JF Mezei wrote on Wed, 22 May 2019
15:36:18 -0400:

On 2019-05-21 23:08, Fred J. McCall wrote:

Except it doesn't work that way. Try to buy an Intel 80486 processor.
You can't. And that will apply to almost every part in the LEM
blueprints.

Since they need hardened CPUs and RAM, they'll use whatever is available
on the market (usually older vintage) or special order some.


Yes, they will, which means all the avionics (including heat
dissipation, which affects structure) will be a clean sheet design.


I am not
advocating they use the same computers as on the 1960s LEM. I even
mentioned they could run this on an iPhone if they wanted it.


What you were advocating was, as usual, unclear, then.


But for structures, I have to wonder why they wouldn't re-use the
general design of the LEM, as ugly as it was since it fit the purpose.


Probably because they don't want the limitations of that design. Why
do you think Blue Origin didn't just do that for their Blue Moon
lander? Are they so much stupider and so much more inexperienced than
you? Somehow I just don't think so.

But all your parts are going to be from new vendors using new assembly
lines. You're going to have to certify everything as if it was a
brand new vehicle.

Yes, but re-using a design you know has worked well saves you on the
design stage.


Not really, no. Whatever you build needs to interface with boosters
in a standard way and be of a size to fit inside the payload fairing
of whatever rockets you plan on using to get it out to Gateway. You'd
like to use modern alloys to build the thing. It needs to provide
power and heat dissipation for all the electronics you stuff in it.
You'd like to use modern, more efficient engines that use propellants
that you can make in situ out of water ice. I could go on.

Now lets see how the old LEM stacks up. It's too physically large to
fit inside the payload fairing of anything other than SLS or Falcon
Super Heavy. It relies on a docking adapter that doesn't exist
anymore. It's battery powered and only has power for a 75 hour
duration. It's made largely out of, well, tissue paper. Atmosphere
is pure oxygen at 5 PSI or so. It uses old hypergolic engines fueled
by Aerozine 50 and using dinitrogen tetroxide as the oxidizer.

See what a poor fit that is for what we actually want to do?


When totally new, you have to certify the design will work and then
certify the hardware as built meets the design. When re-using an
ecxisting design, you only have to certify the new hardware fits the design.


You've never actually been exposed to engineering, have you?


--
"Ignorance is preferable to error, and he is less remote from the
truth who believes nothing than he who believes what is wrong."
-- Thomas Jefferson