[sandworm101]

Complicated and less weight-efficient. Designing a structure for gravity/g/force in one axis is wasteful enough. That strength is useless once in space. Horizontal integration means the structure must be strong in two axis: double waste. It might not matter when you are launching cubesats, but in a spy satellite the size/weight of a bus that extra reinforcement means sacrifices in many other areas.

[avmich]

But it's more economical, money-wise, as Russian launchers history shows. In general, American rocket school tends to have better mass efficiency but less economical efficiency that Russian rocket school.

"When he wants more thrust, Ivan doesn't look for a fancy propellant with a higher specific impulse. He just builds himself a bigger rocket. Maybe he's got something there." - J. Clark, Ignition! https://library.sciencemadness.org/library/books/ignition.pd...

[dnautics]

> When he wants more thrust, Ivan doesn't look for a fancy propellant with a higher specific impulse. He just builds himself a bigger rocket

On the other hand the Soviet Union did develop syntin... (also from Ignition!)

[avmich]

Of course the point was that one can use simple and crude solutions, or effective and sophisticated ones. Another example would be that in Russian rocket engines pumps tend to be put on the same axis as the turbine, so frequencies of turbine and pumps are the same and some of them can be non-optimal. In American tradition one uses gears, which makes both turbine and pumps (more) optimal, for the cost of gear mechanism. Practice shows that both approaches can work, but, just as with vertical assembly, which requires a tall building or a vertical transportation of a rocket, some ways look simpler than others. Simpler not necessarily better - but in rocket assembly it's probably cheaper to do it horizontally.

[jccooper]

It's a bit more than cubesats. Nearly every satellite is or can be fine with horizontal integration. Witness every SpaceX and Russian payload ever launched.

Only exotic (presumably optical) sats from three-letter agencies really demand it, and even then we don't know if they really need it or would rather just spend the money to make it the launcher's problem rather than do a redesign or evaluation of their system.

[valuearb]

Today’s cheap and high cadence commercial launch systems should make the extra weight needed for horizontal assembly a non-factor.

[TeMPOraL]

"Cheap and high cadence commercial launch systems" are just beginning to happen right now, it'll take time for the industry practices to readjust.

[valuearb]

SpaceX undercut the market price for space launches by nearly 70% in 2010, and has averaged a launch every two and a half weeks for the last four years.

How much tine does the industry need to adjust?

[JshWright]

Lead times for large satellites are measured in years. The industry is absolutely adjusting, but it's also very risk averse.