SAAB JAS 39E/F Gripen - General discussion

[Necronomica]

@quartas121

not always true.

In what situations would an increase in speed not allow for higher altitude operations for ramjets?

[Flame2512]

@quartas121

Does this paper account for the limited maximum altitude of a ramjet

Yes

Spoiler

@quartas121

and drag created by the intakes

The paper does talk about the problems caused by low altitude drag. While it does not explicitly compare the drag of the proposed missile to a non-ramjet missile it is clear they conider it in all thier simulations. At the end of the day this isn’t a paper written by a bunch of students, it’s written by engineers from the Air Vehicle Performance Department of the Defence Research Agency; who’s job is to accurately simulate aircraft / missiles.

@quartas121

If the paper is just for something “similar” then it doesn’t work very well either, many things could be different that would affect max range

The paper is about the performance of a hypothetical TDR ramjet powered BVR AAM, designed under the constraints that it must be pretty much the same length / diameter as the UK’s existing BVR missiles (i.e. Skyflash & AMRAAM). And it is written by people from the DRA, which would go on to be involved in the development of Meteor.

Meteor is a TDR ramjet powered BVR AAM which was designed in part by the same people, and with those same design constraints and performance goals. In addition the general design and layout of the missile they propose very closely marches Meteor. And many of the data points they use in their proposed missile closely match what is known publicly about Meteor and it’s prototypes (such as A3M). For example:

• The booster ISP they use pretty much matches that of A3M (well is actually a little low)
• The booster burn time they used almost exactly matches A3M
• The ratio of boost to sustain fuel appears to match Meteor pretty closely based on the cross sections we have of Meteor
• The turn down ratio they propose (10) pretty much matches Meteor (albeit Meteor is a little higher)

So it seems likely that the missile described in the paper is probably the best declassified approximation we have of Meteor’s performance. And that Meteor likely exceeds the performance described in the paper, for the reasons noted in my previous comment.

[quartas121]

things like intake design and the ramjet itself limit altitude, and vary between missiles/aircraft. for example, the cruising altitude for the Kh-31 ramjet missile is only 15km.

@Flame2512

So it seems likely that the missile described in the paper is probably the best declassified approximation we have of Meteor’s performance.

fair enough. would you say meteor can do 20-30km better than the 220km at .9 6000m, just as a estimate?

[Timpun]

The improvement from this analysis to the real meteor would likely be higher than 20-30km thanks to even further developments and optimisation as well as the boron loaded fuel that Flame also mentioned in an earlier post.

[Necronomica]

@quartas121

things like intake design and the ramjet itself limit altitude, and vary between missiles/aircraft.

Yes? that i don’t dispute. Higher speeds do still result in a higher possible altitude ceiling (of course there is an inherent design limit on top of that).

@quartas121

for example, the cruising altitude for the Kh-31 ramjet missile is only 15km.

Cruising altitude is not the same as max, long range missiles are designed to operate optimally at specific speeds and altitudes to achieve max range. if that missile moved faster it could go higher. It wouldn’t be as optimal but it could.

@quartas121

would you say meteor can do 20-30km better than the 220km at .9 6000m, just as a estimate?

I personally don’t doubt that it could. Released at like 10km alt and at Mach 2 it doesn’t need to waste as much fuel to get up to Mach 4 and doesn’t need to waste energy to climb. If i don’t misremember those numbers were also with the premise that it should arrive at the target still going Mach 2 at impact. Add to that a few decades of development, research and testing.

[quartas121]

@Necronomica

if that missile moved faster it could go higher. It wouldn’t be as optimal but it could.

only up to a point, and the missile is already meant to go to its limits to squeeze out as much range as possible.

@Necronomica

I personally don’t doubt that it could.

yeah, with improvements since the 1990’s with boron propellant and other things, 20-30km should be added onto that scenario just as a personal guess. but i do think its worth considering the limitations in simulation when this paper was made, which is why that number isnt higher than 30km

[Necronomica]

For reference here is the paper in full (the discussed parts begin at page 30):

Obligatory front page with de-classification (@Flame2512 you should include this EVERY TIME you post about a document that can reasonably be thought to be (or have been) classified, i’ve flagged posts of yours for not including this in the past):

( Client Challenge )

[Michael-IR]

Good talk there. I enjoy reading these

[MBDA_MICA]

I’m following these kinds of posts about missiles and jets for 7 years now and it is interesting. Though it gets heated sometimes when certain people’s beliefs come in.

[astral_invader]

Look everyone it’s John MICA.

[Nirvana7125-live]

I agree on this, the Aim-174 is into the area of atmospheric skipping for more range, not really able to be put in the same boat as stuff like the meteor