NASA’s next human-rated spacecraft completed a successful test flight at the end of last year – and now the hard work of checking its hundreds of components has begun in a bid to make it the safest ship ever built. The process will be long, complex, and will require advanced engineering techniques.
Orion, which replaces the retired Space Shuttle, will be used to send astronauts on missions to an asteroid, as well as hosting the first human spaceflight to Mars. Although it’s the most advanced spacecraft to date, Orion has plenty in common with the Apollo programme that America first used to land on the moon.
Rather than the Space Shuttle’s reusable body, Orion uses a modular system similar to that of Apollo, with rocket stages propelling the rest of the spacecraft out of the atmosphere and beyond. Called the SLS or Space Launch System, Orion’s ride to Mars is the most powerful rocket ever built – with an eventual capability of 130 metric tons. At the end of the mission, it’s the job of the separate re-entry craft to glide through the atmosphere and return the crew safely to Earth.
Making Orion safer than the Shuttle
Exploration Flight Test 1, or EFT-1, took place in December 2014, but NASA has only just brought the spacecraft’s 16.5ft-diameter heat shield to its Space Flight Center facility in Huntsville, Alabama. There, engineers will use the centre’s advanced seven-axis milling machine to check the most crucial component of the project.
The heat shield is designed to withstand temperatures hotter than molten lava, generated by friction with the Earth’s atmosphere. A crucial barrier between the crew and the elements, it was a loss of heat-shield tiles that resulted in the disintegration of Space Shuttle Columbia in 2003. Killing all seven crew aboard, it marked a two-year suspension for the Space Shuttle programme.
Made from heat-resistant Avcoat material, the Orion heat shield is designed to endure temperatures of around 4,000˚F (2,204˚C) and speeds of 25,000mph – far hotter and faster than the Space Shuttle ever experienced. Instead of transferring energy into the crew module, Avcoat instead burns away and takes the heat with it. NASA estimates that around 20% of the 1.6in-thick heat shield was eroded during the latest test flight.
Around 180 partially melted and incinerated tiles will be removed for testing, along with sensors and other materials. These will then be shipped to NASA’s research facility in Ames, Mountain View, for further analysis. NASA will also be extracting critical entry-environment and thermal protection-performance data collected during the EFT-1 flight.
NASA will be extracting critical entry environment and thermal protection performance data collected during the EFT-1 flight, in a bid to make Orion the safest, most efficient spacecraft yet.
Weight saving
Although the Orion is set to be strapped to the most powerful rocket ever made, NASA will also be analysing ways of further reducing the spacecraft’s weight. “Mass affects your ability to execute the mission, how far you can go, how long you can stay, and how many people you can take,” said Julie Kramer White, chief engineer on the Orion MPCV program.
As Mike Kirsch, project manager and principal engineer of the NESC’s Orion Heat Shield Carrier Structure Assessment Team, added: “Wouldn’t you rather carry extra water, food, oxygen and propellant? By being efficient in our structural design, we can bring along more of those consumables. And when it comes to splashdown, a lighter vehicle comes in with less energy upon impact.” NASA has already successfully reduced the weight of the original 3,200lb design by 1,300lbs, bringing down manufacturing costs as well as landing forces.
Orion’s first operational mission is expected in 2017, with more planned from 2020.
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