How SpaceShipOne Works

        Science | Spaceflight

The White Knight turbojet aircraft climbs over the Mojave desert with SpaceShipOne attached to its underbelly.  See more space exploration pictures.
Photo courtesy Scaled Composites, LLC

In the past, space travel has only been possible with the backing of well-funded, huge government space programs. But the creators of SpaceShipOne, the first non-government manned spacecraft, have set out to change that.

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The ship is already a success on one level -- on October 4th, 2004, it won the $10 million Ansari X Prize. The competition challenged independent designers to safely put three people into space twice in two weeks with a reusable spacecraft.

This prize wasn't the ultimate motivation for the development of SpaceShipOne, however. The spaceship's creators envision a world where space travel is a thriving commercial business catering to anyone who has the desire to venture to the stars.

While that may sound far-fetched, consider that Charles Lindbergh's historic 1927 solo flight from New York to Paris won the $25,000 Orteig Prize. And it was Lindbergh's successful flight that ushered in the modern airline industry. So, years from now, when space tourism is as common as a trip to Disney World, we may look back on SpaceShipOne as the undertaking that turned a page in history.

HowStuffWorks learned about SpaceShipOne from Matthew Gionta, chief engineer of the company that built it -- Scaled Composites. In this article, Matthew tells us how SpaceShipOne works and what it's like to fly in this spaceship. We'll also look at the details of the design, the propulsion system, and the privately funded space program that spawned it all.

How Does SpaceShipOne Work?

Pullout maneuver
Pullout maneuver
Image courtesy Scaled Composites, LLC

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.

Repositioning the craft for atmospheric re-entry
Repositioning the craft for atmospheric re-entry
Image courtesy Scaled Composites, LLC

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 -- 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.

Landing configuration
Landing configuration
Image courtesy Scaled Composites, LLC

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.

What's the Ride Like?

SpaceShipOne glides down for approach to the Mojave airport.
SpaceShipOne glides down for approach to the Mojave airport.
Photo courtesy Scaled Composites, LLC

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.

White Knight

The White Knight launch aircraft carries the spaceship (followed by Bob Scherer's Starship chase aircraft).
The White Knight launch aircraft carries the spaceship (followed by Bob Scherer's Starship chase aircraft).
Photo courtesy Scaled Composites, LLC

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.


SpaceShipOne sits on the ramp on its landing gear.
SpaceShipOne sits on the ramp on its landing gear.
Photo courtesy Scaled Composites, LLC

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.

Image courtesy Scaled Composites, LLC

According to SpaceShipOne: Riding a White Knight to Space:

SpaceShipOne ... is designed to reenter like a stable shuttlecock, then glide and land like an airplane. The wings, with an ultralow aspect ratio of 1.7, span 16.4 ft [~5 m]. Their size is based on the requirement to provide enough lift to rotate the vehicle into its ascent attitude after horizontal launch, and to permit conventional gliding approaches and landings. At the top of the climb, the rear part of the wing and the tailbooms -- still known collectively as the "feather" -- hinge upwards. As the spacecraft starts to reenter the atmosphere, the feather stabilizes it in a flat attitude with the slab-like wings at right angles to the airflow. This creates so much drag in relation to the vehicle's weight (without fuel) that peak heating is moderate. SpaceShipOne is constructed from conventional graphite-epoxy composite materials, with some limited use of high-temperature epoxies. Hotter sections are protected by a simple "trowel-on" ablative thermal protection layer. In the worst case envisaged by the test team, the fuselage may be damaged but the occupants will be unharmed.

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.

Image courtesy Scaled Composites, LLC

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

SpaceShipOne features:

  • Airborne launch
  • INS/GPS navigational & flight director
  • Rubber-nitrous hybrid rocket propulsion system
  • Graphite/epoxy primary structure
  • Three-place "sea level, shirt sleeve" cabin environment
  • Cabin nose removal for emergency egress; use of side plug door for normal entry and exit
  • Dual-pane windows, dual seals on doors and controls
  • New, low-maintenance thermal protection system
  • "Feather" atmospheric entry Features list generated by Scaled Composites LLC

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


Workers prepare the spaceship for its historic flight. The large rocket motor will produce 17,000 lb of thrust.
Workers prepare the spaceship for its historic flight. The large rocket motor will produce 17,000 lb of thrust.
Photo courtesy Scaled Composites, LLC

Gionta explains:

There wasn't a rocket motor just off the shelf that we could buy and install onto our spaceship. We had to develop our own rocket motor from scratch. It was a daunting task for a company that's never done rockets before. And we got some help from outside vendors, but we really came up with the configuration ourselves and did a lot of the work on the rocket motor ourselves.

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

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:

We developed our own avionics system and display unit for navigating straight up. I don't believe there are any spaceships that are hand-flown. This one is hand-flown by a pilot looking at a display like [an airplane] pilot would. That's kind of unique. The avionics are very critical, and it also needs to be very precise for the pilot to do what he wants to do, and do it well.

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


SpaceShipOne undergoes preflight inspection before its historic June space flight.
SpaceShipOne undergoes preflight inspection before its historic June space flight.
Photo courtesy Scaled Composites, LLC

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:

[There are] all kinds of areas that we've never delved into before. Supersonic flight -- we've never done a supersonic airplane before. As a matter of fact, I don't think any small company's ever done a supersonic airplane before. So, I think we're the first to bite off all the transonic aerodynamics with such a small group of people.

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:

Our whole goal was to prove that sub-orbital space tourism could be done very economically, and in so doing we always had to opt towards the least sophisticated but most robust solution for any problem that we were up against -- and always try to keep the cost down. So that was a biggie.

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:

When we're out in space, all you need to do is release a puff of air in a direction to give you a reaction force to push you the other way. That's pretty much what [a reaction control system] is. We have high-pressure air stored in bottles on the ship, and we release a little blast of air for about one second on, say, the right wing tip pointing up. And that is enough when you're in space to push that wingtip down. So it effectively rolls the aircraft, and that's your controls when you're out in space. It's the same thing a spaceship or the shuttle uses, except on a much, much smaller scale and much more economical. So we had to develop that. We created a fixed-based, full-mission simulation of the craft so we could size our reaction control system.

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

... air launching another vehicle -- that was another something we hadn't done before ... Other craft B-52s drop vehicles pretty regularly, but it was something new to us so that was a bit of a challenge, too. And it worked well, and so far we've just gotten pretty darn lucky, or, I don't know, maybe we know what we're doing. Who knows?

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

Tier One

Paul Allen and Burt Rutan discuss the results of a recent SpaceShipOne test flight.
Paul Allen and Burt Rutan discuss the results of a recent SpaceShipOne test flight.
Photo courtesy Scaled Composites, LLC

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:

Every time SpaceShipOne flies, we demonstrate that relatively modest amounts of private funding can significantly increase the boundaries of commercial space technology. Burt Rutan and his team at Scaled Composites have accomplished amazing things by conducting the first mission of this kind without any government backing.

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.

Shown just before touchdown at 90 mph (145 kph), SpaceShipOne returns to the runway.
Shown just before touchdown at 90 mph (145 kph), SpaceShipOne returns to the runway.
Photo courtesy Scaled Composites, LLC

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

Our concept design work began in 1996, and some preliminary development began in 1999. Our full development program began in secrecy in April 2001. This extensive experimental research effort is a complete manned space program. It consists of all new hardware including a launch aircraft [the White Knight], a three-place spaceship [the SpaceShipOne], a hybrid rocket propulsion system, a mobile propulsion test facility, a flight simulator, an inertial-nav flight director, a mobile mission control center, all spacecraft systems, a pilot training program and a complete flight test program. All our hardware components are full-scale, full space-capable performance, not mockups or interim vehicles.

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