SpaceX Starship a tougher project than any of our Mars missions: NASA engineer

SpaceX's Mars rocket Starship is the company's most complex project so far, but is also a tougher one than any of NASA's past or current missions on Mars, according to NASA's chief engineer.The fully-reusable shuttle to Mars is the newest homegrown marvel in SpaceX and CEO Elon Musk's drawing board – a 180-foot tall stainless steel mammoth. The rocket has been designed with two radical features that has Musk super excited and NASA's chief engineer "very worried", according to a Business Insider report.The first of those is Starships's stainless steel body. This is a big shift away from Space's usual choice of carbon-fiber for the body.But its the second change that has aerospace industry experts sweating bullets: Starships' one-of-a-kind cooling system that will keep it from incinerating in Earth's and Mars' atmosphere.[caption id="attachment_5890441" align="alignnone" width="683"] Elon Musk tweeted this image of the "real" spacecraft, and not a rendition, to his and SpaceX's followers on 11 January. Image: Twitter/ElonMusk[/caption]NASA uses hundreds and thousands of ceramic tiles to shield its spacecrafts from heat as they zip through the atmosphere. Musk described to Popular Mechanics how Starship will "bleed" rocket fuel from tiny pores on its surface to cool down – a "radical and delightfully-counterintuitive" concept for heat shields in rocketry.While Musk is certain of Starship's build and design, a NASA aerospace engineer and director of the NASA's Space Technology and Exploration Directorate at Langley, Walt Engelund is not as confident.The SpaceX rocket for Mars is built to ferry 100 passengers along with 100 tons in cargo when at its best. This is something NASA has been studying for decades – entering, descending and landing a huge spacecraft with special cargo – with gradual, incremental success."We've spent a lot of time and given a lot of thought to how we might do it at Mars," Engelund told Business Insider. "We've landed the metric-ton Curiosity rover — the biggest thing we've ever put down on the surface of Mars."[caption id="attachment_5797111" align="alignnone" width="1280"] The SpaceX 'Starship' prototype made from stainless steel. Image: Twitter/Elon Musk[/caption]The leap that Starship is aiming for – a hundred times more ambitious – is to successfully land and return a spacecraft the size of a building (a building with 100 people in it)."It won't be easy for us or SpaceX," Engelund said. His specific concern was not the design of the heat shield itself, which has been attempted by NASA before (using astronaut urine instead of rocket fuel). His doubts (echoed by many engineers in response to Musk's descriptions of the technology) is how the tiny holes that will "bleed" rocket fuel on the surface might avoid getting clogged.It wouldn't take much to clog something like that if they were microscopic pores, Engelund told Business Insider."What if a bird poops on your rocket and it plugs up a few holes? And then when the thing is returning, no coolant comes out of those holes and that section of the vehicle overheats?" Dwayne Day, a NASA engineer who helped investigate the Columbia space shuttle accident, added.[caption id="attachment_5983101" align="alignnone" width="1280"] A selfie taken by NASA's Curiosity rover on Mars Sol 2291 (15 January) at the "Rock Hall" drill site on Vera Rubin Ridge. Image Credit: NASA/JPL-Caltech[/caption]And once those challenges on Earth have been considered, there's more to worry about at the other end: fine dust that blows through the year on Mars.Musk has only shared Starship's build and features in bits and pieces, still to unveil the rocket in full detail.Yet, the NASA engineer's aren't dismissing the possibility that SpaceX's newest rocket in the pipeline won't succeed."(SpaceX has) surprised a lot of people, and have a lot of smart people working for them, and Elon seems to be really committed and dedicated to this," Engelund said."Perhaps there are some things (NASA) could do with them. I suspect there will be."