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Old November 19th 19, 01:25 PM posted to sci.space.policy
Jeff Findley[_6_]
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Default Steel for Shuttle

In article ,
says...

On 2019-11-18 07:24, Jeff Findley wrote:

This statement makes no sense. Starship is an upper stage whose
propellant tanks contain both cryogenic methane and cryogenic LOX.


Active cooling of some sensor near the skin would require piping and
valves to bring the cryo to that point when needed. Valves also need
elextrical wiring to control them. This means extra weight and conplexity.

You didn't even click on the links I provided to high temperature
aerospace wiring, did you?

I don't doubt that wiring that resists heat is readily available. I have
some in the stove at home. But sensors are different. Consider the
Shuttle would pop out an pitot for air speed during the "gliding" phase
before landing. Whatever Starship uses will liekly need something near
to the skin (and antennas likely need to be under a non-steel portion of
skin).

Yep, things can be solved. But the issue is at what cost in weight.
Remember that this is a decision to allow for much higher tempoeratiure
of structure to save some weight in the heat shield.


When your spacecraft has a dry mass greater than 100 tons, you've got
quite a bit of mass margin to work with. SpaceX isn't designing this
using the "performance uber alles" philosophy of traditional aerospace
engineers. And if it's a ton or two overweight, so what? Is 148 tons
to LEO significantly different than 150 tons to LEO (especially when
compared to the competition)?

SpaceX has
designed not one, but two reentry vehicles so far (Dragon and Dragon 2).


Both of which are traditional in structure with a covering of the skin
to protect against heat. And much smaller in scale. So the SPaceX are
not merely applying same experienced onto StarShip, they need to develop
new way of protecting Starship that will have some exposed/naked Steel.


And that problem is actually easier due to the fact that Starship will
be mostly empty tankage on reentry. That means it's more "fluffy" which
means far lower total heat to deal with during reentry.

But as a business, it is possible that having a super heavy dump

truck
may turn out to be a better business than having a lightweight ferrari
to deliver the same payloads.


The above is word salad. Starship is no "lightweight Ferrari". The
prototypes mass 200 tons *dry*.


Exactly. I said that it might be possible the super heavy thing may have
terrible performance due to being overweight but still be a better at
generating profits.


On what planet is 150 tons payload to LEO "terrible performance"?

The problem with being an overweight dump truck is that when you are
pushing limits such as going to Mars, you might actually require the
perfornmance of a Ferrari.


More word salad.

Jeff
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