Saudi F-15 shot down over Yemen

:doh:

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Mach 4.5? With an R-27T launched "up-hill" from standstill? Are you kidding me?

Mach 4.5? With an R-27T launched "up-hill" from standstill? Are you kidding me?

Not your typical scenario, but I'm sure the thrust >> weight though and the calculation is only intended as a ballpark illustration. Equally, the first M1.0 is achieved with only 1/19th of the energy required for M1.0-M4.5, so standstill is a negligible factor. SLAMRAAM also has the same quoted speed as AMRAAM. But even if you half the speeds, you still get ~9km (30kft) from the same calculation, so a minimum of 20kft seems likely, even if the average speed is only 500m/s, which is hugely likely to be an underestimate since these things don't tend to steer very well below M2.0.

Additionally, it's a clear day and you can't even see the plane until the fire breaks out.

Neither SLAMRAAM nor R-27s will get up to M4.5 or anywhere NEAR M4 when launched from M0 at SL. Period. They don't even get there when launched from an M0.9 aircraft.

And if you want a missile simulator for this task, get a flanker, launch the R-27T from a Cobra at SL (in DCS) ... it'll be slow enough to pretend it's a SAM site. You can argue back and forth about the drag in DCS but even if you cut the drag down to radar-guided missile levels it won't get anywhere near those speeds.

Also, they steer quite well under M1.0. That's what those huge moving wings are for.

DCS is not reality, you only have to look at the zero drag R-24s (don't know if fixed yet) to notice that.

The speed depends on altitude and tends to be quoted for a medium altitude. Your assertion that neither missile will reach near those speeds is nonsense without confirming what launch AND travel altitude you're talking about. Yes drag is higher at SL but the SAM doesn't remain at SL throughout its flight, it is only at lower altitude during the slower part of its flight where excess thrust is in abundance.

Not on DCS they don't.;) And nope, those wings are pathetically small relative to aircraft wings, they were intended for manoeuvring at high speeds not subsonic. The chase is over long before the missile slows to the same speed as the aircraft if any manoeuvring is involved, hence why energy is more important to missile intercept Pk than manoeuvrability. At low speeds, those small winglets require huge AoA, which quickly bleeds even more energy that it doesn't have.

That said, the missile doesn't need to be near that speed to get to 30,000ft in that time, the 1000m/s was quite a conservative average, below Mach 3 (and even a little Stinger can reach M2.6). A missile peaking at M4.5 would average nearer M4 due to the rapid increase in drag with speed. That said 17 x 1000m is still 17km and assuming 45deg angle that amounts to 12km (40kft). So there is plenty of room for the missile to have reached 30kft and then levelled out before the intercept and I think a suggestion of 10kft is definitely wrong as that would amount to an average vertical velocity of only 176m/s, which is lower than the capability of the aircraft it's chasing.

And safe to say, the aircraft is well beyond MANPADS intercept parameters, AND DEFINITELY outside MANPADS burn range.

So there is plenty of room for the missile to have reached 30kft and then levelled out before the intercept and I think a suggestion of 10kft is definitely wrong as that would amount to an average vertical velocity of only 176m/s, which is lower than the capability of the aircraft it's chasing.

Let's do the back of the envelope math, shall we?

68kg of fuel expended in 6 seconds in an all-boost configuration for a 253kg missile, at 250 ISP. That's from old Russian academic books about the missile design, BTW, it isn't a guess.

Let's take the average weight, 219kg (since the rocket fuel mass is removed from the missile as we burn it, acceleration increases over time).

We have ((68kg x 250 ISP)/219kg) * 9.8 ~= 760m/s at rocket motor burn out. That's mach 2.2-ish without considering gravity or drag. That's quite far from M4.5.

At the end of 6 seconds this missile would have travelled 2300m, so, going straight up it can certainly reach a target at 10000' or maybe even 15000'. 20000' is probably pushing it.

In the video the missile hits the target after about 16-17 seconds of flight. Conservatively speaking, taking half of that peak speed computed above as average speed, the missile flew 6km. Not straight up, just total distance. And again, that's without taking drag, gravity, or any missile maneuver into account. But hey, if you want to argue the error bar should be between 5 and 7km, I'm ok with that.

In that same time, the target aircraft will have flown some 4-5km (between M0.7 and 0.9) so target altitude is guaranteed to be relatively low.

(NOTE: Leaving my 'mistake' here so that people can see how quickly one can make assumptions on the back-of-envelope math):

After a quick (and optimistic for this missile) computation of the average speed, it will have traveled 8.5km with an average speed or 500m/s. The target aircraft still retains its travel speed, and the altitude will still have to be below 20000' due to the significant horizontal flight component seen in the video.

The mistake above was being lazy about assuming the average speed.

And safe to say, the aircraft is well beyond MANPADS intercept parameters, AND DEFINITELY outside MANPADS burn range.

As for SLAMRAAM, official documents have it protecting a 10nm radius vs subsonic strikers (Rmax is at 10nm). That's not exactly M4.5 material.

Let's do the back of the envelope math, shall we?

 

68kg of fuel expended in 6 seconds in an all-boost configuration for a 253kg missile, at 250 ISP. That's from old Russian academic books about the missile design, BTW, it isn't a guess.

Let's take the average weight, 219kg (since the rocket fuel mass is removed from the missile as we burn it, acceleration increases over time).

We have ((68kg x 250 ISP)/219kg) * 9.8 ~= 760m/s at rocket motor burn out. That's mach 2.2-ish without considering gravity or drag. That's quite far from M4.5.

 

At the end of 6 seconds this missile would have travelled 2300m, so, going straight up it can certainly reach a target at 10000' or maybe even 15000'. 20000' is probably pushing it.

 

In the video the missile hits the target after about 16-17 seconds of flight. Conservatively speaking, taking half of that peak speed computed above as average speed, the missile flew 6km. Not straight up, just total distance. And again, that's without taking drag, gravity, or any missile maneuver into account. But hey, if you want to argue the error bar should be between 5 and 7km, I'm ok with that.

 

In that same time, the target aircraft will have flown some 4-5km (between M0.7 and 0.9) so target altitude is guaranteed to be relatively low.

 

(NOTE: Leaving my 'mistake' here so that people can see how quickly one can make assumptions on the back-of-envelope math):

 

After a quick (and optimistic for this missile) computation of the average speed, it will have traveled 8.5km with an average speed or 500m/s. The target aircraft still retains its travel speed, and the altitude will still have to be below 20000' due to the significant horizontal flight component seen in the video.

 

The mistake above was being lazy about assuming the average speed.

 

MANPADS is lighter and will slow down faster, but can, in some cases, peak at higher speeds.

 

As for SLAMRAAM, official documents have it protecting a 10nm radius vs subsonic strikers (Rmax is at 10nm). That's not exactly M4.5 material.

The video shows the rocket motor burning for ~12s, a long way past 6s for sure.

Aside from that your assumptions are garbage. The average speed would not be half the peak due to v^2 drag relationship, not that a peak of M2.2 sounds remotely realistic - pretty sure it's peak will be higher than that of a Stinger.

And strange how you're now arguing that an R-27 is past burnout after a 'low' target, when earlier, it could have been a MANPADS that hit whilst still in burn.

Do you even think a missile doing 760m/s at 2300m will retain enough energy to make an unpowered intercept 11s later in what appears to be a mostly rear-aspect tail chase?

You need to look at the video first, which should correct obvious mistakes and then rethink your maths.

Additionally, your calculation is complete BS even for the figures you provided.

Ve = g * Isp = 9.81 * 250 = 2452.5m/s

Delta V = Ve * ln(Mo/Mf) = 2452.5 * ln(219/151) = 912m/s

The video shows the rocket motor burning for ~12s, a long way past 6s for sure.

An E motor would burn for 10. Non-E burns for 6. Is this an E? I can't tell just by looking at it (the rocket portion of the fuselage would have a larger diameter), the video isn't that good.

Now, COULD this be an E version rocket motor? Maybe. I can't really tell from the video - the rocket portion of the body would be a larger diameter. In that case you'd have (IIRC) 135kg of fuel, 2 sec boost, 8 sec sustain and a 350kg missile. I can get the thrust values for both stages later. That missile is capable of reaching mach 4 at high altitude when launched ~M1.

Aside from that your assumptions are garbage. The average speed would not be half the peak due to v^2 drag relationship, not that a peak of M2.2 sounds remotely realistic - pretty sure it's peak will be higher than that of a Stinger.

Your attitude is garbage. I've already posted my correction. :).

And strange how you're now arguing that an R-27 is past burnout after a 'low' target, when earlier, it could have been a MANPADS that hit whilst still in burn.

Against a target whose altitude we don't know ... yep. Could have been a MANPADS. Nothing strange about this.

Do you even think a missile doing 760m/s at 2300m will retain enough energy to make an unpowered intercept 11s later in what appears to be a mostly rear-aspect tail chase?

I don't need to think it can, I know it can. Courtesy of having flyout profiles available.

You need to look at the video first, which should correct obvious mistakes and then rethink your maths.

 

Additionally, your calculation is complete BS even for the figures you provided.

 

Ve = g * Isp = 9.81 * 250 = 2452.5m/s

 

Delta v = Ve * ln(Mo/Mf) = 2452.5 * ln(219/151) = 912m/s

Nice job. But it's 253/185, which still evaluates to 768m/s. The 219kg was the average weight of the missile.

With an E motor it'll evaluate close to 1200m/s, but that's not a realistic figure because of the boost-sustain configuration. Of course, as long as we're evaluating in a vacuum, props to you, you genius ;)

The video shows the rocket motor burning for ~12s, a long way past 6s for sure.

Nono, you see this is water vapor.

An E motor would burn for 10. Non-E burns for 6. Is this an E? I can't tell just by looking at it (the rocket portion of the fuselage would have a larger diameter), the video isn't that good.

 

Now, COULD this be an E version rocket motor? Maybe. I can't really tell from the video - the rocket portion of the body would be a larger diameter. In that case you'd have (IIRC) 135kg of fuel, 2 sec boost, 8 sec sustain and a 350kg missile. I can get the thrust values for both stages later. That missile is capable of reaching mach 4 at high altitude when launched ~M1.

 

 

 

Your attitude is garbage. I've already posted my correction. :).

 

 

 

Against a target whose altitude we don't know ... yep. Could have been a MANPADS. Nothing strange about this.

 

 

 

I don't need to think it can, I know it can. Courtesy of having flyout profiles available.

 

 

 

Nice job. But it's 253/185, which still evaluates to 768m/s. The 219kg was the average weight of the missile.

 

With an E motor it'll evaluate close to 1200m/s, but that's not a realistic figure because of the boost-sustain configuration. Of course, as long as we're evaluating in a vacuum, props to you, you genius ;)

Well that may be the problem. There's increasing suggestion that these missiles originated outside Yemen, so maybe we are looking at an E model and the burn time is definitely >6s. So assuming a 6/10 ratio, that means 113kg of fuel, and a recalculation yields:

Delta V = 2452.5 x ln(219/106) = 1780m/s or ~M5.3@SL and M5.9@11km

Add in external forces and you get M4-4.5.

Or maybe the E model just has a smaller electronics section. Where's the evidence it weighs 350kg? Even an R-33 only weighs 490kg and that's almost 3 times the c/s area.

I know, I just felt like being crappy about it, especially since I struggled to understand what the hell your calculation was supposed to be about due to the error.

That MANPADS theory is starting to look very unlikely though, not that it ever was likely.

I doubt it. The missile will decelerate very fast in thick air once the thrust is removed. Tail chase, an AIM-120C at SL manages about 5km range on a rear aspect target, even with a ~9s burn.

You quoted 219kg but then we're allowing you to come up with figures for fuel weights and Isp with no source whatsoever. But 253kg with 113kg of fuel for E model gives Delta V = 1451m/s. Even a MICA VL is stated to have a ceiling of 10km (33kft) and an R-27ET is huge relative to those and actually available sources state M4.5.

350kg looks wrong to me, unless there's a reputable source.

Nono, you see this is water vapor.

You still sure it's not a MANPADS? It looks kind of big for a MANPADS to me.

Well that may be the problem. There's increasing suggestion that these missiles originated outside Yemen, so maybe we are looking at an E model and the burn time is definitely >6s. So assuming a 6/10 ratio, that means 113kg of fuel, and a recalculation yields:

 

Delta V = 2452.5 x ln(219/106) = 1780m/s or ~M5.3@SL and M5.9@11km

 

Add in external forces and you get M4-4.5.

Your masses are incorrect:

R-27: 253kg, 68kg fuel

R-27E: 350kg, ~135kg fuel

Or maybe the E model just has a smaller electronics section. Where's the evidence it weighs 350kg? Even an R-33 only weighs 490kg and that's almost 3 times the c/s area.

Su-27 employment manual (the real one), manufacturer website etc.

That MANPADS theory is starting to look very unlikely though, not that it ever was likely.

That's ok, it's just one possibility.

I doubt it. The missile will decelerate very fast in thick air once the thrust is removed. Tail chase, an AIM-120C at SL manages about 5km range on a rear aspect target, even with a ~9s burn.

I think 5nm is more correct but in any case, consider the actual distance flown in an air to air engagement.

You quoted 219kg. But 253kg with 113kg of fuel for E model gives Delta V = 1451m/s. Even a MICA VL is stated to have a ceiling of 10km (33kft) and an R-27ET is huge relative to those.

Err well, numbers for R-27s above :) The 219 was 253-(68/2).

R-27ET will definitely have a high ceiling, non-E is far less stellar.

Where's your source for those E masses. 350kg looks very, very wrong. The motor (less than half missile length) diameter is only increased to 260mm from 230mm. A 28% c/s area increase for 40% of the missile's length does not give a 40% increase in weight. More like 11%.

Link?

If the pilots were suicidal and stupid.

The equation you used was wrong though.

http://roe.ru/eng/catalog/aerospace-systems/air-to-air-missile/r-27er1/

Among others. You can get your hands on the Su-27 operations manual yourself :)

As for the equation I used, you're right and thanks but who cares - it's literally good enough for back-of-the-envelope math on this. The difference is so small that it's insignificant.

Where does the added weight come from though? And we still need a source for Isp and fuel weight.:D

Okay this site quotes 343kg.

http://www.artem.ua/en/produktsiya/aviation-means-of-attack-and-defense/air-to-air-missiles-r-27r1

This gives 1227m/s. Now you might say 1000m/s with external forces and average of 750m/s but that's still 13km (43kft). At a 45deg angle = 9km (30kft). And definitely >20kft.

Where's your source for those E masses. 350kg looks very, very wrong.

Vympel (Russian manufacturer) gives the ET mass as 343 kg, the EP as 346 kg and ER as 350 kg.

Artem (Ukrainian manufacturer) gives exactly the same masses.

Okay, well calculation still supports 20-30kft comfortably. Well outside MANPADS reach.

Vympel (Russian manufacturer) gives the ET mass as 343 kg, the EP as 346 kg and ER as 350 kg.

Artem (Ukrainian manufacturer) gives exactly the same masses.

Do you have the Vympel link?

Do you have the Vympel link?

vympel doesn't disclose any tech specs on their website, but their mother company KTRV does:

http://eng.ktrv.ru/production_eng/323/503/509/

Okay, so that just leaves the Isp and fuel weight for a proper calculation.

Fuel weight is from Russian publication and it is correct - you might find fragments of it on the Russian forum.

ISP is from memory but frankly, a little up or down isn't going to change things.

I like verifiable sources. But cutting a long story short, I think 343kg, 250s Isp and 135kg fuel still supports my case. 1230m/s peak, 17s flight time. It could have been at 20-30kft...

...but certainly well beyond MANPADS range, otherwise Russians would have 10kg missiles on their wings instead of 343kg ones.

Yes I'm telling you where to find them because it's not 'just a google away' and I don't want to spend time on hunting them down.

I like verifiable sources. But cutting a long story short, I think 343kg, 250s Isp and 135kg fuel still supports my case. 1230m/s peak, 17s flight time. It could have been at 20-30kft...

 

...but certainly well beyond MANPADS range, otherwise Russians would have 10kg missiles on their wings instead of 343kg ones.

Mig29 9.13 manual states for example how much difference in altitude can be, for high Pk... if fighter is flying @5km, 900km/h(!) it can shot at target which @max. flying above him as follows:

R27T - dH 5.5km into hot, 3km cold, R27ET - dH 13km into hot, 7.5km into cold target aspect.

So if we go by ballpark... to include the fact of launch @GL with 0km/h.. cold aspect shots are your best fluke.

I like verifiable sources...

Like Dutch magazines?