And we said no to buying solid rockets for that reason and for one other. There are all the same problems, even if I go to Morton Thiokol and buy them, but the major problem is, if I go to Morton Thiokol and say, "Gentlemen, I would like to buy ... please, and here is the money up front," we are confronted by several issues. One, they all use turbopumps, and four years ago there was no such thing as an industrial turbopump that was base-rated as the kind we needed. The turbopumps that were available represented the absolute cutting edge of the art. So we said, "Okay, not turbopumps." That left us with one very interesting possibility - the possibility that is being followed upright now by another private rocket venture called Pacific American. That possibility was a pressure-fed liquid fueled engine. Pressure-fed liquids were what were proposed many years ago for what was called the "big dumb booster," and pressure fed liquids may indeed work.

However, at that point, our third partner, Bevin McKinney, said hybrid motors. What is a hybrid motor, A hybrid motor is what it's name suggests. It is halfway between a liquid and a solid. That is, in a solid, you take a solid fuel and a solid oxidizer and mix them together, cast them into a chamber, ignite them and they burn end to end. In a liquid fueled rocket, you take a liquid fuel and a liquid oxidizer, and spray them into a combustion chamber and ignite and they burn very nicely.

A hybrid has one component solid and the other component liquid. Hybrids, as I said, were proposed in the 1930's. Normally, if you call something a hybrid, that means the fuel is solid and the oxidizer is liquid. If you call it a reverse hybrid, that means it has a solid oxidizer and liquid fuel. We were interested in classic hybrids.

If you can imagine a tube of rubber cast into a m,tal tube with a shower head on top, that is the combustion chamber of a hybrid rocket. What we cast into that chamber is rocket fuel. It is a rocket fuel that, since it has no oxidizer in it, I carry around in my briefcase and carry it on planes. They don't arrest me for being a terrorist and what that solid fuel happens to be is artificial rubber. It is hydroxyl-terminated polybutadiene with a few other things in it, which we refer to as the "3% secret herbs and spices."

The idea of a hybrid is very simple. The idea is that you have this tube of solid rocket fuel with no oxidizer in it. You carry the oxidizer in a separate tank, and there is a valve in between and a shower head at the top. You turn it on and you can ignite it in a number of different ways with a pyrophoric liquid or with various kinds of pyrotechnic devices, and it starts burning. It burns on the inside of the tube, and it burns outward until you turn it off. You turn it off by turning off the oxidizer. In this case, it is a wagon wheel grain. We don't have a board so I can't illustrate it, but if you look at it from the top down, it looks like the shape of a wagon wheel, with the rim and spokes being the fuel. Is it really a tube, The answer is no, it is not a tube; it is a very complex shape.

Hybrids have a number of advantages. One, they are safe to manufacture. We make this rocket fuel ourselves and make our engines ourselves in a 40,000 sq. foot plant in downtown Cambrio, California with lots of other businesses around it. When we fir came to town, the assistant county fire chief got up on a table and jumped up and down and yelled that we were going to kill everybody within three miles. And he meant it, but he realized pretty soon that we were telling the truth, that it is safe to make. It is also safe to transport. Our truck drivers who drive our engines back and forth to Edwards carry a letter from the Department of Transportation that sys, in effect, "Yes we know this is a rocket engine, and it is so safe we don't even regulate it." It is safe to operate. Number one, if you want to turn it off, you turn it off. Your turn off the oxygen and it stops burning. You saw that right here. That was a command shutdown, and you will see it in the other video, too. Another thing is that it can't explode.

When I went looking for insurance for a rocket company, and after I had been spun around and thrown out of a few insurance agencies a few times, I got on the phone and went to London and talked to Lloyds and said, "I have a rocket engine that doesn't explode." They said, "Yes, you probably have a bridge to sell us in Brooklyn, too."

The truth is, and you think about it for just a second, the reason that something explodes is when there is a fuel and an oxidizer in intimate contact. In the hybrid engine, the only place where the fuel and oxidizer come into intimate contact is when the fuel is vaporizing off the surface, because it is burning at the boundary layer where it encounters the oxygen, which is migrating in from the center of the port. Even if you take this and soak it in liquid oxygen under pressure for 48 hours, take a blasting cap and put it on it and take it out into a field and try to set it off and collect up all the pieces that are left, it doesn't blow up. Nothing goes off. There's no more energy release in that than there is by the blasting cap itself.

Incidentally, that is one of the things we had to do to prove to the Air Force that, in fact, this won't explode.

There is no way to intimately mix the fuel and the oxidizer. In a solid rocket, the fuel and the oxidizer are already intimately mixed. In a liquid rocket, you have go two liquids that go to vapor very easily and that is what all those booms were in "The Right Stuff." So, it is safe and it is reliable. United Technologies built a small hybrid demonstrator motor in the 1950's that they started 50,000 times. It had a reliability of around 99.9%. There is another hybrid motor that United Technologies also built,that powers a drone called the Firebolt that Top Gun guys shoot at. It's a supersonic drone. According to a chief scientist in the Air Force whom we contacted, there has never been a propulsion failure on that vehicle, and it has flown thousands of times. So, again, it is very safe and reliable.

It's also very low cost. The basic fuel, formulated and made up, costs about 1/10th what a solid rocket fuel costs. But even that barely begins to give you an appreciation for the inexpensive nature of the process, because about 50-75% of the cost of operating a rocket today is simply the enormous standing army of white-coated safety people following everything around. We don' t have to have those people. When one of our engines, like this engine that you saw, is on the pad, even when there is LOX loaded in the tank next to it, we can walk out onto the pad and walk around. Visitors come and walk out of the plan to the pad and touch the engine and all that sort of thing, because there is no explosive hazard.

In fact, we have what is called a quantity distance, TNT equivalent, of 0. That is an official number that you get which means how far back everybody has to stay when you bring your rocket, for example, onto Vandenberg Air Force Base. We have a quantity distance of 0. Safety, reliability, low cost.

Now for the matter of manufacturability. Unlike a solid rocket engine, it has very little sensitivity to cracks or defects in the fuel grain. Why is that, It's because there is no oxidizer. If there is a crack in a solid rocket motor, the burning can progress down the crack and increases the pressure, which increases the burning rate, which increases the pressure and goes boom. Here, if you have a crack in the fuel grain, there is no oxygen down there. There is no way for the flame front to progress down there. The flame front happily burns by it and never burns down the crack.

Furthermore, because the way that a hybrid works is very different from the way a solid rocket works, that is, the combustion takes place at the boundary layer and not at the surface of the propellant grain, hybrids tend to be self-stabilizing. With a solid rocket, if you put a little pulse into the motor and increase the pressure that way, you are likely to increase the temperature which increases the pressure, which increases the temperature, which causes it to go boom. Here, the boundary layer, if you pulse it, moves closer to the fuel which gives a smaller area for the fuel to evaporate from which reduces the amount of fuel that is being burned, which reduces the burning, and pressure. If you pulse a hybrid, it tends to damp out.

So, we chose hybrids because of manufacturability, overpressure-fed liquids. We would still have had the problems with two liquids that could go boom together. We believe that if you're going to build a commercial space transportation service, you need something that could be manufactured rapidly and inexpensively in and industrial environment. The key word here is "industrial." That was what we were going for and so we chose hybrid rocket engines, and the rest is history. I hope it will be on the 21st of July.

I would now like to take a minute to show a 6-7 minute video which gives you an idea of what we are doing and how we have done it. You will see several rocket motors being tested. Yu will notice that when they start up, they have a very ragged looking dirty flame. This is because of another particular advantage of hybrids and that is you can start them up at idle, nearly 0 lb thrust. With a solid fuel motor, you start it up and once it is going you better go, as in the shuttle or Delta.

A couple of quick comments here. As was noted in the video, another reason we chose hybrids is that they are environmentally clean. We thought that was important. The largest combustion product is water. The second largest combustion by-product is carbon dioxide. The third largest by-product, which is a pollutant, is carbon monoxide and the measured level downwin, under all the proper condition is approximately 1/35th of the allowable level of carbon monoxide.

I just want to say one more thing. One of the things that we did was to decide at the beginning we were not going to be able to build a whole series of rocket engines right away. We were going to have to start with a single module. We were then going to have to be able to take that module and, for example, fly it as we will fly it in July as a single module or put two more strap-ons here, which gives us a high-class sounding rocket, or with two strap-ons and an upper stage, which gives us a Scout-class small launch vehicle. We could put four more strap-ons on, for a total of 7 modules altogether.

Our first design for a Delta class orbital vehicle had 22 modules. The first stage had 12, the second, 6, and then 3 and 1, all around central liquid oxygen tanks. What we have done since is we have done a number of trades and decided that we are going to build a new motor module, a 500,000 lb. thrust module, and use the 70,000 lb thrust module as an upper stage. Again, you can build them up the same way as before.

In fact, our first orbital vehicle which we plan to fly next year is the 7D, referred to in the shop as the 7 Dwarves. What this is, is the 7 modules, 6 around the outside and one in the center, and a single liquid oxygen tank. The single LOX tank, because it is very light, actually goes all the way to orbit, with the payload bay on top. These seven engines are staged off4, 2, and 1. That's the modularity of the system.

Next installment: Questions and Answers

Read Part 8: After The Fall, Resurrection
Read Part 7: The Proof Of The Pudding: SET-1
Read Part 6: The Rocket
Read Part 5: Questions & Answers
Read Part 4: Propulsion
Read Part 3: Electronics
Read Part 2: In The Beginning
Read Part 1: Introduction