Max size of a rocket?

[Nuke]

i want to say the biggest rocket i launched in ksp was 2000t on the pad. and ultimately the only think keeping me from building bigger would be the size of the vab and the framerates < 1.

[rdfox]

In 1967, NASA's Marshall Space Flight Center (or was it still the Manned Space Flight Center? I can never keep track of the name changes) in Huntsville was doing engineering studies for evolved Saturn launch vehicles for anticipated post-lunar programs. One proposal essentially took the first and second stages of FOUR Saturn Vs and clustered them together under a large payload bus; this was listed as theoretically being able to launch 1000 tons to LEO.

[Sam Cottle]

NASA is discovering this currently (to their chagrin) with the SLS. The limits are imposed by the strength of the materials used and there are many projects out there currently (Rocket Lab, SpaceX, etc) planning on using carbon fiber, and other, stronger, materials to construct rockets. Since carbon fiber is 3.8 times as strong as aluminium, it seems likely that a carbon fiber-framed rocket could reach a maximum of 1,454ft (based on the dimensions of the Saturn V). I suspect they could be larger than that since carbon fiber is significantly lighter than aluminium and, hence, you could build thicker, stronger frames from carbon fiber. It depends on whether or not you really need a rocket larger than the Empire State Building.

[wumpus]

On 9/14/2022 at 12:00 PM, Sam Cottle said:

NASA is discovering this currently (to their chagrin) with the SLS. The limits are imposed by the strength of the materials used and there are many projects out there currently (Rocket Lab, SpaceX, etc) planning on using carbon fiber, and other, stronger, materials to construct rockets. Since carbon fiber is 3.8 times as strong as aluminium, it seems likely that a carbon fiber-framed rocket could reach a maximum of 1,454ft (based on the dimensions of the Saturn V). I suspect they could be larger than that since carbon fiber is significantly lighter than aluminium and, hence, you could build thicker, stronger frames from carbon fiber. It depends on whether or not you really need a rocket larger than the Empire State Building.

Both the SLS and Saturn  V use hydrogen as a major component of fuel (everything but the boosters for SLS, everything past stage 1 for Saturn V), so I'd expect that a more modern methane-based rocket might not scale the same as a Saturn V.

Also if you are building an extra large rocket, making it wider starts making a lot more sense making the thing taller.  Rockets are made tall both for aerodynamic reasons, and logistical.  The falcon 9 is sized to be put on a truck and moved via US roads.  I remember an aside from Scott Manley stating that the Falcon 9 (block 5) was roughly at the limit of length for a rocket that fits the Falcon 9 width requirements.  And don't forget that they didn't build straight to the limit.  They incrementally increased the size of the thing and only after 4 more upgrades got to the limit.

If you are dealing with the square-cube issue for thrust, don't forget SRBs.  They deal out nearly arbitrary amounts of thrust even if they are much more expensive than  what Jeb taught you in KSP (but the ISP isn't nearly as bad).  Check out the AJ260 for a really big SRB.

Edited September 16, 2022 by wumpus
s/wider/taller

[magnemoe]

15 hours ago, wumpus said:

Both the SLS and Saturn  V use hydrogen as a major component of fuel (everything but the boosters for SLS, everything past stage 1 for Saturn V), so I'd expect that a more modern methane-based rocket might not scale the same as a Saturn V.

Also if you are building an extra large rocket, making it wider starts making a lot more sense making the thing wider.  Rockets are made tall both for aerodynamic reasons, and logistical.  The falcon 9 is sized to be put on a truck and moved via US roads.  I remember an aside from Scott Manley stating that the Falcon 9 (block 5) was roughly at the limit of length for a rocket that fits the Falcon 9 width requirements.  And don't forget that they didn't build straight to the limit.  They incrementally increased the size of the thing and only after 4 more upgrades got to the limit.

If you are dealing with the square-cube issue for thrust, don't forget SRBs.  They deal out nearly arbitrary amounts of thrust even if they are much more expensive than  what Jeb taught you in KSP (but the ISP isn't nearly as bad).  Check out the AJ260 for a really big SRB.

Yes, height is limited by engine trust / surface area, width is not limited this way.  SpaceX has talked about an wider starship, it would not be much higher however.  Yes you can tapper the rocket who is practical for an rocket like Saturn 5 there the 3rd stage would be impractical short and wide if it was the width of the first stages.