The Copernican

NASA goes green

The NASA ion thruster in action.  

The NASA budget request for the fiscal year 2015 is studded with nuggets indicative of how the behemoth space agency plans to take its space exploration program forward. In total, it is asking for $17.5 billion, about 1% less than what it received in 2014 and up $600 million from what it receiving in 2013. Broken down, the biggest chunks are for human exploration operations ($7.8 billion) and scientific research ($4.9 billion).

Some of the more resplendent nuggets among the request are development of an asteroid sampling mission, the proposed launch of a spacecraft to study Europa (one of Jupiter’s moons that was recently seen ejecting plumes of water vapour) in the mid 2020s, more Mars missions, and keeping the James Webb Space Telescope launch on track for 2018 (after multiple overruns in the last few years). With the exception of the Europa mission, none of these are surprising.

But >take a closer look at the request and you’ll see that the space agency is also developing a slew of greener alternatives to various existing systems, notably >propulsion. Under the space technology category, the agency is proposing development of “high-powered solar electric propulsion capability”, “higher-performing alternative to toxic hydrazine”, and the launch of a propellant-free spacecraft called the “Sunjammer Solar Sail”.

The Sunjammer is named for the Arthur C. Clarke story of the same name, >published in 1963. The mission itself aims to launch a spacecraft equipped with a 13,000-square foot sail which will use sunlight to tug the craft like the wind pulls along a sailboat. Despite its big size, it weighs about 32 kg because it is only 5 μm thick, made from a synthetic fabric called kapton. It is expected to be launched in January 2015.

Although >the Sunjammer sail is the largest solar-sail to have been built, the idea is not new and has been tested before. In 2010, the Japanese space agency JAXA launched >Ikaros, which sailed toward Venus equipped with a sail that became the first successful demonstration of the technology in interplanetary space. In 2011, NASA itself deployed the >Nanosail-D, a nanosatellite that floated around our planet powered by a 9.2-square meter solar sail.

If the 2015 mission is successful, NASA has said it will look at more ambitious missions. This will be alongside other greener propellants it is considering as an alternative to hydrazine. A liquid fuel which is highly corrosive to the touch, hydrazine's use incurs higher transportation costs, and the rocket can be loaded with hydrazine only at the launchpad, not anytime before. In July last year, NASA announced one such alternative it was developing had passed a critical test, paving the way for its first deployment in 2015.

Dubbed AF-M315E, the liquid is simply hydroxyl ammonium nitrate. Although ammonium nitrate is >an explosive substance, the presence of the ‘hydroxyl’ means that its melting point drops from around 170 degrees Celsius to around 70 degrees Celsius, making it harder to ignite. On the counts more relevant to rocket fuels, however, NASA has said it is way more efficient than hydrazine. A propulsion system to work with M315E is being developed by Utah-based Ball Aerospace and a subcontractor, Aerojet Rocketdyne.

The third piece of technology - electric propulsion - is being geared for orbit transfer manoeuvres of satellites, and to “accommodate” their “increasing power demands”. Perhaps you’ll remember a >popular video in September, 2013, that demonstrated an ion drive in action, which is basically an electric propulsion system. Such a system accelerates ions using electric and magnetic fields, and uses their resultant kinetic energy to cause thrust of about 15-50 km/s.

The ion drive, encompassed by the NASA Evolutionary Xenon Thruster (NEXT) project, burns less than one-tenth the volume of fuel than do conventional fuels to generate the same momentum. This means more space is available on board the spacecraft for scientific payloads.

Aside from the fact that NASA’s decision to go greener signals the start of the decoupling of distance and quantity of fuel, the progress is made more fortuitous by being accompanied by more space- and fuel-efficient spacecraft design. In the words of the British essayist J.G. Ballard: “Everything is becoming science fiction. From the margins of an almost invisible literature has sprung the intact reality of the 20th century.” Let’s make that the 21st as well.

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Printable version | Nov 24, 2020 1:21:02 AM |

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