Falcon 9 Block 5 Updates and Discussion

[rst]

Well that is disappointing. I thought one of the goals was to make it so they wouldn't have to remove the legs.  Unless they have to keep doing it until all the block 4s are used up and they can update the handling equipment.

The aim is for a flow without much post-landing inspection -- but I was expecting the inspections the first few times through anyway, to verify that whatever strengthening they added would meet design goals.  For those inspections, the legs might very well just be in the way.

[niwax]

One leg left to remove. #Block5 #bangabooster

Legless stage already.

Well that is disappointing. I thought one of the goals was to make it so they wouldn't have to remove the legs.  Unless they have to keep doing it until all the block 4s are used up and they can update the handling equipment.

Maybe for analysis purposes? I wouldn't want to retract the legs and land on blind faith alone next time.

[pospa]

Well that is disappointing. I thought one of the goals was to make it so they wouldn't have to remove the legs.  Unless they have to keep doing it until all the block 4s are used up and they can update the handling equipment.

A huge booster stage re-enters from space and lands impeccably on a small barge in the ocean. - And people express their disappointment that the legs are detached after landing.

Sorry, but it was:

1) 25th successful landing of the booster, which is great achievement, but also kind of mastered technique, so not surprising.

2) many times promoted 1st flight of the most advanced F9 with ability of faster turnarround (I know, i know those 24 hrs will come later next year) with the following feature (Elon's quote):

"The landing legs, you'll notice if you look carefully that there are no outward scallops on the perimeter of the landing leg, which were used to clamp down the leg during ascent. We have now brought those features inside the leg itself. So you'll see sort of a cleaner outer contour. And it has an internal latch mechanism that can be opened and closed repeatedly with ease. So essentially deploying the landing gear and stowing the landing gear is now a very easy thing to do, whereas previously it required several hours to re-stow the landing gear. Which can now be done with an actuator, pretty easily."

Obviously I'm not the only one SpX fan who expected this would be demonstrated by this 1st block 5 flight. As it doesn't happened we are just a bit dissapointed ... but I belive still very happy that the primary mission went 100% well. 

[Tulse]

Can someone explain why the Block 5 titanium grid fins have scalloped edges on the side facing re-entry (unlike, I believe, the flat aluminum fins)?  I would have thought that shaping like that would produce excess heating on the points of the scallops, and that the preferred shape would be flat to ensure even heating.

[mme]

Can someone explain why the Block 5 titanium grid fins have scalloped edges on the side facing re-entry (unlike, I believe, the flat aluminum fins)?  I would have thought that shaping like that would produce excess heating on the points of the scallops, and that the preferred shape would be flat to ensure even heating.

My understanding is that the "scalloped" leading edge improve the grid fins control authority in the transonic range. Sadly I can't find the specific reference now.

[brihath]

Well that is disappointing. I thought one of the goals was to make it so they wouldn't have to remove the legs.  Unless they have to keep doing it until all the block 4s are used up and they can update the handling equipment.

A huge booster stage re-enters from space and lands impeccably on a small barge in the ocean. - And people express their disappointment that the legs are detached after landing.

Sorry, but it was:

1) 25th successful landing of the booster, which is great achievement, but also kind of mastered technique, so not surprising.

2) many times promoted 1st flight of the most advanced F9 with ability of faster turnarround (I know, i know those 24 hrs will come later next year) with the following feature (Elon's quote):

"The landing legs, you'll notice if you look carefully that there are no outward scallops on the perimeter of the landing leg, which were used to clamp down the leg during ascent. We have now brought those features inside the leg itself. So you'll see sort of a cleaner outer contour. And it has an internal latch mechanism that can be opened and closed repeatedly with ease. So essentially deploying the landing gear and stowing the landing gear is now a very easy thing to do, whereas previously it required several hours to re-stow the landing gear. Which can now be done with an actuator, pretty easily."

Obviously I'm not the only one SpX fan who expected this would be demonstrated by this 1st block 5 flight. As it doesn't happened we are just a bit dissapointed ... but I belive still very happy that the primary mission went 100% well. 

I understood Elon Musk's comments included that SpaceX was going to disassemble this booster to get a good understanding as to how the improvements performed compared to their expectations.  Perhaps removing the landing legs while the first stage is on OCISLY just part of that inspection/evaluation process.

[Kabloona]

Can someone explain why the Block 5 titanium grid fins have scalloped edges on the side facing re-entry (unlike, I believe, the flat aluminum fins)?  I would have thought that shaping like that would produce excess heating on the points of the scallops, and that the preferred shape would be flat to ensure even heating.

My understanding is that the "scalloped" leading edge improve the grid fins control authority in the transonic range. Sadly I can't find the specific reference now.

Here you go. In this paper, the "scalloped" shape of the grid fin leading edge is called "locally swept." So think "scalloped" every time you read "locally swept."

https://www.sto.nato.int/publications/STO%20Meeting%20Proceedings/RTO-MP-AVT-135/MP-AVT-135-35.pdf

. The biggest disadvantages of these wings are their relatively high
drag levels at given lift characteristics as well as the weak stability at transonic speeds. The first one
emerges because of the multi-plane construction of grid fins. The second disadvantage is due to the
choking of the cell flow in the transonic regime, which happens because of the typical rectangular form
of each grid fin cell. These are serious disadvantages and can have a negative effect on realistic
applications.

The paper goes on to show that the "locally swept" (ie "scalloped") design improves the L/D of the grid fin, perhaps somewhat mitigating the choking effect in the transonic regime (though the paper only deals with M>1, unfortunately).

[LouScheffer]

I understood Elon Musk's comments included that SpaceX was going to disassemble this booster to get a good understanding as to how the improvements performed compared to their expectations.  Perhaps removing the landing legs while the first stage is on OCISLY just part of that inspection/evaluation process.

I think removing the legs makes perfect sense.  Then send them back to Texas for trials on their leg-testing rig. Verify that they are as good as new, or find out what still needs to be fixed.  At least that's what I'd do with a new leg design, rather than just launching it again to see if it works.

[Tulse]

Here you go. In this paper, the "scalloped" shape of the grid fin leading edge is called "locally swept." So think "scalloped" every time you read "locally swept."

https://www.sto.nato.int/publications/STO%20Meeting%20Proceedings/RTO-MP-AVT-135/MP-AVT-135-35.pdf

Thanks -- that's hugely informative.

[Kabloona]

Here you go. In this paper, the "scalloped" shape of the grid fin leading edge is called "locally swept." So think "scalloped" every time you read "locally swept."

https://www.sto.nato.int/publications/STO%20Meeting%20Proceedings/RTO-MP-AVT-135/MP-AVT-135-35.pdf

Thanks -- that's hugely informative.

Honestly, thank the Google.  I Googled "grid fin scallop transonic" and that was the second result. Really impressive algorithm.

[su27k]

One leg left to remove. #Block5 #bangabooster

Legless stage already.

Has the white powdery stuff on the underside (black side) of the leg been discussed?

[Hominans Kosmos]

Here you go. In this paper, the "scalloped" shape of the grid fin leading edge is called "locally swept." So think "scalloped" every time you read "locally swept."

https://www.sto.nato.int/publications/STO%20Meeting%20Proceedings/RTO-MP-AVT-135/MP-AVT-135-35.pdf

Thanks -- that's hugely informative.

Honestly, thank the Google.  I Googled "grid fin scallop transonic" and that was the second result. Really impressive algorithm.

It's not quite as impressive when you consider the document mentions transsonic only in the introduction. It would be quite a bit more impressive if the algorithm had weighed that study report somewhat lower due to the search word having not appeared at body and conclusion and findings sections near the end, or the referenced works had a focus on it.

In the end this paper does not tell us whether locally swept lattice wings have better or worse transsonic performance. We do know it improves supersonic and hypersonic performance at least.

[mme]

Here you go. In this paper, the "scalloped" shape of the grid fin leading edge is called "locally swept." So think "scalloped" every time you read "locally swept."

https://www.sto.nato.int/publications/STO%20Meeting%20Proceedings/RTO-MP-AVT-135/MP-AVT-135-35.pdf

Thanks -- that's hugely informative.

Honestly, thank the Google.  I Googled "grid fin scallop transonic" and that was the second result. Really impressive algorithm.

It's not quite as impressive when you consider the document mentions transsonic only in the introduction. It would be quite a bit more impressive if the algorithm had weighed that study report somewhat lower due to the search word having not appeared at body and conclusion and findings sections near the end, or the referenced works had a focus on it.

In the end this paper does not tell us whether locally swept lattice wings have better or worse transsonic performance. We do know it improves supersonic and hypersonic performance at least.

I refrained these earlier but here you go:

1. DESIGN OF A GRID FIN AERODYNAMIC CONTROL DEVICE FOR TRANSONIC FLIGHT REGIME
2. Swept-back Grid Fins for Transonic Drag Reduction

[1] Kabloona's first post gave me the clue to use the word "swept" in the my google searches...

[skymech231]

Could the harness attached to the inside of the leg be an active cooling system for the leg?

Sent from my XT1710-02 using Tapatalk

[Nomadd]

 Are they using better shocks than the old aluminum crush cores now? Those might have been a main reason the legs needed work between flights before.

[JamesH65]

Well that is disappointing. I thought one of the goals was to make it so they wouldn't have to remove the legs.  Unless they have to keep doing it until all the block 4s are used up and they can update the handling equipment.

A huge booster stage re-enters from space and lands impeccably on a small barge in the ocean. - And people express their disappointment that the legs are detached after landing.

Sorry, but it was:

1) 25th successful landing of the booster, which is great achievement, but also kind of mastered technique, so not surprising.

2) many times promoted 1st flight of the most advanced F9 with ability of faster turnarround (I know, i know those 24 hrs will come later next year) with the following feature (Elon's quote):

"The landing legs, you'll notice if you look carefully that there are no outward scallops on the perimeter of the landing leg, which were used to clamp down the leg during ascent. We have now brought those features inside the leg itself. So you'll see sort of a cleaner outer contour. And it has an internal latch mechanism that can be opened and closed repeatedly with ease. So essentially deploying the landing gear and stowing the landing gear is now a very easy thing to do, whereas previously it required several hours to re-stow the landing gear. Which can now be done with an actuator, pretty easily."

Obviously I'm not the only one SpX fan who expected this would be demonstrated by this 1st block 5 flight. As it doesn't happened we are just a bit dissapointed ... but I belive still very happy that the primary mission went 100% well. 

When, on the first use of anything, do you expect to move straight in to 'standard' or 'long term' procedure? It's very rare. There are always things to check, to tweak, to confirm. And they were going to have to take the legs off anyway...

I'm sure that in the next few flights, we'll see the legs retract, (hopefully not on landing), but to expect it on the first test seems unreasonable. I'm not disappointed, I'm sure it'll happen within my lifetime.

[Kabloona]

I refrained these earlier but here you go:

1. DESIGN OF A GRID FIN AERODYNAMIC CONTROL DEVICE FOR TRANSONIC FLIGHT REGIME
2. Swept-back Grid Fins for Transonic Drag Reduction

Thanks, those are even better. The nuggets I got from them:

Ref #1
-Leading edge sharpness and sweep-back reduce drag in transonic flight (p. 14)
-Thin grid walls are better to reduce transonic choking (p. 44)
-Curved fin (to fit against rocket body) reduces drag about 4% relative to flat fin (p. 73)
-But curved fin also significantly increase required actuator torque relative to flat fin (p. 75)

Ref #2
-Swept-back, thin leading edge has 30% less drag than flat blunt leading edge in transonic flight, due to reduced choking in grid cells. (p. 7)

Unfortunately, none of these papers explicity treats the effect of sweep-back on control authority, but the reduced choking caused by sweep-back in transonic flight should also improve the control authority, I would think.

[RocketLover0119]

Rocket is horizontal, per the Orlando princess webcam.

[edzieba]

One leg left to remove. #Block5 #bangabooster

Legless stage already.

Has the white powdery stuff on the underside (black side) of the leg been discussed?

TEA-TEB reaction residue, same as the white powder seen inside the engine bells after landing.

[abaddon]

Has the white powdery stuff on the underside (black side) of the leg been discussed?

TEA-TEB reaction residue, same as the white powder seen inside the engine bells after landing.

That seems unlikely to me; the legs don't come down until well after the final engine ignition.  I don't recall that we've ever seen TEA-TEB on the rocket body before, just in the inside of the engine bells.