NASA’s moon-mission airgun
by B.B. Pelletier
Today’s guest blog is written by Dr. William Abong, formerly of NASA. Dr. Abong worked at NASA on the Apollo Moon Mission, where he was a member of the extraterrestrial life sciences team.
If you’d like to write a guest post for this blog, please email us.
Guest bloggers must know how to take clear photos and size them for the internet (if their post requires them), and they must use proper English. We’ll edit each submission, but we won’t work on any submission that contains gross misspellings and/or grammatical errors.
by William Abong, Ph.D.
Until recently, the gun I will present to you today was highly classified. NASA has now declassified this part of the moon mission and given me permission to write about it.
How it began
Back when we were getting ready to go to the moon, there were concerns for the safety of the astronauts on these far-flung missions. You don’t read about it today, but back in those days we took the UFO threat very seriously. So many of the early astronauts had seen and photographed extraterrestrial phenomena that we felt we had to give them something to protect themselves.
Firearms were ruled out early on because the astronauts are often working in oxygen-rich environments that would not handle a chemical explosion very well. We came up with the idea of making them a defensive airgun — something that would not endanger the environment.
The gun we built was different than anything you see today. First, it had to work reliably in a vacuum. Second, we had no guidelines as to how powerful to make it for we didn’t know the threat. Oh, we had some data on the anatomy and resilience of the Grays; but since they’re not the only species known to exist, we felt we had to design for something more powerful and deadlier. In the end, we pegged our design on something that was three times more difficult to kill than a cape buffalo.
The gun we built is called the LOOPH Lunar air rifle, with LOOPH standing for Lightweight Open Orifice Pellet Heaver. You would call it a precharged pneumatic air rifle because it operates on 1,000 psi air, but it is unlike any PCP you have every heard of. For starters, there are 25 air valves lined up sequentially along the top of the barrel. Each opens just as the projectile passes it to maintain a constant 1,000 psi thrust on the projectile. It was difficult to time these valves; but once we did, we operated them with special electronic switches that can be controlled very precisely.
It was our design to keep the pressure behind the projectile constant for greater acceleration. A normal PCP has one valve that opens and closes. When it closes, the air pressure in the barrel immediately starts dropping off. The LOOPH delivers constant air pressure, so acceleration always increases. The gun is very loud on Earth, but since it’s designed to be used in a vacuum, it makes no difference because in space no one can hear you scream.
The gun is too dangerous to let safety pass lightly, so the design team decided to make it the safest gun ever made. There are 12 different safeties on the weapon. They take over a minute to disconnect if you are in shirt sleeves. We never tried it in a spacesuit, but we estimated it would take over five minutes. Since the astronaut may encounter situations where it is desirable to get into action faster than that, we put in a voice override. If the astronaut says “Shoot!” all the safeties come off, making the gun instantly ready to fire. Because of the primitive state of the early voice recognition software/firmware, we had to limit the astronauts who could use this feature on the gun to those with a Northeastern or Midwestern accent. Southerners could not make it work. Unfortunately, a high percentage of astronauts come from the Southern states, plus it was popular in those days for an astronaut to affect a Texas drawl, so not too many people in the program could use this feature.
The team was concerned about electromagnetic interference (EMI) from various sources, so we considered TEMPEST-ing the whole gun. But after learning that would approximately double our development budget of $27 million, we decided to just put two wraps of tinfoil around the receiver until use. After all, tinfoil is a well-known safety precaution when dealing with alien RF emanations and most of the design team wore some whenever they were in the mission mode anyway, plus it cost us less than a dime for each use.
Projectile and caliber
Since we had no known threat on which to base our design (killing Grays is like shooting frogs, you know) we decided to go overboard and design for the worst threat we could imagine. The caliber of the gun was the most difficult choice we made. The team leader wanted it to be .30 caliber, but several of our younger members were aware of the U.S. Army’s experimentation with a new .22 caliber round. Debates went on for over a year, and we finally had to have a sequestered off-campus team session in Las Vegas to decide. In the end, we got a book written by Mr. Jack O’Connor, who touted the .270 caliber as the finest compromise of all. Since compromise is the hallmark of the Agency, we settled on a caliber of 0.2767 inches. That’s not exactly the same as a .270, but we couldn’t just use a conventional caliber without risking criticism from some quarter, so we made one up. That way, there was nothing to complain about.
If the caliber was the hard part, the material for the projectile was easy. Iridium. It’s dense, has a high melting point and is resistant to almost all known acids. This was at a time before the movie Aliens, but we actually did think about the possibility of encountering a race that had concentrated acid for blood. In fact, I think one of the team members later collaborated on the script for Aliens.
The projectile weight is 11.5 gm (177.471 grains), and it leaves the muzzle at 1,399.9464 m/sec. (4593 f.p.s.). That gives an energy of approximately 8,315 foot-pounds. Since it’s shot in a vacuum, it continues at that speed until acted upon by some outside force.
The one thing we didn’t figure was the cost to produce the projectile. Iridium is extremely difficult to machine. So, the individual rounds cost something like $5,000 each to make. At NASA, our motto is “Pick the very best. We’ll find a way to fund it.” So, we don’t worry too much about things like cost unless we get close to the end of our budget. However, with a projectile costing as much as this one, we found that at the end of each budgetary year, we could spend the remainder of our funds buying extra projectiles. I think we ended up with something like four tins of 200 rounds each. For those of you who are budget types, that represents more money than our entire development budget. But we also had a yearly allowance that wasn’t costed into the same budget, so we spent a lot more than $27 million on this project.
We incorporated a heads-up display on the inside visor of the astronaut’s space helmet, so there are no sights or displays on the gun itself. You point the rifle normally and watch the HUD until the pipper gets on target, then take the shot. Since we were required to have complete redundancy, we arranged valve No. 4 so if you align the right side of that valve with the end of the muzzle you got a reasonably good sight. I guess if you buy the rifle today, you’ll have to use that method because I don’t think NASA will sell you an active helmet.
The extra stuff
You probably noticed all the tools coming out of the top of the receiver. They’re there because of some arguments we got into during development. Management kept asking us to add this and that feature to the gun, until it was completely unworkable. So our team leader decided to stifle them by building in a kit of special tools that astronauts would always have on hand if they had the rifle. They don’t detach from the receiver, though, so unless you’re weightless they’re of limited value. But just having them appear on our briefing slides stopped a lot of the random comments.
From reading this blog, I know that most of you value the best materials in an airgun. Well, we certainly put them into the LOOPH! Most of the gun is made from tool steel; and where synthetics are employed, we went with a dense Styrofoam to save weight. We were going to blue the metal parts, but because of the environment in which the gun will be used, we had to settle with vacuum-deposited platinum. I think it looks pretty snazzy.
You have to save money somewhere, so we decided to do it by not firing the rifle except during testing. The astronauts never got to shoot an actual round in the real gun. However, we were part of the mission training and simulation team; and for only $1.5 million plus software, we developed a training device that they could use. Individual shots on the trainer were less than a thousand dollars, which saved us a bundle in ammunition costs. Plus, we didn’t have to open a tin, so they were available to all the moon missions.
We never actually fired the gun during testing except one time to make sure it all worked. But I developed a simulation that we used to test with. The gun seems to be very destructive and should do well against any reasonable threat. Of course, it won’t stop Superman, but we feel confident that there isn’t a species of alien with his powers out there. If there is, too bad for all of us!
In the simulations, the gun was quite accurate. It could drill a Gray at 100 yards before he started warming up his temporal lobes to defend himself — not that we ever did that, of course. I guess it would put 5 rounds through a 5-inch circle at 100 yards.
The Apollo 13 astronauts had to leave their gun in the Command Module upon their return to Earth. Of the seven guns made, only six remain today. When the mission ended, we asked NASA management for permission to fire the guns a couple of times, but they felt it was too dangerous and declined. Besides, it was very expensive.
I learned a lot during this development. The most important thing was that there are very few problems that exotic materials and more money can’t solve. And, when you do encounter one of those unsolvable problems, just revise your goals to keep what is possible within your grasp. Do that and you’ll probably never go wrong.
Happy April first!