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Tumansky R-15 Turbojet Question  
User currently offlineBlackbird From , joined Dec 1969, posts, RR:
Posted (6 years 7 months 4 days 15 hours ago) and read 8248 times:

I was told it was a five-staged turbojet with a single staged turbine. Does anyone know what it's pressure ratio or dimensions were?


Andrea Kent

55 replies: All unread, showing first 25:
 
User currently offlineN74JW From , joined Dec 1969, posts, RR:
Reply 1, posted (6 years 7 months 4 days 14 hours ago) and read 8248 times:

The R-15B-300 was a single spool, reheated turbojet.

Mass flow: 144 kg/sec
Pressure ratio: 4.75
Reheated thrust: 10,210 kg st
Consumption: 2.7 kg st. h
Max Dry thrust: 7,500 kg st
Consumption: 1.25 kg st. h
Inlet temp: 1,215 K
Structure compressor: 5
Weight: 2,625 kg
Flow control: hydroelectric

- From 'Mig OKB History;


User currently offlineUH60FtRucker From , joined Dec 1969, posts, RR:
Reply 2, posted (6 years 7 months 4 days 13 hours ago) and read 8228 times:

Yeah, what the heck... five seconds on google, and I had the answers. What gives?

User currently offlineN74JW From , joined Dec 1969, posts, RR:
Reply 3, posted (6 years 7 months 4 days 13 hours ago) and read 8221 times:



Quoting UH60FtRucker (Reply 2):
What gives?

Dunno... I bought a book written by R.A. Belyakov and J. Marmain. Belyakov took over the Mig design bureau after Mikoyan's stroke in 1969.


User currently offlineCaptOveur From , joined Dec 1969, posts, RR:
Reply 4, posted (6 years 7 months 4 days 11 hours ago) and read 8196 times:



Quoting UH60FtRucker (Reply 2):
ive seconds on google, and I had the answers. What gives?

It's more fun to start 5 threads a day here.


User currently offlineN74JW From , joined Dec 1969, posts, RR:
Reply 5, posted (6 years 7 months 4 days 10 hours ago) and read 8182 times:

It is a great question! Tumansky claims that the Mig-25 could supercruise at FL800. Interesting claim...

User currently offlineBlackbird From , joined Dec 1969, posts, RR:
Reply 6, posted (6 years 7 months 4 days 8 hours ago) and read 8161 times:

How the hell did they get any reasonable amount of thrust out of that thing with that mass flow value and a pressure ratio of 4.75 to 1? And with such a low pressure ratio and all that afterburner how did they only max out at 2.8 to 3.2?


Andrea Kent
P.S. Does inlet temp mean compressor inlet or turbine inlet temp?


User currently offlineN74JW From , joined Dec 1969, posts, RR:
Reply 7, posted (6 years 7 months 4 days 5 hours ago) and read 8145 times:



Quoting Blackbird (Reply 6):
And with such a low pressure ratio and all that afterburner how did they only max out at 2.8 to 3.2?

I would say weight was a big factor in the Mig-25's performance. The Mig-25 was made from seam-welded stainless steel. Heat is also a big drawback. If the Mig-25 went any faster, the heat outside would start to melt the perspex. Mach 3.2 was a big stretch for the Mig-25. After all reported operations at that speed, the engines were no good any more and needed to be replaced.

Turbine inlet temp...


User currently offlineBlackbird From , joined Dec 1969, posts, RR:
Reply 8, posted (6 years 7 months 3 days 17 hours ago) and read 8110 times:

Stainless steel can take a LOT of heat last I checked, slightly more than even titanium. Also, are you sure they used perspex on the window-canopy or a different substance?

Still, I'm amazed that with a 4.5 : 1 PR you'd be able to get any significant amount of thrust out of an engine with that core-airflow value.

How heavy was the MiG-25 anyway?


Andrea Kent


User currently offlineN74JW From , joined Dec 1969, posts, RR:
Reply 9, posted (6 years 7 months 3 days 12 hours ago) and read 8089 times:

Mig-25PD (Interceptor)

Takeoff weight w/ 100% fuel & 4 R-40 missiles, 80,930lbs
Takeoff weight w/100% fuel & no missiles, 76,965lbs

Mig-25R (Reconaissance)

Normal takeoff weight, 81,550lbs
Max. takeoff weight, 90,805lbs

The Mig-25R series was unarmed.


User currently offlineMichlis From United States of America, joined Jul 2007, 737 posts, RR: 2
Reply 10, posted (6 years 7 months 2 days 20 hours ago) and read 8052 times:



Quoting UH60FtRucker (Reply 2):
eah, what the heck... five seconds on google, and I had the answers. What gives?

Do you believe everything you read on the Internet?  Big grin



If you know the enemy and know yourself, you need not fear the outcome of a hundred battles.
User currently offlineN74jw From , joined Dec 1969, posts, RR:
Reply 11, posted (6 years 7 months 2 days 19 hours ago) and read 8044 times:



Quoting Blackbird (Reply 8):
Also, are you sure they used perspex on the window-canopy or a different substance?

It would have been whatever they were using circa 1964-1965. The Mig-15/17 has a front windscreen made from 64mm thick glass, and allegedly bullet-proof.


User currently offlineBlackbird From , joined Dec 1969, posts, RR:
Reply 12, posted (6 years 7 months 2 days 10 hours ago) and read 8013 times:

You sure they wouldn't have used a higher temperature glass for the MiG-25? The skin did use stainless steel to deal with heat, why wouldn't they have taken similar measures with glass?

Might be looking a bit "conspiracy theory ish"... but do you think they listed the MiG-25's top speed as being a little bit lower than it really is, or even a lot to cover up the speed of the Blackbird or for some other reason?


Andrea Kent
Should I get cancer, disappear mysteriously, or have a heart-attack, you know who to blame.


User currently offlineN74JW From , joined Dec 1969, posts, RR:
Reply 13, posted (6 years 7 months 2 days 9 hours ago) and read 8009 times:

The Mig-25R's top speed was actually recorded by the Americans and the Israelis. Many of the Mig-25's records were not disclosed outside of the USSR for security reasons. I don't doubt the Mig-25 was as fast as advertised, but perhaps the details were fudged a bit. The Mig-25's skin was made from Duralum (D19), with Titanium on the leading edges. The supporting structure is made from welded steel. Half of the Mig-25's airframe was seam and spot welded, Ar arc welding 25%, fusion/inert gas welding 1.5%, the rest was rivets and bolts.

Metallurgy:

Tempered Steel: 80%
Titanium alloy: 8%
D19 duralum 11%

Metallurgy was not the only 'hot-spot', pardon the pun, but it was the electronics. The CPU in my Macbook Pro will shut off @ 135F, & this is 21st century technology...


User currently offlineBlackbird From , joined Dec 1969, posts, RR:
Reply 14, posted (6 years 7 months 2 days 8 hours ago) and read 8001 times:

Yes it's top speed was recorded. But the figures that were listed; who's to say they didn't just lie about them. I mean "officially" the Blackbird can do Mach 3.2, but we obviously know it can do faster than that. Way faster.

I mean, I can tell you I'm a little petite blonde, but it doesn't necessarily make me one. In reality, I don't think any culture on earth excepting some obscure african tribe would consider me little or petite (I'm over 6' tall), I'm also not blonde haired.


Andrea Kent


User currently offlineN74JW From , joined Dec 1969, posts, RR:
Reply 15, posted (6 years 7 months 2 days 5 hours ago) and read 7992 times:



Quoting Blackbird (Reply 14):
Yes it's top speed was recorded. But the figures that were listed; who's to say they didn't just lie about them. I mean "officially" the Blackbird can do Mach 3.2, but we obviously know it can do faster than that. Way faster.

The figures had to be reported to the FAI, but could be independently verified due to the 'Iron Curtain'. Western RADAR was able to confirm Soviet claims of the Foxbat's performance, but did not know the under-pinnings of Mig-25 operations. Early versions of the Mig-25P/R had numerous 'teething' problems, such as the 150 hour time between overhauls for the early versions of the R-15. The fact the figures which were submitted to the FAI in Paris were excepted do give some merit to the Soviet's claim. The Ye-266 prototypes were used as the work-horses for the record attempts. Ye-266 was a spurious designation to throw off any Western intelligence services, the original Mig-25 prototypes, Ye-155, were actually used.

Plexiglass is the material noted in use for the Mig-25's canopy...


User currently offlineBlackbird From , joined Dec 1969, posts, RR:
Reply 16, posted (6 years 7 months 2 days 5 hours ago) and read 7992 times:

They could have seen anything on that radar... what you know is what they WROTE. As I said, I'm a short little petite blonde... I wrote it.


Andrea Kent


User currently offlineN74JW From , joined Dec 1969, posts, RR:
Reply 17, posted (6 years 7 months 2 days 5 hours ago) and read 7984 times:

Sure, you are correct, but I cannot imagine a source more genuine than a book written by the former director of the Mig design bureau. Why would he lie in a historical memoir, written almost 20 years after the fact? The cat is out of the bag concerning the Mig-25 in 1994 when the text was published.

Here is a link to the FAI records set by the Mig-25 prototypes, that still stand...

http://records.fai.org/general_aviation/aircraft.asp?id=675


User currently offlineBlackbird From , joined Dec 1969, posts, RR:
Reply 18, posted (6 years 7 months 1 day 11 hours ago) and read 7950 times:

N747JW,

I suppose you make a good point. However, while I might not necessarily be right about the MiG-25's top-speed here, I should note that years after the fact the Blackbird's top speed is still lied about.


Andrea Kent

[Edited 2008-01-01 12:50:13]

User currently offlineN74JW From , joined Dec 1969, posts, RR:
Reply 19, posted (6 years 7 months 1 day 10 hours ago) and read 7935 times:



Quoting Blackbird (Reply 18):
should note that years after the fact the Blackbird's top speed is still lied about.

Or just not disclosed... The top speed of the SR-71 is quoted at Mach 3.5+. Squadron patches for blackbird drivers feature a 3+ in the design. While I do not doubt the SR-71A's capability, there is that unknown factor. The SR-71 was a one of a kind design that was decades ahead of it's time. I would not be surprised if the SR-71A's top speed was not much faster than indicated, and the 3.5 is a form of mis-information on behalf of the USAF/CIA.


User currently offlineBlackbird From , joined Dec 1969, posts, RR:
Reply 20, posted (6 years 7 months 4 hours ago) and read 7884 times:

I was thinking about something...

The J-75, a smaller engine with a higher pressure ratio than the R-15 can do Mach 3.0. It's true, in fact even in a YouTube video about the F8U-III Super Crusader it even said it could propel the plane to Mach 3+. While the plane itself due to the windscreen design was restricted to lower speed, they had planned to remedy this problem and pilots said it definetly had the thrust to, and aerodynamically could do it.

An F-106A allegedly in level flight could redline at M = 2.80... this was mentioned by a guy who was ex-USAF who worked on them. The F-106B was 0.1 Mach faster because of it's longer twin-seat cockpit which is better area-ruled. So that would be M = 2.90 in level flight. During a (shallow?) dive he stated that one achieved (a -B model) 1,800 kts, which is about Mach 3.14. Might sound crazy, but the individual in question was reliable. I also read once in a book which covered early supersonic fighter development that the non-area ruled F-102 could do 812 mph, which equates out to M = 1.23, and the area-ruled F-102A was more than twice as fast. Twice as fast is 2.46, and most likely more than twice as fast means around 2.5. The F-106A was faster than the F-102A, had more powerful engines and a variable-geometry inlet.

For these reasons, I have trouble believing that the MiG-25 with an engine that had such thrust, and such a little pressure ratio (which combined with it's huge nozzles just reeks "HIGH SPEED") -- compared to the J-75 (even with technological differences between the US and, then USSR at the time) that is.


Andrea Kent
I doubt anything I said is classified as the F-106 and the J-75 are very old. But should I disappear, get a heart-attack, some incurable disease, etc... you know who to blame for it.


User currently offlineSovietjet From Bulgaria, joined Mar 2003, 2578 posts, RR: 17
Reply 21, posted (6 years 6 months 4 weeks 1 day 1 hour ago) and read 7802 times:
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Quoting Blackbird (Reply 20):
For these reasons, I have trouble believing that the MiG-25 with an engine that had such thrust, and such a little pressure ratio (which combined with it's huge nozzles just reeks "HIGH SPEED") -- compared to the J-75 (even with technological differences between the US and, then USSR at the time) that is.

I think you may have left out a couple of words here. What do you have trouble believing? You think that the Mig-25 can go faster?

Concerning the canopy, it is made from E-2 heat-resistant Plexiglas. As for the rest of the airframe, N74JW has the correct materials. I will expand it a bit to say that the tempered steels used are VNS-2, VNS-5, EI-878, SN-3, EI-703 and VL-1. D19T aluminum and OT4-1 heat-resistant titanium are the other two major materials.

According to the book about the Mig-25 by Yefim Gordon(the second one from 2007), the top speed is limited to M2.83. Surely it can go faster. How much faster? I don't know, but in any case above M3.0 there is risk to the engines and the alcohol cooling system would also not be able to effectively cool the aircraft.

I don't consider myself an expert in jet engines although I will be taking a class on propulsion this year. Would someone mind to explain how mass flow rate and pressure ratios are related and why Blackbird thinks the thrust is low?

I will guess and say that the pressure ratio is low because it only uses a five-stage compressor, but I may be wrong. My sources indicate a maximum reheat thrust of 11200kgp and turbine temperature of 1230K.


User currently offlineN74jw From , joined Dec 1969, posts, RR:
Reply 22, posted (6 years 6 months 4 weeks 16 hours ago) and read 7772 times:



Quoting Sovietjet (Reply 21):
According to the book about the Mig-25 by Yefim Gordon(the second one from 2007), the top speed is limited to M2.83. Surely it can go faster. How much faster? I don't know, but in any case above M3.0 there is risk to the engines and the alcohol cooling system would also not be able to effectively cool the aircraft.

The USAF/Israelis clocked one at M3.2 in the 70s.


User currently offlineBlackbird From , joined Dec 1969, posts, RR:
Reply 23, posted (6 years 6 months 4 weeks 12 hours ago) and read 7745 times:

I think you may have left out a couple of words here. What do you have trouble believing? You think that the Mig-25 can go faster?

It's just that we had engines that could reach that speed, and had fighters like the F-106A that could do 2.80, with the F-106B doing 2.9 -- faster than the MiG-25's max speed, and it's engines were older, had a higher pressure ratio (which even despite the technological advantages we had would not be so advanced that with a 12:1 pressure ratio we could do the same speed they could with 4.5 : 1 -- it would seem that they would have had to have gone faster)

Quote:
Concerning the canopy, it is made from E-2 heat-resistant Plexiglas. As for the rest of the airframe, N74JW has the correct materials. I will expand it a bit to say that the tempered steels used are VNS-2, VNS-5, EI-878, SN-3, EI-703 and VL-1. D19T aluminum and OT4-1 heat-resistant titanium are the other two major materials.

What's the temperature limit of E-2 heat-resistant plexiglas (if not classified)? What's VNS-2/VNS-5/El-878/SN-3/El-703, VL-1, D19T, and OT4-1 maximum operating temperatures?

Quote:
According to the book about the Mig-25 by Yefim Gordon(the second one from 2007), the top speed is limited to M2.83. Surely it can go faster. How much faster? I don't know, but in any case above M3.0 there is risk to the engines and the alcohol cooling system would also not be able to effectively cool the aircraft.

Who's Yefim Gordon? The airplane uses alcohol as a coolant instead of the fuel itself?

Quote:
I don't consider myself an expert in jet engines although I will be taking a class on propulsion this year. Would someone mind to explain how mass flow rate and pressure ratios are related and why Blackbird thinks the thrust is low?

No... I said the thrust seemed unusually HIGH for the unusually low pressure ratio and mass-flow used. At least one source I remember reading listed it's thrust at around 27,000 lbf not 24,000 and change as well.

Quote:
I will guess and say that the pressure ratio is low because it only uses a five-stage compressor, but I may be wrong. My sources indicate a maximum reheat thrust of 11200kgp and turbine temperature of 1230K.

I know why it has a low pressure ratio. To the best of my knowledge a 2,730 degree (F) hot turbine temperature is pretty damn impressive especially then.


Andrea Kent


User currently offlineSovietjet From Bulgaria, joined Mar 2003, 2578 posts, RR: 17
Reply 24, posted (6 years 6 months 4 weeks 9 hours ago) and read 7724 times:
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Quoting Blackbird (Reply 23):
No... I said the thrust seemed unusually HIGH for the unusually low pressure ratio and mass-flow used.

I guess I got confused...but it seems from what you said here:

Quoting Blackbird (Reply 6):
How the hell did they get any reasonable amount of thrust out of that thing with that mass flow value and a pressure ratio of 4.75 to 1?

that you're implying they shouldn't have gotten that much thrust out of this engine. Either way, the thrust is high. Numbers aside, look at the sheer size of those nozzles and you can see where the thrust comes from  Smile.

Quoting Blackbird (Reply 23):
What's the temperature limit of E-2 heat-resistant plexiglas (if not classified)? What's VNS-2/VNS-5/El-878/SN-3/El-703, VL-1, D19T, and OT4-1 maximum operating temperatures?

I don't have time right now to look them up, but try www.matweb.com

Quoting Blackbird (Reply 23):
Who's Yefim Gordon? The airplane uses alcohol as a coolant instead of the fuel itself?

He has a ton of books on Russian aviation and with much detail too. The Mig-25 used about 200 liters of a 40/60 methanol/water mixture to cool the generators, radar, ECM equipment and radio. The rest used the fuel for cooling. There is an interesting story about this that I read about the Mig-25 in Bulgarian AF service where the cooling system failed to work at full capacity. The plane landed and when they opened the service hatches in the nose the internals were literally flowing out.


25 N74JW : The Mig-25 does, Alcohol is also used to de-ice the aircraft and the crew...
26 Post contains images Blackbird : N747JW, How effective is alcohol as a coolant? What's the limit as to how much it could cool would you guess? Regarding it's de-icing properties, I wo
27 N74JW : Very effective, alcohol freezes at a much lower temperature (around -175F). Some of the Northern exposures that the Migs would operate from would fall
28 Blackbird : N747JW, Was the book translated into English? Or was it in Russian? Perhaps they lied about it's speed for the same reason that the US lied about the
29 N74JW : The book was co-written by a French author and Belyakov. The cooling alcohol is probably not the same type of fuel alcohol (ethanol). Pure denatured a
30 Sovietjet : Like I mentioned above, the alcohol is not pure and is a 40/60 methanol/water mixture. It is used for cooling not deicing and only for the parts I men
31 N74JW : SovietDude, I have conflicting information from Mig-MAPO that indicated alcohol was used to de-ice the aircraft. Where did you find your information?
32 Blackbird : What's T-6 Jetfuel? Andrea Kent
33 N74JW : T-6 is a thermo-stabilized fuel made from Eastern Sulfuric Petroleums with the anti oxidation ionol additive.
34 Blackbird : How does it's flash point compare to American jet fuels? Andrea Kent
35 Post contains links Sovietjet : The flashpoint of T-6 is 62 degrees Celsius which is about the same as JP-7(fuel used on the SR-71). Here's a very detailed analysis of all Russian fu
36 Sovietjet : Both books on the Mig-25 from Yefim Gordon. Various Bulgarian and Russian literature about the Mig-25 I have also mentions this with first-hand accou
37 Post contains links Blackbird : N74JW, This is an interesting link, while I'm not sure if it confirms or denies my point or if it's even accurate at all it lists 2.83 as maximum spee
38 Sovietjet : 62 not 620. JP-7 is 60 Celsius. Alcohol only cools the radar, ECM gear, radio and other generators, not the whole plane. It is not the primary coolan
39 N74JW : SovietJet, I would agree with that. Perhaps the SR-71 uses some unique as well....
40 Blackbird : If the fuel's flashpoint is 62C, how does the plane manage to take any time at supersonic speed without bursting into flames? I have a feeling JP-7's
41 Bengan : From wikipedia: "The flash point of a flammable liquid is the lowest temperature at which it can form an ignitable mixture in air. At this temperatur
42 Blackbird : But the A-12/SR-71 is dripping fuel... as it transitions through the soundbarrier up to at least Mach 2 there's probably still fuel coming out of it..
43 Blackbird : Am I wrong? Andrea Kent
44 Sovietjet : You are confusing flash point with autoignition temperature(as the case of a hot surface such as a wing would suggest). The autoignition temperature
45 Blackbird : The MiG-25's fuel being comparable to JP-7 in terms of low vapor-pressure, high flash-point, auto-ignition temperature etc... how did they get their e
46 Sovietjet : T-6 is not as hard to ignite as JP-7 despite the similar flash point. The Mig-25 and currently the Mig-31 do not need TEB
47 Blackbird : Back to the engine here... The reason I have doubts regarding the plane's speed is simply in regard to the engine's pressure ratio, especially with th
48 Blackbird : N74JW, I do actually remember the MiG-25 could fly supersonically to some degree without afterburner... I've heard a number of figures, Mach 2.35 to M
49 Sovietjet : Not true. Data for Mig-25RB: Range at M2.35: 2045km Range at M0.92: 2280km Endurance at M2.35: 1hr 7 min Endurance at M0.92: 2 hrs 26 min AFAIK it ca
50 Blackbird : Is the afterburner an on/off kind of deal (all or nothing) or is it modulated into stages, or vernier-controlled (like how you'd throttle the engine)
51 Blackbird : I was reading something that mentioned the R-15 having AB-1 and AB-2 for it's afterburners? Anybody know anything further, is this a modulated system
52 Sovietjet : You got me there...I don't know...I'll try finding out for you.
53 Blackbird : To Sovietjet, Thank you
54 Post contains links Sovietjet : Andrea, I have dug up some of my sources both in books and forums. So to answer some of your questions. Besides for the sheer size of the engine, a ma
55 Blackbird : Sovietjet, Thank you for the information on the AB-1 and AB-2 settings. When you have the time, can you find out how the second AB setting regulate it
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