The NASA official who looks after computers on the International Space Station on the role played by both Linux-based and Windows systems throughout the station's history, the rise of mobiles in space and plans for the Microsoft HoloLens.

Image: ESA/NASA

Circling the earth at about 18,000 mph, the multinational crew of the International Space Station float high above the tensions that dominate the planet's international relations.

And just as US and Russian crews leave behind any political antagonism, technologies that compete on the surface are also just part of the melting pot of different systems used on board.

Since the first van-sized module blasted into orbit in 1998, the crew of the International Space Station (ISS) have relied on both Linux and Windows laptops to carry out their daily duties.

For NASA, the spread of operating systems is a pragmatic choice. From the first days of the station, NASA astronauts have used Linux-based laptops to interact with the avionics, the critical systems that keep the station in orbit and the air breathable. Meanwhile Windows machines have always been used for general support, performing roles such as housing manuals and timelines for procedures, running office software, and providing that all important link with home, supporting communications by email and more recently by video chat. Windows machines are also used for playing music, films and other entertainment.

SEE: NASA's unsung heroes: The Apollo coders who put men on the moon (PDF download) (TechRepublic)

Laptops are also essential for managing and monitoring the many different scientific experiments run on board the ISS, as well as to control the several robotic arms that helped assemble the station and continue to play a vital role in maintenance and handling payloads.

Stephen Hunter, manager for computer resources on board the ISS, explained why NASA initially chose Linux for the laptops that interact with the core systems on the station.

"It was just the applicational needs," he said, describing how the laptop software that talked to the station's command and control systems in those early days was designed to run on a Linux-based OS.

As for why NASA picked Windows for systems handling day-to-day office tasks and operations, it was mainly that the crew were familiar with the OS, he said.

"For the operations use and early payload items it was easier to migrate them to the more commercial platforms to make it easier for them to use."

Sticking with the same operating systems has allowed NASA to minimise the time and money spent on redesigning software during the almost 18-year lifespan of the ISS, said Hunter.

Beyond NASA astronauts, each national space agency chooses the operating system and software they run - resulting in an array of OSes used on board. However, while the OS each laptop runs may differ, the hardware remains identical, with the same NASA-procured machines used throughout.

So which laptops and operating systems have been used on the space station since construction began in 1998? The sidebar and this gallery shows the full list of the laptops and the operating systems used by the NASA crew.

The laptops used on board the ISS 1998 launch of station - IBM ThinkPad 760XD Operating systems: Windows 95 and 'early Linux'. Windows 95 machines were later switched to Windows 2000

CPU: 166MHz Intel Pentium I MMX

Display: 12.1" TFT (1024x768)

Memory: 48MB EDO RAM

Storage: 3GB HDD 2003 - IBM ThinkPad A31p Operating systems: Windows 2000, later switched to Windows XP alongside a "variety of Linux distros"

CPU: 1.7GHz Intel Pentium 4-M

Display: 15.1" TFT (1600x1200)

Memory: 1GB DDR SDRAM

Storage: 60GB HDD

Battery: 3.6Ah rating. 2.6 hours recharge 2009 - Lenovo ThinkPad T61p Still the main laptop in use today. Operating systems: Windows XP, later migrated to Windows 7. Scientific Linux for laptops that interface with command and control systems, and Debian Jessie 8.x.

CPU: Intel Core 2 Duo T7700 / 2.4GHz

Display: 15.4" WUXGA (1920x1200)

Memory: 4GB DDR2 SDRAM

Storage: 100GB HDD

Battery: 7800mAh rating April 2016 - HP ZBook 15 NASA is in the process of transitioning the station to ZBooks, with the first batch of 30 mobile workstations sent to ISS in April. Operating systems: Windows 10 Enterprise, with possibly odd Windows 7. Will have similar mix of Linux to A31p. Scientific Linux for laptops that interface with command and control systems, and Debian Jessie 8.x.

CPU: Intel Core i7-4810MQ Quad Core

Display: 15.6 inch LED FHD (1920x1080)

Memory: 32GB 1600MHz DDR3L RAM

Storage: 1TB 7200RPM, 256GB Z Turbo Drive PCIe Solid State Drive

Battery: 8 Cell 75WHr

NASA's choice of OS is also related to stability, with the agency going straight from XP to Windows 7, skipping the poorly-received Windows Vista.

"If you look at some of the Microsoft products, we tend to try to stay on the most stable of the operating systems. With XP, we stayed all the way through SP3. We did not make the leap to Vista, because of issues with it and waited until to Windows 7."

The agency also gave Windows 8 a miss, although Hunter said this was due to the timing of when it upgraded its laptops, rather than opposition to the operating system. Because NASA stuck with its Lenovo T61p laptops for so long, it ended upgrading directly from Windows 7 to 10.

Within NASA, despite the headlines that the 'ISS has replaced Windows with Linux' or vice-versa, the balance of operating systems the agency uses on board generally remains the same, said Hunter, who adds that such reports are sometimes taken out of context following small-scale shifts.

Spaceman on a space LAN

The guiding principle for NASA is how to make life as easy as possible for the ISS' crew when it comes to looking after the station's computer systems.

"One of the global strategies that we have for the ISS is, how we can both minimise and maximise crew time?" said Hunter.

Expecting the crew to stay on top of laptop maintenance would be impractical, given the station is staffed by six people but runs about 100 laptops. In general, if there is a problem or a laptop needs updating, mission control will attempt to fix it from the ground.

"We'll use the flight controls on the ground to do the majority of the system upgrades so it doesn't take away from the crew's time and has minimal impact. The ability to have remote administration has been a godsend for us, in terms of being able to deploy and help to manage our growing network node on board ISS," said Hunter.

The most difficult repairs that will be asked of the astronauts are slotting in a replacement battery or hard drive. If fixing a laptop requires a more complicated adjustment, the computer will typically be replaced outright. NASA keeps 20 percent more laptops than needed on the station for use as spares.

The crew will typically use each generation of laptops for about six years, although machines will begin to be replaced with a newer model after four years.

That two year transition period between laptops means the station is "never just absolutely on one platform", says Hunter.

The exception is the Lenovo T61p ThinkPad laptop that NASA still uses today, despite having been in use since 2009. Hunter said its longer than usual lifespan is due to the machine's low failure rate, which enabled the agency to skip a generation of laptops on board.

Given the long lifecycle of the laptops, it's expected that some PCs will go wrong, as Hunter puts it: "We use these platforms truly until failure."

The laptop part that fails most often is the screen, either the LCD display suffering a pressure crack or just outright failing after some 25,000 hours of being on "pretty much on all the time".

Not wanting to waste a valuable resource, if NASA can establish the computer is still working, it will remotely repurpose the laptop to perform operations that don't require a screen.

But why exactly does the station need so many laptops, more than 20 machines per person?

"People always ask 'You have six crew members and you have 100 laptops?'," said Hunter, explaining that the large computing infrastructure stems from the size and multi-faceted nature of the space station.

"It's the largest thing that's ever been made in space. It is a workspace away from home, it's where the crew live, it's where they work. It takes a lot of systems to not only control the vehicle but also the amount of science we're doing on board has really increased since our construction phase. Now we're in the complete utilisation phase, it's ever growing."

The laptop plays a "very, very significant role" in the expansion of what work can be carried out on board the space station, says Hunter.

"We've been able to automate a number of things, so we actually say it's our electronic crew member."

Of the 100 laptops used by NASA and its fellow space agencies on board today, about 15 are used to interact with the avionics systems and about 30 are used for storing and retrieving manuals and other general office tasks.

Those laptops are spread between NASA crew and their Canadian, European, Japanese and Russian counterparts. NASA provides the same laptops to everyone on the ISS in order to make them simpler to maintain.

"It makes maintenance and repair on board easy, since we only have to maintain one set of spares," said Hunter.

Where the 1980s and 2010s collide

NASA buys off-the-shelf laptops for the space station but given each machine will need to remain useful during their six year sortie, NASA chooses premium PCs aimed at businesses and specs them as high as they will go.

"We've always tried to target a high-end business class laptop, not a consumer-grade," said Hunter. As the specs improve, so the laptops are tasked with doing more, with NASA able to use the latest HP ZBook laptops to render video related to crew eye exams, a task that previously required a dedicated workstation on board.

There isn't just a gap between the computing power of the laptops and that of the station's onboard computers, there is a gulf.

Unlike your average home PC, the station's systems are designed to run for between 20 to 30 years. These are machines whose processors were already long in the tooth when they were rolled out, a result of extensive testing to ensure the electronics could survive the harsh and irradiated environment of space.

Consequently the processors in these systems are almost as old as the astronauts, relying on a mix of chips based on Intel 386 and even 35-year-old 8086 designs.

While some of these systems have been upgraded to the 23-year-old Pentium processor, their computing power still pales compared to the laptops used on board. As time goes on, NASA is using the laptops to handle a growing number of non-critical, non-realtime tasks on the station.

"A lot of things have moved over to this platform because it's actually more economical to place that on a laptop and communicate it over our Ethernet network," said Hunter, while adding that the decades-old station hardware is plenty powerful enough to carry out the ISS' core functions.

For the the station's central systems, resilience to failure is more important than raw power, with the central command and control system that routes commands to the avionics, power, environmental control and other vital electronics, relying on three redundant computers.

Reliability is also important for the laptops, although to a lesser degree. Laptops destined for the ISS have to be able to withstand being bombarded by the higher levels of radiation that exists in low-earth orbit. Machines also have to survive the shakes, knocks and bumps of the journey to the station.

NASA checks how the laptops perform while being irradiated, as well as carrying out thermal testing where it induces failures such as a fan stopping. The agency also carries out extensive checks on battery safety, power demands and the ability of the laptops to interact with onboard systems. Many other tests - such as the ability to withstand vibrations - are already carried out by the laptop vendors, which in the past have also made small modifications for NASA.

"As laptops have been becoming more ruggedised we can minimise the amount of testing that we have to do on our back end," said Hunter.

The rise of phones and tablets

The space station hasn't ignored the rise of mobile computing, with an increasing number of smartphones and tablets having found their way on board.

Various iPhone and Android Nexus 5 handsets have made the trip. Among the many uses for such devices, perhaps the most interesting is the SPHERES program. These are remote-controlled, floating drones built around smartphones that are being tested on their ability to perform simple tasks are often either too risky or too repetitive and mundane for the crew. Think the practice droid used by Luke in the Millennium Falcon during Star Wars: Episode IV, only without the laser blasts.

Image: NASA/ISS

Several generations of iPad, as well as the iPad Air 2, have made it to the station, alongside three Microsoft Surface Pro 3 tablets. The Pros are being used in various experiments, most interestingly as a bio-DNA sequencer.

The iPads are used by both US and Russian crews, both for experiments as well as for keeping in touch with family and for entertainment. The crew are able to access the internet, for instance to access social media, albeit in a controlled fashion, with all traffic carefully managed by Houston, to minimise throughput and safeguard the security of onboard systems.

It was an iPad app that recently allowed British astronaut Tim Peake to run the London Marathon -- albeit a digital version -- while pounding a space station treadmill 250 miles above earth.

Augmented reality and the HoloLens

As is befitting for a space station, the ISS is also home to kit designed to make good on the science-fiction promise of augmented reality (AR). The ISS recently tested out the Microsoft HoloLens, a headset that lays digital information into wearer's vision, for example, adding a virtual label to a real-world object in their view.

During tests in February this year, a NASA operator on the ground was able to provide remote assistance to a crew member wearing the HoloLens. Using the HoloLens cameras, the operator was able to see what the crew member saw and provide them with real-time guidance, annotating objects in that crew member's vision and talking them through tasks.

Image: NASA

Hunter says a major benefit of the HoloLens could be allowing a flight controller or system expert on the ground to guide a crew member through a complex procedure, which in the past would have required two crew members -- one to perform the task and another to walk them through the instructions.

"We can save time when we have complex procedures where it would take two crew members."

Hunter was pleased with the HoloLens' performance. "It performed well. It performed in the way that we expected it to," he said, saying that NASA was particularly happy about how robust the communications were, given the obvious constraints when relaying messages to and from the ground via satellite. Messages are passed between the ISS and NASA's Johnson Space Center in Houston via geosynchronous satellites - creating a round trip latency of about 600ms.

As for the future plans for the HoloLens, NASA wants to make the device integral to its operations

"We have long-term plans to utilise it, to support operations, payload and experiment use, also repair and other procedures or complex tasks," said Hunter, adding that NASA would wait until the commercial HoloLens headsets were available before expanding its use.

NASA's forays into augmented reality, willingness to shift more work to powerful modern laptops and experiments with the diverse capabilities of smartphones reflect the agency's desire to continue finding new ways to exploit computers.

Besides, if NASA were to stop sending new and more powerful kit to the station, Hunter jokes the trip into space might lose its lustre.

"If we didn't have the necessary computing power, then people wouldn't want to come."