Wednesday, August 5, 2020

Starship's first 'hop'

SpaceX's Starship is new technology.  Its 'Raptor' engine burns cryogenic methane, not the purified version of jet fuel most rockets burn.  It was developed by SpaceX from scratch.  And Starship is built from stainless steel, not carbon-fibre composites, like most other rockets.

So there have been pauses for running repairs on the road.  Although the first cutback version of Starship, Starhopper, 'hopped' 150 metres, demonstrating the efficacy of the Raptor engine, all subsequent tests of versions of the Starship failed.

Until now.

The methane and liquid oxygen is held at 7.5 bars (i.e. 7.5 times the pressure of the atmosphere at sea level), and each tank tested (bearing in mind that they were made of a novel aeronautical construction material) sprung leaks, or exploded, or, in one case, imploded.  But with each failure, SpaceX learned something.  And yesterday, a real Starship, though without its nose-cone and fins, but still nine storeys tall, and with a steel cube to simulate the weight of a payload, lifted off from the company's base in Boca Chica, Texas, and 'hopped', reaching 150 metres altitude.

Of course, this is a long way from reaching Mars.  All the same, it is a huge step forward.  SpaceX has demonstrated that rocket ships can be built from steel. And can take off.  And land again.  The next step will be higher hops, and then testing of a full version of the spaceship, with a full complement of Raptor engines, flying to 20 km above the Earth, and trying to land again using the famous skydiver or belly-flop technique to burn off orbital velocity.






This is a prodigious achievement.  SpaceX only pivoted away from carbon-fibre composites to steel in December 2018.  Compare this swift development to the sluggish, even glacial, pace of conventional space companies and bureaucracies.

Stainless steel is about 3% of the cost of carbon-fibre composite, withstands both cryogenic temperatures and the 1500+ degrees C of re-entry.  Musk has stated that each Starship will cost just $5 million, and each launch of the Starship/Super Heavy combination under $2 million.  This compares with NASA's SLS (Space Launch System) of $1.5 BILLION  per launch.  Starship will lift 150 tons or 100 passengers to LEO (low Earth orbit).  This is a cost per kilogram of $13, compared with the cost, until SpaceX broke open the monopoly of dinosaur space companies, of $22,000/kg.   0.06% of the previous cost. 0.06%!!!!

Musk has stated that the really hard part of the whole process of constructing Starship and its booster Super Heavy is creating the assembly line that will build them. He's well on the way to doing this.  Already there is another prototype, SN 08, already close to completion.  It's being built of a slightly different steel alloy, as SpaceX continues to experiment and improve.  Starhopper took 8 months to build.  The latest versions of Starship seem to take 3 or 4 weeks.  The assembly line is speeding up.

Musk has said that he plans building 100 Starships a year.  He wants to send the first uncrewed Starships to Mars in late 2022, when Mars is in opposition to the Earth (in "orbit sync" as he pithily describes it)  The original plan was to send 2 cargo Starships in 2022 and 2 cargo and 2 crewed ships in 2024 to Mars.  But that was when the Starships would be constructed from carbon-fibre composites, and would be 10 times as expensive as the stainless steel versions will be.  Does that mean 20 cargo ships in 2022, and another 20 in 2024?  Or am I being overambitious?  Other SpaceX spokesmen have said that the first batch of Starships will be used as temporary habitats for the first settlers, in other words, they weren't going to return to Earth.  Only with subsequent missions would Starships return, because of the time that would be needed to make propellant on Mars to fuel their return journey.

Extraordinary.  Watch the video.  This is it—the first critical step on the road to making mankind multi-planetary.  I hope I live to see the first boots on Mars in 2024.


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