Monday, June 1, 2020

Suborbital Starship

It's clear that Starship can't reach orbit without a zero payload, nor would it be able to land safely back on Earth.  Single stage to orbit (SSTO) spaceships have been a recurring dream in the space industry since it began, and of course, they are a staple of science fiction.  So far, none has been built.  The physics is just too hard.

SpaceX's original plan for point-to-point hyperfast travel on Earth was to use a giant booster, called Super Heavy, to launch the Starship upper stage into orbit. 

But then, a year ago, Musk talked about a Starship doing suborbital flights, capable of reaching Mach 20 (20 times the speed of sound/24,700 kph/15,500 mph), travelling up to 10,000 kms, and carrying 450-500 passengers.  These suborbital flights would not need the Super Heavy booster, which makes the whole idea far more practical. On the other hand, a flight length of 10,000 km won't cover the journey from the USA to Australia, though it is enough for L.A. to Tokyo and L.A. to London.  Most cities on Earth could be reached with one or two flights.  This will be potent competition for long range air travel.  Passenger jets fly at speeds below Mach 1.

That brings us to five slightly different versions of Starship: three LEO types (passenger, freight, fuel), a Moon version and the suborbital shuttle.  They'd all be variants of the same basic model.

By the way, does the explosion of SN4 on the test stand mean that the dream of Starship is finished?  Definitely not.  Each "unscheduled rapid disassembly" has happened further along in the testing chain.  In this case, it wasn't the vessel itself which failed but a methane fuel line connection to the Starship.  SpaceX isn't just advancing down a construction learning curve, it's also going along a procedures learning curve.  You can be sure that they won't make this same mistake again.  Prototypes of Starship are being built so rapidly that there is already one completed vessel (SN5) and another half completed (SN6).  My expectation is that we'll still see 100 k "hops" this year [Update 10/7/21 -- orbital flights will take place later this year.  Elon time!]

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