Elon seems to have given up rather quickly on the idea of Starsgip
landing with legs etc, and the focus now is on "Stage 0" with the arms
that hope to grab both the boosters and Starship as they land.

I know, iterative design. Get it to fly before worrying about landing.

The Stage 0 cradle capture is fine if Starship is to launch a satellite
and come back to Texas.

But since the goal is to go to Mars and Moon, those missions will
reaquire some real landing legs. And these legs will require some hefty strength to absorb the weight+impact at landing, as well as support a
fully fueled vehicle prior to departure.


I note that the booster has externally mounted COPV tanks for various
gases (and they are having to build aerodynamic shrouds for them).

I am curious on whether this is the result of iterative design (by the
time they discovered the need for such tanks it was too late to
integrate inside fuselage), and whether the same thing risks happening
with landing legs/gear if, by the time they get serious about it, they discovere theye is so room to have proper landing legs that can be deployed

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JF Mezei <[email protected]> wrote:

Elon seems to have given up rather quickly on the idea of Starsgip
landing with legs etc, and the focus now is on "Stage 0" with the arms
that hope to grab both the boosters and Starship as they land.

I know, iterative design. Get it to fly before worrying about landing.

The Stage 0 cradle capture is fine if Starship is to launch a satellite
and come back to Texas.

Or landing on one of their floating platforms that they're converting
from existing oil rigs.

But since the goal is to go to Mars and Moon, those missions will
reaquire some real landing legs. And these legs will require some hefty >strength to absorb the weight+impact at landing, as well as support a
fully fueled vehicle prior to departure.

The landing legs for the Moon can be WAY smaller and lighter than the
ones necessary for Earth, that 0.1654g is an massive advantage.

Heck, arguably the biggest problem landing on the Moon is that the
main rockets can't be used because they're so powerful and close to
the ground that they'd blow up too much dust - hence the special and
less powerful landing thruster placed high on the Starship.

And it's not just lower gravity on the Moon, since it's not going to
be refuelled on the Moon it will also have way less mass, furher
reducing the strength needed.


The landing legs for Mars obviously can't be as light as the Moon
variant but even at 0.3794g they can still be much lighter than on
Earth AND they're quite a bit down the development pipe.

In this case they do need to be able to bear the full mass since it'll
be refuelled on the ground but that's a static load which is much less stressful than landing with the same mass.

Also AFAIK the plan is to long-term use the same landing system for
Mars, but obviously the first X landings/take-off will need legs.
Later they skip them to increase the payload fraction.

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On Oct/31/2021 at 11:32, Torbjorn Lindgren wrote :
[snip]

The landing legs for Mars obviously can't be as light as the Moon
variant but even at 0.3794g they can still be much lighter than on
Earth AND they're quite a bit down the development pipe.

Do you know something about SpaceX schedule for going to Mars that I
don't? Last I heard Musk wanted to reach Mars around 2026. I never
thought that SpaceX would keep that schedule, but I don't think that
Musk wants to push the development of Mars landing legs "quite a bit
down the development pipe".


Alain Fournier

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Alain Fournier <[email protected]> wrote:

On Oct/31/2021 at 11:32, Torbjorn Lindgren wrote :
[snip]

The landing legs for Mars obviously can't be as light as the Moon
variant but even at 0.3794g they can still be much lighter than on
Earth AND they're quite a bit down the development pipe.

Do you know something about SpaceX schedule for going to Mars that I
don't? Last I heard Musk wanted to reach Mars around 2026. I never
thought that SpaceX would keep that schedule, but I don't think that
Musk wants to push the development of Mars landing legs "quite a bit
down the development pipe".

No special knowledge and I probably overstated it a bit, what about
"not an immediate concern"?

To my mind they have plenty of things they need to get done before
starting full work on the design-work for the Mars landing legs,
though I expect SOME work is already ongoing for all the various
landing legs (because it has implications for other things).

Re: schedule - IIRC the goal was originally to use the 2024 Q4 launch
window, now it's more like the window after that, IE Q4 2026. With
Elon-time and various other factors I personally consider a more
realistic expectation that it might launch in the window after that
(IE 2028 Q4 to 2029 Q1, it's 2 years and a little extra between each).

That doesn't mean they shouldn't have the 2026 window as the
aspirational goal, if they stop aiming for that too early it's likely
to add delays.

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Alain Fournier submitted this idea :

On Oct/31/2021 at 11:32, Torbjorn Lindgren wrote :
[snip]

The landing legs for Mars obviously can't be as light as the Moon
variant but even at 0.3794g they can still be much lighter than on
Earth AND they're quite a bit down the development pipe.

Do you know something about SpaceX schedule for going to Mars that I don't? Last I heard Musk wanted to reach Mars around 2026. I never thought that SpaceX would keep that schedule, but I don't think that Musk wants to push the development of Mars landing legs "quite a bit down the development pipe".

But if you've listened to his tour with Tim Dodd, he's explicitly said
that refueling isn't front-of-mind until after Starship achieves orbit.
Refueling needs to be solved before legs for Mars or even the moon.

/dps


--
"That’s where I end with this kind of conversation: Language is
crucial, and yet not the answer."
Jonathan Rosa, sociocultural and linguistic anthropologist,
Stanford.,2020

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On 2021-11-03 06:45, Snidely wrote:

Refueling needs to be solved before legs for Mars or even the moon.

What happens if the use the space in the skirt for refueling and once
that is done , set, cast in concrete, they realise there is no space
left for proper landing gear?

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On Wednesday, JF Mezei yelped out that:

On 2021-11-03 06:45, Snidely wrote:

Refueling needs to be solved before legs for Mars or even the moon.

What happens if the use the space in the skirt for refueling and once
that is done , set, cast in concrete, they realise there is no space
left for proper landing gear?

The concrete is the landing /field/.

And who says the legs have to be in the skirt?

[It looks like refueling has already moved outside the skirt, since the
Quick Disconnect doesn't reach in and goose Starship while it's stacked
on Super Heavy.]

/dps

--
"Inviting people to laugh with you while you are laughing at yourself
is a good thing to do, You may be a fool but you're the fool in
charge." -- Carl Reiner

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