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Sturgeon's House

UR-700: Father of Proton

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During the 1960s, there were many competiting designs for the rocket that would be used in the Soviet Lunar Program. Ultimately, the N1 was chosen, and proceeded to detonate and/or deflagrate vigorously on all four of its launches. One of the hypothetical competitors to the N1 was the UR-700.




A development of Chelomei's 'Universal Rocket System' (which also included the UR-100, UR-200, and UR-500 (Proton)), there were several important differences between the UR-700 and N1. For one, while the N1 was to have used kerosene/LOX fuels, the UR-700 would have used hypergolics, namely UDMH/N2O4. This fuel combination has reduced specific impulse compared to cryogenic fuels. However, considering that Chelomei's other rockets in the series were developed as ICBMs fueled by hypergolics, it is easy to see why they would have been chosen for the UR-700. Additionally, while the N1 had no less than 30 first stage engines, the UR-700 first stage was to have been powered by only nine RD-270 engines. To be fair, the RD-270 was much larger than the NK-15 used on the N1.


The UR-700 was planned to put 130-170 tons into LEO, which the Soviets judged to be the required amount for a direct ascent lunar mission. The choice of direct ascent, as compared to the lunar orbit rendezvous approach used by the Apollo missions (as well as Korolev's N1 based mission profile) results in a less efficient architecture. Most likely, Chelomei chose a direct ascent approach due to fears over the Soviet's lack of docking. Since the Americans had worked these issues out during the Gemini program, by the late 1960s, they were confident in the decision to use LOR.




Given the numerous issues in the Soviet Lunar Program, it is unlikely that choosing the UR-700 over the N1 would have got a cosmonaut on the moon before Armstrong. However, it's an interesting what-if? Could the UR-700 have been modified for use in an LOR mission? I believe it could have, given the UR-series' modular nature. Of course, it is likely that the UR-700 would have run into many other unforeseen issues, which could have resulted in failure. I'm curious to see y'all's opinions on it.



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  • 3 weeks later...

So that's what that giant thing in Buzz Aldrin's Space Program Manager was. Super neat. Cutting out the docking seems like it might have been a good idea, the real question was whether they'd be able to put the money and effort into making an amazing rocket like the F-1 was, or whether way too many engines was the right decision for the Soviets.

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Direct ascent seems like asking for trouble, to me.

Rockets get more problematic damn near exponentially as they get bigger. It's a pretty big miracle that Apollo had as few problems as it did (and it effectively killed six people), to do something even bigger even earlier sounds like a megacatastrophe waiting to happen.

Hell, just look at what a disaster the N-1 was.

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In addition to suffering issues because of bigness, the N1 also failed for a couple main reasons;


  • Having 30 small engines (rather than 5 large ones) greatly complicated plumbing, electronics, control systems, etc.
  • The Soviets never built a test stand for the N1 first stage as a whole, instead just testing individual engines.
  • Components were shipped to Baikonur by rail (increasing the risk for vibration damage), and not subjected to full testing on arrival


If you feel like reading walls of text, here's a blog post / essay about the failure of the Soviet Space Program; http://scramcannon.blogspot.com/2014/10/an-analysis-of-failure-of-soviet-lunar.html

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All true; I read your book.


Of course, the bigger you get, the greater you have to risk using more engines in the first place. Unless you take to developing truly enormous engines, which, while safer, does cut into your development time. There's also no guarantee the larger engines will work.

So I think LOR really was the way to go.

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  • 2 weeks later...
  • 1 year later...

I was doing some thinking today, and I realized that the RD-270 is utterly insane.


  • It weighs about half as much as the F-1 (4470 kg vs 8391 kg)
  • Despite this, it has almost as much thrust (6713 kN vs 7741 kN)
  • While having about 40 seconds more sea level Isp (40 seconds is huge)

Also, so far as I know, it's the only rocket engine with fully staged combustion (the entire propellant flow is used to power the turbopumps (not all of it is combusted, obviously), and the higher mass flow means lower turbine speeds and better reliability). IIRC SpaceX's Raptor is supposed to use it. So, capitalism is only ~40 years behind the Soviets in this case.

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Ehhhh, not like the Soviets really cared about that kind of thing


Actually, they did, it's one of the biggest reasons why the UR-700M would have used cryogenics. A Proton blew up near the pad in the late 60s and they couldn't clean it up until after a rainstorm washed most of the UDMH and N2O4 away. With the UR-700 being that much bigger, it would have been that much more of a pain in the ass.



By January 1969, Chelomei was proposing the UR-900 for the Mars expedition. Chertok asked Chelomei what would happen if, God forbid, such a booster exploded on the launch pad. Wouldn't the entire launch complex be rendered a dead zone for 18 to 20 years? Chelomei's reply was that it wouldn't explode, since Glushko's engines were reliable and didn't fail. Aside from that, these propellants had been used in hundreds of military rockets, deployed in silos, aboard ships and submarines, with no problem. Fear of these propellants was irrational. Related propellants were used by the Americans on the Apollo manned spacecraft.

Less than three months later, on 2 April 1969, the unimaginable happened. A Proton rocket, one tenth the size of the planned UR-900, was launched in an attempt to send an unmanned probe to Mars. The leadership of the Soviet Rocket Forces and most of the Chief Designers were present for the event. The Proton rocket lifted off, but one engine failed. The vehicle flew at an altitude of 50 m horizontally, finally exploding only a few dozen meters from the launch pad, spraying the whole complex with poisonous propellants that were quickly spread by the wind. Everyone took off in their autos to escape, but which direction to go? Finally it was decided that the launch point was the safest, but this proved to be even more dangerous - the second stage was still intact and liable to explode. The contamination was so bad that there was no way to clean up - the only possibility was just had to wait for rain to wash it away. This didn't happen until the Mars 1969 launch window was closed, so the first such probe was not put into space until 1971.

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  • 2 weeks later...

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