Rafale wins Indian order
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Rafale wins Indian order
First hand experience in India with the Hawk contract says that the contract will hinge on whether the French allow HAL or Mahindra to build the Rafale in India.
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It's easy to see the practical attractiveness of Rafale over Typhoon. Being built by one country, with one main contractor, Rafale has acheived far more of its design capability in less time than Typhoon. India knows it won't have to put up with the riciculous in-fighting that has almost cost Typhoon its very existance over the years. If I were them, I would take a lot of convincing to go for a jet with promised capabilities over one that already has them. Especially given all the broken promises and missed milestones over the years.
Originally Posted by earswentpop
So they don't want the aid. Whatever. Can we have our call centres back? Especially that god-awful one for BT Broadband.
Hell, we might even buy the Typhoon if you do!
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Bombay Duck, are you confident that Rafales can handle newer Chinese fighter aircraft, some of which incorporate patented technology stolen from the F-35?
Diverterless supersonic inlet
From Wikipedia, the free encyclopedia
This article needs additional citations for verification. Please help improve this article by adding citations to reliable sources. Unsourced material may be challenged and removed. (November 2011)
Diverterless supersonic inlet
A diverterless supersonic inlet (DSI) is a type of jet engine air intake used by some modern combat aircraft to control air flow into their engines. It consists of a "bump" and a forward-swept inlet cowl, which work together to divert boundary layer airflow away from the aircraft's engine while compressing the air to slow it down from supersonic speed. The DSI can be used to replace conventional methods of controlling supersonic and boundary layer airflow, such as the intake ramp and inlet cone, which are more complex, heavy and expensive.[1]
Research into the DSI was done by Lockheed Martin in the early 1990s. The first DSI was flown on 11 December 1996, installed on a F-16 Block 30 fighter and replacing aircraft's original intake diverter. The modified F-16 demonstrated a maximum speed of Mach 2.0 and handling characteristics similar to a normal F-16. It was also shown that subsonic specific excess power was slightly improved. A DSI was later incorporated into the design of the Lockheed Martin F-35 Lightning II.[1]
The JF-17 Thunder also uses a DSI. Work on the DSI was started in 1999 ( Note the timing. -- Elmo ) with the aim of improving aircraft performance and took almost two years, during which a number of models underwent wind tunnel tests at different speed regimes. It was found that the DSI gave high performance, high total pressure recovery, low integrated distortion and good engine/intake matching.[2]
The Lockheed Martin F-35 Lightning II, JF-17 Thunder, Chengdu J-10B and Chengdu J-20 fighters all incorporate DSI.
Text below is from Lockheed's "Code One" house organ magazine Code One Magazine: JSF Diverterless Supersonic Inlet:
...
Basic research of the inlet concept continued through the mid-1990s. Traditional wind tunnel testing of small plastic inlet models built with stereolithographic techniques augmented a CFD-based development process for the DSI. Engineers made enough technical advances during this period that two US patent applications were filed, one dealing with the overall design and the second dealing with the integration process of the new technology. (Both patents were granted in 1998.) The diverterless inlet designs built and tested with this combination of CFD and small-scale wind tunnel models formed a database of inlet configurations that would subsequently prove valuable to the Lockheed Martin JSF design.
...
LM Aeronautics JSF Design Adopts DSI
The DSI concept was introduced into the JAST/JSF program as a trade study item in mid-1994. It was compared with a traditional "caret" style inlet. The trade studies involved additional CFD, testing, and weight and cost analyses. The new inlet earned its way into the JSF design after proving to be thirty percent lighter and showing lower production and maintenance costs over traditional inlets while still meeting all performance requirements.
The flight tests on the F-16 validated the aerodynamic properties of the inlet, which will be validated further on the upcoming flights of the Lockheed Martin JSF demonstrator aircraft in 2000. The flight test also proved that the analytical performance and inlet flow stability predictions from the CFD analysis matched operations in the real world. The JSF program further refined the production version of the DSI design using these CFD tools.
The DSI inlet used on the JSF has evolved through several design iterations. The shaft-driven lift fan on the STOVL JSF required the use of a bifurcated duct with one inlet on each side. The initial version was essentially the same design used on the lower surface of the F-16 rotated up onto either side of the JSF forward fuselage.
This design had a cowl that was symmetrical about the centerline of the bump. This version of the inlet appears on the X-35 demonstrator aircraft. Later CFD analysis and testing led to refinements of the design to improve its performance at high angles of attack by shifting the upper and lower cowl lips to take advantage of the side-mounted location and to improve high angle-of-attack performance. This later version has been fully tested in the wind tunnel and will be used on the EMD and on production aircraft.[/SIZE[/I]]
Diverterless supersonic inlet
From Wikipedia, the free encyclopedia
This article needs additional citations for verification. Please help improve this article by adding citations to reliable sources. Unsourced material may be challenged and removed. (November 2011)
Diverterless supersonic inlet
A diverterless supersonic inlet (DSI) is a type of jet engine air intake used by some modern combat aircraft to control air flow into their engines. It consists of a "bump" and a forward-swept inlet cowl, which work together to divert boundary layer airflow away from the aircraft's engine while compressing the air to slow it down from supersonic speed. The DSI can be used to replace conventional methods of controlling supersonic and boundary layer airflow, such as the intake ramp and inlet cone, which are more complex, heavy and expensive.[1]
Research into the DSI was done by Lockheed Martin in the early 1990s. The first DSI was flown on 11 December 1996, installed on a F-16 Block 30 fighter and replacing aircraft's original intake diverter. The modified F-16 demonstrated a maximum speed of Mach 2.0 and handling characteristics similar to a normal F-16. It was also shown that subsonic specific excess power was slightly improved. A DSI was later incorporated into the design of the Lockheed Martin F-35 Lightning II.[1]
The JF-17 Thunder also uses a DSI. Work on the DSI was started in 1999 ( Note the timing. -- Elmo ) with the aim of improving aircraft performance and took almost two years, during which a number of models underwent wind tunnel tests at different speed regimes. It was found that the DSI gave high performance, high total pressure recovery, low integrated distortion and good engine/intake matching.[2]
The Lockheed Martin F-35 Lightning II, JF-17 Thunder, Chengdu J-10B and Chengdu J-20 fighters all incorporate DSI.
Text below is from Lockheed's "Code One" house organ magazine Code One Magazine: JSF Diverterless Supersonic Inlet:
...
Basic research of the inlet concept continued through the mid-1990s. Traditional wind tunnel testing of small plastic inlet models built with stereolithographic techniques augmented a CFD-based development process for the DSI. Engineers made enough technical advances during this period that two US patent applications were filed, one dealing with the overall design and the second dealing with the integration process of the new technology. (Both patents were granted in 1998.) The diverterless inlet designs built and tested with this combination of CFD and small-scale wind tunnel models formed a database of inlet configurations that would subsequently prove valuable to the Lockheed Martin JSF design.
...
LM Aeronautics JSF Design Adopts DSI
The DSI concept was introduced into the JAST/JSF program as a trade study item in mid-1994. It was compared with a traditional "caret" style inlet. The trade studies involved additional CFD, testing, and weight and cost analyses. The new inlet earned its way into the JSF design after proving to be thirty percent lighter and showing lower production and maintenance costs over traditional inlets while still meeting all performance requirements.
The flight tests on the F-16 validated the aerodynamic properties of the inlet, which will be validated further on the upcoming flights of the Lockheed Martin JSF demonstrator aircraft in 2000. The flight test also proved that the analytical performance and inlet flow stability predictions from the CFD analysis matched operations in the real world. The JSF program further refined the production version of the DSI design using these CFD tools.
The DSI inlet used on the JSF has evolved through several design iterations. The shaft-driven lift fan on the STOVL JSF required the use of a bifurcated duct with one inlet on each side. The initial version was essentially the same design used on the lower surface of the F-16 rotated up onto either side of the JSF forward fuselage.
This design had a cowl that was symmetrical about the centerline of the bump. This version of the inlet appears on the X-35 demonstrator aircraft. Later CFD analysis and testing led to refinements of the design to improve its performance at high angles of attack by shifting the upper and lower cowl lips to take advantage of the side-mounted location and to improve high angle-of-attack performance. This later version has been fully tested in the wind tunnel and will be used on the EMD and on production aircraft.[/SIZE[/I]]
Last edited by Modern Elmo; 7th Feb 2012 at 03:09.
ME, sort of begs the question; can Typhoon? if no what do you see as one types advantage over the other, if yes why is UK investing in F35 when such technology has been dealt with?
Not the full story by any means I'm sure, but I hope you can see where I'm going
Not the full story by any means I'm sure, but I hope you can see where I'm going
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Originally Posted by JFZ90
In general, the radar aperture (antenna area) doubles with a 1.41 times increase in diameter. With all else being constant it takes an increase in aperture of 10x to double the range of a radar. Technologies like AESA antennas increase the output and sensitivity of a radar for any given size. Advanced T/R module technology and smaller T/R modules also do that. PESAs generally reduce sensitivity. Both types of ESAs allow instantaneous beam steering and high beam focus. Only the AESA can form multiple beams simultaneously. .
Radar range (in the physics sense) is driven by the total power output of the transmitter, the reflectivity of the target, and the sensitivity of the receiver - not by the antenna aperture. It varies with the fourth power of Tx energy (power squared for the outbound journey, power squared for the return journey); if you want to double the range of a radar, you don't double the antenna size, you up the power output by sixteen. The antenna size is more relevant for main beam width. That and your PRF schedule and pulse-to-pulse detection probabilities drive your scan rate, which drives... a lot of other design decisions.
Google "radar range equation".
Aperture size only becomes relevant if you're talking about the Tx energy being made up of lots of active array elements which each have a maximum power output - the AESA total Tx energy varies with the aperture size only if you assume identical Tx/Rx modules. All else being equal, the 16x increase in the number of elements required to double your AESA range comes from a x4 radius increase. Of course, an upgrade to the power output of each Tx/Rx module can achieve exactly the same thing - and such improvements keep coming along. Or, you could use a swashplate design, and add more T/R elements for the same frontal diameter.
Another thought is that it isn't as simple as "total power per element times number of elements" - not all of the elements will transmit at full power all of the time, for various reasons.
I'm not sure how Moore's law affects T/R elements, but I suspect that it's a fast-evolving area (google "graphene" for the latest fun). You may find that a smaller, newer AESA ends up with better performance than a larger, older one.
Last edited by Gravelbelly; 7th Feb 2012 at 13:26. Reason: edited cause I is a numpty and did a rushed 2**3 not 2**4
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My distant recollection is that aperture directional gain makes up part of the Rx gain. This reference tends to agree, with my fading memory:
Radar Systems
Radar Systems
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Originally Posted by engineer(retard)
My distant recollection is that aperture directional gain makes up part of the Rx gain.
True - I was focussing on the "Tx power ** 4" bit. You can do cute stuff with the same-sized antenna to give you better directional gain (see "not all of the elements will radiate with the same power"); but I was focussing on what I thought was a "if you want twice the range you need 10x aperture" argument from the original poster.
In other words what i was trying to say was that if you apply the same radar technology to typhoon or rafale, the potentially larger effective aperture of typhoon will be an advantage?
At typhoon at 700mm vs rafale at 600mm, the area is potentially 36% larger. This increase is directly proportional to the power returning to the receiver, for equivalent tx power, antenna gain, range and rcs. Does that translate into an 8% benefit in range?
Last edited by JFZ90; 7th Feb 2012 at 23:30.
Bombay Duck, are you confident that Rafales can handle newer Chinese fighter aircraft, some of which incorporate patented technology stolen from the F-35?
The IAF is moving on from 1v1 warfare and has invested in "force multipliers" (not sure if this phrase is in common usage) such as AWACS and in-flight refuelling, while now attempting to shore up its superiority in numbers on at least the western front.
Moving on to Chinese aircraft: The FC-1/JF-17 may incorporate a DSI but... it's not a game-changer. I'd be interested to know what sort of kit the Chinese have gotten working inside the radome, and if they ever got the SD-10 AMRAAM-equivalent missile working.
The J-10 looks fairly good - but again I'm not sure what sort of kit they have in them, and I'm fairly sceptical of internet-based rumours.
If there is one aircraft I'm not at all worried about, it's the J-20. If they want to waste money on developing, buying and maintaining "stealth" fighters, more power to them.
But all this is just me, and it's a layman's opinion.
BombayDuck.
Er,
When you say:
"MMRCA is meant to be primarily a strike aircraft.... it is meant to replace legacy Jaguars, supplement new-build Jags and take over from Mirage 2000s in that rol...."
According to the Indian AF, MMRCA is a Mig-21 replacement.
Er,
When you say:
"MMRCA is meant to be primarily a strike aircraft.... it is meant to replace legacy Jaguars, supplement new-build Jags and take over from Mirage 2000s in that rol...."
According to the Indian AF, MMRCA is a Mig-21 replacement.
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Originally Posted by JFZ90
At typhoon at 700mm vs rafale at 600mm, the area is potentially 36% larger. This increase is directly proportional to the power returning to the receiver, for equivalent tx power, antenna gain, range and rcs. Does that translate into an 8% benefit in range?
What radar mode are you operating in? What tradeoffs have you made between pulse duration, duty ratio, scan speed? What tradeoffs have you made in antenna setup for sidelobe performance, ECM, etc? How far off-axis is the target? Have you got a swashplate design, or a fixed forward-only array? How sensitive are your receivers, how much loss is built into the system? How much does the aircraft nose cone distort the signal? How effective are your signal processing algorithms? How much processing power did you build into the signal and data processors to carry out those algorithms?
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According to the Indian AF, MMRCA is a Mig-21 replacement.
"the MRCA tender was floated with the idea of filling the gap between its future Light Combat Aircraft and its in-service. The IAF planned to replace the MiG-21 fleet with the indigenously-built HAL Tejas (LCA) aircraft. "
So I think they are not doing an apples for apples but re configuring for the current scenario where Mig 21 - 27 and the Jags will be retiring to be replaced by a single aircraft to carry that load.