Talk:RD-170

Chamber failure

"Even if one thrust chamber fails, others can compensate by firing for a longer duration." - I'm sure it's not true. I think if one chamber fails, you get a bit BOOM (pressure of hundreds of atmospheres). Even in hypothetical low-pressure version of RD-170, there is no valve to cut off gas flow from pump(s) to ruptured/broken chamber, so you still end up with Bad Things Happening. —Preceding unsigned comment added by 193.120.148.177 (talk) 17:02, 5 November 2007 (UTC)

Regarding units and aircraft templates - Thrust to weight ratio

Remember, jet engines are not rocket engines. The aircraft template is informative but not ruling, for spacecraft components. Georgewilliamherbert 00:52, 20 April 2006 (UTC)

True. But I checked Sutton 7th edition for example it reads:

"The thrust to weight ratio F/Wg is a dimensionless parameter that is identical to the acceleration of the rocket propulsion system (expressed in multiples of g0) if it could fly by itself in a gravity-free vacuum; it excludes other vehicle component weights."

Seems pretty clearcut.

To be honest you rarely or never see *any* aerospace thrust/weight ratio specified in lbf/lb or N/kg, for a rocket or aeroplane. I did some googling and didn't find many hits at all.

Try: googling:

"lbf/lb" "thrust to weight" -wikipedia (I get 679, some of which are wiki related)

"thrust to weight" -wikipedia (125000 hits)

WolfKeeper 01:02, 20 April 2006 (UTC)

Yeah. T/W is pretty clearly dimensionless in common usage (incorrectly so, in a strict sense, but that fight is long lost). Same thing with Isp in seconds... it's really lbf*sec/lbm, but it's "seconds". Wikipedia should follow standard industry usage, which is dimensionless T/W and Isp in seconds and the like. Georgewilliamherbert 01:16, 20 April 2006 (UTC)

Thrust and weight are both forces. Thrust should really be measured in either N or lbf, and weight is measured in N or lbf too. For weights and measures purposes though you have to refer back to the weight at sea level, otherwise how the heck do you compare (gravity goes down by 1% at 30km =~ 100 kft, does that mean that thrust/weight goes up? No.) The classic example is the lunar lander... thrust:weight of 0.34, who says you need thrust:weight > 1 to takeoff? :-) WolfKeeper 01:29, 20 April 2006 (UTC)

What you want, and what you get as well, is thrust to mass ratio. Thrust to weight ratio has what you want for your calculations, dimensions of acceleration: 1 lbf/lb = 32.174 ft/s². Or for that lunar module, 0.34 lbf/lb may be useful if you are using the engineering system of units which includes both pounds and pounds force, or some system which includes units of acceleration called gees, but if you want to use a coherent system of units such as the gravitational fps system or the SI, you'd need to convert it to something useful like 10.9 lbf/slug = 10.9 ft/s² or 3.33 N/kg = 3.33 m/s², numbers which you can then compare to the local acceleration of gravity in units usually used to measure that. Gene Nygaard 12:21, 20 April 2006 (UTC)

No, what we want is a (preferably dimensionless) number that can be used for fairly comparing aircraft and engines. The fact that the current number relies on the acceleration due to gravity is in practice pretty convenient since 99.99999+% of humanity lives under 1 earth gravity their entire lives. But the argument is dead anyway. The wikipedia needs to be consistent, both internally and externally with the various manufacturers. If you want to go around adding thrust/mass in brackets as well, I won't remove it, that's actually NPOV but you *must* leave the dimensionless number.WolfKeeper 16:30, 20 April 2006 (UTC)

I thought that you wanted to work within the format at: Wikipedia:WikiProject_Aircraft/page_content. bobblewik 19:23, 20 April 2006 (UTC)

See jet engines are not rocket engines above and standard industry usage in the space industry. Nobody uses lbf/lb in the space industry. I'm putting it back to dimensionless. Georgewilliamherbert 20:35, 20 April 2006 (UTC)

Wikipedia is not an industry publication. So usage within the domain is not the only issue for Wikipedia. bobblewik 21:48, 20 April 2006 (UTC)

Of course. But usage contrary to the domain should be looked at very carefully, especially when usage is both contrary to normal everyday practice and to the domain. Using a physicist construct which is not in common normal usage nor in engineering field domain common usage is not a good idea for WP. The only people who do use it are a minority of the physicists who cross over into aerospace engineering, but even most of them adopt the domain usage of dimensionless (and Isp in seconds or Ve in m/s or ft/sec, etc). Gene mightily objects to this, but Gene is not the last final authority. Georgewilliamherbert 22:02, 20 April 2006 (UTC)

And the lbf/lb were here before I started editing Wikipedia 16 months ago, George—not in this article, of course, because it didn't exist then, but in other articles. Gene Nygaard 01:42, 21 April 2006 (UTC)

FWIW: I consider this link to be definitive: http://www.grc.nasa.gov/WWW/K-12/airplane/fwrat.htmlWolfKeeper 22:04, 20 April 2006 (UTC)

Sure, call on the Mars Climate Orbiter people as experts on units. On their pages written for elementary school children.

Of course, when the real engineers at NASA do their work, they measure that "weight" of the lunar module as 10,776.6 lb at liftoff. Gene Nygaard 01:42, 21 April 2006 (UTC)

You've lost me now, Wolfkeeper. Are you telling me that you can't compare 7 inches and 4 inches, and figure out how they relate to each other?

What possible information can you get by comparing 0.260 to 0.310, that you can't get from comparing 2.55 N/kg to 3.04 N/kg? Or for that matter, what information do you lose if you use the actual units of the first set of numbers, and compare 0.260 kgf/kg to 0.310 kgf/kg, or 0.260 lbf/lb to 0.310 lbf/lb? What is "unfair" about comparing 2.55 N/kg to 3.04 N/kg? Gene Nygaard 22:07, 20 April 2006 (UTC)

Quick! Which is bigger, a thrust/weight of 1.1 lbf/lb or 9.81 N/kg. Or 4.5 N/kg and 0.5? Given that so far as google will admit to, 99% of people use the dimensionless number, and given the references I show how it's derived why on earth would we want to quote anything else?WolfKeeper 22:16, 20 April 2006 (UTC)

There's nothing wrong with measuring it in the most SI compatible units. Presenting that as the only example, however, is a mistake. It's not a mistake because SI is wrong. It's a mistake because space people use the domain specific usage which is not entirely SI pure and fresh. Trying to make everything 100% SI perfect is a crusade which you are not getting much real-world traction on, Gene. If aerospace people won't do it only or primarily your way, WP shouldn't either. Georgewilliamherbert 22:33, 20 April 2006 (UTC)

Nobody ever took out the 1.1 lbf/lb numbers, did they? But if we are going to accomodate people, so that they get in in the units they use, we need to include the N/kg numbers too. So why did you delete them, if your goal is to keep from having to make those difficult comparisons between incompatible units? Gene Nygaard 01:44, 21 April 2006 (UTC)

Who exactly Nygaard? It's not like you've been able to come up with any references to this lbf/lb or N/kg being any kind of official standard for thrust/weight ratios. Thrust to mass, sure. Thrust to weight. No. Given that we are specifying thrust/weight here and throughout the wikipedia, you don't really have a leg to stand on.WolfKeeper 03:18, 21 April 2006 (UTC)

It is never a different number. It is never a different measurement. Nobody ever uses both terms, thrust-to-weight and thrust-to-mass, at the same time, and we shouldn't do so on Wikipedia either. It is simply that some people avoid using weight in its normal meaning as a synonym of mass, and others do not. Gene Nygaard 14:02, 21 April 2006 (UTC)

Quite. I think the agreement is closer than the disagreement. The ancient word 'weight' is used ambiguously in daily life ('net weight 50 grams'), in the scientific world (e.g. 'atomic weight') and in the technical world:

• WolfKeeper said: my anecdotal impression is that most aircraft publications tend to refer to weight even when specifying mass

bobblewik 14:40, 21 April 2006 (UTC)

There are, of course, two different ways that people try to be careful in avoiding weight in its meaning as a synonym for mass in its physics jargon meaning (mass, of course, also has many other meanings, but the others aren't normally used with numbers to express their magnitude).

1. Some just say mass instead of saying weight.
2. Others throw in a conversion factor not called for by the physics involved, to pretend that the mass measurement is is a force measurement, multiplying by a constant 9.80665 m/s² (and thus not getting the actual "weight" as the force due to the local acceleration of gravity, but rather a fictional "standard Earth weight"). Note that even if you limit yourself to sea level, the actual acceleration of gravity on Earth varies by more than one part in 190, and the average sea-level acceleration of gravity[1] is 9.79764 m/s², not 9.80665 m/s².

Most people, of course, don't even bother making such distinctions.

The meaning of weight as in the net weight of commerce is clear and uniform and consistent; the word weight is only ambiguous there because in other contexts, the word weight is used with different meaning—not because it is used with more than one meaning in commerce. Gene Nygaard 15:04, 21 April 2006 (UTC)

Yes. It can be used as an unambiguous synonym. My point was that it hardly matters. I see it in a similar way to the terms 'heat' and 'cold'. We don't go around saying that use of the word 'heat' is wrong in: "it costs a lot to heat my house", "this coffee is cold", "it is cold sitting on concrete", "my feet are cold". If anyone wants to be specific, science gave us the specific terms and units. bobblewik 16:01, 21 April 2006 (UTC)

Specifications

Ignition in the Specifications is noted as Hypergolic. Propellants are listed within Introduction as RP-1 (Russian equiv) and LOX. These do not appear to be Hypergolic, see http://en.wikipedia.org/wiki/Hypergolic_propellant July 14, 2009 FabianWilcox (talk) 17:14, 14 July 2009 (UTC)

Some engines use hypergolic fluids as an ignition source. This is independent of the actual propellants. Indeed, the F-1 engines of the Saturn V used hypergol cartridges as their ignition source.63.3.21.1 (talk) 08:27, 30 January 2010 (UTC)

Does this mean that this engine (as well as F1) is not restartable? Or there is enough hypergolic fuel for several engine starts? Mikus (talk) 23:22, 29 April 2010 (UTC)

It's true, the F1, RD-170, and most first stage liquid engines are not designed for restartability. The J2 on the Saturn V upper stages was, however, designed to be restartable (this was useful for allowing it to launch into a temporary parking orbit to get into location for the final burn to the moon). The J2 couldn't be throttled at will like a hypergolic rocket, though.108.131.13.16 (talk) 23:45, 10 March 2015 (UTC)

the most powerfull engine

is F-1A. Not RD-170. —Preceding unsigned comment added by Kostera (talk • contribs) 12:29, 16 April 2010 (UTC)

the most powerfull engine is Space Shuttle Solid Rocket Booster RD-170 is a most powerful liquid engine. 87.249.56.160 (talk) 10:55, 26 August 2011 (UTC)

The F-1A was never built, it was only ever designed. The RD-170 is the largest liquid fueled rocket engine ever actually used.108.131.13.16 (talk) 23:40, 10 March 2015 (UTC)

The F-1A was certainly built. You're thinking perhaps of the F-1B JohndanR (talk) 21:27, 14 August 2020 (UTC)

Turbine power

The first paragraph states that the turbine is rated at 170 MW. Specifications states that it produces 192 MW. Clarification needed. (There are also a couple typos: RD-170 - developed for use (delete the) on the Energia... RD-180M - possibility of constructiNG several new variants...) 69.72.92.207 (talk) 21:06, 1 November 2014 (UTC)

RD-180M "variant" misleading or incorrect

I'm dubious the article correctly conveys information in the available sources related to the term, "RD-180M." The implication of calling this a variant is that it would be something different from RD-180. But that's not the actual history. Early in the 1990s, as part of a contract with Pratt-Whiteny, RD-180 was under development at Energomash. In 1995, before any engines where shipped, the agreement regarding the RD-180M requirements was enter into. RD-AMROSS was created in 1997; first flight of an RD-180 was in 2000. So the engine which first flew as "RD-180" was already an "RD-180M." (sdsds - talk) 05:48, 17 October 2015 (UTC)

Variants / RD-170

RD-170 was only developed for the booster of the Energia complex. For the Energia itself they took four one-chambers engine RD-0120. So in summary they had four RD-170 engines, one in each booster, and four RD-0120 engines in Energia launch vehicle. --2k11m1 (talk) 17:00, 17 July 2021 (UTC)

I have fixed the typo you pointed out. The Energia article has it right, and is properly sourced. Greg (talk) 08:17, 27 November 2022 (UTC)

Designed for reuse, tested after use, but ever reused ?

Designed for reuse, some were recovered, some tested after use ?, but were any ever reflown ? - Rod57 (talk) 15:55, 4 December 2021 (UTC)

Ukraine

The article text currently has a section about the RD-171MV, and that it's all Russian. But it fails to say much about the RD-171M itself. I'd guess that the RD-171M has Ukrainian involvement? It would be nice to have a properly neutral mention of it. Greg (talk) 08:20, 27 November 2022 (UTC)