[AR] Re: Quiet times, so OT question

  • From: John Schilling <john.schilling@xxxxxxxxxxxxxx>
  • To: arocket@xxxxxxxxxxxxx
  • Date: Wed, 21 Dec 2022 11:25:28 -0800

On 12/20/2022 4:40 PM, Alain Fournier wrote:

On Dec/20/2022 at 18:38, John Schilling wrote :
One obvious issue for Falcon Heavy utilization is the lack of a destination.  Low Earth Orbit may be halfway to anywhere, but you really need a logistics base at that halfway point, and ISS isn't really a logistics base.  Or a tourist hotel, or much of anything else useful in its current form.

At $2600/kg, it might be worth someone's time to build their own LEO infrastructure from scratch, but if the CSTS is correct, only marginally so.  So it's not too surprising that we don't have budding space industrialists coming out of the woodwork to build their own space stations yet.  Ideally Elon would handle that, but he's too busy playing the social-media game.  And his future plans seem to involve going directly from the Earth's surface to the Martian surface with no fixed orbital infrastructure at all, which seems daft to me.

        John Schilling


Can you elaborate on why you don't like plans for going directly to Mars with no orbital infrastructure?

Personally, I don't really have an opinion on the matter. Orbital infrastructure might be useful but it also might be too expensive for the benefits.


For roughly the same reason I don't like plans for sailing directly from St. Louis to Stuttgart without building ports in New Orleans and Rotterdam.  Yes, you *can* build a flat-bottom riverboat that can survive an Atlantic crossing, or an oceangoing ship with a draft shallow enough for the Mississippi, but those aren't the right tools for the job.

A "rocket ship" designed to fly from the surface of the Earth to the surface of Mars and back, is a concept best left to science fiction - and preferably not the hard stuff.   The requirements for an Earth-to-LEO launch system, an interplanetary transit system, and a Mars-LMO shuttle, are sufficiently different that any single vehicle is going to be highly suboptimal for at least two of those missions.  And you don't save money by designing only a single vehicle, because you don't get rid of any of the requirements, you just further burden them with e.g. "...and even though this part is only ever going to be used in microgravity, it has to survive launch loads and fit inside a launch vehicle fairing, with everything else".

You can conceivably do Earth Orbit Rendezvous without a LEO space logistics facility, but that's roughly equivalent to scheduling your Mississippi riverboats to go out and rendezvous with deepwater freighters just off the coast.   Maybe reasonable if you're only going to do it once or twice, but by the time you've done it a dozen times you're going to be saying "yes, New Orleans is a swamp, but we're still going to be building a dock and a warehouse there, and a steam-engine repair shop".  And Elon's only-orbital-refueling plan still leaves you with the Starship having to fill four distinct roles (LEO launch vehicle, LEO tanker, interplanetary transfer vehicle, and Mars lander).

        John Schilling


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