Re: Space Access Update #112 9/19/05


"Tom Cuddihy" <tom.cuddihy@xxxxxxxxx> wrote in message
news:1130389214.909289.311920@xxxxxxxxxxxxxxxxxxxxxxxxxxxxxxx
> Before Shuttle The Conventional Wisdom was that if we built a national
> reusable 'space shuttle,' the cost of access to orbit would go down.

<snip>

> Infrastructure is something that costs more as it ages, and costs more
> to build the longer you wait to upgrade it.
>
> I.e. the more fluid and responsive your infrastructure is, and the more
> often you upgrade it, the cheaper its use gets. With that in mind, the
> very long timelines a high level reusable vehicle would require to
> design, build, and fly makes the infrastructure worse off in the
> meantime.
> On the other hand, the quicker you you can start launching, upgrading,
> and starting designing again, the better off your infrastructure will
> be. That argues for quick and dirty methods to orbit, like ELVs.
> Design, build, fly, upgrade, design, build, fly...much quicker to
> upgrade with a throwaway system like that.
>
> This is one of the reasons CEV is NOT stipulated to require
> reusability.
>
> They still fly 80s computers on the Shuttles, right? Not to mention the
> thing was designed in the early 70s. If it takes you 10 years to design
> and declare working your reusable vehicle, by the time your first
> commerical satellite was delivered to orbit, the entire infrastructure
> might be obsolete.

You're missing a key point. Flight rate. If the hardware would have
supported it, and if there really were enough payloads to fly, the shuttle's
per flight costs could have been much cheaper than it is because you would
have had a much higher flight rate. That gives you the opportunity to
spread out your fixed (infrastructure) costs out over far more launches.
Also, if this would have happened, the shuttles would have reached the end
of their lifetimes much quicker, and a Shuttle II program might have been
possible (i.e. keep the external mold lines and update all the internal
systems).

The same flight rate point applies to the CEV. If you're going to fly 100
times a year, making it reusable makes sense. You'll still wear them out
fast enough to incorporate changes in the next model quickly. You'll also
get more experience with the changes you make much faster, which will help a
lot in the reliability department.

If you don't make the CEV reusable, and only fly it say 6 times per year,
you can still make changes to the craft as you build new ones, but the
problem there is that you'll gain very little experience with those changes.
This type of approach is far more like a research program (an expensive one
at that) rather than an operational program. Note that's essentially what
we've got with the shuttle. The orbiter airframes are reused on every
flight, but many changes have been made to the system over the years.

The key to lowering costs and producing a truly operational system is to fly
often. Reusability, or lack of reusability, isn't as important as flight
rate.

The lesson here is forcing reusability on a low flight rate system, doesn't
gain you much of anything.

Jeff
--
Remove icky phrase from email address to get a valid address.


.

Relevant Pages

  • Re: Japans Moon Ambitions - Theyre KIDDING, Right ?
    ... and losing vehicles and pilots occasionally ... >> Because of the absurdly low flight rate, and the fact that it's not ... if you want to have low costs. ... >And if reusability is good, why isn't some reusability better than ...
    (sci.space.policy)
  • Re: Manned space flight after the moon landing
    ... >> there were politicians who saw through that and realized the shuttle ... >> for the shuttle program would drop, but NASA's overall costs would ... > projects from a variety of sources, of which NASA was just one. ... "reusability" isn't really driven by economics. ...
    (sci.space.history)
  • Re: shuttle & ISS mistake news article
    ... > That does not necessarily make it true of all reusable vehicles. ... > quite arguable that the shuttle is expensive not because it's partially ... So the shuttle is over three times more unsafe than Soyuz and more ... reusability has ...
    (sci.space.shuttle)
  • Re: shuttle & ISS mistake news article
    ... >>> That does not necessarily make it true of all reusable vehicles. ... the shuttle is the only one we know anything about. ... >> Only because of the vast sums we throw at it at the expense of many ... reusability ...
    (sci.space.shuttle)
  • Re: Space Shuttle costs.
    ... Robert Kitzmueller wrote: ... >> Derek Lyons wrote: ... almest every aspect of the Shuttle program was flawed from ... >> flawed economics model treated reusability as an add-on cost. ...
    (sci.space.policy)