totoroHow do all these guesses and claims stack up to the info that can be extrapolated from those SAC documents Peter G linked to on the superhornet propaganda topic?
There is clearly said both f15 and f4, with a load of 4 sparrows, can do something like mach 2.3. F15 with four sparrows and 3 empty pylons (underwing and centerline) doing 1290 knots. That would be tad over mach 2.23. Same document showed a graph of f15 speed performance with the example of f15 carrying 4 sparrows and two mk84 bombs on underwing pylons, and it still did clearly over 1200 knots. That would still be slightly over mach 2.0.
If we accept those documents at the truth, and those documents seem mighty official, how can todays modern planes do much worse with aam loads? Isnt it much more logical explanation that all these 1.8, 2.0 figures are merely capped for public use, and real capabilities are higher? Same like with the publicly often cited ranges for amraam. And it becomes clear that drag from extrernally carried weapons is not that great.
totoroWell due lift/thrust limits. As the aircraft climbs higher, it’s ability to climb diminished due numerous reasons, until it can fly 1g sustained and that’s absolute ceiling. However, it’s impractical to go there (need to zoom climb over and then accelerate in dive to finally balance at max height), so 100fpm is taken as an agreement value for easier measurement.
I understand the concept which governed the need for such a rule, 100 fpm and so on. But what is strange to me is the fact that there are two altitude ceiling values listed, one where the plane has less energy left (100 fps) and one where it has more energy left, and a broader flight envelope (500 fps). Yet, they are both very similar, around 56.000 feet. How can such a big difference in climb rate – 400 fps, produce such small difference of altitude ceiling of just 330 feet?
Carrying 2 2000 bombs plus 4 sparrows, and still doing mach 2.2 is mighty impressive. But what about ‘close air support’ loadout? The plane has dropped its 16 mk82 bombs, it has 3 pylons and 3 multibomb carriages left. As we could read in the ferry loadout column, 3 pylons alone dont really make a dent in planes top speed. Yet, here where we have those extra 3 empty bomb carriages, suddenly the speed drops by over a 450 knots. What is more remarkable, the speed at 45.000 feet is 892 knots, yet at 35.000 feet it is higher, 959 knots. Those bomb racks really arent that big nor do they look much less streamlined than a pylon. Could it be a structural bomb rack related limit? Or how do we explain it?
Also, f16a, on that chart, is credited with mach 1.2 speed with a decent loadout. 2 sidewinders, 2 370 gal tanks, a jammer and 2 2000 lbs bombs. Could anyone venture to extrapolate similar values for a F15c? There probably is a somewhat predictable curve to it all…
totoroCombat ceiling is the altitude at which a plane can still generate some performance lift/thrust-wise and the 500 ft/sec is an agreement value, as is 100 ft/sec for service ceiling.
I understand that, but how come the ceiling for the agreed minimum climb rate of 500 fps is lower than the ceiling for the 100 fps climb rate? Or am I interpreting the chart in a wrong way?
The difference is in loadout. “Combat loading condition” is the condition in which the aircraft is after expending bombs and/or tanks. Therefore “pylon” remark, for example.
Different combat speeds, altitudes and climb rates are related to different flight profiles (high, low, etc…).
Hm… So there isn’t any mention of max speed with starting loadout? Or at least I am not seeing that… and I’m really curious what is the difference between max speed with 4 sparrows and max speed with 4 sparrows, a tank and two bombs.
And again, what is the diffference between combat speed and max speed? We’re talking for the same category of combat loadout conditions.
totoroI would like to talk more about those great SAC documents Peter G linked to. A fine example of the issues I have with them would be f-15c document (without cft). On page 4, loading and performance, it lists several typical missions, their loadouts and corresponding performance values. Link is here. http://www.alternatewars.com/SAC/F-15C_Eagle_SAC_-_February_1992.pdf
Under ‘combat loading conditions’ it says service ceiling (with 500 fps in parenthese) is 56.100 feet. Then right beneath it it says another instance of service ceiling (this time with 100 fps in parentheses) is 56.440. So, which is which? I thought service ceiling is a standard definition, when a plane cant climb faster than 100 fps. So how come there is another service ceiling, 500 fps one, where the plane should evidently have more altitude to gain, since it still has decent climb ability, yet the service ceiling value itself is even lower than the 100 fps one. What’s the deal there?
Another question would be concerning speeds. One the same page, under the same ‘combat loading conditions’ section, there are several speed values, for each loadout. One is ‘combat speed’, others are ‘max speed’ at 35.000 and 45.000 feet. What is the difference between combat speed and max speed there? Why are they sometimes, for some loadouts, so different, and sometimes, for other loadouts, they are almost the same? Specifically, ‘area intercept’ loadout, which seems to be the same as ‘air superiority’ loadout, both in fuel and in missiles, yet the combat speed difference is 500 knots, while max speeds are *almost but not quite* the same. Is the combat speed some arbitrary limit for the given mission, so fuel consumption is better controlled?
More about speeds. All these are listed as speeds at 45.000 ft. While i can accept an almost clean f15c, carrying only 4 semi recessed Sparrows, can have a max speed of 1335-1340 knots, how on earth can max speeds for loadout with 4 sparrows plus 2 pylons, each carrying a 2000 lb bomb, be 1303 knots? There is even ‘counter air’ loadout of 4 sparrows, 2 pylons each carrying a 2000 lb bomb plus a centerline pylon carrying a fuel tank – and the max speed for that is listed as 1290 knots.
And how on earth can the ferry loadout – three pylons carrying three fuel tanks carrying extra almost 12.000 lbs of fuel – have a max speed of 1356 knots. That’s the highest speed of any loadout!
Lastly, what is the deal with climb rates? Again there is a combat climb and max climb. But all values seem huge. Like 50.000 feet per minute. for all the loadouts. Am I reading this the wrong way or is the document really claiming f15c, in ‘counter air’ mission, with take off weight of 55.000 pounds, carrying 4 sparrows, a tank and two 2000 lbs bombs, can, at any point of its climb, reach a climb rate of 57.000 feet in one minute, or 950 feet per second?
totoroOne possible answer might be to get a more realistic experience for the deck crews training with the mock up models. A carrier has a main deck at least several stories high. Even actual planes could be dragged around, provided the inner construction of the roof and columns supporting it, is good.
totoroI guess that’s it, then. I’ve got no more questions concerning ballistic missiles. Thanks, Rodolfo. There’s only the first question left, unrelated to ballistic missiles.
1. We know that the average BVR AAM is usually qouted with max speeds of some mach 4, perhaps going up to mach 5. Doesnt matter if its amraam, sparrow, mica or r-27. Now those speeds are usually qouted as theoretical maximum, when used at high altitude. Much thinner air means the given impulse/drag ratio of the rocket motor will give the missile greater speed which will give it greater energy, thus giving it greater range.
It is also said the same missile fired near sea level will have much shorter range. The difference in air density at sea level and at, say, 40.000 feet, is some 250%, does that mean that the maximum speed of the missile is also going to be reduced by that amount? Sea level density is 1, 40.000 feet density is little under 0.4 How much will max speed be at sea level if it was mach 5 at 40.000 feet? mach 2? Or something else?
totoroOnce again, thank you. Would i be then correct in assuming that a similar, albeit smaller ballistic missile with 500 kg payload, having a range of 2000 km, would hit apogee around 450 km altitude, its speed would reach 4 km/sec in around 60 seconds, then drop to 3 km/sec around 300th second, accelerate once again to 4 km/sec around 550th second and hit its target around 570th second with impact speed of around 1,2 km/sec?
totoroThank you! That graph is great, i was hoping for something like that, which would give me a whole range of values. I noticed the max velocity (for the given range) in the first graph is the same as the velocity in the second graph (for the same range). Do you think one could linearly scale down and scale up other range values?
totoroThank you, Rodolfo. I shall certainly try to find more precise data and, if i manage to do that, I will share it here.
totoroTrue, but there are plenty of missiles using sarh guidance and CW illumination for the terminal stage of the attack while during the most of the flight time theyre just coasting along on inertial guidance or command guidance. What perpexles me is often quoted statement that the P version of sparrow had the ability to receive midcourse corrections. Why would that even be necessary if the missile was guided by CW during its entire flight? Doesnt that rather insinuate that near simultaneous guidance of two sparrows was possible, where both missiles would receive midcourse corrections to their respective targets and only in the last several seconds would the radar provide CW illumination to guide first one, then the other missile to their targets. Granted, thatd require both targets to be fairly close by, fairly cooperative and time period between two interceptions would have to be several seconds at least, if not a dozen seconds, or more.
totoroSadly, I simply cant find any sources confirming multiple SARH missiles guided to separate targets. If anyone has a source please help…
totoroInterestingly, i find it extremely hard to find sources for guidance of two sparrow missiles at two targets, no matter which plane and which radar we’re talking about. I was sure at least some later 80s versions of F15 could do it, but google just doesn’t give any proof of that. Actually, the only mention of two sarh missiles being guided at the same time to two targets is by infamous karlo kopp for the su-30mki and r-27 missiles, but that’s basically 90s tech and with an ESA.
Could fighters with MS arrays guide two sarh missiles to two targets back in the very late 80s or early 90s, before amraam came to the scene?
totoroThank you for your time, Rodolfo. Sadly, I didnt see any concrete speed info in that paper, and the references are unatainable for me, since theyre all paper publications.
Hopefully someone will join in and share their knowledge…
totoroWas there ever any analysis of number of us-a satellites in soviet inventory during the cold war? Be it from a western or soviet source, just a wild guess, ballpark figure, whatever? We know how many satellite pairs were launched, over the course of two decades, and they mustve helped testing and development of the next gen of such satellites. There never was a real crisis so we never saw many launches but there must’ve been a stockpile of ready to launch satellites in actual case of cold war going hot. Anyone?
totoroBuilding a 20 by 20 meter hangar with a roof of 3 or more meter thick layers of reinforced concrete is, naturally, pricy, but perhaps it does have its merit. 3 meters + of concrete is enough to prevent SDBs from penetrating it, which means the only weapon available are the blu113 penetrators, which are all 2000 lbs class weapons. So instead of, say, 8 SDBs, a plane would be able to carry only 2 weapons. Less targets to strike.
I’ve actually asked a constructor collague of mine how much would such a structure cost and he actually calculate it all for me and said somewhere in around 3 million dollars, site prep, work cost and material. Naturally, that’s without the design cost, but it is also a one off structure cost; a whole series of such bunkers built at one time at one place would lower the cost per bunker.
Another option is to mix such huge bunkers with bunkers that would be the same from outside, but built to much lower standards and with much weaker material, built to witstand only submunition hits but not strong enough to withstand a SDB, for example. Then to mix those two kinds of bunkers, 2 weak ones for each strong one and build some 100 or so of those around the airbase.
Or just use the weak design, made to cope with submunitions, which could then be made smaller, as it doesnt have to look like a very hard bunker, but then make A LOT of them. 300 or so. While it seems a lot, such a project could be done for under 300 million dollars per airbase. Naturally, provided there’s enough real estate for it. And then airplanes could be moved from one to another during crisis, so most of the time 90% of those bunkers would be empty anyway, but still each one would require at least a direct hit with a SDB. Even if each attacking plane carries 16 SDBs, it’d require a strike force of some 20 or so planes to even get a chance at every bunker.
And a plane carrying 16 sdbs wouldnt have much of a range for deep strikes. Not to mention that certain stealthy planes would be able to remain stealthy while carrying more than 8 SDBs.
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