Category: technology

A Thrust-to-Weight Ratio of 6.6:1

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Bill Sweetman teases out some information which sheds some light on the relatively low thrust to weight ratio of the F-35 JSF, the fact that the Pratt & Whitney F135 engine has a thrust to weight ratio of only 6.6:1.

By comparison, the F-100 engine (F-15, F-16), whose contract was awarded in 1970, has a thrust/weight ratio of 7.8:1, and the more modern F414 and EJ2000 (Superbug and Typhoon) exceed 9:1 thrust to weight.

Additionally, he notes that the vertical lift system used on the F-35B weighs 10,472 pounds with a thrust of 40,550 pounds, giving a thrust to weight ratio in that mode of 3.87:1, as compared to 5.6:1 for the Rolls Royce Pegasus used on the Harrier.

There is a saying that you can’t make a race horse out of a pig, but you can get an awfully fast pig, the F-4 Phantom comes to mind, but this is not a fast pig.

Pics of the F135 promotional brochure are from here.

Japanese Company Developing Regional Jet Engine

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Japanese aero engine manufactuer IHI is working on a a low fuel consumption turbofan (paid subscription required) to compete with US and European engines on future regional jets.

One of the interesting features of the engine, IHI calls it the Eco turbofan, mockup shown is how the fan wraps around its hub, so as to cover more of the frontal area of the engine, which is intended to improve efficiency.

In its initial form, it should put out around 9,000 lbs of thrust with a 7:1 bypass ratio.

IDF Develops New Counter-Battery Radar

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The IDF has started deploying a new radar geared toward counter-battery fire.

The Elta’s EL/M-2084 Multi-Mission Radar (MMR) phased array radar can pick up artillery and rocket rounds at launch, and determing both the launch point and impact point.

It will be integrated with Israeli rocket interception systems, though I wonder if it might also be incorporated into counter-battery fire control too, as it appears that this would allow the IDF Artillery Corps to have rounds on a target firing at them in less than something less than 2 minutes.

A160T Hummingbird Drone Achieves New Milestone

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Boeing has announced that it’s Hummingbird drone has has successfully changed the final drive ratio of its transmission in flight, which will allow two rotor speed settings, one being about ½ of the other.

It turns out that slower rotational speeds work better at hover and low speeds, but limit forward speed, because of retreating blade stall, and most helos therefore operate as a compromise. (The A160T set its record in slow rotor mode).

All in all, this program is moving along at a blindingly fast pace, with US special forces already making purchases of the diminutive helicopter.

Boeing’s PR is here.

Defense May Boost Orbital Power Generation

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It looks like the military is seriously looking into developing orbital power stations in order to reduce the logistical tail for remote bases. (paid subscription required)

The theory here is that if a relatively cost effective power station can be developed, then things like remote forward bases in Afghanistan would not require regular resupply of fuel for generators, which are both expensive and vulnerable.

They are in the very early stages, but the notational concept appears to be a 5-10 MW pilot power plant in about 10 years.

If they can manage that, we might start seeing commercial applications in the decade following that.

Russia Unveils FCS Killer RPG

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The folks at Danger Room quote the Russian descriptions as an “Abrams Killer”, but the RPG-30 is really designed to defeat active protective systems and reactive armor, neither of which are currently used on the M-1, which they note.

It’s pretty simple in concept. The RPG-30 launches two projectiles, the main 105mm projectile, and a smaller decoy, which it launches a few milliseconds ahead of it.

It would serve as a decoy against active protection systems, which intercept incoming rounds, and with even a tiny warhead, and it looks to be about 30mm in diameter, so there is space for this, it could serve to pre-detonate reactive armor, allowing for better function of the main charge.

Neat technology, and another nail in the FCS manned ground vehicle concept of substituting technology for armor.

Son of HOTOL

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When I was in college, I recall, reading about a British program called HOTOL (Horizontal Take-Off and Landing, click picture to be taken to a page on it) which was supposed to use a “liquid air” engine in order to more efficiently reach orbit.

A short description of the cycle was that it was fueled with LH2 and for much of the way up, it would use the cold liquid hydrogen to extract liquid oxygen out of the air.

It got canceled, or more accurately, when the program ended it was not taken to the next phase.

I kind of figured that technical issues, my guess at the time (which appears to be wrong) was getting the heat exchangers small enough and light enough.

The real problem appeared to be that the engine was heavy, and in an aft mounting configuration, maintaining the center of lift far enough aft compromised performance.

In any case, a company called Reaction Engines are having another go at the concept with the Skylon, (paid subscription required) , which uses the Sabre (Synergic Air-Breathing Engine).*

As is clear from the picture, they dealt with the CG issues by placing the heavy engines at the center of lift on the wing tips.

It’s supposed to function as an air-breather until it reaches 30km altitude and “around Mach 5”, and then function as a normal liquid fueled rocket the rest of the way up to orbit.

They are looking at testing a 9% scale precooler (left) in January on a test stand, using a RR Viper turbojet behind the cooler (left below)

There are two problems with Liquid Air Cycle Engines (LACE), hydrogen embrittlement of the heat exchanger, and condensation of water and CO2 on the heat exchanger, which will plug it up.

It solves these problems by not cooling the air to full liquid state, but instead having a high-pressure turbo compressor behind the air to liquefy it, and by using helium as an intermediate medium for the heat exchanger, along with an unspecified proprietary frost control technique. (bottom pic)

It’s a neat concept, but I’m dubious of any project that is not fully funded, or almost fully funded by government sources, and at this point, they are getting just a trickle from the British National Space Center and the the European Space Agency (ESA).

*Let me note here that the Brits come up with cool names.

Israel Tests Black Hawk Gunship

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It looks like Israel is looking at an armed variant of the UH-60 Black Hawk demonstrator.

From the photo, it appears that they would be carrying an chain gun and a targeting turret, along with a fair number of ATGWs, something on the order of 16 Hellfire class missles, though, given that this is an Israeli developed project, Rafael’s Spike, or some variant thereof, would likely be the actual weapon deployed.

It’s kind of a return to the old UH-1 gunships developed in Vietnam.

X-47 UAV Program Expanded

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A few months back, it looked like that the Navy/Northrop-Grumman X-47 CUCAS-D (unmanned combat air system demonstration) was on the chopping block.

This is perhaps the most ambitious UAV currently in development, given that among other things, it’s supposed to make an arrested landing on a carrier deck.

It now appears that in addition to demonstrating combat capabilities and carrier ops, the program has been expanded to include autonomous air-to-air refueling, which will greatly improve the strike capability of the aircraft.

Autonomous refueling has been kind of a holy grail in the UAV community, and is really essential for any system that actually sees operational use.

Shipborne Rolling Vertical Landing Aid Demonstrated

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The folks at Quinetiq have demonstrated a landing aid for SRVL on the HMS Illustrious.

The idea behind shipborne rolling vertical landing is that an F-35 can return to deck in forward flight, with some of the lift coming from the wings, and some from the lift fan, which would allow for greater “bring” back in terms of weapons loads, and less wear and tear on the engine:

For the latest trial, a demonstration visual landing aid dubbed a “Bedford array” was installed in the port catwalk adjacent to Illustrious’s flight deck. Taking inputs from inertial references to stabilise against deck motions, this is combined with a ship-referenced velocity vector in a helmet-mounted display to enable a pilot to fly an accurate approach to the deck on a constant glidepath. A second lighting array was rigged on the carrier’s flight deck, and was used during a parallel evaluation of its visual acuity.

Me, I’m dubious.

The idea of making a rolling landing on an aircraft carrier with a 60,000 lb aircraft without an arrester hook seems to me to be a dicey proposition.

Defective Even by the Standards of Taser International

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Taser, International has always maintained that their little toy that should be treated as a lethal weapon is safe.

They even have studies to prove it.

Only, it turns out that their products do not meet the company’s own dubious standarsa:

A new study has found that the type of Taser stun gun used most by police officers can fire more electricity than the company says is possible, which the study’s authors say raises the risk of cardiac arrest as much as 50 percent in some people.

So, not only is their own science dubious, but their manufacturing processes are too.

Blow Up UAVs

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It looks like the folks at U.S. Army Research Laboratory at Aberdeen Proving Ground have come up with concepts for inflatable structures for UAVs.

The folks at the lab believe that the use of inflatable structures would allow for lighter weight, which translates into slower flight speeds and less noise, both of which are optimal for the use of UAVs in an urban scenario.

Goodyear did actually develop and fly an inflatable aircraft, the Inflatoplane, in the 1950s, but the army decided it was too vulnerable to ground fire, and shelved the project.

Still, it has always surprised me that someone in the ultralight community did not go further forward with this. An ultralight made using this technology could fit in the trunk of a midsized car.

About a decade ago, I put an inqwuiry into Goodyear regarding the Airmat, basically balloon material with threads running between opposite walls to provide rigidity when inflated, material they used for the structure, but there was nothing left there.

Why go Bullpup

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In what should be a surprise to no onw, the Israeli Defense Forces have adopted the MTAR-21 Micro-Tavor as their weapon of choice.

Once again, it allows us to look at why the M4/M16 needs to be replaced in US service.

In addition to its gas tube operation requesting excessive cleaning, it’s just too damn long:

Overall Length

Barrel Length

TAR-21

725 mm (28.5 in)

460 mm (18.1 in)

MTAR-21

590 mm (23.2 in)

330 mm (13.0 in)

M16

1000mm (39.5 in)

508 mm (20 in)

M4

838 mm (33 in) (stock extended)

757 mm (29.8 in) (stock retracted)

368 mm (14.5 in)



While it’s clear that the both MTAR-21 and the M4 having 13½ and 14 inch barrels respectively, will have lethality problems at range. The 5.56 mm round is light and uses high velocity to carry to provide lethality, but the M4 is much more extensively used, because for any urban situation, the M-16 at 1m long is simply unmanagable, while the TAR-21, the normal rifle for the IDF with an 18 inch barrel is shorter than the M4.

The additional 4 inches of barrel also get the mussel velocity high enough to avoid the lethality issues at 100 m or so.

That is an very small package though.

Rolls Plans ‘Puller’ Open Rotor Work While GE Readies for Noise Tests

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It looks like Rolls Plans ‘is looking hard at a “puller configuration” for it’s advanced propfan. (paid subscription required)

They believe that the issues involved in mounting the fan in the immediate vicinity of hot exhaust from the core are challenging, so they are looking at a more conventional “turboprop like” layout.

Of course, it’s all tradeoffs, as the “puller” configuration has issues of the interaction between the prop wash and the pylons and inlets too, which need to be carefully managed to handle noise, which is generally considered to be the Achilles heel of propfans.

New “Piston” Engine Enters the “Mogas” Sweepstakes

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The Mistral Engines G-300 (paid subscription required) is a multi fuel Wankel rotary engine.

Though the term “multi-fuel” means that it can run on both aviation (100LL) and automotive (87 Octane) gasoline, it’s spark ignited, though their web site states that they are working on Jet fuel capable engines.

Obviously there are fewer parts than a conventional piston engine, there are no conventional valves in a Wankel, but it still has a reduction gear, which was the major maintenance headache in the Thielert engine.

Interesting Regulatory Take on Open Rotor Engines

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Are they unducted fans, are they high tech propellers, or are they, as one wag put it, a bunch of bananas whirling around.

I don’t know, and it appears that regulatory authorities are in a similar conundrum.

The regulations if they are classed as turbofan blades are stricter, and thus the would add more weight, and the regulations if they were classed as a propeller.

It’s a non-trivial issue that needs to be resolved.