Why not engage AB before missile launch?

This was posted on AFM... any thoughts?

If, the F-35 can indeed fly just above Mach 1 at Military Power. (which more and more people speculate that it can) Why couldn't it just engage its afterburner for a short period to get up to say Mach 1.3 - 1.5 to fire its AMRAAM's. As this would give it a similar Kinetic Energy as the F-22 during super cruise!

Let's not forget the F-35 has a more fuel than just about any fighter currently flying..

Already thought of.

SnakeHandler wrote:Already thought of.

Well, I must have missed it... would you care to enlighten me or at least direct me to the posting???

As you can probably guess, the faster you are when you launch a missile the less thrust it takes to get it up to speed and/or the greater range it has. That's why the Space Shuttle and the foreign rockets launch from as close to the equator as possible. The reason the Soviets had to design much more powerful rockets was because they couldn't take advantage of the spin of the earth at such a high latitude as Kazakstan(sp?). So, if you can cruise around in the .85M region and just use AB to get above the mach then you'll save a lot of gas over the guys who supercruise. Remember, just because you aren't using AB to supercruise doesn't mean you aren't using a lot of gas to go that fast.

SnakeHandler wrote:As you can probably guess, the faster you are when you launch a missile the less thrust it takes to get it up to speed and/or the greater range it has. That's why the Space Shuttle and the foreign rockets launch from as close to the equator as possible. The reason the Soviets had to design much more powerful rockets was because they couldn't take advantage of the spin of the earth at such a high latitude as Kazakstan(sp?). So, if you can cruise around in the .85M region and just use AB to get above the mach then you'll save a lot of gas over the guys who supercruise. Remember, just because you aren't using AB to supercruise doesn't mean you aren't using a lot of gas to go that fast.

Well, so the F-35 "may" have some very distinct advantages after all?

It will have quantum leap advantages. It's 20 years newer.

Corsair1963 wrote:This was posted on AFM....any thoughts?

If, the F-35 can indeed fly just above Mach 1 at Military Power. (which more and more people speculate that it can) Why couldn't it just engage its afterburner for a short period to get up to say Mach 1.3 - 1.5 to fire its AMRAAM's. As this would give it a similar Kinetic Energy as the F-22 during super cruise!

Let's not forget the F-35 has a more fuel than just about any fighter currently flying....

This is pretty standard practice for 4th generation fighters. The issue is that if you start at Mach 0.9 and accelerate to Mach 1.6 for instance it'll take some time. That same time elapsed would have enabled a supercruising fighter to go from Mach 1.6 to say Mach 2 for even better missile kinematics.

Remember, acceleration takes take. This is why 4th generation fighters typically never exceed Mach 1.5~1.6 even if they are technically acapble of say Mach 2.5. The reason being that you don't dash around at supersonic speeds on CAP or a fighter sweep. By the time you are aware of an enemy contact and accelerate towards it, you'll typically only reach Mach 1,5 or so before its time to fire and break or merge. Being able to stay at Mach 1.5~1.7 reasonably economically gives you a good kinetic energy lead going into most engagements. Having lots of fuel to burn (lots of afterburner time if you will) like the F-35 also helps, but not to the same extent as operationally practical supercruise capability.

dwightlooi wrote:Remember, acceleration takes take. This is why 4th generation fighters typically never exceed Mach 1.5~1.6 even if they are technically acapble of say Mach 2.5.

Cheers to that, dl!

Acceleration, acceleration, acceleration, baby.. Man do I hope US congress sees a need for 40-60 more F-22.

Heck, even an AIM-120C7 on an 'accelerated' F-22 would give what... 60km NEZ?

Tell that to congress when we're looking at decreased strategic air combat deterrence every day out to about 2018 at least, as it is, until adequate IOC F-35 squadrons can be activated.

I'm curious how you came up with that number geogen?

By 2025 or so the F-35 may well be equipped with a more powerful engine. The F-136 is already more powerful that the F-135. They have plenty of time to develop a 3D nozzle if they want too.

Although honestly when the JDRARM is available, I doubt that the kinematics of the aircraft itself will count.

Also, isn't it true that it is possible to combine 2 AESA radars to emulate a bigger radar? If that's true 2 APG-81 together may have the same range as 1 APG-77.

Is there really a need for more F-22s right now? It's unfortunate but its price has not gone down. If the F-35 was to be armed with 8+ AAMs ant if it's really much cheaper, I don't think the F-22 is worth it anymore.

dwightlooi wrote:This is pretty standard practice for 4th generation fighters. The issue is that if you start at Mach 0.9 and accelerate to Mach 1.6 for instance it'll take some time. That same time elapsed would have enabled a supercruising fighter to go from Mach 1.6 to say Mach 2 for even better missile kinematics.

Remember, acceleration takes take. This is why 4th generation fighters typically never xeceed Mach 1.5~1.6 even if they are technically acapble of say Mach 2.5. The reason being that you don't dash around at supersonic speeds on CAP or a fighter sweep. By the time you are aware of an enemy contact and accelerate towards it, you'll typically only reach Mach 1,5 or so before its time to fire and break or merge. Being able to stay at Mach 1.5~1.7 reasonably economically gives you a good kinetic energy lead going into most engagements. Having lots of fuel to burn (lots of afterburner time if you will) like the F-35 also helps, but not to the same extent as operationally practical supercruise capability.

I am not talking about accelerating from subsonic to say Mach 1.5. More like if the F-35 was already supercruising at Mach 1.2 and then it accelerated to Mach 1.3 - 1.5 Which, is not the equal of the Raptor. Yet, much better than current types.

Viperalltheway wrote:By 2025 or so the F-35 may well be equipped with a more powerful engine. The F-136 is already more powerful that the F-135. They have plenty of time to develop a 3D nozzle if they want too.

Although honestly when the JDRARM is available, I doubt that the kinematics of the aircraft itself will count.

Also, isn't it true that it is possible to combine 2 AESA radars to emulate a bigger radar? If that's true 2 APG-81 together may have the same range as 1 APG-77.

Is there really a need for more F-22s right now? It's unfortunate but its price has not gone down. If the F-35 was to be armed with 8+ AAMs ant if it's really much cheaper, I don't think the F-22 is worth it anymore.

Well, the P & W F-135 was stated in the 40,000 lbs class. Now it widely discussed at making around 43,000 lbs and some USAF sites even claim 48,000 lbs! Of course that doesn't even include the supposedly more powerful GE F-136!!!!

Personally, I think alot of people are going to be in fora surprise....

And you know the F136 is more powerful from where?

I'd ask the same question. "You know the F136 is more powerful from where?

I read a lot about engines and engine technology, and I've not seen any speculation from any credible sources that even hint that either the F135 or F136 is more powerful. (Except for a small margin either way...) If they were that much different, the statements "interchangeable" "plug and play" or "transparent to the pilot" would not be used by anyone in the program.

Since the F136 has been "canceled/defeated" something like 3 times now, I'd think it would suffer from funding issues and/or delay. I'll also point out the current DoD FY09 budget still excludes funding for the F136.

PW and GE will both engineer "thrust growth potential" into their respective products. (Why wouldn't they?) In previous engines (F100 and F110) both OEMs have shown the possibilities of infusing newer technologies to improve performance and reliability. The F100-PW-229 gained tech from the F119 and F135 where the F110-GE-129/-132 has received benefits from the YF120 and F136.

PW beat GE twice on new fighter contracts; (F119 and F135) they have played the "lower operational cost" and "greater reliability" cards. These same cards have helped PW gain favor with most new and repeat Viper customers. Block 52/52+ sales have outpaced the sales of Block 50/60. (PW seems to have a better customer service base that may have something to do with all of this as well)

PW isn't going to make the same mistakes it did during the Great Engine Wars. Even if the US Congress does press the F136 into service I doubt it will result in a mixed-fleet for any one branch or country. (IE - USAF=F135 perhaps US NAVY=F136, RAF=F136, IAF=F135, USMC=F135 - who knows!?!) The deployment/logistics of the GE/PW Viper mix hampers funding over the long term. Example: When the USAF spends $50M on "improvements" for the F100, both the PW Vipers and Eagle benefit. When the USAF spends $50M on the F110, only the GE Vipers benefit. Imagine if all $100M went into one design that would benefit ALL your fighters... The F119 and F135 will share many key technologies and will both benefit from advances as PW makes them; divert money to the F136 and money spend there will not be "backward compatible" with the Raptor.

I'd be very interested to read anything about the F136's performance (Or the F135's) I'm always "on the prowl" to learn about engines and most of the information we're debating here will be classified for many years to come. (Like "true" figures for the F119 ) If anyone has credible industry sources concerning "possible" thrust figures for these engines, please provide it so the rest of us can take an educated look at the data.

Rest assured, PW won't fall victim to the "newer is better" ploy of years gone by. IMO - They'll hold a few aces up their sleeves until the proper time to play all the cards...

Keep 'em flyin'
TEG
(edit for spelling, must be the fuel fumes?)

JetTest wrote:And you know the F136 is more powerful from where?

We don't know that the F-136 is more powerful. In fact, the original requirements did not call for a more powerful GE alternative powerplant. What it did call for is a second powerplant which is fully interchangeable without any airframe modifications with the F-135. In short, you should be able to take an F-35A into a hangar, slide the F-135 out and slide the F-136 in at anytime.

However, historically, powerplants which are second to market usually tries to out do its predecessor in one way or another to forge itself a viable market position. In fighter engines this usually comes in form of more thrust. We do know that the F-136 prepared for the X-32 demonstrator produced 52,000 lbs of thrust. However, that engine had a larger fan that can be used in the F-136 engines slated for the F-35.

Regardless, both the F-135 and F-136 cores can support higher thrust and I am sure that at some point in the lifetime they will. The question is when.