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USAF plans F-15 modernization

Josh_TN

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The 50% only makes sense if the original trajectory had no loft at all. Energy densities of rocket motors haven't changed drastically over the decades. The other possibility is that more fuel was stuffed into the body at the expense of warhead of guidance (or guidance electronics were further miaturized). But I always had a hard time believing the 50% number, personally.
 

GARGEAN

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The 50% only makes sense if the original trajectory had no loft at all. Energy densities of rocket motors haven't changed drastically over the decades. The other possibility is that more fuel was stuffed into the body at the expense of warhead of guidance (or guidance electronics were further miaturized). But I always had a hard time believing the 50% number, personally.
Problems are: A - we know that proper loft for long range shots was present since forever, and B - we know that it uses same engine as was used since AIM-120C-5.
 

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The 50% only makes sense if the original trajectory had no loft at all. Energy densities of rocket motors haven't changed drastically over the decades. The other possibility is that more fuel was stuffed into the body at the expense of warhead of guidance (or guidance electronics were further miaturized). But I always had a hard time believing the 50% number, personally.
Problems are: A - we know that proper loft for long range shots was present since forever, and B - we know that it uses same engine as was used since AIM-120C-5.



This says the C-7 has the new +5 (5-inch longer) rocket motor and shortened control actuator module, and the D has a new actuator control module and (obviously) the new guidance section.
 

Colonial-Marine

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I think the C-7 variant introduced the lofted trajectory for the AMRAAM series and the C-5 had already introduced the improved rocket motor. The D model having a 50% longer range over the C-7 doesn't seem feasible.

At some point the AIM-120D was envisioned as having a dual-pulse rocket motor but that never happened even though it really should have by now.
 

GARGEAN

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This says the C-7 has the new +5 (5-inch longer) rocket motor and shortened control actuator module, and the D has a new actuator control module and (obviously) the new guidance section.
This motor was introduced with C-5. And yeah, guidance section change is more than expected)
 

TomS

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This says the C-7 has the new +5 (5-inch longer) rocket motor and shortened control actuator module, and the D has a new actuator control module and (obviously) the new guidance section.
This motor was introduced with C-5. And yeah, guidance section change is more than expected)

Annoyinfg that even the Air Force seems confused.

Fortunately we have a dedicated AMRAAM thread that seems to have better info.


Jennings [Raytheon's AMRAAM business development director] said, "The AIM-120C-5 extended the range of the AIM-120B fairly significantly, by shortening the control actuation system in the back and adding fins to the back end of the rocket motor. That added pretty decent range capability when you go from AIM-120B to AIM-120C-5. The C-7 and the D share the same rocket motor, and the same form, fit, function, size, and control actuation system. And both the C-7 and D have the same rocket motor as the C-5. Throughout AMRAAM's development, there have been improvements into the flight profile of the missile to get to the target. These improvements have led to range increases as well, and the jump from the B to the C-7 was fairly significant. The D can fly slightly farther than the C-7, and the C-7 can fly farther than the C-5. But this range increase is in the order of low double-digit percentages."

So it appears that there was a big jump with the C-5 (which fits with the bigger motor and smaller actuator section), then smaller increases the C-7 and D, presumably due to better trajectory shaping and tweaks.

One thing that jumps out is that sometimes people talk ab out the D haveing a much improved no-escape range. That's very different from the maximum kinematic range and could well be due to improvements in guidance techniques, for example.
 

GARGEAN

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So it appears that there was a big jump with the C-5 (which fits with the bigger motor and smaller actuator section), then smaller increases the C-7 and D, presumably due to better trajectory shaping and tweaks.
Yup, exactly my point. Just blindly going with "AIM-120D has 50% range increase over AIM-120C-7" is just so wrong...
One thing that jumps out is that sometimes people talk ab out the D haveing a much improved no-escape range. That's very different from the maximum kinematic range and could well be due to improvements in guidance techniques, for example.
That part is indeed reliant on software somewhat more than pure longshots, but I wouldn't expect really substantial increase in range here either, at least if software wasn't heavily flawed before. Which it definitely wasn't.
 

Josh_TN

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The 50% only makes sense if the original trajectory had no loft at all. Energy densities of rocket motors haven't changed drastically over the decades. The other possibility is that more fuel was stuffed into the body at the expense of warhead of guidance (or guidance electronics were further miaturized). But I always had a hard time believing the 50% number, personally.
Problems are: A - we know that proper loft for long range shots was present since forever, and B - we know that it uses same engine as was used since AIM-120C-5.



This says the C-7 has the new +5 (5-inch longer) rocket motor and shortened control actuator module, and the D has a new actuator control module and (obviously) the new guidance section.
I didn't realize the motor changed physical sizes in the more recent vesrions. So did the overall missile retain the same dimension but the control section was reduced to allow more propellant?
 

TomS

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So it appears that there was a big jump with the C-5 (which fits with the bigger motor and smaller actuator section), then smaller increases the C-7 and D, presumably due to better trajectory shaping and tweaks.
Yup, exactly my point. Just blindly going with "AIM-120D has 50% range increase over AIM-120C-7" is just so wrong...
One thing that jumps out is that sometimes people talk ab out the D haveing a much improved no-escape range. That's very different from the maximum kinematic range and could well be due to improvements in guidance techniques, for example.
That part is indeed reliant on software somewhat more than pure longshots, but I wouldn't expect really substantial increase in range here either, at least if software wasn't heavily flawed before. Which it definitely wasn't.

I've learned something today, for sure. Now, the next issue is how to square the info on the AIM-120D with the Navy's implications that it matches the range of AIM-54. But that's probably a question for another thread.
 

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