Author Topic: Was N1's failure due to the number of engines? (seeking clarification)  (Read 11519 times)

Offline Arch Admiral

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Differential throttling in the X-33 might have worked in yaw, but I always had doubts that the lever arm in pitch was great enough. And pitch was the axis with the most problems with wind shear etc. due to the lifting-body shape. And how would this work in roll??

Offline e of pi

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Differential throttling in the X-33 might have worked in yaw, but I always had doubts that the lever arm in pitch was great enough. And pitch was the axis with the most problems with wind shear etc. due to the lifting-body shape. And how would this work in roll??
They had multiple engine "units" in the line. If port does a pitch positive diversion of its thrust and starboard does pitch-negative, the net effect is a roll.

Offline john smith 19

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I'll just note AFAIK this is the only large rocket that has planned to be steered with differential throttling, not any kind of gimbaling, or object being moved into the engine thrust.
VentureStar / X-33 also planned to use differential throttling.
Another design that wasted $Bn+ and delivered nothing, except a larger payday to LM stockholders.  :(
It's not looking good as design approach if you want reliability in a vehicle, is it.
« Last Edit: 10/24/2017 10:55 PM by john smith 19 »
"Solids are a branch of fireworks, not rocketry. :-) :-) ", Henry Spencer 1/28/11  Averse to bold? You must be in marketing."It's all in the sequencing" K. Mattingly.  STS-Keeping most of the stakeholders happy most of the time.

Offline acsawdey

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I'll just note AFAIK this is the only large rocket that has planned to be steered with differential throttling, not any kind of gimbaling, or object being moved into the engine thrust.
VentureStar / X-33 also planned to use differential throttling.
Another design that wasted $Bn+ and delivered nothing, except a larger payday to LM stockholders.  :(
It's not looking good as design approach if you want reliability in a vehicle, is it.

I really don't think X-33's failure had much to do with differential throttling, more the ability to make a LH2 tank shaped like a lifting body. And even there it's more failed technology management than a complete inability to actually build such a thing.

And the N-1, well maybe it wasn't such a good idea to have so many engines if all you have is analog computers (that are too slow to prevent RUD) to handle shutdown. Also one of the failed flights, the computer was miswired so when engines failed, it shutdown the wrong ones. Oh, and having engines that can't be test-fired so you have to do statistical testing of batches certainly didn't help either. The Merlin 1D is completely bulletproof by comparison. So differential thrust has to get in line behind a whole bunch of other factors for that one.

Really, anyone who wants the blow-by-blow narrative about why N-1 failed should go read Rockets and People Volume IV:

https://history.nasa.gov/SP-4110/vol4.pdf


Offline spaceman3

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Really, anyone who wants the blow-by-blow narrative about why N-1 failed should go read Rockets and People Volume IV:

https://history.nasa.gov/SP-4110/vol4.pdf


Or you could read my book at:

https://ntrs.nasa.gov/search.jsp?R=20000088626

(although it may have a bit too much detail)

Offline Coastal Ron

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Really, anyone who wants the blow-by-blow narrative about why N-1 failed should go read Rockets and People Volume IV:

https://history.nasa.gov/SP-4110/vol4.pdf


Or you could read my book at:

https://ntrs.nasa.gov/search.jsp?R=20000088626

(although it may have a bit too much detail)

Any chance you could give us the Cliff Notes version?   :D
If we don't continuously lower the cost to access space, how are we ever going to afford to expand humanity out into space?

Offline acsawdey

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Really, anyone who wants the blow-by-blow narrative about why N-1 failed should go read Rockets and People Volume IV:

https://history.nasa.gov/SP-4110/vol4.pdf


Or you could read my book at:

https://ntrs.nasa.gov/search.jsp?R=20000088626

(although it may have a bit too much detail)

Well ... by some definition the other is "your book" as well :-)

Online Blackstar

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And the N-1, well maybe it wasn't such a good idea to have so many engines if all you have is analog computers (that are too slow to prevent RUD) to handle shutdown.

Perhaps "too many engines" is too simplistic an answer, and you really need to consider the overall complexity of the system. In other words, it was a failure of systems engineering, connecting all the stuff that has to be done right in order for it to work.

I wonder the extent to which the early choices really limited their later options. For instance, they did not do a static test of the complete first stage. Why? Was it too expensive, or did they think that it was unnecessary? (Or, as is often the case, it was too expensive, so they convinced themselves that it was unnecessary.)


Offline john smith 19

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I wonder the extent to which the early choices really limited their later options. For instance, they did not do a static test of the complete first stage. Why? Was it too expensive, or did they think that it was unnecessary? (Or, as is often the case, it was too expensive, so they convinced themselves that it was unnecessary.)
Yes.   :)

Earlier posters mentioned that only the manned programmes got more extensive testing, but that makes no sense, as the rocket carrying the crew to the Moon I'd have said the N-1 was part of the manned programme, except in the most pedantic sense of

Crew not carried in this part --> Not a manned programme.  :(

Skimming the accounts of the programme I'm hearing "Danger! Danger! Second systems effect." The tendency to throw away clean, known design in favor of radical, definitely higher risk but potentially higher performing systems.

How else to explain abandoning conventional gimbaling TVC (which I'm sure the Russians were aware was what the US was going to use) for differential throttling and batteries for on board generation when you've got a hard (immovable) deadline to meet with no extensions possible?

Couple that with low performance computer hardware and a failure to do a qualification test on every engine (a deeply undeserved reliance on what we would call Statistical Process Control) for foreign objects inside the engine and substantial underfunding given the scale of the task and you have a recipe for disaster.

I don't think the high number of engines was a show stopper, but multiplied  by the poor QC, and then multiplied further by unknown levels of interference from the new AC generating system on the power and data buses (How could you not see that coming??) and possible software development issues I think was a lethal combination.   :(

BTW People say the KORD computer system was low performing but is that by the US standard (the one on Saturn was only in the 10s of KIPS at most) of the time or by modern standards?
Pre-Shuttle any flight computer (literally) above the speed of a modern pocket calculator was "high performance"  by that yardstick.

Nemesis awaits all who would harbor false pride in their achievements and the N-1 programme got an extended visit from her.  :(

Had it all worked it would have been a technological triumph. Not just SoA but Start of the Art in several areas.

But it didn't.

Steering by diff throttling has become an emergency flight mode on some aircraft decades later. AFIK Shuttle is the only LV/spacecraft to not rely on batteries as a primary power source. Batteries are still the SoA for LV's. Even today no LV uses on board generation, despite electric TVC flying on Vega for a decade.
« Last Edit: 10/27/2017 08:37 AM by john smith 19 »
"Solids are a branch of fireworks, not rocketry. :-) :-) ", Henry Spencer 1/28/11  Averse to bold? You must be in marketing."It's all in the sequencing" K. Mattingly.  STS-Keeping most of the stakeholders happy most of the time.

Offline WallE

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The N-1 program was operating on something like 30% of Apollo's budget so no they didn't have the money for a test stand. A large number of factors were at work here including the less advanced Soviet technological capabilities and the fact that the Kremlin simply didn't place a high priority on science and exploration of space--national defense was paramount above all. They didn't mind scoring space firsts for propaganda value if it could be done cheaply, but landing on the Moon was not exactly cheap.

Technological handicaps aside, the Soviet aerospace industry did not have a sophisticated enough organizational and managerial structure for projects on this scale. The different heads of design bureaus did not trust each other and were constantly scheming against rivals, often because of feuds that went back to the Stalin-era purges.

As for the technical problems brought up in this thread, no, the Saturn instrument unit predated microprocessor electronics and was hardly an advanced computer. Unlike the KORD however, it had something resembling proper Q/C and testing, aside from not being asked to control 30 engines at once.

The N-1 first stage was a terrible design--30 engines made it far too heavy, way too much plumbing, and too hard to control in flight. The end result, absurd as it sounds, was a launch vehicle with more first stage thrust than the Saturn V but less lift capacity. This would have greatly limited the complexity and scope of a Soviet lunar landing--the crew couldn't do a lot more than plant a flag, take pictures, and grab a few soil samples. This was unfortunately another result of Soviet technological handicaps as they didn't have the ability to build large LOX/RP-1 engines and avoid combustion instability issues. The other option was Chelomei's UR-700 which required far fewer engines but flying a Saturn V-class launch vehicle with N2O/UDMH propellants would be a safety nightmare--they estimated that a launch failure within the first 20 seconds of flight would leave the impact site sterilized for at least 20 years.

As for other propellant options, the Soviets hadn't mastered large solid rocket motors either and Glushko considered LH2 unviable as a propellant--only in the 70s after the Saturn V proved otherwise did he cave and authorize the development of LH2 engines.

Offline Dmitry_V_home

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In my opinion, failure of the N-1 project had three reasons:
1) Deficiency of resources
2) Lack of political support till 1964
3) Low level of management.

All other factors are a consequence of these reasons.

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