[ExI] Rocket lander control systems

Sun Jan 3 22:00:19 UTC 2021

From: extropy-chat <extropy-chat-bounces at lists.extropy.org> On Behalf Of Dave Sill via extropy-chat
Sent: Sunday, January 3, 2021 11:36 AM
To: ExI chat list <extropy-chat at lists.extropy.org>
Cc: Dave Sill <sparge at gmail.com>
Subject: Re: [ExI] Rocket lander control systems

On Sun, Jan 3, 2021 at 1:23 PM BillK via extropy-chat <extropy-chat at lists.extropy.org <mailto:extropy-chat at lists.extropy.org> > wrote:

Something to get Spike even more excited!   :)

Elon Musk is thinking about an alternative landing system. The problem
is that the lander legs have to be strong enough to support the weight
of the lander section. And strength means extra weight. For the new
Heavy Booster the weight is getting a bit excessive. So he is going to
try and catch the lander (while it hovers) with the launch tower arm
to support the weight.  Needless to say, that's a bit tricky!

>…Seems like landing in some kind of cradle would be a lot easier.

-Dave

I am running with Dave’s idea a bit.

Imagine four sturdy towers with a mesh net made of nylon cord of about 3 cm diameter with cord centers at about 30 cm.  The cords are attached at every intersection by something flimsy that will break, such as zip ties, just strong enough to hold the cords in place in a mesh configuration.

Imagine this net with dimensions about 50 meters width by about 200 meters length, suspended about 120 meters above water on one end, perhaps 40 meters on the other.

Imagine a fly-back first stage where the target is the spot shown.  The notion is to have the stage punch thru the mesh and get caught on the aft control surface, at which time it will hang upside down:

This booster stage I have envisioned as a jet fuel/Lox burner.  The payload (a second stage) rides up top with the second stage nozzle  over a four rail tepee structure with rollers on the rails.  The reasoning is that the stage would fly back, hit the net at an angle of about 20 degrees from horizontal, the rails push the cords to either side without cutting the cords (the rollers let the cords roll back) at which time the aft control surfaces catch the cords.

I thought of having an ascent configuration as shown on the right side and a descent/catch configuration shown on the left side below.

The reasoning is that the leading edge is sharp but the trailing edge is wide or rounded so you don’t cut the cords during the catch event.

He notion then would be to fly back, bleed off as much speed as possible, use the aerodynamic lift to fly back at a glide ratio of perhaps 3 to 1, maybe 4 to 1.

Late in flight, the aft control surfaces are rotated thru 180 degrees.

In the last second before impact with the net, the forward control surfaces are jettisoned so the rocket can pass thru the net, and the booster is caught by those aft control surfaces.  Note the aft control surfaces are forward of the aft lift surfaces.

This landing scheme allows the first stage booster to use every bit of the fuel in the tanks.  It lands the booster back at Cape Canaveral where it started, reducing recovery cost and time.  It protects all that expensive sexy control hardware in the aft end of the bird.

spike

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