Griffin Wants Inline SDLV and 5 Segment SRB/CEV

"Rand Simberg" wrote in message
.. .
On Sun, 10 Jul 2005 22:17:45 -0400, in a place far, far away, "Murray
Anderson" made the phosphor on my monitor glow
in such a way as to indicate that:

They didn't know how refurbishable the solid would be either.

They did, since they don't refurbish it--they rebuild it from the
recovered segments, with new grain.

It's the same with a liquid booster, except for the engine assembly -
you
just refill the tanks.

No, it's not that simple. The solids consist of segments, which can
be broken down and rebuilt. A liquid would have huge tanks that would
have to be inspected.


That doesn't establish an advantage for the solids. You could just as
well
say the liquids have tanks that only have to be inspected whereas the
solids
have to be rebuilt.

It's easy to inspect a "tank" that's a segment. It's much harder to
do so with a complete tank (one that would also be much lighter
weight, and thus more suspect, and subject to more damage upon hitting
the water).


The difference in weight would be about a factor of 2 (7% versus 14%), and
the liquid tanks could be made somewhat heavier if necessary.
If you take a solid rocket booster apart you have to put it back together
with the attendant risk of damage, since the segments tend not to be
perfectly circular when you put them back together.

The engine nozzle and gimballing system of the solid are supposedly
recovered and reused, which would be like the engine assembly on the
liquid - except for the turbopump system.
There would be a difference if the turbopump system were harder to
protect
from seawater than the gimballing system on the solid.

As indeed it would.

You have a source for this?

Just common sense, and it was the judgement at the time. I really
don't understand why you're second guessing all of this.


The gimballing system requires a power source, which is provided by a
turbine driven by the decomposition of hydrazine. This drives the hydraulic
pumps - so you have the same sort of system to protect from sea water as
with a liquid rocket engine turbopump system.
It's not just common sense.

That's a restatement of the problem in other words, together with a
rationalization. What was it they wanted to do and didn't have the
money
for? A better thermal protection system would help, but that wasn't
on
offer, was it?

With more money, yes. They could have, for example, used a titanium
structure underneath, instead of aluminum.

But the problem is the susceptibility to debris damage, not the
insulating
qualities of the tiles.

That's only part of the problem.


And what is the other part of the problem?

The maintainability of the main engines, the toxicity of the OMS and
RCS, and APU propellants, the fragility of the TPS, the complexity of
payload integration, etc.

Murray Anderson

Rand Simberg wrote:
On Sun, 10 Jul 2005 22:17:45 -0400, in a place far, far away, "Murray
Anderson" made the phosphor on my monitor glow
in such a way as to indicate that:

And what is the other part of the problem?

The maintainability of the main engines, the toxicity of the OMS and
RCS, and APU propellants, the fragility of the TPS, the complexity of
payload integration, etc.

Those are the concrete causes of failure. But IMO it had other
problems:
* The original requirements were outrageous (jack of all trades), and
are now obsolete.
* The design was pushed top-down. After several studies, the beast
emerged in full form. As usual, most problems only manifested
themselves later as time went by and the system remained mostly
static (new environmental rules and procedures made hydrazine more
expensive, cancelation of Shuttle-Centaur due to Challenger made
the Shuttle less useful for commercial and military payloads, etc).

A reusable vehicle enables incremental testing. Let us use this ability
instead of trying to design everything to be 100% perfect the first
time.

There were upgrade programs of several sorts which mitigated some
lingering issues (thermal protective blankets, glass cockpit, SSME
redesigns, etc), others were planned but never came to be (non-toxic
OMS, RCS and APU propellants).

Most of the cost of developing a new vehicle is in the engines
(especially RLV engines). I think it would be an interesting exercise
to try to design a new RLV with more reasonable initial requirements,
initially based on Shuttle engine technology and expendable parts, then
progressively test new components and refine the vehicle until a true
reusable would emerge.

The requirements could be:
* Fully automated RLV.
* Delta-IV medium payload class.
* One week turn-around time.
* Minimize standing army as much as possible.

As mentioned before, it should use existing Shuttle propulsion
technology with potential for improvement in the future.

The heat shield could be expendable. The shield should have a simple
shape and as few parts as possible to enable easy replacement.

Parts which require replacement or heavy maintenance should be easily
removeable for replacement or inspection. This includes the heat shield
and engines.

After the initial vehicle integration and GNC was proven and in use
launching actual payloads, the design could be progressively refined
into a true RLV, most expensive component first (likely the engines,
perhaps the heat shield). I know Pratt and Whitney and Rocketdyne had
proposals for SSME replacement engines with easier maintenance (RS-83,
COBRA). These would be interesting to pursue later.

I doubt it will ever come to be however.

On Mon, 11 Jul 2005 21:33:12 -0400, in a place far, far away, "Murray
Anderson" made the phosphor on my monitor glow
in such a way as to indicate that:

It's easy to inspect a "tank" that's a segment. It's much harder to
do so with a complete tank (one that would also be much lighter
weight, and thus more suspect, and subject to more damage upon hitting
the water).


The difference in weight would be about a factor of 2 (7% versus 14%), and
the liquid tanks could be made somewhat heavier if necessary.
If you take a solid rocket booster apart you have to put it back together
with the attendant risk of damage, since the segments tend not to be
perfectly circular when you put them back together.

Nonetheless, it's like rebuilding a motor, as opposed to inspecting a
more fragile one.

The engine nozzle and gimballing system of the solid are supposedly
recovered and reused, which would be like the engine assembly on the
liquid - except for the turbopump system.
There would be a difference if the turbopump system were harder to
protect
from seawater than the gimballing system on the solid.

As indeed it would.

You have a source for this?

Just common sense, and it was the judgement at the time. I really
don't understand why you're second guessing all of this.


The gimballing system requires a power source, which is provided by a
turbine driven by the decomposition of hydrazine. This drives the hydraulic
pumps - so you have the same sort of system to protect from sea water as
with a liquid rocket engine turbopump system.

The power levels are in no way comparable.

It's not just common sense.

It is.

"Rand Simberg" wrote in message
.. .
On Mon, 11 Jul 2005 21:33:12 -0400, in a place far, far away, "Murray
Anderson" made the phosphor on my monitor glow
in such a way as to indicate that:

It's easy to inspect a "tank" that's a segment. It's much harder to
do so with a complete tank (one that would also be much lighter
weight, and thus more suspect, and subject to more damage upon hitting
the water).


The difference in weight would be about a factor of 2 (7% versus 14%),
and
the liquid tanks could be made somewhat heavier if necessary.
If you take a solid rocket booster apart you have to put it back together
with the attendant risk of damage, since the segments tend not to be
perfectly circular when you put them back together.

Nonetheless, it's like rebuilding a motor, as opposed to inspecting a
more fragile one.


That doesn't argue for one over the other.

The engine nozzle and gimballing system of the solid are supposedly
recovered and reused, which would be like the engine assembly on
the
liquid - except for the turbopump system.
There would be a difference if the turbopump system were harder to
protect
from seawater than the gimballing system on the solid.

As indeed it would.

You have a source for this?

Just common sense, and it was the judgement at the time. I really
don't understand why you're second guessing all of this.


The gimballing system requires a power source, which is provided by a
turbine driven by the decomposition of hydrazine. This drives the
hydraulic
pumps - so you have the same sort of system to protect from sea water as
with a liquid rocket engine turbopump system.

The power levels are in no way comparable.


The power levels make no difference as to whether it's damaged.

It's not just common sense.

It is.

Murray Anderson

On Tue, 12 Jul 2005 07:22:27 -0400, in a place far, far away, "Murray
Anderson" made the phosphor on my monitor glow
in such a way as to indicate that:

There would be a difference if the turbopump system were harder to
protect
from seawater than the gimballing system on the solid.

As indeed it would.

You have a source for this?

Just common sense, and it was the judgement at the time. I really
don't understand why you're second guessing all of this.


The gimballing system requires a power source, which is provided by a
turbine driven by the decomposition of hydrazine. This drives the
hydraulic
pumps - so you have the same sort of system to protect from sea water as
with a liquid rocket engine turbopump system.

The power levels are in no way comparable.


The power levels make no difference as to whether it's damaged.

They make a difference as to its likelihood of being damaged, because
the weight because high-power turbopumps are much more delicate, and
getting high power out of them while maintaining flight weight makes
them much more so.