How SpaceShipOne Works

Let's start at the heart of the matter: How does the craft work? Read as Matthew Gionta describes what will happen on this historic flight step by step.

HSW: So, how does SpaceShipOne work?

Matthew Gionta: SpaceShipOne is slung underneath the belly of the White Knight aircraft, two aircraft that we've developed from scratch here. The White Knight is a turbofan-powered airplane that carries the SpaceShipOne up to 45 to 50,000 feet so that we can start our space flight from a relatively high position in the atmosphere where the air's already pretty thin. We're through about 85 percent of the Earth's atmosphere already when we go down 45,000 feet. The air is very rarified up at that altitude so it's a great place to start from. From there we drop the spaceship off of the White Knight and it glides for 10 seconds while the pilot sets up, gets the aircraft all trimmed up, ready for the rocket boost and he throws the switch, and the hybrid rocket motor in the SpaceShipOne accelerates the pilot at about two to three times normal gravity. It accelerates at about twice normal gravity forward and the pilot immediately commences a pullout maneuver to approximately vertical -- he's going pretty much straight up.

And the ship continues to accelerate going straight out for a little over a minute. We don't give out the exact numbers -- then someone can reverse engineer.

So we go about one minute straight up and we burn out about 150,000 feet, roughly. The motor stops burning at that point, but now the ship is moving over 2,000 miles per hour, straight out, and so it coasts. From there it coasts up another 150,000 feet roughly, up until it reaches apogee [the point at which SpaceShipOne is farthest from Earth]. Just before it reaches apogee, the pilot flips another switch that drives some pneumatic actuators -- it takes the tail of the aircraft and the back half of the wing and kinda [makes them]... like a jack-knife is probably the way to think of it.

The aircraft is jack-knifed, and that is positioning the craft, or reconfiguring the craft, for the atmospheric re-entry that it's about to experience. And so you've still got that while he's heading up, and so he starts and that takes about 15 seconds for that feather, as we'll call it, the back half of the craft to go up about 65 degrees. And then he goes through apogee all the while he's experiencing pretty close to zero g -- it's real close to zero g [weightlessness] -- from after burnout all the way through apogee.

And then he starts to fall back in, and he falls, he falls along the same parabolic or ballistic trajectory that he would if he were just a rock. If someone threw a rock up there, it'd be the same kind of parabola. He's on a ballistic trajectory and can't do much about it. If the craft starts to fall back into the atmosphere, picking up speed, it reaches just about zero speed at the top and picks up more and more speed. And as it starts falling into the thicker and thicker air, this jack-knife craft presents its whole belly, just like a belly flop straight onto the air flow to give itself a large cross-sectional area that it's trying to drive through the air to decelerate it.

And that slows it down. The pilot experiences between about 5 or 6 g's of deceleration as he comes back into the atmosphere. And he rides that down to about 50,000 feet or so, maybe 60,000 feet, where he flips the switch to turn it back into a normal airplane with a tail and trail it where it's supposed to be. And he dives out of that maneuver and starts flying again like an airplane, like a glider. He is a glider at that point.

And then he glides from there another... about 10 to 15 minutes back to the airport from which we took off at, here in Mojave.

In the next section, we ask Matthew what its like to ride on SpaceShipOne.

SpaceShipOne is designed carry a pilot and two passengers into sub-orbital space. In our conversation with Matthew Gionta, we asked what a passenger could expect from a ride on SpaceShipOne.

HSW: Could you explain to our readers what it would be like to ride in SpaceShipOne?

M. GIONTA: It's the wildest roller coaster you've ever ridden on, and I may be stealing a quote from my boss [Burt Rutan], but I think he's got a good characterization of it there. If I were to describe the acceleration going up ... you've got gravity pulling down on you. There's 1 g of acceleration, but you're actually moving vertically at two or more g's. The pilot feels about 3 g's -- eyeballs in, as we call it; your back is feeling three times the weight of your whole body -- and so, pretty strong acceleration going up. When the motor shuts off, now there's drag on the vehicle but no thrust, so you fly forward in your seat belts until they're holding you out there in space; otherwise you'd be flying through the front window and out the front of the craft. So you're suspended in your seatbelts at that point, and that's for maybe 5 or so seconds, and then you kinda fall down into the seat. And at that point, the g is continually decreasing until it's about zero g, and you've got about 4 minutes of weightlessness as you go over the top, then coming back, and while you're up there the view is spectacular.

Some of the views you've seen of Earth from low-Earth orbit satellites or even from the space shuttle at some of its lowest altitudes are essentially the exact same view you get out of the window of this craft. And we've got some spectacular footage on our Web site...

... [So you've] got a few minutes of weightless before you start coming back in the atmosphere. It's a loud, rumbling, shaking, lots of g's, peaking at maybe 6 g's. And it gets pretty hard to even stay conscious at that point, but you can do it if you're in pretty good shape and you've trained for it. And then, you fly out of that as a glider, and it's just a peaceful glider ride. You've got another 15 minutes or so to sightsee as you come back in, realizing you just went to space. You earned your astronaut wings ... That's the altitude to qualify as an astronaut.

HSW: Wow.

M. GIONTA: See, it's pretty cool. We think there are a lot of wealthy people who would be willing to pay the amount of money we think it's going to take, to go take a ride.

HSW: And then the idea of course, eventually, is to make this more and more cost effective until...

M. GIONTA: Yeah, who knows where this extends? Maybe it extends to orbital space tourism, right? I think that's a logical progression. It'd be kinda cool to take a little vacation in space, don't you think?

In the next section, we'll look at the design of the White Knight craft that assists SpaceShipOne on its journey.

As we learned from Matthew, SpaceShipOne can't make a journey to the stars alone. It requires the help of a carrier ship called the White Knight. One of the greatest expenses and dangers in space travel comes from launching spacecraft from the ground. Just the cost of the fuel needed for a ground launch is extraordinary. In order to streamline the process, SpaceShipOne launches from the belly of White Knight at an altitude of around 50,000 ft.

The White Knight, which made its debut in April 2003, is a high-altitude, twin turbojet research plane. Its primary job is to serve as an aerial platform to launch SpaceShipOne into space.

White Knight takes off like a plane from a normal airstrip, with SpaceShipOne attached to its belly. The two ships fly together under White Knight's power to a predetermined altitude. Then White Knight releases SpaceShipOne and drifts away. Once clear of White Knight, SpaceShipOne begins its journey to sub-orbital space.

In the interest of efficiency, White Knight also serves a second, very important function. The White Knight is designed with the exact same cockpit, avionics, electronic control system, pneumatics, trim servos, data system, and electrical system as SpaceShipOne. That makes White Knight perfect for training pilots to fly SpaceShipOne.

To add additional realism to SpaceShipOne pilot training, the White Knight was designed with a high thrust-to-weight ratio and powerful speed brakes. These features help to simulate space flight maneuvers.

As an airplane, White Knight is a remarkable craft all on its own. According to Scaled Composites, White Knight's unique design also makes it well suited for "reconnaissance, surveillance, atmospheric research, data relay, telecommunications, imaging and booster launch for micro-satellites."

In the next section, we'll take a look at the SpaceShipOne craft.

While White Knight is an impressive aircraft, there is no doubt who is the star of the show: SpaceShipOne.

SpaceShipOne is described by Scaled Composites as a "three-place, high-altitude research rocket, designed for sub-orbital flights to 100 km altitude." Perhaps one of the most amazing things about SpaceShipOne is the fact that it transforms into three different configurations during the course of its flight. These configurations put SpaceShipOne in the ideal shape for boost, entry and landing. (See the previous section How Does SpaceShipOne Work? for images of all three configurations.) While it is technically a spaceship, it spends most of its time in the Earth's atmosphere during the course of its flight. The one configuration that stands out the most is the "feather" configuration.

According to SpaceShipOne: Riding a White Knight to Space:

SpaceShipOne launches vertically into space from high in the atmosphere. Once it reaches the top of the arc created by its rocket boost, it loses momentum and falls back to Earth. To slow its descent, SpaceShipOne transforms into a configuration that exposes the greatest surface area to the air flow. This creates tremendous drag and slows the ship down as it falls.

That is just the tip of the iceberg as far as innovation built into SpaceShipOne.

SpaceShipOne features:

In the next section, we'll discuss the unique rocket motor that throws SpaceShipOne into space.

Gionta explains:

SpaceShipOne uses what Scaled calls a hybrid motor. This is because the motor has combined elements from both solid and liquid rocket motors (see How Rocket Engines Work). This makes for a unique motor capable of accelerating SpaceShipOne to twice the speed of sound. But the fuel it burns to do this is even more interesting.

All types of rocket fuel are made up of two components: the fuel and the oxidizer. By adding a large burst of heat to the fuel, then introducing the oxidizer, you get the sustained explosive result that will propel a craft into space. In solid rocket fuel, the oxidizer is embedded into the fuel; in a liquid system the two components are stored separately on the craft and combined during ignition. The problem with this latter system is that traditional fuels and oxidizers are expensive and dangerous to store. To cut down on both cost and risk, SpaceShipOne is propelled by a mixture of hydroxy-terminated polybutadiene (tire rubber) and nitrous oxide (laughing gas). The rubber acts as the fuel and the laughing gas as the oxidizer.

The inherent properties of laughing gas help save a few more dollars on the project. Nitrous oxide self-pressurizes at room temperature. This makes it unnecessary to outfit SpaceShipOne with a complicated system of pumps and plumbing to combine the oxidizer with the fuel during flight.

In the next section, we will get inside SpaceShipOne.

Inside SpaceShipOne is a small cockpit, 60 inches (152 cm) in diameter, that you enter through the nose of the ship. The cockpit is an air-tight pressure vessel. The pressurized cockpit creates a pressure differential between the cockpit and the near vacuum of sub-orbital space. This internal pressure pushing out on the structure of the craft allows the structure to endure the large forces acting on it during reentry.

The cockpit is outfitted with dual seals, and the whole structure is surrounded by a second space-worthy shell. Each of SpaceShipOne's many windows are special double-paned glass, and each pane alone can withstand the pressure and force of flight. This doubling up ensures that if either window were to crack, the passengers would still be safe.

The air inside the cockpit is made breathable by a three-part system. Breathable air is added at a constant rate by oxygen bottles. The exhaled carbon dioxide is removed from the cabin by an absorber system, and humidity is controlled by an additional absorber created to remove water vapor from the air. During the entire flight, the cockpit remains comfortable, cool and dry.

This whole system creates what Scaled calls a "shirt-sleeve environment." Passengers don't need to wear space suits inside SpaceShipOne thanks to the design of its cockpit.

To discuss SpaceShipOne's unique controls, we turn to Chief Engineer Matthew Gionta:

In the next section, we will discuss some of the challenges of creating SpaceShipOne.

Creating a totally new kind of spacecraft from the ground up comes with its own set of challenges. Chief Engineer Gionta delves into some of the hurdles the Scaled team faced when creating SpaceShipOne.

"Lots of technical challenges," Gionta says to sum up the experience. He continues:

The design of a craft capable of traveling at faster than the speed of sound has unique characteristics and requirements. The designers have to pay special attention to performance, aerodynamics, load characteristics, stability and control of a ship that is meant to travel at both sonic and supersonic speeds.

The equipment needed to create and test such a craft isn't exactly an off-the-shelf technology. And that equipment came at no small price. Gionta explains:

In many cases the Scaled team had to create the tools and features needed to make SpaceShipOne work. As an example, Gionta explained how the reinvented reaction control system on SpaceShipOne works:

Additional challenges came in the form of air launching a spaceship:

In the next section, we'll look at the privately funded space program that is producing SpaceShipOne: Tier One.

Scaled Composites CEO Burt Rutan and Microsoft co-founder Paul G. Allen are spearheading the effort to prove that safe, economical, commercial space travel is possible. This effort has taken shape in the form of the privately funded, fledgling space program known as Tier One.

Rutan is known for many accomplishments in the field of aeronautical engineering. Among them is his design of the aircraft Voyager. Voyager was the first plane to fly around the Earth without refueling. As the team leader, Rutan has committed himself to proving that Tier One is a feasible space program by building a ship that can carry people into sub-orbital space. Allen is committed to providing the funds, resources and support needed to get the job done. Together, the two have become the face of the drive for commercial space travel.

Allen's belief in the project and those working on it is evident:

Rutan and his Scaled Composites team are building this space program from scratch. In just a few years and with fewer than 30 people, the Tier One program has turned out some of the most innovative designs in the industry.

Burt Rutan had this to say about the history and direction of Tier One:

For more information on SpaceShipOne and other spacecraft, check out the links on the next page.