing support.
Brass IS pretty good about stretching quite a bit before a catastrophic failure. This property is what allows case fire-forming (http://en.wikipedia.org/wiki/Fire_forming). It's also a pretty awesome safety feature.
Cases are so bad by themselves about containing the force of expanding gas, that ammunition fires aren't nearly as dangerous as you might expect them to be. (https://www.youtube.com/watch?v=3SlOXowwC4c) It's a long video, but if I recall correctly, it demonstrates that a rifle cartridge fired without a chamber doesn't have the energy to penetrate cardboard at like an 11 inch range.
I had a box of cartridges in a fire - they didn't go more than a few inches. The cartridge fragmented, like a firecracker with no net momentum to the bullet in any particular direction.
He seems to make it unnecessarily complicated. Average thrust (momentum flux) is m_bullet x v_muzzle x fire rate, which needs to be higher than m_rocket x g for it to work.
Well it was the 50s. Both sides of the cold war tried to come up with various uses of nuclear power. From civilian cars to military strategic bombers. Never mind using nukes to dig harbors...
There were some crazy conventional technologies also. One scientist, as a joke, did a calculation about the effects of adding mercury to rocket fuel. It wouldn't react with the fuel, but it would add a lot of weight which would make the thrust more efficiently move the rocket forward.
This was tested, found to be true, and thankfully never put to use in any actual rockets.
Ha! Great reference, iirc the humans put a pusher plate under a battle ship (uss missouri?), launched into orbit and pummeled the aliens. I also recall something about fighter craft and 16 inch cannons. Great read.
I recall mainly the jury-rigged pipes that a character based on one of Niven/Pournelle's friends kept working at the cost of his own heroic death. Apparently they asked him what the fate of his character should be, and he picked death.
Based on physical appearance, he surely was also the prototype for the question-asker in "What Can You Say About Chocolate-Covered Manhole Covers?" That basically obscure story was big in my life because it's one of the things that introduced me to Roger Zelazny (it referenced his Agnostic's Prayer).
There is a game that puts this into concept called Jetpack Joyride (made by creators of Fruit Ninja): https://appsto.re/us/TybrB.i.
My physics class actually did a lab report to find the relationship between the # of bullets and distance propelled in the air with the game. While it was nowhere near as accurate as this simulation, it was definitely interesting to see the results.
This analysis and the xkcd one linked below both neglect the concept of staging - which could get you higher. As a first order try you could replace the human on the bed of guns with a smaller bed of guns supporting a squirrel - now you're twice as high! Of course at that point there is nothing stopping you from reaching the moon except for your gun budget and how much unobtanium you can get for the bed connecting structure.
The ammunition mass is a more effective way of increasing your stored energy than extra rifles, so it is at least addressed implicitly in the section that examines the ammo to carry (1 gun with 2 bullets obviously beats 2 guns with single bullets, I guess more complicated situations would follow).
You always want to fly with the minimum number of guns necessary to provide your desired thrust and then as much ammo in addition to that.
"The average recoil force of the GAU-8/A is 10,000 pounds-force (45 kN), which is slightly more than the output of one of the A-10's two TF34 engines (9,065 lbf / 40.3 kN each). While this recoil force is significant, in practice a cannon fire burst only slows the aircraft a few miles per hour in level flight"
> The airframe vibration led to fatigue cracks in fuel tanks, numerous radio and avionics failures, the necessity of using runways with floodlights for night flights (as the landing lights would often be destroyed), tearing or jamming of the forward landing gear doors (leading to at least three crash landings), cracking of the reflector gunsight, an accidental jettisoning of the cockpit canopy and at least one case of the instrument panel falling off in flight.
It also used to produce so much oxygen-free gas that the engines would flame-out. The engines were modified to deal with it. Its in the same wikipedia article.
I was thinking of a sort of violent version of _Up_, in which Carl launches his house by shooting an assortment of machine guns attached to the bottom his house to propel it upwards instead of using balloons.
So it's rather amusing to me that things are coming full circle, and that Worlfram's guys are now using Munroe's topic to demonstrate SystemModeler, another Wolfram product.
[1] https://what-if.xkcd.com/62/