SpaceX Super Heavy Grid Fins Will Be Welded Steel Instead of Titanium

42 thoughts on “SpaceX Super Heavy Grid Fins Will Be Welded Steel Instead of Titanium”

1. Typo… NH₄ClO₄ … not NH₃ClO₄

2. I think the Russians probably have the largest cast bits for some of their sub designs

3. Titanium is cast using an investment process under vacuum to prevent oxidation of the molten titanium. The minimum practical section thickness at any particular area of an investment casting is determined by local solidification characteristics. Large isolated surface areas, like grid fins, often must be made thicker than required for strength, in order to produce a sound, defect-free casting.

   A welded structure made from wrought material can be made as thin as strength or thermal conditions allow.

4. “If they are still there, and look like grid fins”
   I like this. Well done, very funny.
   🙂

5. That always bugged me as sometimes the shield was described as adamantium and sometimes vibranium, your description ties it in a nice bow. thank you for that lol

6. 3 D printed .

7. Formerly a big comic book fan. (Until they started messing with all the characters and continuity, and I decided I didn’t want to keep it up.)

   Adamantium and vibranium were never the same thing. Adamantium was a synthetic alloy with absurd properties in terms of strength, rigidity, and heat tolerance. For all practical purposes indestructible unless you had a “molecular manipulator” available or godlike/cosmic powers.

   Vibranium, by contrast, was an *element*, not native to Earth, found only in Wakanda at the site of a meteor impact. It had really exotic vibration absorbing properties.

   Cap’s shield was a combination, the front side was pure adamantium, while the back side was a unique adamatium/vibranium alloy. Consequently it wasn’t just basically indestructible, but also didn’t transmit back to him any impacts. He could stop an anti-tank gun with it and not be crushed to a smear.

   Apparently vibranium was immune to conservation of momentum…

8. I was under the impression that adamantium and vibranium were the same thing? I think they changed it at some point because the universes were thought to be unique and obv…the same material would cause canonical issues, but then they were merged and its all a confusing mess for a simple macguffin.

9. Any 3D printer that prints from metal powder has an inert atmosphere chamber built in. That’s part of why they’re expensive.

10. Shoot… yes, of course.

11. You must mean Columbia. Challenger was lost when external tank blew up on takeoff.

12. Not an easy thing to live with. But worthy.

13. I think the covers for the engines were titanium. That is why that did not have anything fancy where it hits the air fairly flat unlike the nose and the leading edge of the wings.

14. I’ll admit that the actual price of the material did skip past me if it was mentioned in the movies.

    I did grasp that it was super rare.

15. In a world where cost is no issue,

    I wish I lived in that world.

16. My point is that there is a good chance that in this case steel is BETTER for this application, so the very good and cheap is the enemy of the almost as good and highly expensive.

    I wouldn’t be the slightest surprised if the larger rockets need more heat tolerance but at the same time don’t care as much about saving a few hundred kg. So smaller rocket -> Titanium larger rocket -> steel.

17. Previous grid fins were single piece cast, but aren’t the chinese doing aerospace grade 3D printed titanium parts at stupid large sizes now? They seem to think it’s okay for critical parts. Though for these fins, you would need a fairly large (long cylinder doesn’t seem that hard…) inert gas chamber for the 3D printer to roll around in…

18. In a world where cost is no issue, Tungsten-Steel alloy composite metal foam plated with tungsten would be ideal. Its possible to get like a 50% reduction in density with 90% strength retained. Tungsten has the highest thermal tolerance and tensile strength of any metal. A metal foam version could potentially have the equivalent strength of SS and a thermal tolerance much higher and can retain strength at over 1500C in steel alloys. It melting point is like 3400C in pure form. Its just dense, so a metal foam could work to reduce density since its insanely strong as well a little strength loss would likely not matter.

19. The booster has a lot of reserve thrust, so no need to squeeze every last pound with titanium.

20. How much of a weight penalty using steel?

21. Hmmm… I wasn’t aware of that (obviously). Thanks

22. bits of aluminum are in fact part of the ‘mix’ of chemicals that are used for the solid-rocket-boosters of various US mainstream rocketry programs. For just that purpose. Aluminum, when coërced to freely oxidize, burns with a furious white heat. Quite appealing in a SRB. Its also one of the main reasons for the Space Shuttle’s super-voluminous white smoke on takeoff. Aluminum oxide, Al₂O₃. And a bit of iron oxide, too. 

    The butyl rubber C₄H₈(CH₂C(CH₃)₂))ₓC₄H₈ and ammonium perchlorate NH₃ClO₄, if by themselves burning, would result in a fairly transparent exhaust. 

    Just Saying,
    GoatGuy ✓

23. use spools of titanium or magnesium thread,for rocket/thruster, fuel if it burns that good.
    dense metals like hydrogen pack more ions?

24. a great spot to test out heat resistant/cooled,active passive ect systems.
    there are materials that cool when heated,emit water ect.
    coat the grid with tiles ect.
    or squirt them with cold nitrogen as needed.

25. “The Challenger (Space Shuttle) was a textbook example of what happens when titanium catches fire on hitting hypersonic atmosphere. ”

    Maybe it should have been, but in fact, the Shuttle was built of aircraft aluminum. That’s why it needed those remarkable tiles, because it would have annealed to bubble gum strength if exposed to anything even remotely like reentry temperatures.

    In fact, they had to hook up a truck and blow cold air through the airframe immediately after landing, before the heat could soak through the tiles and anneal it.

26. Really? I was under the impression that they thought Cap’s shield looks exceptionally dopey when he first wielded it so they gave up on mass-producing it ;-P

27. I would go with unobtanium if it was me..

28. ⊕1.  They are counting on being “wide”, so a lot of rocket engines can simultaneously fire.

    Here’s a ‘mental picture’ to clarify: a long skinny rocket with a single engine. Long enough for a million liters of fuel and oxidizer (‘fuelox’).  

    Light up, see if she takes off.  
    Nope.  
    Not enough reaction-mass exiting the nozzle per second.  

    Eventually if kept on pad, the loss of fuel will be enough so that it takes off.  
    But insufficient fuel for orbit.  
    Not good.  

    Take the same 1,000,000ℓ of fuelox, and put them into a more squat shell … SBFR … and lash 20 of the same engines to the bottom.  

    Light ’em up.  
    Does it take off?  
    YES!  

    But instead of 1 engine’s mass, now there are 20.  So … still not enough fuelox to make orbit.  

    Simple engineer’s solution … figure the mass-and-overhead of just stretching the 20 engine frame for additional fuelox. OK, there’s some length which now stores enough fuel to make orbit, AND still get off the spaceport launch pad.  

    (At this point, I’m not writing to you ScaryJello, but the community) This turns out how real-world rocketry has, is, and will be done from a science-and-engineering perspective.  

    Believe it or not (most peeps don’t), these calcs CAN be done on a napkin, at a restaurant, in 1955, with pocket slide rule. The final design is rarely more than 25% distant from the napkin calcs. Really.

    Just Saying,
    GoatGuy ✓

29. ⊕1 for the RealPolitik point of view. “if the fins are still there, good … if not, bad.” ⊕1

30. Could also be that when exposed to hypersonic atmosphere, titanium has a vexing ability to catch fire and burn white-hot. Not good for ‘parts’ of a rocket. The Challenger (Space Shuttle) was a textbook example of what happens when titanium catches fire on hitting hypersonic atmosphere. 

    Maybe, right?

    Indeed … to me its just about the only real reason to lose the titanium. In terms of working temperatures an softening, there are titanium alloys that work up to glowing-red temperatures. Unusual ones, with molybdenum, vanadium, zirconium and even iron, but still high temp.  

    In the above quote “largest piece of cast titanium in the world”, it is factually incorrect. Absolutely ginormous (10× the size) pieces of titanium are cast and machined all the time in industry. Unlike iron-and-steel which CAN be successfully welded with blessedly commonplace equipment, titanium welding takes inert atmospheres, and still carries substantial risk of post-welding-catch-fire.  

    Just Saying,
    GoatGuy ✓

31. True, but knowing what shipyard work is like, that’s concerning to me. Maybe if they tell the foreman she’s in the first manned launch the quality will go up.

32. Warning! LabPadre is addictive.

33. We are going to find out if a rocket built to Ship Yard Tolerances will actually get into space and back.

34. Perfect is the enemy of Good Enough.

35. Did you somehow miss the fact that Wolverine’s skeleton represented something like a billion dollars worth of the stuff? It’s not cost effective. (Which is also why they didn’t mass produce Cap’s shield and give one to every grunt leaving boot camp.)

36. It’s a minor part (in terms of mass) on a massively overpowered rocket. It’ll be fine.

37. I’d just go with handwavium and get it over with.

38. I think the whole point of this exercise is that it should be more like suv and less like rocket.

39. The first re-entry will answer the question. If they are still there, and look like grid fins, steel will be OK. If not, or if the vehicle is lost due to loss of control, then not OK. 🙂 I assume they have good data from past flights, and can model the process well enough to make a decision on materials.

40. Yes, and welded steel is cheap and casted titanium grid fins are like gigant jewelery parts…

    Once manufactured:
    Steel: 24.000$/m3
    Titanium: approx 200.000$/m3

41. Titanium is apparently good for an operating temperature up to maybe 600 deg C, while some steels are good at up to 1000.

    Seems like this could be a factor.

42. I surprised boy genius didn’t just use adamantium. Even the least educated among us knows it is way better than steel. Maybe vibranium would be an alternative.

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