Editing Missiles
-
Actually, the HARM was made to be faster than a Shrike. The AGM-78 problem was that it was exceedingly heavy.
-
intereresting. so you think the speeds are accurate? it just seems very counter intuitive to have your newer missile operate slower than you replacement It also goes against the sources quoted, do we have anything that demonstrates a -78 going M5+?
-
Some sources are not open.
-
17 nautical miles isnt exactly long range, though. RIM-66 doesnt narrow it down much molni - three different rocket motors for ‘RIM-66’.
Also worth noting is that the High Speed ARM is flying almost half the speed of the missile it replaced… why not call it to SLow ARM instead?
Interestingly, ausairpower cites the SR113 as containing only 303 lbs, or 137.4 kg, of propellant. Seems low for a high speed missile.
Ah! But its a lightweight missile, only 360kg at launch. That makes more sense.
Well, I figure the HARM should have a delta-v around 1.1 kps… not drastically dissimilar to the STARM. Its unclear to me whether BMS internally uses the rocketry equation for missiles?
The thrust for both missiles is quite different, and I dont have any sources to compare either to. The BMS AGM-78 has 1 second of no thrust, 4 seconds of 17 klbsf thrust, then 10 seconds of 5.1 klbsf thrust. The BMS AGM-88 has 4 seconds of 10.6 klbsf thrust, then 36 seconds of 888 lbsf thrust. That is probably the major source of the HARM in BMS flying much slower.
If you take as granted that the STARM flies too fast, you could rectify that by decreasing the sustain thrust and increasing the duration of that sustain. While I suspect that is likely the case, without more data on it its a bit beyond my capabilities to assess - I dont think I can make an estimate for burn rate and thrust profile without more information. Nothing stopping you from using the LAR method - Looks About Right - to get the missile to fly slower.
-
Burn duration can be guesstimated from old live fire videos of SM1s.
-
17 nautical miles isnt exactly long range, though.
This value concering on what?
Do not forget the target of RIM-66 is moving and even is non maouvering it means at edge of range missile speed is t least ~400 m/s. Target of AGM-78 does not move so even the missile is subsonic can hit the target.
The big question how different was the engine thrust char. of AGM-78 comparing to RIM-66.Interestingly, ausairpower cites the SR113 as containing only 303 lbs, or 137.4 kg, of propellant. Seems low for a high speed missile.
Almost all AAM and similar SAM missiles have very similar propellant weigth/launch weigh, about 0.32-0.37.
-
This value concering on what?
Do not forget the target of RIM-66 is moving and even is non maouvering it means at edge of range missile speed is t least ~400 m/s. Target of AGM-78 does not move so even the missile is subsonic can hit the target.
The big question how different was the engine thrust char. of AGM-78 comparing to RIM-66.Almost all AAM and similar SAM missiles have very similar propellant weigth/launch weigh, about 0.32-0.37.
The RIM-66 block III and block IV, the only two RIM-66 versions that share a motor class with the AGM-78, had a notional range of 17 nautical miles to complete an intercept. The block V and onwards, using the Mk56 rocket motor, had a range of around 25 nautical miles.
l3, that is a very good point. The only question there though, is that of the difference between the Mk27 mod 0 used in the RIM-66A block III and block IV, and the Mk27 mod 4 used in the AGM-78. I dont know what the difference is, but someone thought it a significant enough difference to label it such. Thrust profile of the grain would be a very good reason to label the motor a mod X…
-
The RIM-66 block III and block IV, the only two RIM-66 versions that share a motor class with the AGM-78, had a notional range of 17 nautical miles to complete an intercept. The block V and onwards, using the Mk56 rocket motor, had a range of around 25 nautical miles.
If you drop a bomb at 24000k feet with 300 m/s its impact distance projected on ground is close to 10 km (6 nm). It is very hard to belive that an AGM-78 max. impact distance on ground from high alt is only 17 nm. Just doing a loft with the missile without thrust can result such impact range… Such one value range data is useless for comparsion…
I have somwhere the range enevelope oh Kh-58 missile. At low level is less than 40 km, az very high alt the range in above 120 km… So 17 nm at SL is maybe true but launching at high alt…
-
If you drop a bomb at 24000k feet with 300 m/s its impact distance projected on ground is close to 10 km (6 nm). It is very hard to belive that an AGM-78 max. impact distance on ground from high alt is only 17 nm. Just doing a loft with the missile without thrust can result such impact range… Such one value range data is useless for comparsion…
I have somwhere the range enevelope oh Kh-58 missile. At low level is less than 40 km, az very high alt the range in above 120 km… So 17 nm at SL is maybe true but launching at high alt…
You havent read the post then… I did not say that the AGM-78 had a range of 17 nm. Go back and reread the post, then try again.
-
You havent read the post then… I did not say that the AGM-78 had a range of 17 nm. Go back and reread the post, then try again.
Do you have a bad day or someting?
So the intercept point of RIM-66 can be 17 nm? It seems to me real. The same missile in case is launched from a very high platfrom could have 2,5 times larger range (not launch range) even against air target and much larger against ground target…Concerning on first post. As long as is no exact data about AGM-78 you have to find or use Kh-58 as reference pont. At very high alt M5.5 is likely too big but M4.5 would not be.
(AIM-54 is much more inaccurate currently in BMS4, has similar or worse kinematics than AIM-7F/M…)
-
Yes in fact, but thats no excuse for a poor attitude on my part. My apologies.
-
(AIM-54 is much more inaccurate currently in BMS4, has similar or worse kinematics than AIM-7F/M…)
Yeah, I need to tackle that one of these days.
I also confirm that the flight profile makes a huuuuge difference for a long range SAM. So much so that a VLS is pretty much the optimal way to fire a SM2 or a SA-10 anyway This is why they were able to gain a ton of range by going from a pure SARH with the SM-1 to a datalink/TVM type with the SM2, all else being equal - they could tailor the flight profile for max performance.
Regarding the missile flight model in BMS, it is actually pretty detailled and you can get very close to RL performance if you have enough data. Engine thrust, aerodynamic lift & drag, atmospheric model etc. are all modelled decently and give realistic results. The guidance is a bit monolithic (you only have proportional navigation, with a loft G bias at first) but you can tweak the gains depending on the part of the flight, allowing you to adust the flight profile quite a lot.
-
Concerning on first post. As long as is no exact data about AGM-78 you have to find or use Kh-58 as reference pont. At very high alt M5.5 is likely too big but M4.5 would not be.
Potentially, if it was launched at or above mach 0.8 and at high altitudes. Again, launched at say 90,000 ft you could see mach 4 to mach 5. Well, launching aircraft speed plus mach 3.7, basically.
-
Gents,
Is the consensus that the modeling in BMS is probably about 25% too fast?
Can I please have the physicists give a direct response to this question? (Blu3wolf, l3crusder, moli)?
We are trying to decide to go forward with modifying it for our 80s ITO mod or not - we need to know if we should modify it based on our hunch that it’s too fast or if we should just leave it and move on. Thank you.
-
Gents,
Is the consensus that the modeling in BMS is probably about 25% too fast?
Can I please have the physicists give a direct response to this question? (Blu3wolf, l3crusder, moli)?
We are trying to decide to go forward with modifying it for our 80s ITO mod or not - we need to know if we should modify it based on our hunch that it’s too fast or if we should just leave it and move on. Thank you.
Honestly I dont think so, and it is hard to tell anyway without precise data on the real thing, so I’d say dont bother. Keep in mind that if you modify something in the flight model, you will have to redraft the range table to get an accurate DLZ.
-
I dont think we reached a consensus. I am fairly certain its too fast, but cant verify without more data. With no disrespect intended, I think we have been inadvertently comparing apples and oranges, as I suspect we have been discussing differing variants of the rocket motors involved.
My recommendation would be to keep the total impulse around the same by upping the thrust duration and lowering the thrust for the sustain stage. If anything, lowering the total impulse slightly may be warranted. Specific impulse around 240 should be fine. Unsure if BMS uses that value anyway, though.
Id agree with the hunch its too fast, but without more data on the rocket motor I cant back that up as anything other than supposition on my part.
-
looks like a Standard M2 shipboard missile…
-
Well, given that they share an awful lot of the same components, including the body, thats probably to be expected.
-
I am not an expert. One of possibility could be because of TAS value in Tacview. I am wondering that TAS value in high speed seems to be strange in Tacview.
When I look the figure uploaded by Gza036, CAS speed is 2468 knot in alt 19500. Roughly calculation to TAS is ~2700 knot, ~M4.4, not M5.5
Is M4.4 reasonable?
Thanks,