The largest rocket on the planet is about to carry NASA's dreams into a highly inclined orbit around the Earth. Exploration Test Flight-1, the first uncrewed full-system test flight for the new Orion spacecraft is December 4th. Here's what it is, why it's awesome, and how it's the first step in NASA's Next Giant Leap.

Orion mounted on a Delta IV Heavy ready for its test flight on December 4, 2014. Image credit: NASA/Radislav Sinyak

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Orion is the crew exploration vehicle being developed by NASA for deep space missions beyond Earth orbit. The basic design is familiar from other space projects, but super-sized and with more sophisticated technology than anything that came before. In the past few months, we've been tracking as it was assembled and rolled out to the launch pad in preparation for its December 4th test flight. As we await its epic trial by fire during Exploration Test Flight - 1 (ETF-1), it's time to run down what this spacecraft is, how it works, and why it has NASA dreaming of incredible futures.

Like all NASA projects, Orion's mission has been blown by the budgetary winds. It was originally announced as the Crew Exploration Vehicle back in 2004 by President Bush in the wake of the explosion of space shuttle Columbia. Intended for cargo and crew service the International Space Station along with a return-to-the-moon mission, it superseded the orbital space plane concept that had previously been under development. Since then, the project focus has switched. While it should technically still be able to perform emergency crew transport services to the International Space Station if every other option fails, the focus now is for deep space projects beyond the Earth-moon system.

The spacecraft is currently composed of the crew module, service module, launch abort system, and parachutes. By itself, it should be able to support up to six astronauts for just over twenty-one days.

For future longer-duration deep space missions, it will be mated to a larger complex that has yet to be designed. In this quiescent state where life support is provided by the yet-to-be-built module, it should be capable of supporting astronauts on a mission up to six months in duration, the length of a typical stay on the International Space Station.

To accommodate technology improvements over the development and use lifespan of the spacecraft, Orion is designed so that the life support, propulsion, thermal protection, and avionics systems are upgradable.

Launching: The World's Most Powerful Rocket, and a Mini-Rocket Just In Case

Eventually, Orion will be launched from the biggest rocket ever built, the Space Launch System (SLS). It's not done yet, so for now, Orion is hitching a ride into space on United Launch Alliance's Delta IV Heavy rocket. As the Delta IV is the most powerful rocket currently in production with just the main engine producing over 700,000 pounds of thrust, Orion is still taking advantage of rocket-power superlatives even for the earliest test flights.

The Delta IV Heavy blasting off. Image credit: ULA

The Delta IV Heavy is a massive workhorse of a rocket. It also has an unnerving tendency to catch on fire during launch, but in a purposeful, "No, we meant to do that" way. This is because a bit of liquid hydrogen leaks out during the launch sequence, catching fire during ignition. The fires can be intense enough to even leave the booster cores smouldering and charred, further enhancing the feelings of impending doom.

Orion's crew module carried to safety by the Launch Abort System during a 2010 test. after Image credit: U.S. Army's White Sands Missile Range

To increase safety during launch, Orion marks the return of a launch escape system like those seen during the Mercury and Apollo missions. If something goes horribly wrong in the first few moments of flight, the Launch Abort System will activate to carry the crew module and its squishy astronauts away from imminent catastrophe at transonic speeds. (Although in this first uncrewed test flight, no squishy astronauts will be on-board in need of a rescue.) Built by Orbital Sciences, the Launch Abort System consists of three motors: a launch abort motor, an attitude control motor, and a jettison motor.

The launch abort motor is a solid rocket with more thrust than the Atlas 109D that carried John Glen around the Earth for the first American crewed orbital spaceflight.

Isolated abort motor test. Image credit: NASA

The solid rocket motor is built by Alliant Techsystems, and is the powerhouse of the Launch Abort System. In the worst-case scenario, it can activate within milliseconds to exert up to 400,000 pounds of thrust, carrying the crew module free of impending doom. This is enough to carry the rig to an altitude of approximately one mile, flinging astronauts to safety.

The attitude control motor, also manufactured by Alliant Techsystems, is a solid-propellent gas generator used to steer the system. Eight vents equally-spaced around the motor combine to exert up to 7,000 pounds of steering force. It can be used to steer the abort system in any direction necessary to direct the crew module free of any exploding wreckage, and position it for a safe landing.

Launch abort system tests. Image credit: NASA

Aerojet Rocketdyne's jettison motor is the one component that will be used in successful launches. If all goes well, it will fire to pull the Launch Abort System away from the rest of the rocket. This is a necessary step not just to shed excess weight, but because otherwise the Launch Abort System fully blocks the parachutes necessary to slow Orion down before splashdown.

The entire Launch Abort System was tested together in 2010 at White Sands Missile Range in New Mexico. For Exploration Test Flight - 1, only the jettison motor will be activating as part of the tests to prove that each of the component systems function as an integrated spacecraft. The entire Launch Abort System won't be tested together again until Ascent Abort - 2, when it will be mounted on an Orion mock-up and launched by the first stage of a Peacekeeper missile at Cape Canaveral. This test will take it up to Mach 1, reaching the aerodynamic limits under which it is expected to perform. This will be the final test of all three motors before the system is used on human-crewed test flights.

The Shortstack Spacecraft: Crew and Service Modules

The core of the Orion spacecraft is a crew and a service module. The crew module is where astronauts will hide (although this first test flight will be uncrewed), and the service module carries all the essential bits that make this a spacecraft and not a tin can in space. Both modules are constructed of an aluminum-lithium alloy, the same material used for the external tank for the space shuttles, the Delta IV rocket, and the Atlas V rocket. Reading through the tech specs for these modules is a mix of history lesson and affirmation that science and technology builds on what came before: so much of the Orion spacecraft is an echo of other projects, but new, improved, and tweaked to be bigger and better than the originals.

Short stack of the crew module, service module, and a spacecraft adapter to mount the stack onto its booster rocket. Image credit: NASA/Daniel Casper

Lockheed Martin's Crew Module: A Super-Sized Apollo Capsule

While this first test flight will be uncrewed, humans will eventually be crowded into the crew module. The crew module is a cone-shaped nub that is visually extremely similar to the Apollo capsules from the moon missions. The crew module was built by Lockheed Martin, and borrows significantly from earlier projects.

It's about 5 meters diameter, making 50% larger by volume than Apollo. At 2.5 times the habitable space of Apollo, it will be capable of carrying 4 to 6 astronauts of a much wider range of heights than accommodated by modern spacecraft, and is the only part of Orion intended to return to Earth. The module will carry crew, research instruments, and any consumables for the duration of the mission. Unlike Apollo and its notorious plastic baggies, it will feature a better waste management system with a camping-style toilet and relief tube similar to systems used on Skylab, Mir, Soyuz, and the International Space Station.

Orion crew module under construction. The isogrid gives the structure strength. Image credit: NASA

Along with the Launch Abort System, astronaut safety is also increased by fitting the crew module with a fibreglass Boost Protective Cover to increase aerodynamics for the first 2.5 minutes of flight. Between these systems, NASA is claiming that Orion will be ten times safer during launch than the space shuttles ever were.

The module will be controlled by a glass cockpit design derived from Boeing's Dreamliners. This means the control system will be electronic and digital displays on LCD screens, not analog dials or gauges.

Orion will use a glass cockpit of electronic and digital displays. Image credit: NASA

This allows for greater automation, accuracy, and integration between controls and readouts than traditional systems. It also makes the readouts easier to read under stress while reducing the number of mechanical parts that can break and cause false readings. Orion's glass cockpit can even include feedback loops and self-checks, automatically alerting pilots of impending problems before they're an emergency.

The module has a docking port, so will also be where the spacecraft will attach to other craft in orbit. Unlike the space shuttle's fully-manual docking, Orion's crew module will incorporate automated docking akin to Russia's Progress spacecraft, and the European Space Agency's ATV cargo tug, with an option for emergency crew-override.

The thermal protection system consists of a heat shield for the areas that will bare the brunt of atmospheric friction during reentry, and a thermal blanket to coat the rest of the spacecraft. The ablator heat shield is the next generation of AVCOAT used on Apollo, a honeycomb of silica fibres and resin updated for modern environmental codes.

Apollo (left) and Orion (right) ablator heat shield material, before (top) and after (bottom) char tests. Image credit: NASA

Anywhere that isn't subject to critical heating will use a Nomex thermal blanket. This is exactly the same way the thermal blanket was used on the space shuttles around places like the bay doors, fuselage, and upper wings. It's also been field-tested by protecting the Galileo spacecraft and the Huygens probe during deep space missions.

Assembling Orion's heat shield. Image credit: NASA

Originally planned to return to Earth on land swaddled in airbags, the crew module was swapped over to splashdowns as a weight-saving design change. This had a carry-on effect of meaning that the crew module couldn't use a new green fuel, but instead would need to rely on hypergolic fuels that will break down in salt water in the event of a spill. With a bit of luck, the crew module will be semi-reusable: each module should make it through ten missions before being retired.

European Space Agency's Service Module: An Enhanced Automated Transfer Vehicle

The service module is a cylindrical tube holding all the dull-but-important things: the propulsion systems and expendable supplies. "Expendable supplies" is the nicely oblique way of referring to something utterly essential for human spaceflight: oxygen and water. Built by the European Space Agency, the design borrows heavily from the now-retired Automated Transfer Vehicle (ATV) cargo modules.

The in-flight propulsion system is bi-propellant rocket engine made by Aerojet Rocketdyne capable of generating 7,500 pounds of thrust. The service module will also borrow from other modern spacecraft, wearing a pair of deployable solar panel wings. This cuts down on the need to pack in heavy, unreliable fuel cells, further streamlining Orion to be as light as safely and functionally possible.

The service module also has an unpressurized cargo space. It will be enough to bring bits and pieces for astronauts to actually get some science done whenever they get to where they're going.

Landing: Heat Shields, Parachutes, and Splash Down

This first test flight is going way beyond our regular jaunts to Low Earth Orbit, so Orion will be coming back to Earth at nearly 80% of the speed it would reach on the return from a lunar-captured asteroid mission. Because Earth has such a delightfully thick atmosphere, using atmospheric friction and a sturdy heat shield will be enough to drop the speed from truly outrageous to merely unreasonable. After that, it's up to a system of parachutes to further slow the spacecraft to something a bit less life-threatening so it can splash, not crash, into the Pacific Ocean.

Parachute test with a model of the Orion crew module dropped in the skies above Arizona. Image credit: NASA/Rad Sinyak

After atmospheric friction drops Orion's velocity to a reasonably outrageous number, parachutes will deploy to slow the crew module even further. The parachute system for Orion isn't just one parachute: it's a whole series of parachutes set to deploy is a staggered pattern to slow the craft.

Quite a few parachute tests have taken place over the past few years. Engineers have deliberately screwed with the deployment schedule to see how badly things would fail, increased the maximum pressure the spacecraft could possibly exert, and otherwise torment the thin, strong sheets. Sometimes the tests went well and the parachutes still managed to slow the craft before it crashed into the Arizona desert. Other times, less so.

Testing how the system would respond if three parachutes all deployed early. Hint: Not well. Image credit: NASA

In the most recent and complicated tests using a full-scale weight-appropriate model for the crew module, the parachutes performed flawlessly. The test rig was dropped from a C-17 cargo plane 35,000 feet above the U.S. Army's Yuma Proving Ground in Arizona and left to free-fall for ten seconds to build up velocity and aerodynamic pressure before popping the protective covers and deploying the parachutes.

Orion mock-up with parachute system in a C-17 cargo plane before being drop-tested. Image credit: NASA

The test engineers even sabotaged the system, setting one of the main parachutes to skip over reefing, going directly from deployed to fully-unfurled. It was the first time some of the parachutes had been tested at such a high altitude, yet they all worked great.

For Exploration Test Flight - 1 returning Orion from Earth orbit, the parachutes will engage after atmospheric friction has slowed the spacecraft down to a still-insane 300 miles per hour. Two drogue parachutes and three main parachutes will deploy to slow the craft to a less teeth-jarring 20 miles per hour before it splashes down in the Pacific Ocean.

Practicing recovery operations off the coast of Southern California. Image credit: NASA

What Happens Next?

Exploration Test Flight 1 is on-schedule to blast off on December 4, 2014. This uncrewed test flight will be the first integrated system test to ensure all the system components can function together as a functional spacecraft. The high-apogee test flight will take the spacecraft to approximately 3,600 miles altitude, over fifteen times Low Earth Orbit where astronauts hang out on the International Space Station.

This will be the first realistic test for the various components: no matter how harshly we test things on the ground, we just can't match the everything a true space environment does to equipment. The test flight will be used to collect data critical to dropping 10 of the top 16 risks identified that would endanger astronauts during future test flights. It will also be a chance to identify areas where engineers can tighten up efficiency for future production, and will build experience capacity for the operations teams.

Keeping up NASA's tradition of bringing emotion into their missions, they've loaded up Orion with a whole lot of sentimental objects. This raises the stakes on what we can lose if things go catastrophically wrong, but it also ups the ante for how awesome it will be if things go right. The non-scientific cargo on board for the test flight includes:

  • oxygen hose from an Apollo 11 lunar spacesuit;
  • a tiny sample of lunar soil;
  • prehistoric fossil from a Tyrannosaurus Rex from the Denver Science Museum;
  • a microchip with the names of more than a million people who submitted their names to be part of NASA's exploration efforts;
  • an assortment of flags, coins, patches and pins for museums and schools;
  • music, including a recording of "We Shall Overcome" by Denyce Graves arranged by Nolan Williams, a recording of "Mars" rom Gustav Holst's "The Planets" performed by the National Symphony Orchestra;
  • poetry, including "Brave and Startling Truth" by Maya Angelou, and an unspecified poem by Marshall Jones;
  • art, including a small sculpture by Ed Dwight called "Pioneer Woman;" and
  • Sesame Street props: Cookie Monster's cookie, Ernie's rubber ducky, Slimey the Worm, and Grover's cape (their names are also on the microchip);

This isn't an unprecedented cargo: we have a habit of loading commemorative goodies onto flight manifests. Mercury astronauts tucked dimes in their spacesuits, Apollo astronauts carried family photos and stamped envelopes, and space shuttle astronauts carried a tiny package of whatever was most meaningful for their lives. Most recently, Reid Wiseman carried a tiny giraffe from his daughters and a series of wristbands honouring friends dealing with childhood cancer, and Terry Virts packed Olaf in his bags. We even do it with our robots, sending Voyager out with the Golden Record, and equipping Curiosity with a penny for camera calibration.

Assuming everything goes well during December's test flight, the next major milestone tests will be in 2017 for Exploration Mission-1 (EM-1), another uncrewed flight taking Orion on a circumlunar trajectory. By 2021 or later, Orion will start carrying humans with the start of the crewed test flights with Exploration Mission-2 (EM-2), currently intended to carry astronauts to visit a captured asteroid in lunar orbit. After that, it's time to start getting serious about picking an objective for a deep space mission: a return to the moon, asteroid capture, or something else to support an eventual human presence on Mars.

We'll be keeping the Orion coverage going as we count down to the test flight, with more details as to what to expect and how to follow along.

All hyped up about the Orion test flight on December 4th? Build yourself a paper model to decorate your desk or run a flight test at home, or download the alphabet colouring book to colour your way through Orion from A to Z.