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Early Aircraft Projects / Re: Specification O.27/34
« Last post by royabulgaf on Today at 07:22:19 pm »
How closely were the design bureaus at Vickers and Supermarine tied together?  You mentioned the Vickers 666 looked like a Stuka.  I immediately thought of something along the lines of the Supermarine 224.

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Military / Re: Littoral Combat Ship - Freedom/Independence
« Last post by Moose on Today at 07:19:34 pm »
Perhaps what LCS should have been?

Source:
http://cimsec.org/strength-in-numbers-the-remarkable-potential-of-really-small-combatants/


They did pitch a larger version of this during the LCS competition.  It lost.  That being said, this ship program is racked with its own problems as well.

Wait, Visby had LCS levels of issues?
Different scale of program but yes Visby class has had a lot of problems. They look cool as hell but for about a decade about all they could do was navigate and fire the deck gun.
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Postwar Aircraft Projects / Re: Fairchild A-10 Projects
« Last post by blackstar on Today at 06:00:51 pm »
"Sales booklet for the two-seat A-10B NAWS aircraft"

Actually, that's what I thought it was too. But look closely and it is for at two-seat trainer version of the A-10. That's not the same as the N/AW A-10. The trainer would be able to be flown from the back seat and used for training, whereas the N/AW was primarily for the attack role.
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Propulsion / Re: Pulsejets & PDE's
« Last post by quellish on Today at 05:45:33 pm »
  • Producing a reliable means of producing an efficient deflagration to detonation process in a duct that is reasonably short
  • Ensuring the fuel/air mixture escapes to the rear: This often involves shutters or proposals for carefully timed valves last I checked
  • Producing a high cyclic rate: This is often limited by the use of shutters to about 250 detonations a second; the desire is for thousands of detonations a second
I'm curious if any of these have been overcome...


All of these have been overcome in various ways. Popular Science did a reasonably good article on it in 2003:
http://www.popsci.com/military-aviation-space/article/2003-08/after-combustion-detonation?nopaging=1
P&W and GE are discussed, and each has their own solutions to the above. In the 80s and 90s Adroit, Boeing, McDD, GD, and Lockheed were all working on PDEs. There are some very interesting patents from GD (Lockheed Ft. Worth/LMTAS when the patents were issued) that are the result of their work.


Look through the patents that reference this one, you will find some interesting stuff:
https://www.google.com/patents/US4741154
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Postwar Aircraft Projects / Re: Fairchild A-10 Projects
« Last post by ouroboros on Today at 05:04:14 pm »
I assume any space not occupied by computers and sensors will be made of steel and/or concrete to fix the Cg shift from losing that huge gun. Are they going to leave the ammo container area empty though, or fill it with a fuel tank, because the guy describes the computer rack as being under the cockpit (presumably for access that the ammo hold wouldn't provide)?
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Aerospace / Re: JMR (Joint Multi-Role) program
« Last post by Triton on Today at 04:41:11 pm »
"US Army's JMR Helo Selection Slips"
Initial Flying Demonstrator Planned for 2017
Aug. 1, 2014 - 05:44PM   | 
By PAUL McLEARY

Source:
http://www.defensenews.com/article/20140801/DEFREG02/308010024

Quote
WASHINGTON — The initial down-select for the technology demonstrator phase of the US Army’s ambitious Joint Multi-Role (JMR) helicopter program has missed its original July deadline, and Army officials are now saying they’ll inform industry teams about who is moving forward sometime this month.

The Army said on Friday that it will gather the four industry teams working on the JMR program in “late August or early September” to discuss the way forward on the program. But an official added that the down-select to two competitors from the current four will have already been made by time the big sit down with industry takes place.

Program manager Dan Bailey said the meeting will “showcase the teams and technologies selected for the air vehicle demonstration” while further discussing how this technology demonstration phase fits into the larger Future Vertical Lift program.

Still, Army officials, including Bailey, have long sounded confident that the down-select would happen in July.

Overall, the change likely will not prove to be overly significant, as long as it is limited. The service wants to begin flying demonstrators in 2017 and is looking at the mid-2030s for operational use of the Future Vertical Lift (FVL) program, of which the JMR is the initial technology development phase.

But Army officials could not offer a reason for the slight slippage in the schedule.

The service has pre-sequestration plans to spend about $350 million on the JMR program through fiscal 2019.

Speaking July 1 at the Center for Strategic and International Studies, Bailey said he didn’t see the return of sequestration in fiscal 2016 as a huge impediment to the program due to the fact that Pentagon officials have said it is such a critical part of the Army’s plans for the future.

“I have full confidence we are not at risk,” he said while sitting alongside representatives from the companies competing for the work. “I don’t have many contingencies because I do not feel at risk that the JMR-TD will lose its resources.”

The technologies that the FVL is being designed to replace: Cold War-era Black Hawk and Apache attack helicopters that are not getting any younger. “When you think about the future in urban areas we’re going to be operating in, vertical lift is going to be absolutely essential,” Bailey said.

In a sign of movement on the program, however, on July 11 the team of Boeing and Sikorsky was selected by the Army to help develop the Joint Common Architecture (JCA) standard for the JMR program.

The JCA is considered the “‘digital backbone’ through which mission systems will be integrated into the FVL system’s design,” Samir Mehta, president of Sikorsky Defense Systems & Services, said in a statement.

The Sikorsky-Boeing team has also submitted its Defiant aircraft — based on Sikorsky’s X2 rotorcraft design that features counter-rotating coaxial main rotors and a pusher propeller — to the Army in consideration for the program.

In 2013, the Army awarded development contracts worth $6.5 million each to Bell, AVX, Karem and Boeing-Sikorsky to work on the technology demonstration program.

While the coming selection will likely eliminate two of the four teams, Bailey has for months insisted that the door will remain open to competition and the Army may very well choose technologies from a variety of companies to come up with a design that it thinks will be effective for the missions it envisions.

“We will certainly ... have opportunities for every one of the four vendors that we would like to continue at some level,” he said.

Still, given the 2017 demonstration date and the budget limitations that the Pentagon is operating under, “we’re at a critical point in the schedule. I would love to take all four [contractors] forward, but financially we do not have the resources to allow us to do that.”

When it comes to dividing up the funding among the winners — and then potentially any other technology that the service wants to include on the aircraft — “all we have to do is tell them what we want to continue with,” he said.

“We continue to fund, and they continue to march. If it’s something less than the full scope, then we’ll have to do some negotiations with them to reshape the investment agreement.”
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Sorta MRAP-ish, but also sorta MPC-ish...
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Propulsion / Re: H-Magjet 4400 hybrid turbofan ramjet engines
« Last post by ouroboros on Today at 04:32:35 pm »
This is incredibly complicated: Are they talking about using a turbojet to drive magnets to spin the fan and accelerate the flow through the engine?

It's a little more complicated than that. Perhaps the best analogy is a turbojet where the shaft is replaced by the electric equivalent of a CVT. The intention is to decouple (loosely couple?) the RPM of any given compressor or turbine stage from the others by going shaftless, which dramatically frees up the design space for an engine. Assuming the electrical losses of converting and modulating power from turbine/power stages to compressor/fan stages can be overcome, hence the superconductor usage. There are examples in industrial pump/turbine systems where the equipment is linked electrically rather than physically, but usually for very different reasons, where the losses incurred are tolerated, or the increased weight is allowable. To actually pull it off on a flightweight engine is very difficult.

NASA, in it's N+3 work, seems to think a LNG fueled turboelectric airplane is possible (particularly for a distributed propulsion system) if it uses fuel cooled high temperature superconductors. The NASA designs typically are BWB's featuring two wingtip conventionally designed turboshaft engines driving superconducting generatos, feeding a long array of wing embedded superconducting electric propulsor fans. One of the participants in the studies (ES Aero) went back and looked at the numbers, and claims a N+2 class 737 sized aircraft is doable with advanced (but not superconducting) motors/generators. That design is a midwing turboshaft generator feeding an inboard boxwing array of large embedded electric fans.

Indirectly driven fans are not a new thing, as past work into compressor bleed bypass air tip turbine driven fans has a long lineage, particularly in VTOL work. In such applications, lift fan needs are grossly out of sync with forward propulsion. One solution there is to physically decouple the lift fan and send most high pressure air from a low bypass ratio turbojet's compressor stage to the lift fan via ducts. There it drives a tip turbine ring, with the lift fans blades on the inside of the ring. Variations exist, such as hot bypass, where raw combustion gases are bypassed prior to going through the main turbojet tubine, and warm bypass, where some combination of post turbojet turbine exhaust gases and bleed compressor air is used to increase mass flow and cool the gases to not melt the ductwork.

VTOL lift fans were not the only application of indirectly driven fans. There was serious research into parallel fan configurations for military jets where bleed air drove a fan or compressor that was next to the main compressor. I don't recall the main reasons why, but something about mass flow/pressure being too high after the main compressor.

With the renewed interest in electric propulsion systems, looking again at electrically driven fans shows interesting possibilities. With sufficient temporary power storage, it's possible to exceed the turbine response to propulsion demands for short durations (the oft cited spool up lag for aborted landings being why turbofans are unpopular for certain cargo missions, compared to turboprops, though turboprops cheat by having pitch control).

As for this engine design though, it's seriously pushing the limits of credibility. At the very least, until there's a test bench level demo of the cycle, people will have a hard time believing. But, precisely because of the decoupled nature of the parts of the cycle, individual stages can be tested separately for viability before doing an all up test bench demo. Such a test bench demo need not even be a complete engine, again having each stage be shown in parallel rather than series configuration but connected electrically together.
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Propulsion / Re: Pulsejets & PDE's
« Last post by ouroboros on Today at 03:45:33 pm »
I think there was a patent for a rotary shutter combustor that should be applicable.

http://www.secretprojects.co.uk/forum/index.php/topic,7651.0.html

 The idea was to replace conventional combustor cans with a big slotted wheel that lines up with the ducts such that as the main shaft rotates, you have periodic blocking of the ducts. The patent was for efficient turbofans, but nothing stopping you from running as a low bypass turbojet in essence.
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Military / Re: Littoral Combat Ship - Freedom/Independence
« Last post by ouroboros on Today at 03:09:16 pm »
Perhaps what LCS should have been?

Source:
http://cimsec.org/strength-in-numbers-the-remarkable-potential-of-really-small-combatants/


They did pitch a larger version of this during the LCS competition.  It lost.  That being said, this ship program is racked with its own problems as well.

Wait, Visby had LCS levels of issues?
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