totm nov 2023 SpaceX Discussion Thread

[JoeSchmuckatelli]

22 minutes ago, RCgothic said:

SN10 is getting stacked! Nearly ready to go even before SN9's flight!

 

 

Is there anything changed between how SN 10 is structured compared to SN8?  (also: isn't SN9 virtually the same build as 8?)

IOW: will SN 10 be showcasing any 'lessons learned' from SN8's flight in terms of physical characteristics - rather than just updating the programming?

[RealKerbal3x]

Just now, JoeSchmuckatelli said:

Is there anything changed between how SN 10 is structured compared to SN8?  (also: isn't SN9 virtually the same build as 8?)

SN10 is broadly similar to SN8, but there are probably a few changes here and there. SN9  and SN10 are very similar to SN8 but while some components of SN8 still used the old stainless steel alloy (301), SN9 and 10 are fully built from the new alloy (304L).

1 minute ago, JoeSchmuckatelli said:

IOW: will SN 10 be showcasing any 'lessons learned' from SN8's flight in terms of physical characteristics - rather than just updating the programming?

SN10 began construction before SN8 flew so there probably aren't any major physical changes.

[StrandedonEarth]

Chugging right along, as usual. I wonder when they'll start building a proper payload-deploying nose, instead of the plain structural one? Around the time SH1 moves to the mount for testing?

And which SN will be the first to have the three Vactors? Will it also have a cargo nose?

[RealKerbal3x]

5 minutes ago, StrandedonEarth said:

Chugging right along, as usual. I wonder when they'll start building a proper payload-deploying nose, instead of the plain structural one? Around the time SH1 moves to the mount for testing?

And which SN will be the first to have the three Vactors? Will it also have a cargo nose?

Elon mentioned that significant changes would be coming around SN15. We don't know what that will entail, but maybe it'll get a payload-deploying nose (as Elon also said a while back that the mid-teens would be the first to orbit) and/or RVacs.

[magnemoe]

43 minutes ago, StrandedonEarth said:

Chugging right along, as usual. I wonder when they'll start building a proper payload-deploying nose, instead of the plain structural one? Around the time SH1 moves to the mount for testing?

And which SN will be the first to have the three Vactors? Will it also have a cargo nose?

Probably not, unlike many I think reentry will be harder than the flip and its pointless with an cargo door on something who will not reach orbit. 
Now if its problematic enough they might start launching starlink on the test launches assuming reentry or landing is the issue. 
Think semi disposable. 

[magnemoe]

Kind of relevant regarding the Falcon 9 super cooling fuel and oxidizer. 

First time I heard about it outside of falcon 9. 

[StrandedonEarth]

 

[sevenperforce]

The “catch by the grid fins” idea reminds me of the structural loading design of the Soyuz family of rockets. The four side boosters are suspended from the four payload arms and the sustainer stage hangs off of them while also supporting the upper stage in compression. This works really, really well because it mimics how the loads are distributed in flight: the side boosters are lighter, so the sustainer “hangs” from them in flight while continuing to support the upper stage in compression. 

Elon’s idea isn’t too far from this. The grid fins are supporting a dramatic amount of weight during entry (remember that the booster will have a significant amount of propellant prior to landing) and have to be fixed to the booster with enough strength to provide significant torque and pitch control. I am pretty sure that the booster decelerates by more than one gee during the extremes of re-entry. So they should be more than capable of supporting the weight of an otherwise-empty booster. The combination of hot-gas thrusters and the ability to hover should make that touchdown quite gentle.

What would be REALLY cool would be if the grid fins also provided the primary support during launch. But that might be asking too much. The booster is vastly heavier at launch, and unlike the Soyuz, it is supported in flight entirely from the 28-engine thrust puck.

[tater]

[GuessingEveryDay]

Is it just me, or is that Cybertruck looking small?

[RealKerbal3x]

Just now, GuessingEveryDay said:

Is it just me, or is that Cybertruck looking small?

It does look a little small, yes, Cybertruck has a width of approximately 2m and Dragon is 3.7m diameter.

It could just be perspective though.

[magnemoe]

1 minute ago, GuessingEveryDay said:

Is it just me, or is that Cybertruck looking small?

Very small, F9 stack is 3.5 meter wide. with if truck is less than half of it. 

[CatastrophicFailure]

2 hours ago, GuessingEveryDay said:

Is it just me, or is that Cybertruck looking small?

Maybe it’s the promised mini-Cybertruck for the European market. 

[KSK]

1 hour ago, CatastrophicFailure said:

Maybe it’s the promised mini-Cybertruck for the European market. 

Whatever it is, it would make a nice upgrade from the old Apollo lunar rovers.  Bet you could really kick up some regolith in one of those bad boys.

[Kerminator K-100]

6 hours ago, GuessingEveryDay said:

Is it just me, or is that Cybertruck looking small?

Kinda thicc if you ask me.

[mikegarrison]

8 hours ago, sevenperforce said:

The “catch by the grid fins” idea reminds me of the structural loading design of the Soyuz family of rockets. The four side boosters are suspended from the four payload arms and the sustainer stage hangs off of them while also supporting the upper stage in compression. This works really, really well because it mimics how the loads are distributed in flight: the side boosters are lighter, so the sustainer “hangs” from them in flight while continuing to support the upper stage in compression. 

Elon’s idea isn’t too far from this. The grid fins are supporting a dramatic amount of weight during entry (remember that the booster will have a significant amount of propellant prior to landing) and have to be fixed to the booster with enough strength to provide significant torque and pitch control. I am pretty sure that the booster decelerates by more than one gee during the extremes of re-entry. So they should be more than capable of supporting the weight of an otherwise-empty booster. The combination of hot-gas thrusters and the ability to hover should make that touchdown quite gentle.

What would be REALLY cool would be if the grid fins also provided the primary support during launch. But that might be asking too much. The booster is vastly heavier at launch, and unlike the Soyuz, it is supported in flight entirely from the 28-engine thrust puck.

Well, we'll see if it works. But to me the whole thing is starting to sound like they are getting desperate about figuring out their landing gear issues.

I suppose another concern is that he wants this to be a land/refuel/refly thing, and moving the booster from a landing spot to a launch pad puts a cramp in that. However, the precision required to come down and land exactly where they took off from is pretty crazy. I mean, even a small wind gust could cause a major disaster.

[RealKerbal3x]

6 hours ago, mikegarrison said:

Well, we'll see if it works. But to me the whole thing is starting to sound like they are getting desperate about figuring out their landing gear issues.

Their issues have always been with Starship landing gear. Super Heavy landing gear has always been fairly straightforward, just stick some big fixed ones on there.

This is more about undesigning those legs and moving the shock absorbers out of the booster itself to save mass.

[Deddly]

7 hours ago, mikegarrison said:

Well, we'll see if it works. But to me the whole thing is starting to sound like they are getting desperate about figuring out their landing gear issues.

I suppose another concern is that he wants this to be a land/refuel/refly thing, and moving the booster from a landing spot to a launch pad puts a cramp in that. However, the precision required to come down and land exactly where they took off from is pretty crazy. I mean, even a small wind gust could cause a major disaster.

I imagine the catching mechanism will work on the same principle as Mark Rober's "bullseye every time" dart board.

 

[magnemoe]

19 minutes ago, RealKerbal3x said:

Their issues have always been with Starship landing gear. Super Heavy landing gear has always been fairly straightforward, just stick some big fixed ones on there.

This is more about undesigning those legs and moving the shock absorbers out of the booster itself to save mass.

This, saving weight but also reducing reuse time. I think this is a bit over focused as you could just have more superheavy in the pipeline. You would want two as an minimum is case one can not be used but need servicing or worse is lost you are stuck if you only has one but with two your launch rate goes down. 

[sevenperforce]

15 hours ago, mikegarrison said:

I suppose another concern is that he wants this to be a land/refuel/refly thing, and moving the booster from a landing spot to a launch pad puts a cramp in that. However, the precision required to come down and land exactly where they took off from is pretty crazy. I mean, even a small wind gust could cause a major disaster.

I doubt it. Superheavy is basically a bigger Saturn V. You would need extremely strong winds to have any significant effect. Plus, it will have hot-gas thrusters at both the top and bottom (rather than only the top like the Falcon 9 first stage) for fine translation.

Actually I can calculate that, come to think of it.

Let's say that worse-case scenario you only have two of the ten-tonne RCS thrusters firing continuously, one at the top and one at the bottom. That's 20 tonnes of thrust or 196 kN. What kind of wind can that compensate for? The drag equation says that F_d = C_d*ρ*v²*A/2. So we set F_d = 196 kN and solve for v to find the maximum windspeed that two hot-gas thrusters can compensate for. Solving for v, we get v = sqrt(2*F/(C_d*ρ*A)). The drag coefficient of a cylinder perpendicular to an airflow is approximately 1. Superheavy will have a cross-sectional area of 9 m * 72 m = 648 m². The density of dry air at sea level is 1.225 kg/m³. Plug and chug and you get v = 22.2 m/s or about 50 mph for us Americans. So unless Superheavy is planning on landing during a severe thunderstorm then it should be just fine.

[RealKerbal3x]

17 minutes ago, sevenperforce said:

Plus, it will have hot-gas thrusters at both the top and bottom (rather than only the top like the Falcon 9 first stage) for fine translation.

Do we know that for sure, or are you just speculating?

[sevenperforce]

If they do actually end up doing this I would expect the "catch" mechanism to also be the stabilizing member during Starship loading, similar to the function of the clasper arms on the F9 transporter-erector:

The arms would hold onto the extended grid fins while the Starship is mated and loaded. At T-1 min, they would fold away and the grid fins would fold down for launch.

At landing, the arms would remain open as Superheavy initially approached, then come together quickly to catch the grid fins. Once caught, they would lower the booster on the launch clamps and remain attached for stability until the next launch.

4 minutes ago, RealKerbal3x said:

Do we know that for sure, or are you just speculating?

I am about 95% confident that Elon specifically said the booster would have aft and forward hot-gas thrusters for fine translation control back when he was talking about landing on the launch clamps.

[RCgothic]

 

 

 

[magnemoe]

14 hours ago, Deddly said:

I imagine the catching mechanism will work on the same principle as Mark Rober's "bullseye every time" dart board.

 

Yes, now scale it up a bit so the dart is 200 ton  
Thinking about it using rocket engines to move it around makes sense. 

[Flavio hc16]

2 hours ago, RCgothic said:

 

 

 

tldr:

1)they have some contracts were they can choose between using falcon 9 and starship

2) She is positive about Starship reaching orbit in 2021

3) selling flight proven booster is easier than new ones

4) the sn8 has "de-risked" starship