Could the N-1 have worked with computer-control?

I read that the Russian N-1 moon rocket kept blowing up because the Russians
couldn't control the thrust of 30 rocket engines firing in tandem. I was
wondering: could this problem have been solved by computer controlled
engines? Or is there another structural reason for the failure of the N-1?

I understand that the N-1 was a very good engine. I believe that Kistler
was going to use some for his vehicle by buying unused engines from Russia.
Kistler needed to gimbal them for thrust vector control since the Russians
tried to used throttle control on their application.


"Uddo Graaf" wrote in message
...
I read that the Russian N-1 moon rocket kept blowing up because the
Russians
couldn't control the thrust of 30 rocket engines firing in tandem. I was
wondering: could this problem have been solved by computer controlled
engines? Or is there another structural reason for the failure of the N-1?

In article ,
Uddo Graaf wrote:
I read that the Russian N-1 moon rocket kept blowing up because the Russians
couldn't control the thrust of 30 rocket engines firing in tandem.

The N-1 had various problems -- it was different each time -- but it
wasn't anything as simple as being unable to control the engines. If
memory serves, the first two failures were actual mechanical failures in
the propulsion system, the third was a deliberate maneuver that wasn't
well thought out, and the fourth was an engine fire (at the very end of an
otherwise-successful first-stage flight).
--
MOST launched 30 June; science observations running | Henry Spencer
since Oct; first surprises seen; papers pending. |

Uddo Graaf wrote:

I read that the Russian N-1 moon rocket kept blowing up because the Russians
couldn't control the thrust of 30 rocket engines firing in tandem. I was
wondering: could this problem have been solved by computer controlled
engines? Or is there another structural reason for the failure of the N-1?

IMO the N-1 failed because:

a) the head designer died at an inoppotune moment (Werner Von Braun died
only after skylab)

b) the testing regime more or less guaranteed that the first few
launches would end in disaster- this was a very bad move politically as
it made it look like the program was making bad progress. (Note that
they had a test program of something like 12 launches, but only 4 of
them actually happened.)

c) the engines and other components weren't sufficiently well tested
individually

d) America had already 'won the race' to the moon; so politically there
wasn't the same drive in Russia

I must admit that I find the N-1 the prettiest rocket ever; the Saturn V
visually looked like an ugly kludge in comparison. But that's the
difference between form and function- Saturn V functioned ever so much
better.

"no_one" wrote in message
ink.net...
I understand that the N-1 was a very good engine. I believe that Kistler
was going to use some for his vehicle by buying unused engines from
Russia.
Kistler needed to gimbal them for thrust vector control since the Russians
tried to used throttle control on their application.

The N-1 isn't an engine but a rocket. It used RD-33 engines if I remember
correctly. But the N-1 had 30 of them all firing at once creating enormous
stresses on the airframe if one of the engines' thrust varied.



"Uddo Graaf" wrote in message
...
I read that the Russian N-1 moon rocket kept blowing up because the
Russians
couldn't control the thrust of 30 rocket engines firing in tandem. I was
wondering: could this problem have been solved by computer controlled
engines? Or is there another structural reason for the failure of the
N-1?

Ian Woollard wrote:

b) the testing regime more or less guaranteed that the first few
launches would end in disaster- this was a very bad move politically as
it made it look like the program was making bad progress. (Note that
they had a test program of something like 12 launches, but only 4 of
them actually happened.)

c) the engines and other components weren't sufficiently well tested
individually

If memory serves, they did not test the full rocket in any way except
launching it a few times ... with the known results. They did not have
fund allocation for it...

Robert Kitzmueller

Henry Spencer wrote:

In article ,
Uddo Graaf wrote:

I read that the Russian N-1 moon rocket kept blowing up because the Russians
couldn't control the thrust of 30 rocket engines firing in tandem.


The N-1 had various problems -- it was different each time -- but it
wasn't anything as simple as being unable to control the engines. If
memory serves, the first two failures were actual mechanical failures in
the propulsion system, the third was a deliberate maneuver that wasn't
well thought out, and the fourth was an engine fire (at the very end of an
otherwise-successful first-stage flight).

The hardware failed every time, and there's no doubt that was the
source of the problem. But I did some analysis on KORD, and it did
indeed seem to be rather crudely designed. There's no doubt that similar
throttle-steering systems can and have been made to work with analog or
TTL electronics, it's would have been a lot easier with at least a
simple microprocessor.

One thing is clear - there's no good physical or attitude control
reason to shut off engines in opposing pairs. If you know that one
failed, it's far better to use the control authority of the other
engines "throttle steering" law and simply shut off the propellant to
the failed engine, than to shut off it's opposing number. Not with 25
other engines that have to be throttlable anyway. Shutting them off in
pairs unnecessarily reduces the acceleration.

This is all speculation, but I presume they were smart enough to
have figured this out, but had no way to implement it. The way you would
do it with a processor is to create a pseudo-inverse using the 26 ring
thrusters that maps torque commands from the autopilot to throttle
positions of each engine. If an engine failed, as soon as you knew it,
you would recompute the pseudo-inverse using the 25 remaining engines,
and go about your business.

Doing in analog controls, however, makes this pretty darn tough. I
guess that you would hard-wire the mapping/pseudo-inverse. Trying to
create a logic matrix that is reconfigurable in analog electronics would
maybe be possible, but exceptionally complex. What I expect they decided
to do was to shut them off in pairs, use the same hard-wired
pseudo-inverse, and just "eat" the reduced control gain and whatever
cross-coupling that resulted.

So this may have been one of the rare situations when superior
computing systems WOULD have made a significant difference in the results.

Brett

On Wed, 31 Mar 2004, Henry Spencer wrote:

In article ,
Uddo Graaf wrote:
I read that the Russian N-1 moon rocket kept blowing up because the Russians
couldn't control the thrust of 30 rocket engines firing in tandem.

The N-1 had various problems -- it was different each time -- but it
wasn't anything as simple as being unable to control the engines. If
memory serves, the first two failures were actual mechanical failures in
the propulsion system, the third was a deliberate maneuver that wasn't
well thought out, and the fourth was an engine fire (at the very end of an
otherwise-successful first-stage flight).


The first flight of the N-1 on February 21, 1969 failed in part due to
mechanical problems; small metallic particles got lodged in the #2
engine's gas generator turbine. This in turn caused high frequency
oscillation, which resulted in engine components to wear out and tear off
their mounts. A propellant leak soon followed, a fire broke out not long
after. The KORD system detected the fire, but gave an incorrect signal
shutting down all of the engines at 68.7 seconds into flight. Range safety
destroyed the N-1 vehicle just 1.3 seconds later. Ironically the launch
escape system worked, and the 7K-L1S capsule was recovered.


The second flight on July 3, 1969 also involved a failure partially due to
the KORD system as well.


Metal slag fragments were ingested by the #8 engine's oxidzer turbopump at
just 0.25 seconds after liftoff. A fire soon broke out. and the KORD
reacted by shutting down the engines unecessarily in pairs until the
vehicle acceleration fell below 1G, and quickly fell back onto the launch
pad.


It is rather a shame that the Soviets could not get the N-1 to work, and
progress was being made, abeit slowly, in solving the massive rocket's
problems. The final flight lasted 106 seconds, and was a mere 7 seconds
from first stage seperation; a root cause was never identified for the
failure of the #4 engine oxidizer turbopump explosion. Had the seperation
between the first and second stages occured before the range safety
destruct, it is likely that the 7L flight would have been a success, and
the program could have continued.
-Mike

Brett Buck wrote:
Henry Spencer wrote:

In article ,
Uddo Graaf wrote:

I read that the Russian N-1 moon rocket kept blowing up because the Russians
couldn't control the thrust of 30 rocket engines firing in tandem.


The N-1 had various problems -- it was different each time -- but it
wasn't anything as simple as being unable to control the engines. If
memory serves, the first two failures were actual mechanical failures in
the propulsion system, the third was a deliberate maneuver that wasn't
well thought out, and the fourth was an engine fire (at the very end of an
otherwise-successful first-stage flight).
snip
This is all speculation, but I presume they were smart enough to
have figured this out, but had no way to implement it. The way you would
do it with a processor is to create a pseudo-inverse using the 26 ring
thrusters that maps torque commands from the autopilot to throttle
positions of each engine. If an engine failed, as soon as you knew it,
you would recompute the pseudo-inverse using the 25 remaining engines,
and go about your business.

At that time I'd be tempted to skip electronics.
Small disk, with 26 springs around the edge.
Apply torques and thrusts to disk (springs have stops, to prevent
them extending too far).
On engine failure, remove a spring.
Spring compression = thrust.

Ian Woollard wrote in
:

Brett Buck wrote:
One thing is clear - there's no good physical or attitude control
reason to shut off engines in opposing pairs.

Um. Bearing in mind that the Shuttle can lose 1/3 of its engine, and
still make orbit...

Providing said engine is lost sufficiently late in ascent.


--
JRF

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