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

"Len" <len@xxxxxxxxxxxxxx> wrote in message
news:1130288471.245540.174880@xxxxxxxxxxxxxxxxxxxxxxxxxxxxxxx
>
> For a very small fleet size, I don't think design
> variations should cause too much trouble. So I don't
> have a problem with keeping vehicles built as
> prototypes flying in the initial operational period.
> However, operating with a single vehicle could be
> quite difficult for unscheduled maintenance, or a
> sudden need for a rescue mission.

Perhaps the first two prototypes could test different design approaches
yet be brought on line together, this might also help mitigate any
vehicle specific delays.

> One would still try to avoid unnecessary differences
> that could confuse the pilot. In the reserve, we flew a
> P2Vs that, for some reason or another, had the a 30
> KVA alternator and 30KW DC generator on either
> the starboard or port recip. The other engine had two
> DC generators. Under certain conditions with an
> engine-out, you could blow the single DC generator
> by not cutting the electrical load before shutting down
> the bad engine--which could result in the loss of the
> aircraft. We also used to shift seats in the reserve--
> which was interesting with a symmetrical arrangement
> of intercom and rocket switches.

Yes.

> One needn't adopt the entire system. However,
> Shuttle has proven that gliding reentry and dead-stick
> landing is practical even with high landing speeds and
> very low lift-to-drag ratios. Landing at one-third the
> landing speed and at a significantly higher lift-to-drag
> ratio becomes far less contestable. Similarly, much
> lower reentry temperatures with mechanically
> attached, metallic heat shields also become less
> contestable.

Yes.

> Yes, but I would want to follow the route that works
> first. If the second route is the one requiring much
> more funding, it would follow after adequate success
> with the first route.

I think after such an initial success follow up programs will come
relatively easily. It may be sensible to make the initial program fairly
self sufficient and allow that the follow up larger program/s will be
subject to further refinement integrating lessons learned.

> I am revisting the single-engine carrier and single-
> engine orbiter half-scale approach as a backup to not
> being able to get funding for the full-scale version.
> Allowing the orbiter to be unmanned, as you and
> Fred suggest, does seem to be significantly
> advantageous for the much smaller orbiter.
> (Half-scale --> quarter mass and quarter wing area).

I am very interested to see how this turns out. I suspect unmanned
operation can come later if cargo intensive markets pay for it. Get to
initial flight tests by the lowest cost development approach possible,
far more funding will likely follow success.

Assuming a RD-0124 with around 20 ton stage GLOW, a drymass fraction of
10-12%, (around two ton), might result in around 800-350kg payload. This
could do some useful things, if possible, is it possible?

At this smaller scale I suspect a high degree of structural integration
of the tanks will be required to keep drymass down. The propellant
tanks, fuselage and aeroshell might want to be one and the same. Perhaps
constructed similarly to a conventional rocket stage with wings attached
at the back and a cockpit and/or cargo bay added to the front.

The smaller scale will also increase the relative lifting area of the
fuselage, smaller wings might be possible, though they will have to be a
long way back. Something the shuttle taught us was that subsonic L/D
does not much matter. At the very low wing loadings, the wings are
required more for control and CoG management.

> Perhaps. I think the one RD-0124 manned carrier
> plus one RD-0124 unmanned orbiter may yield a
> performance/mission combination that may be
> saleable in one or more ways.

Yes it could be interesting.

> Perhaps again. However, I think a total system--even
> with compromised performance and economics, but
> lower investment cost, may make more sense. It
> allows the company building and operating the carrier
> to be more aggressive with respect to potential uses.

Yes that is true.

> I think that that level of performance can be achieved
> at an order-of-magnitude lower cost--perhaps for
> less investment than was made in Falcon I.

I think you are right. Elon, while significantly improving on the
status quo, still got it fairly wrong. Maybe you could take an Orbiter
1, followed by an Orbiter 5 approach. :-)

> The first (carrier) stage may require less development
> effort; however, airframe mass is substantially higher
> (and correspondingly more expensive) than the
> orbiter -- even though both stages use a similar
> engine. Initial thrust-to-weight is perhaps 0.4 for the
> carrier, and 1.5 for the orbiter. This is countered
> somewhat by more expensive materials in the orbiter.

> Engine performance for available engines tends to
> drive the initial approach to a reusable orbiter--or at
> least to reusable engines.

Even for the rest of the vehicle, I am not sure that reusable is much
more expensive up front. With integrated as opposed to piecemeal
design, drymass can be greatly reduced and reusability can cost little
more.

Recent delays in the Falcon 1 launch do not sound encouraging. I wonder
if it will require the next Elon Musk to take development to the next
level and opt for fast turnaround reusability from the start.

Xcor and Tspace are both moving in not dissimilar TSTO HTHL directions.
Perhaps there is a degree of design convergence going on. It would not
surprise me if either of them found significant rich angel investment.

Pete.


.

Quantcast