Birds shit could clog Elon Musk's heat shield for SpaceX spacecraft

In recent months, Elon Musk has revealed new details about the upcoming SpaceX launch system, called Starship.

Musk said the new launcher, which he and his engineers recently redesigned, will eventually replace all the rockets in the company. It would be quite reusable and extremely inexpensive to launch, perhaps reducing the cost of access to the space 100 times. Musk thinks that over time, such a system could lead to round-trip tickets to Mars that would cost less than $ 500,000 and "maybe even less than $ 100,000."

But that assumes that ordinary debris, such as dust or even bird droppings, does not allow Starship's giant spacecraft, as it is currently designed, to burn when landing on Mars or his return to Earth.

Musk has not yet unveiled all the details of Starship – he said it could happen in March or April – but he described it for the last time as a 180-foot-tall spacecraft that will launch into orbit above Super Heavy, a rocket booster of about 220 feet tall. . The spacecraft is designed to be refueled into low Earth orbit to propel 100 passengers and more than 100 tons of cargo at a time to Mars.

From left to right: an illustration of SpaceX's "hopper test", the Starship spacecraft, the Super Heavy propeller, the Falcon 9 rocket and the Starship-Super Heavy integrated launch system.
© Kimi Talvitie

Musk launched "radical" and "deliciously counter-intuitive" design changes in November. Since then, he has analyzed the essential details and confirmed the existence of a prototype "test hopper" built by the Texas company.

Read more: $ 1.37 Billion Border Security Agreement May Save Texas SpaceX Launch Site, Where Elon Musk Expects to Launch Lunar and Martian Rockets

One of the major changes to the design is that SpaceX is now planning to build Starship from stainless steel alloys instead of carbon fiber composites, Musk said. The second change involves a "bleeding" heat shield that will let the liquid flow through small pores to keep the ship cool when it moves at high speed.

However, several aerospace experts worry about how SpaceX would build such a system without obstruction.

Why poo, dust and other debris can threaten Starship

An illustration of the next SpaceX spacecraft and the SpaceX Super Heavy propeller. Elon Musk says the launch system will be made from polished stainless steel alloys to give a mirror finish.
© Kimi Talvitie

A heat shield is a must for a spaceship.

When a vehicle comes back from Earth to Earth, it can reach a speed of about 19,000 mph. It's so fast that molecules at the front of a ship turn into superheated plasma that can corrode, melt or even vaporize some of the hardest and most heat-resistant materials.

Musk has m said Starship's nose can be exposed to temperatures of about 2700 degrees Fahrenheit. The type of steel alloy that SpaceX can use on Starship's outer skin, called 310S, melts at around 2400 degrees.

Most spacecraft (including the future SpaceX Crew Dragon vehicle) use "ablative" heat shields designed to burn and insulate the vehicle's hull as it enters the atmosphere. NASA has used this type of technology in the Mercury, Gemini and Apollo space capsules. To protect its fleet of space shuttles against heat, NASA has stuck thousands of heavy ceramic tiles to the bottom of each ship.

But as Musk tells Popular Mechanics, Starship will have a heat shield cooled by sweat.

The system would work like human skin, in which sweat absorbs heat from the body, evaporates to carry heat, and eventually cools. With Starship, the "sweat" would be water or methane, and the "pores" would be innumerable holes in Starship steel belly.

Read more: SpaceX has tested a Raptor rocket engine with "crazy power" for lunar and martian missions. The future of Musk will depend on its unmatched performance.

At least some aerospace experts are worried about the challenges that such a heat shield would face.

"You can imagine that it would not take much to obstruct something like this, if it were microscopic pores," Business Insider Walt Engelund, aerospace engineer and director of the Technology and Technology Branch, told Business Insider. from space exploration to NASA Langley.

Dwayne Day, who helped investigate the loss of NASA's Columbia Space Shuttle Columbia and its crew, said such clogs may be faced with many commonplace factors.

"What if a bird pooped on your rocket and it clogged a few holes, then when the thing comes back, no coolant comes out of those holes and this part of the vehicle overheats?" he said.

NASA rover Mars Opportunity in March 2014. The Martian winds had just blown a layer of dust from its solar panels.
NASA / JPL-Caltech / Cornell University / State University of Arizona

The dust on Mars, which recently killed NASA's Rover Opportunity by blocking sunlight on its solar panels, could also pose a threat to Starship's small steel skin pores.

In addition, said Engelund, the carbon content in fuels such as methane tends to "coke" or turn into solid when exposed to high temperatures, so that it could also pose a risk clogging if Musk chooses methane as a coolant.

Engelund said various liquid cooling systems had been tested in NASA 's hypersonic wind tunnels, which were blowing air at thousands of kilometers at the time to simulate incredible speeds in the upper atmosphere. In these tunnels, a blocked coolant channel may vaporize an aircraft model.

Looking for hooves in thousands of pores before launching a spaceship from Earth would be difficult, but it would be much harder to do it on Mars, where there are no launching towers or gantries .

"How do you make sure all the holes are open? Or at least that there is no significant obstruction?" Said the day.

In an e-mail addressed to Business Insider, SpaceX pointed out that constant changes and modifications to the Starship design were expected – this is part of the company's more comprehensive design approach – while the engineers s & ### Use to make the launching system a reality. Indeed, the system (formerly Big Falcon Rocket and other names before) has already undergone several major revisions since its first detailed description by Musk in September 2016.

"They 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 that," said Engelund. "Maybe we could do some things with them, I guess there will be some."

Read our full article on the new Starship design here.

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