totm nov 2023 SpaceX Discussion Thread

[tater]

 

[tater]

Automated stud welding:

 

[RCgothic]

Not often launches move left!

[Wjolcz]

4 hours ago, sevenperforce said:

Not sure why Tim is confused

He's not. He just likes attention (in his case it's actually profitable). Playing dumb is one way to get it.

[sevenperforce]

High-res closeup of the bolted-on TPS tiles shows no visible fillers or caps whatsoever:

I wonder how they did it.

[Wjolcz]

26 minutes ago, sevenperforce said:

I wonder how they did it.

It's The Technique™. Me too, actually. Like, how are they going to service them? Maybe magnetic bolts and nuts or something?

 

Edited April 20, 2020 by Wjolcz

[tater]

24 minutes ago, sevenperforce said:

I wonder how they did it.

If you look at the stud welder, it obviously passes current through the stud. Touch stud to steel, bang, it's attached. What are the tiles made of? Conductive?

[sevenperforce]

7 minutes ago, tater said:

If you look at the stud welder, it obviously passes current through the stud. Touch stud to steel, bang, it's attached. What are the tiles made of? Conductive?

Perhaps the tiles are not removable? I would have imagined that the tiles are removable, but maybe they are only designed to remove if they need to be replaced, in which instance you just smash them anyway.

[cubinator]

50 minutes ago, sevenperforce said:

High-res closeup of the bolted-on TPS tiles shows no visible fillers or caps whatsoever:

I wonder how they did it.

Somebody left their can of pepsi on the bottom right for scale.

[magnemoe]

1 hour ago, sevenperforce said:

Perhaps the tiles are not removable? I would have imagined that the tiles are removable, but maybe they are only designed to remove if they need to be replaced, in which instance you just smash them anyway.

That is one option, and yes little reason to remove except for replacement. This would however be a bit complex as you would need some sort of void who would catch on an barb on the stud, in short probably a bit hard to make this solid enough. 

[tater]

Looks like KSC just dodged a tornado bullet.

 

[tater]

F9 is apparently inside the hanger.

 

 

[sevenperforce]

1 hour ago, magnemoe said:

That is one option, and yes little reason to remove except for replacement. This would however be a bit complex as you would need some sort of void who would catch on an barb on the stud, in short probably a bit hard to make this solid enough. 

Start with a permanently-welded nut on the skin of starship and a tile manufactured with an internal bolthole. Double-sided bolts come in two sections that can be current-welded together. One section is screwed into the welded nut; the other into the tile. Place and current-weld, permanently joining the two bolt-sections into one. When you need to remove the tile, you smash it and unscrew each bolt from the underlying nut.

[zolotiyeruki]

Or, just have a bolt that's right-hand threaded on one end and left-hand threaded on the other.  Matching nuts on the tiles and the skin.

[sevenperforce]

52 minutes ago, zolotiyeruki said:

Or, just have a bolt that's right-hand threaded on one end and left-hand threaded on the other.  Matching nuts on the tiles and the skin.

This would work if you had a single bolt, but not with a triangle of bolts.

[magnemoe]

1 hour ago, sevenperforce said:

Start with a permanently-welded nut on the skin of starship and a tile manufactured with an internal bolthole. Double-sided bolts come in two sections that can be current-welded together. One section is screwed into the welded nut; the other into the tile. Place and current-weld, permanently joining the two bolt-sections into one. When you need to remove the tile, you smash it and unscrew each bolt from the underlying nut.

Probably an simple solution we did not think about, like high temperature glue in the hole or something more like the expanding screws you use in plaster walls or the nails you can install with an tool from one side. 
And yes the bolt is probably not an simple bolt. but 3, the part who get welded on, the other part and the lathing mechanism who is welded to the second. high chance of an hole and an pin or wire to stop it from unscrewing. 

[mikegarrison]

21 minutes ago, magnemoe said:

Probably an simple solution we did not think about, like high temperature glue in the hole or something more like the expanding screws you use in plaster walls or the nails you can install with an tool from one side. 
And yes the bolt is probably not an simple bolt. but 3, the part who get welded on, the other part and the lathing mechanism who is welded to the second. high chance of an hole and an pin or wire to stop it from unscrewing. 

No, no, it can't be glue. The space shuttle used glue, and we all know that the space shuttle was the font of evil. Surely SpaceX wouldn't use anything that resembled what the NASA did with the space shuttle.

[magnemoe]

9 minutes ago, mikegarrison said:

No, no, it can't be glue. The space shuttle used glue, and we all know that the space shuttle was the font of evil. Surely SpaceX wouldn't use anything that resembled what the NASA did with the space shuttle.

You can get glue handling up to 2000 centigrade. Now use an robot in the VAB to test is any of the tiles is loose with an robot vacuum cleaner on an crane, you could also use paint who change color on the inside of the tank. Use some large plugs, think bottom plug to drain oil from an engine, Pop an camera and an led diode, look around, if some of the paint has changed color, you have an problem, you probably has to rip of lots of tiles and xray it, worst case you have to cut it up and replace an segment so you loose a week. 
 

[tater]

 

[tater]

 

[sevenperforce]

2 hours ago, tater said:

 

I really do wonder from this if they are going single-flap-pair.

Midbody wings with vertical flaps might be enough, with RCS. Similar to a return to the IAC2017 version.

[Wjolcz]

2 hours ago, sevenperforce said:

I really do wonder from this if they are going single-flap-pair.

Midbody wings with vertical flaps might be enough, with RCS. Similar to a return to the IAC2017 version.

Seems reasonable. I know that KSP is not the perfect representation of real life BUT...

I did just that in KSP trying to create a Starship-like rocket a while ago. Was still pretty tricky to control but much easier than paying attention to two sets of flaps at the same time. Instead of perfecting it I went with a featherwing design. KSP's aerodynamics make shuttlecock's reentries much more forgiving than real life.

Edited April 21, 2020 by Wjolcz

[zolotiyeruki]

Going down to two actuating fins might be fine, since there's little need for roll control.  Since you always want the same side windward, as long as you're aerodynamically stable, you don't need control in that axis.  That means that you only need two degrees of freedom (yaw, pitch), and therefore, you can theoretically get all the maneuverability you need with only two control surfaces.  It's analogous to a delta wing airplane with a pair of elevons but no rudder.

[sevenperforce]

2 hours ago, zolotiyeruki said:

Going down to two actuating fins might be fine, since there's little need for roll control.  Since you always want the same side windward, as long as you're aerodynamically stable, you don't need control in that axis.  That means that you only need two degrees of freedom (yaw, pitch), and therefore, you can theoretically get all the maneuverability you need with only two control surfaces.  It's analogous to a delta wing airplane with a pair of elevons but no rudder.

Controlling yaw with just two flaps in the coronal plane, actuating ventrally or dorsally, is impossible. You can control roll easily, though. Lift the left flap to decrease drag and roll left, and vice versa. Lift both to decrease aft drag and send the center of pressure forward of the center of mass, pitching up; extend both to increase aft drag and pull the center of pressure aft of the c enter of mass, pitching down.

The reason for four flaps is that you actually can control yaw aerodynamically. Order the forward flaps to roll left and the rear flaps to roll right, and you'll yaw left.

If you only have two flaps, you can't nudge yaw without a high AoA, but there's no barrier to using RCS for yaw with low AoA.

[Wjolcz]

I was about to say that yaw is kind of useless anyway but then realized that you can actually aim for the landing site using yaw. I guess it makes sense. Instead of carrying an extra pair of wings you go *poof* with RCS to yaw and that actually makes you a bit lighter during the landing.