Could anyone with knowledge about engines explain why Russians always seem to prefer multi-nozzle designs? Is there some inherent advantage in redundancy, cost or some other factor?

As a rocket combustion chamber grows larger, so does the chance of a destructive combustion instability. The Russian solution was to split that up into smaller chambers resulting in multiple nozzles. It was a practical solution to a challenging engineering problem.

Agree. Decision to make engines multi-chambered had to take into account the overall situation existing at the moment.

For example, when in 1954 Energomash was designing RD-107, it had to make a decision which would allow to make engine soon - and they couldn't make single-chamber engine for the thrust required. So they went for multi-chamber design, since they didn't have time to do it differently.

In "Осуществление мечты" an engine professional, who worked in Energomash, mentioned that when Energomash was choosing 4-chamber design for RD-170, there were two groups of specialists defending different approaches. One group - which had experience with RD-107 (multi-chamber engine) and RD-270 (biggest one-chamber Energomash engine) - advocated single-chamber design. Another group - which had experience with RD-253 (single-chamber) and engines for Kosmos launcher - advocated multi-chamber design. The decision was influenced by having the instrumentation necessary to conduct testing of smaller chambers independently.

Thanks! Who knew breaking a large problem into smaller chunks works in rocketry as well ;-)

Is Musk even interested in bidding for military contracts? It seems like that runs contrary to his vision of bringing humans to space, and his broader vision of space exploration for the sole purpose of benefiting (and prolonging the life of) humanity.

Yes. He's been a rather vocal opponent of the current buddy-buddy arrangement between ULA and the US Military. Also, since the military tends to have a pretty full plate regarding rocket launches, having a military contract would give lots of reoccurring experience in building up for future stages of his goals.

SpaceX is involved in an ongoing lawsuit against ULA and the Air Force because they want to change their acquisition process into an open bidding process:

http://www.denverpost.com/business/ci_26041385/spacex-files-...

In other words, yes, he's interested. It's good money that can help to fund the other stuff you mentioned.

I don't see why it would conflict. He gets to prove his rockets function well enough for DoD needs, and SpaceX gets more money/experience.

AFAIK, following the retirement of the shuttles, the US no longer has a heavy lift capability. Looking to indigenous companies for filling that void is probably a medium/long term goal.

The US still has heavy lift capability from the Delta IV, which will be used for the first few launches of the Orion system. It isn't human rated, though, with that replacement coming in a few years with the Space Launch System/

As much as I love civilian space programs... they've always just been excuses for designing incredible rocket based weapons...

"Hey look, we can get a friggin lander to the moon. we can also drop enough nukes from orbit to completely obliterate you too!"

diversification could make the company more robust without sacrificing his vision.

I believe Musk is interested in bringing in money to fund his vision of bringing humans to space. Developing cheaper ways to bring humans to space is very very expensive as we all know. And having military contracts is very very lucrative.

It's good to have options. I'm surprised it took them this long to realize it.