Nasa's Orion: The next generation of spacecraft computing

How IT will smooth mankind's missions into outer space

As the spacecraft likely to carry astronauts to the moon or even to Mars, it's fitting that Nasa's Orion will contain the most advanced computing tech ever sent into orbit.

Orion marks a step change in spacecraft computing, far outstripping the processing power and capabilities of systems onboard Nasa's current manned craft, the Space Shuttle.

"Compared with the computers that fly the Shuttle today - perfectly adequately - the Orion computers are 500 or 1,000 times faster and more capable," Todd Smithgall, Orion avionics systems engineer at Honeywell Aerospace, the company working with Lockheed Martin and Nasa to produce computing hardware and software for Orion, told silicon.com.

But it's not raw horsepower that makes Orion's IT special. The onboard systems will help make Orion one of the most self-sufficient spacecraft ever launched when it begins manned spaceflights later this decade.

Orion's computers are capable of running the spaceship systems without any intervention from the crew, able to monitor spacecraft systems automatically, prioritise critical operations and recover from a flight computer failure.

The self-sufficient nature of Orion will prove essential during the long-term deep-space missions that Nasa has in mind for the spacecraft, such as landing on the moon, rendez-vousing with an asteroid or even undertaking a manned mission to Mars.

During such missions there could be periods where Orion may be both without crew and out of contact with Nasa Mission Control, requiring the ship to look after the navigation and other critical systems onboard unaided.

Brad Holcomb, deputy programme manager with Lockheed Martin Space Systems, said the Orion's self-reliance will make it more adaptable during missions.

"When you undertake a more exploratory mission like intercepting an asteroid, you are leaving behind the infrastructure of ground stations and GPS, and as a result, the spacecraft has to be more independent. It can't be relying on links to the ground for every little daily task.

"As situations come up - for example, a mission experiment may not work as planned - you have some contingencies to fall back on, because the spacecraft is more independent, you can absorb change a lot easier."

The ability of Orion to retrieve data automatically from spacecraft systems and input that data into the onboard computers will...

...simplify the system-monitoring tasks that have to be undertaken by spacecraft crew.

Matt Lemke, Orion avionics, power and wiring manager at Nasa, told silicon.com: "In the Shuttle [the crew] carry big books of procedures and have to do each individual item. You'll have checklists that say 'Flip this switch', 'Record this value here', 'Do this calculation' and then 'Enter this data over here'.

"On Orion, [the crew] are looking at electronic procedures on displays - those procedures have been pre-called-up and pre-loaded-in. For example, the procedures say, 'Go and find the pressure inside this tank'. The computer goes and does it for them and enters the pressure and recommends what it thinks will be the right value.

"It doesn't automatically execute those procedures - the crew still gets a chance to say 'yes' before doing anything - but the data is already integrated for them and if the crew isn't onboard then it can take care of these procedures itself."

Crew onboard Orion - which borrows elements of its cockpit design and software from the forthcoming Boeing 787 Dreamliner aircraft - will also find it easier to pilot and interact with than its predecessors.

The fiddly dials, gauges and switches that littered the cockpit of the Shuttle when it launched will be mostly replaced in Orion by three displays, which are controlled by buttons around their edges and a "cursor-controlled device" that works like a PC mouse.

The crew will be able to call up some 30 different screens on the displays, covering information ranging from the spacecraft's position in orbit to its comms coverage.

The information set out on these displays will be tailored to what crew members need to know to carry out their daily tasks, bringing together multiple spacecraft systems in one place - a change from previous spacecraft where each screen on the display would only show information from individual spacecraft systems, such as electrics or life support.

Space's jack of all trades
Nasa hopes to be flying Orion for decades and sees the spacecraft as something of a jack of all trades - intercepting asteroids one mission and landing on Mars or the moon the next.

Helping Orion to fulfil such diverse mission objectives will be...

...the spacecraft's highly configurable central computer systems and network.

Orion's computers are easier to configure that those onboard the Space Shuttle due to the way Orion's systems parcel up data and send it around the spacecraft network, and how they split processing power and memory between tasks.

According to Honeywell's Smithgall, it reduces the time needed to prepare for a mission. "Preparation for a given mission could conceivably take weeks or months instead of years," he said.

Orion will use a networking technology called Time-Triggered Gigabit Ethernet, which will allow Nasa engineers to categorise different types of data and prioritise how that data should travel through the onboard network.

Time-critical control data, for example - such as that relating to vital systems like navigation and life support - is called time-triggered data and will have guaranteed bandwidth and message timing to ensure it always gets to its destination on time.

Data that is critical for delivery but not for timing - such as file transfers – is called rate- constrained data and is sent immediately whenever time-triggered data is not present. Conventional Ethernet data - used for non-critical tasks such as crew videoconferencing - is called best-effort data and will be delivered over the remaining bandwidth.

The technology means that critical data and non-essential data will be able to travel safely over a single network onboard a spacecraft for the first time. On the Shuttle and the space station critical data travels over a separate dedicated network.

A second technology known as Integrated Modular Avionics (IMA), already used on aircraft such as the Boeing 777, will make it easier for Nasa to configure the onboard computing for different tasks between missions.

"On spacecraft up until now, and the Shuttle is an example of this, you have had different computers for different purposes - for instance, there's an engine-controller computer, there's a flight-control computer, there's a systems-management computer, there's a display processor," Smithgall said.

"They are all built by different people and they all run different OSes and different software languages - so you can imagine that ...

...the infrastructure needed to maintain all that computing across decades becomes significant.

"With IMA you take all the complexity from all those different functions and house them in one computer.

"It operates on a single computer as if it were multiple virtual computers that cannot interfere with each other... [and] you can add computing resources as necessary to cover additional workloads."

The amount of computing power and memory that can be dedicated to each task is also set before the mission so there is no danger of one task swallowing up processor cycles that are needed by a vital onboard system.

System reliability
While Orion's processing power outstrips that of the Shuttle's systems, Honeywell's Smithgall said computing muscle has taken a back seat to reliability when designing the Orion's computing systems.

"Imagine that your life was on the line every time your PC hung up and displayed the blue screen," he said.

"The real innovation with this type of computer is not its performance but its guarantees against ever doing anything unexpected or incorrect."

This reliability is made even more remarkable considering the harsh environment in which Orion's systems will operate - temperatures in space fluctuate between extreme cold and heat, and the spacecraft will be bombarded by high-energy cosmic and solar radiation.

"Spaceflight has vibration and radiation exposures that are quite unlike anything a commercial aircraft ever sees," Smithgall said.

"We end up with the performance level of a desktop computer of about five years ago but with extremely high reliability, low power consumption and which is survivable in adverse environments."

Orion's computer systems have been designed to deal with the uniquely hostile environment of space: "You take a commercial chip and you test it and find out how it is going to fail. For instance, is it going to burn out or flip a bit? And then you design circuitry and software around it to mitigate the effects," Nasa's Lemke said.

On top of the inherent stability of the hardware design, Orion carries...

...two identical flight computers, each able to take over from the other in case of a system failure.

"We have two flight computers on Orion, each one thinks that it is completely controlling the vehicle," Lemke said.

"If you lose a flight computer the rest of the vehicle wouldn't even know that it happened."

Every bit of data sent from Orion's onboard computers is also checked to ensure no incorrect information is sent out over the spacecraft's network.

"The computer fails silently - it puts data out and there are two processors within each computer that have to run in lock-step to make sure they are doing exactly the same thing," Lemke said.

"If ever [one of the processors] tries to put out a command that is not identical on both sides, down to the individual bit level, it doesn't send anything out to the bus.

"The hardware is checking that every bit that goes out is correct, and if it's not, it turns off its transmitter and will never send out bad data."

Keeping the weight off
Weight is a major consideration when it comes to spacecraft design. Every kilo matters when you are trying to break free of earth's gravity and still keep costs down. For example, each Shuttle launch costs about $450m and requires the Shuttle to burn through more than 830,000 gallons of rocket fuel.

To cut the cost of getting into orbit, Orion has been designed to minimise its weight, with the amount of computing and network infrastructure the spacecraft carries reduced by its ability to house different systems on the same computers and network.

The library of paper manuals containing crew procedures have also been digitised onboard Orion, further lightening the spacecraft.

However, just as Nasa is always pushing deeper into our solar system, so the agency and its commercial partners are continually refining computing technology ready for future spacecraft.

"As much as we have shrunk and integrated things for Orion, we are never at the end of that activity," Honeywell's Smithgall said.