The Legend of The JATO-Powered Rocket Car

WHY THE ROCKET CAR DOESN’T WORK

 

One thing I want to make clear from the start is that I’m not pissing on the Rocket Car legend purely as an academic exercise. When my friends and I set out to build the vehicle we test-fired in the spring of 1978, a real-life jet-powered, road-traveling car was exactly what we had in mind. Craig Breedlove was busy breaking land speed records in the Spirit of America, Evel Knievel had graduated from “biker” to “payload” while attempting to jump the Snake River Canyon a few years earlier, and rocket-powered vehicles were a pretty popular notion. Unfortunately, machines like this require a lot of time and money and engineering skill to build and operate.

My friends and I had none of these things.

In 1978, I was 22 years old and still living with my parents. My father owned a scrapyard, twenty-two acres of barren desert scrub ideally suited to having junk thrown on it. The yard was a salvage smorgasbord, covered with everything from dead water heaters to junked airplane cockpits. And since we lived near a major Army storage facility, a lot of the scrap my father bought and sold came from government auctions. To be brutally honest, the main yard looked like a cross between Sanford & Sons and Apocalypse Now. My father would go to the auctions held at the post from time to time, bid on pre-marked lots of God only knew what, then send me out the next day with the big flatbed to collect the latest pile of junk he’d bought. Plenty of people who went to these auctions ended up with nothing more than tons of unusable junk that was worth less than they paid for it, but my Dad always seemed to find the lots that contained valuable stuff. He also knew plenty of people who owned military surplus stores, and usually had some idea of what was in demand and what wasn’t. But since the nearby Army base was a huge storage depot, the auctions weren’t the sort of affairs that the average man-off-the-street would be interested in. The lots for sale were usually measured by the ton, and if a lot seemed to have a few items you were interested in, you had to buy the whole mess. Because of this, my Dad ended up with an amazing amount of unusable military surplus, things like gas-masks and vehicle parts that were worthless in the civilian world.

But from time to time, we’d get weapons, too.

No, he never bought a pile of crap and ended up with a crate full of M-16’s or a Shrike missile, the military was usually careful enough to keep that from happening. But from time to time we did end up with stuff we weren’t supposed to have. One day I opened a crate marked “heater assembly” and found it full of smoke grenades. My Dad found a steel ammo box full of blank M-60 rounds once. And even though these instances were a rarity, the Army had a very strict policy toward scrap dealers who found such things: You had to give them back. No two ways about it. Before even being allowed to place a bid, dealers at an auction were required to sign several forms, one of which stated that they’d return any “explosive, ordnance, fuse, detonator, or other chemically viable part or assembly of a weapons system.” I remember that paragraph well, since it’s the only part of the Army red tape that ever directly pertained to me. The penalties for non-compliance outlined at the end of the paragraph sounded pretty scary (five-figure fines, possible imprisonment, etc), and were enough to make my Dad return the crate of smoke grenades, but not the blank ammo. These were judged to be too trivial to warrant a drive to the base, and my Dad ended up keeping them draped over a file cabinet in his office, as a decoration.

Of course I’m telling you this because it’s how I managed to get hold of the JATO bottle we used for our rocket car. Actually there were four of them, each in a long, hay-filled crate with “BARREL ASSEMBLY” stenciled on the side. One day I went out to the base to pick up a load of junk my Dad had bought at the auction, and while we were going through the stuff back at the yard, I spotted the crates and took a look. And even though I didn’t know what the hell it was at first glance, I knew it wasn’t a barrel for anything. The JATO bottle was a round metal cylinder about four feet long, and less than a foot in diameter. At first I thought it was a gas cylinder of some sort, but written on the side in red paint were the words “M-23 JET ASSIST UNIT”. And rather than the sort of valve assembly you’d see on a gas cylinder, the end of the bottle had an inverted funnel shape to it, with a rubber plug at the lowest point. It was obviously a rocket of some sort. And judging from the weight (it took two people to even budge the things) they were still full of something.

Once I figured out what they were, I decided I had to call Jimmy.

Jimmy and I met in the third grade (or thereabouts), and were best friends for most of our growing-up. His family lived just down the street, and his father ran an auto body shop in town. On more than one occasion Jimmy’s Dad and my own traded parts or services, and our families were pretty close. But while I went to work for my father after graduating high school, Jimmy went to college to study mechanical engineering. He had a natural talent for figuring out things in the physical world, but was never much good at putting them into practice. He could design and visualize, but when it came to hands-on applications, he just wasn’t very talented.

Nevertheless, he was the first person I showed the JATO bottles to.

Actually, I didn’t show them to anyone right away. The campus where Jimmy took classes was almost 150 miles away, so he spent his weekdays in a rented room and only came home on the weekends. I found the JATO’s on a Wednesday, which meant I had three days before I could tell Jimmy about them. More than enough time for me to cook up the idea of the Rocket Car. As a matter of fact, as soon as I realized what that dull metal cylinder represented, I thought about attaching it to a car and taking a jet-propelled ride. I spent the rest of Wednesday, Thursday and Friday planning how it could be done. The principle certainly seemed simple enough. Nail the rocket onto one of the junkers in my Dad’s field, point it down a straight stretch of road, and light the mother up. Sure there’d be minor details to be worked out, but the basic idea was fairly straightforward.

All I can say is thank God I consulted with Jimmy before actually doing anything. If it wasn’t for his intervention, I’d have probably ended up a damp spot on a highway somewhere.

Jimmy came over to the house on Saturday morning, we drove to the yard, and I showed him the rocket. He immediately knew what it was, or at least what it seemed to be. A solid fuel rocket, the kind they’d used in Vietnam to give cargo planes a kick in the ass when they needed to take off from short runways. Very simple, very straightforward. Also very dangerous. I described the idea of the Rocket Car to him, and at first he was pretty enthusiastic. But after thinking the whole thing over for awhile, he not only lost his enthusiasm, but made me promise I wouldn’t actually do anything with the JATO until he had time to check a few things out. I agreed, mainly because I knew I’d need Jimmy’s help if I was ever going to make the Rocket Car work.

We talked about design possibilities for the rest of the weekend, and when Jimmy went back to campus, I stashed the JATO’s in the back of a wasted milk truck rusting in the field. When Jimmy came back the following weekend, we sat down at his kitchen table and he explained precisely why the rocket car wouldn’t work.

It was a sobering (and depressing) lecture.

The main problem was control. Jimmy explained that the JATO bottle would produce something like 2,500 pounds of thrust (albeit for a very short time), which sounded like more than enough to ensure a fun ride. Unfortunately, this huge amount of thrust would not only be unstoppable once it was started, it would probably have to be applied to a point on the car that wasn’t designed to handle such a such a force. Under normal circumstances, a car gets its forward thrust from the back axle, by way of tires against the pavement. Which means that a normal car will never exceed a certain amount of thrust due to the fact that the tires have to touch the pavement to move the car forward. Jimmy described the whole thing using top-fuel dragsters as an example. When the driver hits the gas, the back end of the car tries to lift into the air due to the sudden force applied to the rear axle. But as soon as the ass end starts to lift, the tires lose traction, and the thrust decreases. The back end drops, thrust is restored, and the process starts all over again. So a car of a given weight using driven wheels can only get so much forward thrust. The limiting factors are the weight, the distribution of the weight, size of the tires, and torque applied to the wheels. The fact that a car uses driven wheels creates a self-damping system that ensures the wheels will stay on the ground (at least most of the time). The only reason dragsters and funny cars pop wheelies is that they use oversized tires that screw up the relationship between torque and traction. Unfortunately, a rocket car has no such restraints. A massive amount of thrust is suddenly being applied to a point on the car that wasn’t designed to handle it, and there’s no telling what happens next. Maybe the front end lifts off the ground. Maybe the rear. Maybe the ass end would slew around sideways. The only thing that was certain was that the car would not go in a straight line, and would continue not going in a straight line at a very high rate of speed.

Naturally I asked how Craig Breedlove managed to drive the Spirit of America at 600+ miles an hour, but I knew the answer before I even spit the question out. He hired a team of aerospace engineers and rocket scientists to design a car that was built to have a jet engine sticking out its ass.

After hearing this, Jimmy didn’t even have to outline the rest of the reasons why my idea wouldn’t work, but he did anyway. There was also the fact that store-bought tires couldn’t handle the sort of acceleration a rocket would provide, which was why all land-speed record cars used custom-made, solid-rubber tires. Simply spinning a regular tire at rocket-car speeds would probably create enough centrifugal force to tear it right off the rim. And if that wasn’t enough, there was the problem of stopping the thing once it got rolling. And structural stress. And so on and so on.

By this time I’d pretty much decided that the whole idea was stupid and suicidal, which was why I was amazed when Jimmy proceeded to tell me exactly how the rocket car could work.

Next: “Train Of Thought”