Discussion Starship SN8 RCS ?

[BrianJ]

Hi,
I'm just playing around with another iteration of my SpaceX Starship add-on and I notice we now have some video of RCS testing.
Looks like two right at the bottom on the wing-mounts, thrust direction -Y axis (Orbiter frame convention) for pitch-up.....

....and two on the nose, thrust direction +/- X axis for yaw...but not so easy to see the direction on the video.....

I just wondered if anyone had any other info or thoughts about RCS placement, thrust rating, propellant mass/ISP or anything RCS related.
I guess I'll see if I can get it to work in Orbiter with just what I see on the videos.

Hope to see the real SN8 fly soon!!

Cheers,
Brian

 

[cosmonaut2040]

Hi Brian,
in the 3d picture in the link below from nasaspaceflight.com one can see the nose RCS:

SpaceX Starship : Texas Prototype(s) Thread 3 : Photos and Updates

SpaceX Starship : Texas Prototype(s) Thread 3 : Photos and Updates

forum.nasaspaceflight.com

There is a set of 3 thrusters pointing towards right side of the photo (based on other photos I think they are pointing in the leeward direction when the ship "bellyflops"), and a pair of thrusters pointing radially out. The other round holes, equally spaced around the circumference, are crane attachment points.

Cheers

 

[BrianJ]

Hi Brian,
in the 3d picture in the link below from nasaspaceflight.com one can see the nose RCS:

SpaceX Starship : Texas Prototype(s) Thread 3 : Photos and Updates

SpaceX Starship : Texas Prototype(s) Thread 3 : Photos and Updates

forum.nasaspaceflight.com

There is a set of 3 thrusters pointing towards right side of the photo (based on other photos I think they are pointing in the leeward direction when the ship "bellyflops"), and a pair of thrusters pointing radially out. The other round holes, equally spaced around the circumference, are crane attachment points.

Cheers

Ah! Thank you! So with those "leeward pointing" RCS we can have pitch down, and maybe roll control (used together with the aft RCS on the wing mounts). Starting to make some kind of sense to me (I think!) .

EDIT: I remember seeing a photo from some time back, with what looked like roll control RCS openings, about halfway down the fuselage, on the "leeward" side. I can't see any on SN8 fuselage, but I'll take another look.

 

[cosmonaut2040]

EDIT: I remember seeing a photo from some time back, with what looked like roll control RCS openings, about halfway down the fuselage, on the "leeward" side. I can't see any on SN8 fuselage, but I'll take another look.

I don't see any more RCS on SN8 either, I think the set on the nose plus the ones one the bottom (also "leeward" side) of the wing-strakes are it. I don't think more would be needed anyway, for roll, yaw and pitch. For orbital rendezvous they will certainly need to add some more

 

[cosmonaut2040]

So I found a post with couple of photos of the bottom RCS. There is just a single thruster there:

SpaceX Starship : Texas Prototype(s) Thread 3 : Photos and Updates

SpaceX Starship : Texas Prototype(s) Thread 3 : Photos and Updates

forum.nasaspaceflight.com

And here, just a day later, that thruster has a larger opening around it (perhaps an access cover was removed):

SpaceX Starship : Texas Prototype(s) Thread 3 : Photos and Updates

SpaceX Starship : Texas Prototype(s) Thread 3 : Photos and Updates

forum.nasaspaceflight.com

 

[BrianJ]

Thanks very much for your pointers to those images - very useful!
Yes, Starship SN8 is certainly not built for orbital operations ;-)
I wonder what thrust rating those RCS motors have, I'm currently using aproximate Shuttle RCS thrust rating, but that might be very optimistic! And since I'm not really simulating "angled" aerofoils (only the change in apparent surface area in ZX plane) the aerodynamics are probably way off, but I hope it gives some kind of feel for how the vessel works.
Anyway, it's fun to play with while waiting for the first SN8 flight.
Cheers,
Brian

 

[Kyle]

Shuttle RCS thrust actually sounds about right, but we know basically nothing about this engine. Doesn't even have a name that's publicly known.

 

[cosmonaut2040]

Thanks very much for your pointers to those images - very useful!

You're very welcome! I am a huge fan of the Starship and also of all your add-ons, so I'm glad to be able help

I follow the Starship update threads on Nasaspaceflight quite closely, and I believe I saw it mentioned somewhere that these are just cold-gas thrusters (also I kind of doubt people would work with hypergolic systems out in the open like what we see in Boca Chica). So I would guess they might be similar, or even the same, as the cold gas thrusters on Falcon 9 first stage. Not that I'd know any specifics of those thrusters either...