On 2019-10-14 2:52 AM, JF Mezei wrote:
On 2019-10-10 06:42, Jeff Findley wrote:

This I agree with. But, I seriously doubt extensible nozzles will be
one of them.

Wouldn't 3 engines with variable nozzle weight less and cost less than 6
engines (3 optimized for vacuum and 3 for sea level) ?


Weigh less, yeah there is a distinct possibility. Cost less? No. For
three reasons. One the NRE to design them, two the cost to retrofit the
Raptor to accommodate them and three they wouldn't be necessary for
Super so now you have a specialized nozzle just for Starship and
produced in far less quantity that that of sea level Raptor. Thus losing
out on the saving to be had in mass manufacture of the same nozzles.

And there is another reason. A variable geometry nozzle optimized for
Earth won't be of much help on Mars. So now you are talking about yet
another design. Here's a thought tho. Maybe you take another set of Mars
optimized nozzles along as cargo and swap out the Earth nozzles once on
Mars. Of course, over optimization is the bane of engineering. If it
isn't necessary, why do it? Elon has raised this point again and again.
I'm not going to second guess him.

Dave