4 ms·

Banana for scale: It would take a square bar of regular old 250MPa structural steel about 32x32cm to hold the space shuttle, at full throttle, and it's solid

Banana for scale: It would take a square bar of regular old 250MPa structural steel about 32x32cm to hold the space shuttle, at full throttle, and it's solid rocket boosters down. Or 38 square bars about 5x5cm. And 250MPa is just it's yield strength, that type of steel work hardens and has an ultimate tensile strength usually in excess of 350MPa. There are, of course, much stronger varieties of steel. Steel is strong

DennisP 4y ago
The bar he showed us was quite a bit narrower than 32x32cm, so if there are much stronger varieties, that pretty well fits.
- TheSpiceIsLife 4y ago
  For sure, you'd likely have heard of chrom-molly steels. Got example, 4140 is a 1% chromium - molybdenum medium hardenability general purpose high tensile steel - generally supplied hardened and tempered in the tensile range of 850 - 1000 Mpa. Three to four times greater tensile strength, so two 127mm (5") diameter rods would do it at 1000 MPa.
- perihelions 4y ago
  Google says it's Inconel, - "The in-plane loads are carried from the covers to the cylinder by 96 INCONEL® 718 draw bars with a yield strength of 1 GPa." [0] - "The wedged conductors are CD107 copper, bonded to flat Inconel 718 plates, with a 4:1 copper/reinforcement ratio over the central column area. The yield strength of the copper is 310 MPa, up to 100 °C, while the yield strength of the Inconel plates is 1130-1300 MPa. The peak Tresca stress on the Inconel at the inside radius is calculated to be 580 MPa, while that in the copper is 310 MPa." [1] [0] https://www-internal.psfc.mit.edu/research/alcator/data/fst_cmod.pdf https://www-internal.psfc.mit.edu/research/alcator/data/fst_... [1] https://dspace.mit.edu/bitstream/handle/1721.1/94967/87ja040_full.pdf https://dspace.mit.edu/bitstream/handle/1721.1/94967/87ja040...
cjsawyer 4y ago
Speaking of fruit, I’m interpreting this as an apples and oranges situation. If we’re talking about trust of the engine that’s one thing, but holding back a launching rocket is different. That is the absolute worst case for the rocket (and best case for the rod) due to the weight of the heavy fueled up rocket fighting the trust along with the rod
- TheSpiceIsLife 4y ago
  That's a good point, I was calculating based on max thrust only. If we take in to account all the weight at take off, it'd be a much smaller section.
  - DennisP 4y ago
    Depending on how long the steel has to hold the rocket down :)

DennisP 4y ago

The bar he showed us was quite a bit narrower than 32x32cm, so if there are much stronger varieties, that pretty well fits.

TheSpiceIsLife 4y ago
For sure, you'd likely have heard of chrom-molly steels. Got example, 4140 is a 1% chromium - molybdenum medium hardenability general purpose high tensile steel - generally supplied hardened and tempered in the tensile range of 850 - 1000 Mpa. Three to four times greater tensile strength, so two 127mm (5") diameter rods would do it at 1000 MPa.
perihelions 4y ago
Google says it's Inconel, - "The in-plane loads are carried from the covers to the cylinder by 96 INCONEL® 718 draw bars with a yield strength of 1 GPa." [0] - "The wedged conductors are CD107 copper, bonded to flat Inconel 718 plates, with a 4:1 copper/reinforcement ratio over the central column area. The yield strength of the copper is 310 MPa, up to 100 °C, while the yield strength of the Inconel plates is 1130-1300 MPa. The peak Tresca stress on the Inconel at the inside radius is calculated to be 580 MPa, while that in the copper is 310 MPa." [1] [0] https://www-internal.psfc.mit.edu/research/alcator/data/fst_cmod.pdf https://www-internal.psfc.mit.edu/research/alcator/data/fst_... [1] https://dspace.mit.edu/bitstream/handle/1721.1/94967/87ja040_full.pdf https://dspace.mit.edu/bitstream/handle/1721.1/94967/87ja040...

cjsawyer 4y ago

Speaking of fruit, I’m interpreting this as an apples and oranges situation. If we’re talking about trust of the engine that’s one thing, but holding back a launching rocket is different. That is the absolute worst case for the rocket (and best case for the rod) due to the weight of the heavy fueled up rocket fighting the trust along with the rod

TheSpiceIsLife 4y ago
That's a good point, I was calculating based on max thrust only. If we take in to account all the weight at take off, it'd be a much smaller section.
- DennisP 4y ago
  Depending on how long the steel has to hold the rocket down :)