Category: Propulsion

I Am Not Sure How I Feel about This

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Both DARPA and NASA are moving forward with plans to develop nuclear thermal rockets.

While nuclear thermal propulsion do not match the efficiencies of electric (Ion, etc.) propulsion (an ISP of about 1000 for nuclear thermal as versus up to 5000 for electric propulsion and about 300-500 for chemical rockets) they provide more efficiency than chemical rockets, and more thrust than electric propulsion. 

It makes a lot of sense for satellites in various earth and lunar orbits where you need to change position rapidly. 

I’m not sure how sanguine I am about the possibility of putting a few hundred pounds of enriched uranium in orbit though.

From the NASA story:

More than sixty years after the U.S. began serious studies into nuclear propulsion for space travel, NASA is taking the first steps on a new path to develop nuclear-powered engines for crewed missions to Mars by the end of the next decade.

The agency is reviewing industry responses to the first phase of a plan with the Energy Department to mature a prototype nuclear thermal propulsion (NTP) reactor and engine design for use in space. The congressionally directed initiative, which is also supported by ongoing NASA/Energy Department research into advanced nuclear fuels, will ultimately lead to the building and testing of demonstrators.

Beyond this, the vision extends to the potential development of a full-scale nuclear-powered system for a crewed mission to Mars that would be launched in 2039. The new capability, which could be based on either NTP or synergistic nuclear electric propulsion (NEP) technology, would also provide power for future crewed and robotic deep-space exploration missions as well as faster, more responsive resupply flights to lunar and Martian outposts.

NEP is about having more energy available for an electric propulsion.

It is still a low thrust system, but provides much more delta V over time.

DARPA’s proposal is more about providing satellites that can move between geostationary orbits and lunar orbits quickly and flexibly to deal with treats presented by some sort of rival in space:

A nebulously named “Deterrence Layer” is on the drawing board for the National Defense Space Architecture, and that could mean the return of a functioning U.S.-operated, nuclear-powered satellite in orbit by 2025 for the first time in 60 years.

The need for the Deterrence Layer may depend on what China and Russia do next. If rival militaries establish a presence in the region of deep space between geostationary and lunar orbits, the U.S. Defense Department believes a future spacecraft—an “advanced maneuvering vehicle” (AMV)—will be needed to charge out as far as the Moon, hopefully just to remind an adversary to keep a tight leash on any nefarious plans in cislunar space.

………

What is envisaged for the AMV is a propulsion system that produces a high amount of thrust compared to its weight yet is significantly more efficient than chemical propulsion.

………

In the NERVA ground tests and SNAP-10A orbital tests, NASA and the military used a fission reactor fueled by highly enriched uranium, the same radioactive material used to make nuclear warheads.

For DRACO, DARPA has specified a technology shift to high-assay, low enriched uranium (HALEU) fuel. Unlike weapons-grade uranium fuel that is typically enriched to 80%, HALEU is by definition only enriched between 5% and 20%—although the exact level is not being released. HALEU in the form of uranium metal will be furnished by the government to GA-EMS for the DRACO reactor.

The choice of HALEU exploits a bureaucratic loophole created by former President Donald Trump. His presidential memorandum signed on Aug. 20 delegates approval for the launch of a spacecraft using uranium that is enriched below the 20% threshold to the head of the sponsoring agency instead of the White House. In effect, the memorandum transfers the launch authority decision for DRACO from the president to the secretary of defense, perhaps along with the risk in case anything goes wrong.

Nuclear loopholes in space.  Now THERE’S a reassuring term.

I understand the advantages of such a system, but I am concerned about the potential safety risks, both for NTP and NEP propulsion.

Russians Test Pulse-Detonation Engine

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Russia’s United Engine has has successfully tested a low thrust pulse detonation engine.

The short version of what a PDE is is that it is a formed of pulsed propulsion where instead of just burning the fuel (subsonic combustion) it detonates the fuel (supersonic combustion) creating about 50% more specific thrust.  (Ratio to thrust to all mass flow through the engine)

Higher specific thrust engines are more efficient, thermodynamics favors constant volume combustion, particularly at higher speeds.

My guess would be that the first real-world application might be as an afterburner, but seeing as how this program is funded by Rostec, they clearly see space applications:

Russian powerplant specialist United Engine has carried out initial testing of a pulse-detonation rocket motor which has potential application to orbital spaceplanes or hypersonic aircraft.

Pulse-detonation propulsion combusts fuel and oxidizer using detonation waves, with relatively few mechanical moving parts, offering a more efficient thermodynamic cycle than conventional gas turbines.

United Engine’s Lyulka design bureau – part of its Ufa-based UMPO division – has established a specific development project for such powerplants.

Russian state technology firm Rostec says the bureau has completed the first stage of tests for a demonstrator engine.

“In some operating modes the powerplant demonstrated up to 50% increase in specific thrust compared with traditional engines,” it adds, enabling aircraft range and payload to rise by a factor of 1.3-1.5.

Rostec envisions the design being applied to orbital spaceplanes and other future-generation aircraft operating at supersonic and hypersonic speeds.

I think that this is some seriously neat tech, but much like fusion, its application always seems to be about 10 years away.

Might Make a Faster Pig

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GE’s entry


Pratt & Whitney’s version

Or they might make a pig with longer range.

But it will still be a pig.

The pig in question is the F-35, and the addition of a variable cycle engine might increase its performance:

The U.S. Air Force is poised to award General Electric and Pratt & Whitney contracts for adaptive cycle technology development that will pave the way toward an active procurement program for a sixth-generation fighter engine as well as the potential reengining of the F-35 Joint Strike Fighter.

Contracts for the Air Force Research Laboratory’s (AFRL) Adaptive Engine Transition Program (AETP) are expected to be valued at up to $1 billion apiece for the two engine-makers, setting the stage for a 21st-century version of the “great fighter engine war” between GE and Pratt over dual-sourced engines for the F-15 and F-16. Although Pratt now runs both key U.S. military development programs with the F135 for the F-35 and the engine for Northrop Grumman’s B-21 Long-Range Strike Bomber, AETP opens up potential competition for both the reengining of F-35s as well as proposed sixth-generation fighters for the U.S. Navy and Air Force.

AETP is specifically aimed at maturing three-stream engine technology now considered vital to achieving the high-speed, long-endurance performance requirements of the Navy’s future F/A-XX and the Air Force’s F-X sixth-generation fighters. Although it remains unknown whether the F/A-XX will emerge as a twin-engine design, the three-stream concept is designed to be scalable across a wide thrust range. The AETP is, however, targeted initially at a 45,000-lb.-thrust-class engine baselined to fit within the existing confines of the F-35A engine bay. This makes it a contender to replace the F135 from the mid-2020s onward.

………

The third stream provides an extra source of air flow that, depending on the phase of the mission, is designed to provide either additional mass flow for increased propulsive efficiency and lower fuel burn, or additional core flow for higher thrust and cooling air. It also can be used to cool fuel that provides a heat sink for aircraft systems. The third stream can also swallow excess air damming up around the inlet, improving flow holding and reducing spillage drag.

At the heart of adaptive engines are variable-geometry devices that dynamically alter the fan pressure ratio and overall bypass ratio, the two key factors influencing specific fuel consumption and thrust. Fan pressure ratio is changed by using an adaptive, multistage fan. This increases fan pressure ratio to fighter engine performance levels during takeoff and acceleration, and, in cruise, lowers it to airliner-like levels for improved fuel efficiency. The third stream, which is external to both the core and standard bypass duct, is used to alter the bypass ratio.

I think that the cooling application might be the most important.

Both the F-22 and F-35 are basically thermos bottles which rely on their fuel as a heat sink for cooling other systems, which creates issues when the aircraft sits on the tarmac too long, or when the fuel becomes hot sitting in the sun, which has the USAF repainting all their fuel trucks white.

Any potential improvement in range or performance would be important for the F-35, which is shaping up to be a major pig.

A Little Rocketry Factoid

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I was reading an article about how France is looking into creating a reusable rocket engine powered by Lox/CH4. (Methane)

I was wondering why they would go with Methane as a fuel, so I did some reasons.

These days, there are 4 basic options for launcher fuel, Liquid Hydrogen, Kerosene (RP-1), Hydrazine, and Methane.

Hydrazine has fallen out of favor for boosters, though it is still used in thrusters of various sorts. It has low impulse, and it’s toxic, but the fact that it can be used as a monopropellant means that it is convenient to use for orbital maneuvering, since it requires half the parts, and you don’t need to make sure that the flow of a separate fuel and oxidizer are synchronized for short the “blip” that would be needed for an orbital rendezvous or station keeping.

The commonly used propellants are LH2 and RP-1 each have distinct advantages:

  • Hydrogen has the highest impulse (fuel economy).
  • RP-1 is denser, and requires smaller tanks.
  • RP-1 can be stored at room temperature.

Methane falls in between Hydrogen and RP-1. It’s less dense than RP-1, and more dense than LH2, and is more fuel efficient than RP-1 and less so than LH2.

Methane is also a lot easier to handle than LH2, with hydrogen condensing at -252.9°C, while liquefies at a relatively balmy -161.6°C, much closer to the boiling point of LOX. (-183°C)

Additionally, for reusable and restartable engines, Methane has the advantage that it does not coke up, so recycling the engine for another use is more straightforward than RP-1.

Additionally, if you want to go to Mars or the outer planets, it is relatively trivial to manufacture or extract Methane, while manufacturing LH2 would be extremely difficult, and manufacturing RP-1 would be nigh impossible.

So, now you know more than you want to about why a number of rocket manufacturers are looking into Methane as a propellant.

It Took Long Enough

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SpaceX has finally managed to safely land a first stage on their booster:

SpaceX engineers and on-board software maneuvered the first stage of a Falcon 9 launch vehicle back to a steady, tail-down landing at Cape Canaveral Monday, 10 min. after returning the kerosene-fueled rocket to flight following an ascent explosion on a mission to the International Space Station in June.

Success in recovering the stage, after two unsuccessful attempts to land on a barge in the Atlantic, marks a major step toward the long-sought dream of reusable commercial space launchers. While Blue Origin brought its liquid-hydrogen/liquid oxygen New Shepard vehicle back from a suborbital launch to space on Nov. 23, Monday’s SpaceX recovery was the first known landing for an unmanned orbital launcher.

Silicon Valley venture capitalist Steve Jurvetson, an early SpaceX backer, tweeted “Congrats @SpaceX for landing the rocket back on land!!!! Incredible!!! One giant leap!”

The landing at a surplus launch pad on Cape Canaveral AFS, Florida, came in the middle of three significant milestones for commercial spaceflight. For SpaceX, it marked a return to flight for the Falcon 9 launch vehicle that is the linchpin of the company’s business in the near term. For its customer, Orbcomm, it completed launching of a 17-spacecraft low Earth orbit (LEO) constellation of second-generation Machine-to-Machine “OG2” satellites.

Although only a secondary test objective on the Orbcomm-2 mission, landing the Falcon 9 stage at Launch Complex 13 on Cape Canaveral — a surplus Atlas launch site designed “Landing Complex 1” by SpaceX — was a major achievement for the Hawthorne, California-based company.

I am dubious as to the ultimate significance of the reusable stage.

At least some of the potential savings is eaten up by the additional fuel that needs to be carried to fly home, as are any arrangements for a landing site, with its associated blockhouse and firefighting equipment.

We’ll see.

I Did Not Think that You Could Use Roller Bearings for This

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There are a number of reasons why roller bearings (ball bearings, cylindrical roller bearings, spherical roller bearings, tapered roller bearings, etc.) find use.

They provide a low drag solution, and, particularly for low speed applications, like turret rings, they tend to be the favored solution.

For higher speed applications, things like crankshaft bearings and bearings though, they are not used, because they tend to shake themselves to pieces.

Instead, fluid bearings are used, where the bearing moves with respect to the journal supported on a thin film of a fluid, typically some sort of oil or air. (Think air-hockey puck)

There is more drag in the system, but it functions at much higher speeds.

This is why you do not see roller bearings in jet enginse, at least that was why until now: (paid subscription required)

A recent development in Germany by FAG Aerospace and MTU Aero Engines could affect turbofan engine operations in three key areas: oil consumption, fuel economy and power generation.

The companies designed a main-shaft ball bearing that exceeds, reportedly for the first time, an operational speed parameter of 4 million mm/min. (160,000 in./min.)—66% greater than the 2.4 million mm/min. generated by most conventional bearings during takeoff.

At maximum speed, the bearing reportedly consumes the same amount of oil and generates identical temperatures as conventional bearings. At normal speed up to 50% less oil—6 liters/min. (1.6 gal./min.)—is needed for cooling, temperature is 25C (77F) lower and power loss drops as much as 25%.

Peter Glockner, head of product design at FAG Aerospace, attributes the reduction in oil consumption to, among other features, outer-ring cooling technology and an “integrated squeeze-film damper” that mitigates vibration load. The benefits of lower oil consumption and reduced vibration include power-loss savings, which “increase[s] the mechanical efficiency of the engine” and thus lowers fuel consumption, he adds.

The fuel savings are low: FAG Aerospace estimates the technology could save 200,000 tons of fuel annually for global turbofan fleets. In 2015, total fuel consumption for all aircraft is forecast to be up to 230 million metric tons.

Nevertheless, the technology appears to have clear engine-power advantages, and even minuscule savings add up for large operators, including the military.

Assumign that the price comes down, I would expect to see this in automotive turbocharger bearings, and (eventually) main engine bearings.

When I was in E-school, this was the sort of application for roller bearings that we were basically told, “Don’t even think about it”.

And now someone is trying to sell it.

I am impressed

Son of the PT6

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Click for slide show


The PT6 Bass Ackwards Air Flow


No connection between the gas generator and power turbine


Note the adjacent engines


The reverse flow prevents one engine failure from taking out another

In my pre-engineering school days, I always wondered why the Pratt & Whitney PT6 turboprop had its intake in the rear, and its exhaust in the front.

I also could not understand why this arrangement, which has the airflow reversing course was so popular. as it seemed to add a lot of complexity, as well as losses into the system.

After the my time in engineering school, I actually understood that this.

The reverse airflow scheme allowed for the use of a free turbine, where the meant that the power turbine is not attached to the compressor, etc.

It makes for a simpler layout. You don’t need any concentric shafts, and starting the engine requires much less “oomph”.

Well, it now looks like a very similar arrangement for advanced airliner configurations. (Yes, this is a few months old. I came across this while doing digital housecleaning)

Not bad for an engine design that is over 50 years old:

As designers of future airliners look increasingly beyond traditional tube-and-wing configurations to meet the high efficiency goals of the 2030s and beyond, new territory is being carved out in the critical area of airframe-engine integration.

 Unusual features ranging from recessed inlets to pylon-mounted upper-surface engines have become familiar sights in wind tunnels, but even seasoned researchers are surprised by a new engine architecture proposed by Pratt & Whitney. The concept not only physically separates the propulsor from the gas generator, but also mounts the core backward and at an angle. This novel arrangement is aimed at overcoming installation challenges in new configurations like the D8 double-bubble airliner concept under study by NASA and the Massachusetts Institute of Technology (MIT).

 Aimed at NASA’s N+3 performance goals for an airliner that could enter service around 2035, the D8 is designed to burn at least 60% less fuel than the current generation of narrowbody airliners. The secret behind this leap in performance is a configuration that clusters the engines together atop the wide tail of a flattened fuselage. Besides providing a clean high-aspect-ratio wing for low drag, this enables the engines to reenergize to slow-moving boundary layer flow over the fuselage, increasing efficiency.

 But such a configuration creates several issues. The engines lie so close to the upper surface of the fuselage their fans must be sufficiently robust to cope with flow distortion from ingesting the boundary layer. Fan size will also be large because the engines envisioned for the D8 will have a bypass ratio of at least 20:1, and be targeted at extremely low noise levels of -52 EPNdb below current Stage 4 limits. Scale tests conducted at NASA of a distortion-tolerant fan developed by United Technologies Research Center show the boundary-layer challenge has been met, but other key questions remain.

 Because engine cores are becoming more efficient and operating at higher pressure ratios, they are also shrinking and becoming disproportionately small compared to the propulsor section as bypass ratios increase. This leads to blade heights of 0.5 in. or less at the exit of the high-pressure compressor. At this small scale, tip clearances not only become harder to maintain, but there is little space within the core through which to run the driveshaft connecting the fan to the low-pressure turbine. Additionally, because the core is proportionately longer and thinner, designers face the issue of backbone bending which further affects clearance control.

 “So that’s when we had the breakthrough idea of turning the core backward,” says Pratt & Whitney Technology and Environment Vice President Alan Epstein. Air enters the engine through the fan as normal, but instead of continuing directly into the compressor, it is ducted around the side and back of the core to enter from the opposite direction. In an arrangement similar to Pratt & Whitney Canada’s PT6, in which air flows forward through the engine, hot gas will be discharged forward through a power (low-pressure) turbine connected to the fan via a gear system. The turbine, gearbox and fan will be connected via “a really short shaft, and because the core is not connected to the power side, you can take the core off easily for maintenance,” Epstein explains.

 The concept also overcomes another challenge. The idea of nested engines, as in the D8, does not meet current FAA certification criteria under the “1 in 20” rule. This states that there should be only a 1 in 20 chance of debris from an uncontained engine failure causing a second engine to fail. However, because the core and propulsor are no longer mechanically linked, “the designers have come up with an extraordinarily clever arrangement in which the cores are angled relative to each other,” Epstein says.

 “We cant them at around 50 deg. and the exit from the core turns via a 50-deg. duct to go into the power turbine. So now they are more than 90 deg. off from each other. It’s simple geometry,” he says. “It enables you to have a large bypass ratio, and you are not turning much of the airflow if you are turning just the core flow, so pressure losses are low.”

I love it when advanced technology goes all retro.

I Need Some Pictures to Understand This

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Click for big honking image slideshow


Skylon
Saber Engine


Schematic of engine

Reactions Engines, the British company working on a partially air breathing cryogenic engine which would power a single stage to orbit spacecraft, Skylon, as well as a hypersonic transport, the A2.

This project has taken a major step forward with both the European Space Agency and the Air Force Research Laboratory (AFRL) have found the basic concept sound, including a heat exchanger that cools the incoming air by hundreds of degrees in a fraction of a second without choking up without being choked with frost:

It is a well-established truism in aerospace that leaps in propulsion technology almost always precede major advances in spacecraft or aircraft design.

As the clamor for affordable access to space continues to grow, there is mounting interest in the Synergetic Air-Breathing Rocket Engine (Sabre) concept under development by U.K.-based Reaction Engines. This hybrid powerplant is designed to bridge the infamous power gap between air breathers and rockets, potentially enabling a vehicle to accelerate from a standing start on the runway all the way to low Earth orbit.

Such an engine could power high-speed aircraft, suborbital craft or even multi- and single-stage-to-orbit vehicles. Even more encouraging to Sabre proponents is that, while earlier attempts to harvest oxygen from the atmosphere succumbed to thermodynamic reality, the Reaction design continues to pass muster with experts in Europe and the U.S. The company’s most recent—and possibly most valuable—vote of confidence comes from the U.S. Air Force Research Laboratory (AFRL), which analyzed Sabre under a cooperative research and development agreement.

AFRL’s validation followed a detailed study of the entire concept, particularly the precooler heat exchanger technology, which allows for the practical extraction of oxygen from the air without clogging up the mechanism with frost and ice. Reaction unveiled initial details of the methanol-based frost-control system at the American Institute of Aeronautics and Astronautics Hypersonics and Spaceplanes conference in Glasgow in early July.

AFRL program manager Barry Hellman says analysis “confirmed the feasibility and potential performance of the Sabre engine cycle. While development of the Sabre represents a substantial engineering challenge, the engine cycle is a very innovative approach and warrants further investigation.” As a result, Reaction Engines and AFRL plan to continue collaborating on Sabre, with potential follow-on work focusing on evaluation of various air-breathing-powered vehicle concepts and testing of specific engine components.

The AFRL study will also evaluate other potential uses for the Sabre’s heat exchanger technologies, including looking at broader defense applications. “The question to answer next is what benefit the Sabre could bring to high-speed aerospace vehicles compared to other propulsion systems,” says Hellman. “AFRL is analyzing vehicle designs based on the Sabre engine concept. We are also considering testing their heat-exchanger technology at Mach 5 flight conditions in a high-temperature wind tunnel.”

While AFRL acknowledges that Sabre’s original target—a single-stage-to-orbit space access vehicle dubbed Skylon—remains technically “very risky as a first application,” Hellman says: “Sabre may provide some unique advantages in more manageable two-stage-to-orbit configurations.”

………

The precooler chills the incoming air from more than 1,000C (1832F) to -150C in less than 1/100th of a second, before passing it through a turbo-compressor and into the rocket combustion chamber, where it is burned with subcooled liquid hydrogen fuel. For higher altitude operation and the jump to orbit, the engine switches to an onboard liquid oxygen supply and runs as a conventional closed-cycle rocket engine (AW&ST Nov. 26, 2012, p. 47).

What this means in the short term is not space travel, but it does mean that they are far more likely to get government and private sector funding.

Good folks at Av Week have a description of how Reaction Engines made this work, but I cannot make heads nor tails of it:

………

But after endorsement of the basic technology from the European Space Agency and, more recently, the U.S. Air Force’s Research Laboratory, the company’s synergetic air-breathing rocket engine (Sabre) concept is being taken far more seriously. Designed to power a vehicle from a standing start to Mach 5.5 in air-breathing mode, and from the edge of the atmosphere to low Earth orbit in pure rocket mode, the Sabre engine with a heat exchanger at the heart of the design is attracting widespread interest for potential application on a range of atmospheric and space vehicles.

With patents pending and negotiations with new industrial partners apparently at an advanced stage, Reaction Engines has made the surprise decision to unveil the first details of the critical technology at the core of its hybrid hypersonic propulsion system.

………

“It is pretty mind-bending stuff,” says Reaction Engines technical director and chief designer, Richard Varvill. Speaking at the American Institute of Aeronautics and Astronautics International Space Planes and Hypersonics conference here, he says the system counters the frost that precipitates out of the air as it becomes saturated with increasing relative humidity during the rapid cooling process. The precipitation “looks like the white feathery frost you’d see on a cold winter’s day. Unfortunately, that frost is sufficiently mechanically strong that it can bridge the gaps between the tubes and will block the matrix solid in about 3 sec. flat if you don’t do anything about it.

“So—surprise, surprise—we use an anti-freeze, and in this case it is methanol. But we use the methanol in a rather sophisticated way, with the objective of minimizing the amount you need. Also we don’t want to spray the methanol in and leave it in the air flow because we are actually cooling down the air to the point at which the methanol would freeze itself,” he says.

To do this, Reaction Engines has “borrowed a trick from the chemical process industry,” says Varvill. “We inject the methanol at one of the coldest points, and we effectively get the mix of water and methanol to flow forward in the matrix—against the direction of the airflow.” He concedes this seems counterintuitive, but explains the system generates an effective reverse flow by catching the water-methane mix and reinjecting it further upstream. “We have multiple injection and extraction points in the matrix, but the overall effect is the mix of methanol and water is actually flowing forward in the matrix against the airflow direction.”

The reasoning, he says, is that the condensate composition at the cold end of the matrix is nearly all methanol, and as it flows forward the methanol picks up the water. “At the inlet [of the matrix] it is nearly all water, so the composition is more methanol-concentrated at the cold end than it is at the warm end,” Varvill says. “That then reduces because you have extracted most of the water at the warm end, and that reduces the absolute amount of methanol you need to throw into the pre-cooler to stop it freezing.” And because the amount of liquid water reduces so does the relative humidity. “Eventually you end up with a situation where you have extracted all the water vapor as liquid from the airflow, and that leaves you essentially with dry air below 215K. The partial pressure of the water vapor at this point is so low that you can allow it to pass through the heat exchanger and it does not freeze.”

………

Reaction Engines decided to go public on the frost-control technology because of pending patent applications. “The trigger for patenting was the awareness that to execute this program we are going to have to involve other companies,” says Mark Thomas, the former chief engineer for technology and future programs at Rolls-Royce and now managing director at Reaction Engines. “You can’t keep trade secrets very long in that situation, so it is better to be protected formally and legally on the clever stuff.”

This is all going on while the engine is moving faster than mach 5, though it is slowed to subsonic speeds (the cooling allows the system to avoid the complexities of a scramjet, the shock cone in the inlet is the tell here).

I would really like to see an animation of this, because for the life of me I cannot see how they get coolant to flow forward against that sort of air flow.

It’s weird, but it is a good kind of weird.

Sorry to Harsh Your Warp Drive Buzz ………*

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The reports of the EM Drive appear to be greatly exaggerated:

………

 Perhaps we should take a long cool drink at this point. Let’s start with the “NASA validates” part. NASA is a huge agency, with more than 18,000 employees. The testing was done by five NASA employees in a lab devoted to exploring unorthodox propulsion ideas. The team leader is a researcher named Harold “Sonny” White, himself a proponent of ideas about faster-than-light warp drives that most of his colleagues have classified as physically impossible. The lead author is one of White’s Eagleworks teammates, David A. Brady. Calling this group “NASA”—as almost every popular news story has done—is a gross oversimplification.
till, science is science: What matters are data, not motivations or semantics. Did White et al actually validate Fetta’s version of the EmDrive? The abstract of their paper, which was presented at a propulsion conference in Cleveland, is freely available online. Reading it raises a number of red flags. The methodology description makes it unclear how much of the testing took place in a vacuum—essential for measuring a subtle thrust effect. The total amount of energy consumed seems to have been far more than the amount of measured thrust, meaning there was plenty of extra energy bouncing around that could have been a source of error.

Worst of all is this statement from the paper: “Thrust was observed on both test articles, even though one of the test articles was designed with the expectation that it would not produce thrust.” In other words, the Cannae Drive worked when it was set up correctly—but it worked just as well when it was intentionally
disabledset up incorrectly. Somehow the NASA researchers report this as a validation, rather than invalidation, of the device.

 Did I say that was worst of all? I may have  take that back. In the paper by White et al, they also write that the Cannae Drive “is producing a force that is not attributable to any classical electromagnetic phenomenon and therefore is potentially demonstrating an interaction with the quantum vacuum virtual plasma.” That last bit stopped me. What’s a quantum vacuum virtual plasma? I’d never heard the term, so I dropped a note to Sean Carroll, a Caltech physicist whose work dives deeply into speculative realms of cosmology and quantum theory.

 Carroll wrote back immediately, with a pointed message: “There is no such thing as a ‘quantum vacuum virtual plasma,’ so that should be a tip-off right there. There is a quantum vacuum, but it is nothing like a plasma. In particular, it does not have a rest frame, so there is nothing to push against, so you can’t use it for propulsion. The whole thing is just nonsense. They claim to measure an incredibly tiny effect that could very easily be just noise.” There is no theory to support the result, and there is no verified result to begin with.

 ………

 That’s part of why this space-drive story bothers me so much. Abandoning known science when it feels good to do so is a dangerous proposition. As Carroll later tweeted, “The eagerness with which folks embrace sketchy claims about impossible space drives would make astrology fans blush.” I am personally a huge space enthusiast; I would love to see a new type of propulsion that would make it easier to explore the universe. But having your heart in the right place is no excuse to walk away from normal critical thinking. It is not materially different than the approach of people who reject science when they don’t like what it says about climate change, vaccines, or genetically modified organisms.

(Emphasis Mine)

Let’s be clear here:  The tests are dubious, the detected “thrust” being, “Between 30-and-50 microNewtons, where the limit of the measuring device is 10-to-15 microNewtons,” which makes the setup vulnerable to subtle errors and confirmation bias.

I am not saying that it’s true, but I am saying that we don’t have even the vaguest model to describe this phenomenon, and the scientific method requires skepticism, and this sounds like the Pons and  Fleischmann cold fusion fiasco of the late 1980s.

There needs to be a lot more testing, and some theories that could actually reliably predict the results, before we should start buying Star Trek uniforms.†

*Actually, I do want to harsh your buzz. Seriously. This appears to be complete bullsh%$, or at least irresponsibly immature, and I can feel virtuous by shooting it down.
†On my part, I will not be buying a Star Trek uniform. As an engineer, I would be wearing a red shirt. I do not like those odds.

Interesting Development in Ion Drives

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Iodine looks promising as a replacement for Xenon for the propellant in ion drives: (paid subscription required)

A high-efficiency radio-frequency (RF) ion microthruster in development could give engineers another approach to solar-electric propulsion (SEP) technology for deep-space exploration, particularly for the tiny CubeSat-based probes just coming into their own.

While large-scale SEP is considered necessary to preposition supplies on Mars for human explorers, work is underway at NASA and in universities on CubeSat-class missions to the Moon, Mars and other deep-space destinations as well. Of particular interest is SEP technology that uses iodine as a propellant instead of xenon.

Iodine is easier to integrate into spacecraft and costs much less than the xenon typically used today. Although they sit next to each other in the periodic table, iodine is a solid that sublimates into a useful gas at relatively low temperature, while xenon in its ambient state is a gas that must be contained in a pressure vessel.

Busek Co., a privately held 50-person space-propulsion business in Natick, Massachusetts, has just demonstrated an RF gridded-ion thruster that uses iodine as a propellant and measures only 3 cm across. With iodine, the “BIT-3” thruster demonstrated a specific impulse of 3,500 sec. and a thrust measured at more than 1.4 mN. Designed to propel advanced CubeSats from geostationary to lunar orbits, using 60 watts of power it can generate a Delta-v (velocity change) of 2.5 km/sec. (1.5 mi./sec) with 1.5 kg (3.3 lb.) of fuel in a 13-kg spacecraft, the company says.

“Iodine is a substance that is stored as a solid on a spacecraft, because it has very high density,” says Vlad Hruby, founder and president of Busek. “It also stores in small volume, in a zero-pressure tank. That means the tank can be conformal. You can stick it anywhere in the spacecraft, wherever you have space, and then you heat it up a little bit and it generates enough available pressure to feed [the propulsion system].”

Busek also has used iodine as a fuel in Hall-effect thrusters, and holds NASA small-business contracts for advanced technology development work aimed at deep-space smallsat SEP. The BIT-3 approach uses an RF coil to ionize the sublimated iodine gas, and electrically charged grids to accelerate the ions to the high velocity needed.

While the Hall thrusters are good for “Earth-centric” missions, the efficiency of the gridded-ion thruster makes it more attractive for deep-space applications.

“They have different niches, really,” says Michael Tsay, chief scientist on the BIT-3 project at Busek. “The Hall thruster has very high thrust to power, so you can get higher thrust, but with slightly lower Isp [specific impulse]. The RF ion can give you very high Isp, but you get lower thrust. So it’s mission-dependent.”

For either application, iodine has another advantage over xenon that makes it more attractive as a secondary payload. Since it doesn’t require a high-pressure tank, iodine is safer and less likely to damage a high-priced primary payload if something goes wrong.

………

“It eliminates the need for a high-pressure tank, and it stores more compactly, so it takes up less volume,” says Andrew Petro, NASA program executive for the Small Spacecraft Technology Program within the STMD. “Those two features are especially important because of the small size of the small satellites we are trying to develop.”

………

Iodine has advantages for small satellites, including much lower cost as industry finds new uses for xenon in fields as disparate as photography flashes and surgical anesthesia. But it may not be as scalable as xenon for the large-scale, multi-kilowatt applications NASA’s human-spaceflight engineers are pushing as a way to move habitats, cargo carriers and other large payloads toward Mars (AW&ST June 23, p. 44).

“The challenge with iodine is feeding the propellant,” says Petro. “With the xenon gas it is very simple; it’s a pressurized gas, It will come out through a valve if you open it. The iodine has to sublime into a gas and be fed, and the larger amount of it you have, the more challenging it might be to engineer a tank that will feed that propellant in a consistent and reliable way. It certainly is possible, but it will probably take some more engineering to work that out. I haven’t really seen much. I think the real attraction of the iodine is in the smaller spacecraft, because they already have the problem of limited volume. It is not as much of an issue for the bigger spacecraft.”

Iodine sublimates at 113.7° C, and being a halogen, it is rather corrosive, but I don’t see these as particularly daunting engineering issues in implementing an iodine based system.

First, You Eliminate the Competition, Then You Refuse to Release Price Data for Competitive Reasons

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I knew that the taxpayers would come to regret cancelling the alternate engine for the F-32, the F136, but I did not expect it to happen so soon:

After a long battle to edge rival General Electric out of the F-35 engine market, Pratt & Whitney succeeded in 2011. GE announced it would shelve the F136 after the Pentagon refused to fund it for four years, leaving Pratt in the coveted position of a sole-source engine supplier for the largest international fighter program ever.

Three years later, though, Pratt states that its position with its F135 engine is so potentially competitive it cannot comply with the customer’s request to publicly share the target contract pricing data. At issue is Pratt’s hope for more government funding by garnering a piece of a $1 billion next-generation fighter engine. Although proposed by the Pentagon, this program has yet to be funded by Congress.

“We have already made significant progress in advancing this technology and anticipate a competition will be held to develop this engine. Releasing engine pricing and cost data on the F135 would impact our ability to compete for this potential next-generation fighter engine program,” says Pratt spokesman Matthew Bates.

Senior Pentagon officials have, however, been urging Pratt to release at least some data in a transparency push for the highly scrutinized F-35. Bates cites a 40% drop in engine pricing since the first low-rate-initial-production (LRIP) lot in 2006. But the rate of cost reduction “slowed down when [Pratt] got the monopoly,” said Rear Adm. Randy Mahr, deputy program manager of the F-35. “We are trying to get that information out . . . But, I can’t force somebody to go ahead and report something that by law they are not” required to report. Mahr made his comments at the Sea Air Space 2014 conference here this month. “This is a subject of legal debate but the Department of Defense feels this information should be in the public domain,” according to one defense official who requested to talk on background owing to the sensitivity of the issue.

The last known engine price for the F135 was cited by Air Force Lt. Gen. Christopher Bogdan for the third lot. The F-35A/C propulsion system cost $14 million. The F-35B, which includes a Rolls-Royce lift-fan designed for short takeoff and vertical landing, cost $38 million. He is frustrated at Pratt not bringing down F135 costs as predicted. “Pratt is not meeting its commitment,” Bogdan says. “It is as simple as that. Some of their business base has dried up on other programs and projects [and] they are spreading them right where they can, and I don’t like that.”

Pratt & Whitney has declined numerous requests from Aviation Week over many months to release either its pricing data or its contractual cost targets.

I predicted that the long term budget consequences of eliminating the 2nd engine would be negative, and that the F-35 advocates’ desire to lower front end costs would be swallowed up by the price increases resulting from creating an engine monopoly.

Cessna Jumps on the Diesel Band Wagon

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They will be putting a diesel in the model 182 Sklylane: (Paid Subscription Required)

While avgas consumers and suppliers fret over the future of their leaded fuel, Cessna is partially weaning itself of that toxic brew by equipping its popular Model 182 Skylane with a Jet A-burning diesel engine. Others are likely to follow.

Unveiled at the Experimental Aircraft Association’s recent annual gathering in Oshkosh, Wis. (see p. 35), the Turbo Skylane JT-A (photo) is fitted with the new SR305-230E engine built by SMA, a subsidiary of Snecma of France. The four-cylinder, 227-hp powerplant is already certificated by both the European Aviation Safety Agency and FAA , and Cessna hopes to begin deliveries of its newest model in early 2013.

While Austria’s Diamond Aircraft has been producing aircraft powered by Austro Engine diesels for several years, the entry into that market by the much-larger Wichita aircraft maker with wide name recognition and a global support network is significant and likely to find favor, particularly in lesser-developed regions where avgas is scarce and expensive. Visitors at the Oshkosh introduction told Cessna personnel that the per-gallon price of 100LL avgas at some remote locations had topped $22.

Austro is a former Diamond Aircraft subsidiary (they spun it off) founded to replace the Thielert engine after that company’s implosion.

Expect Cost Escalations and Delays For the Joint Strike Fighter Engine

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Because GE and Rolls Royce have pulled the plug on their joint F136 engine venture:

After 15 years of ups and downs, General Electric and Rolls-Royce have accepted defeat in their battle to power the F-35 Joint Strike Fighter and will today announce the end of the F136 program and the Fighter Engine Team partnership.

By deciding to discontinue self-funding the F136 alternate engine they are also parting ways at an interesting time for the propulsion world. Rolls’s recent, and unexpected, rapprochement with Pratt & Whitney over commercial engines could, for instance, signal the start of new strategic links in the military engine world now that the long-lived experiment with GE is over.

………

The move to kill the F136 comes after an Oct 31 meeting between GE Aviation leadership and Deputy Secretary of Defense Dr. Ashton Carter in which “it became clear that the DoD would not support the FET self-funding effort,” says GE.

So basically, the Pentagon left a horse’s head in their bed.

I expect that all the good news from Pratt & Whitney over the past few months, about them making noise about being ahead of schedule and budget, to end abruptly.

Without a competitor engine, we  are now going to see all the stuff that was swept under the carpet for the F135 percolating back up, and the tax payer will be on the hook for it.

Development Costs of F135 Rise, Marginal Unit Cost Falls

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The Pentagon and Pratt & Whitney have negotiated a cost reduction for the next 37 engines that they deliver, but the non-recurring R&D Costs go up:

Pratt & Whitney has reached an informal agreement with government officials to slash 16% off the total price of the next batch of 37 engines to be ordered for the Lockheed Martin F-35 Joint Strike Fighter.

At the same time, the company acknowledges the cost of the overall F135 engine development programme will grow by about $1 billion to support a three-year extension of flight tests and to improve the engine’s performance and durability.

If you assume $15 million per engine, it means that this cost, assuming that this continues across the production run (it won’t, particularly with the GE/Rolls F136 out of the picture) would end up saving money after the delivery of about 450 engines.

This is taking money out of one pot, and add it to another in the best case, and more likely it’s a stealth price increase.

House Votes to Kill F136 Engine

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While I expect to see some continued efforts by GE, Rolls Royce, and their supporters, I think that this is the death knell for the F136 engine:

The U.S. House of Representatives today voted to kill funding the F-35 Joint Strike Fighter backup engine made by General Electric Co. and Rolls Royce Group Plc.

By a vote of 233-198, the House voted to cut $450 million for the engine from legislation funding the Pentagon for the remainder of the fiscal year ending Sept. 30.

It is the first time in more than four years of votes that the House has come out against the GE-Rolls Royce engine for the F-35, the stealth fighter made by Lockheed Martin Corp. In May, 2010, the House voted 231-193 to continue the program.

This is important for a number of reasons.

First, with this defeat on the table, the onus now falls on the supporter of the F136 to bring the engine back, which is hard.

Second, and more importantly, House Speaker John Boehner, whose district, and neighboring districts, directly benefit from the engine, could not whip the votes necessary to support the engine.

Like I said, the engine is toast.

In the long run, this is a bad thing, because leaving Pratt & Whitney as a monopoly supplier for the engine is likely to increase costs, and reduce performance, a lot down the road.

That being said, I do experience no small amount of amusement because Boehner got seriously served on this.

Vasimr Electric Propulsion System Heading Out to ISS

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NASA will be sending the variable specific impulse magnetoplasma rocket (Vasimr) up to the International Space Station (Paid subscription required) for tests and validation. (Earlier posts)

It’s expected to put out about 5.7 Netwons, about a pound, with an ISP (fuel economy) of somewhere between 10 and 30 times that of chemical propellants.

While a pound does not seem like much thrust, it’s more than enough for station keeping and orbital, or for that matter interplanetary, maneuvering, as you can get the thrust for months, rather than hours, and compared to other electric thrusters systems, like the ion drive used on the Dawn Probe, it provides a lot more thrust. (Dawn has a thrust of only 90mN, about 1/50 that of the Vasimr).

F136 Alternate Engine Included in Stopgap Spending Measure

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So the alternate engine for the JSF is funded through March.

Some people see this as meaningless pork, but I remember the issues with Pratt and Whitney as the soul source supplier for F-15s and F-16s in the late 1970s and early 1980s, and it was ugly, so I am inclined to support the engine as a 2nd best alternative, with the first best alternative to be cancellation of the JSF.

Senate Appropriations Committee Pulls F136 Alternate Engine Funding

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In addition to zeroing out the alternate engine, they also cut 10 production aircraft from the FY 2011 for failure of the program to execute per schedule.

This implies to me that neither cut could have gone through on its own, but together, both those who have concerns about the JSF, and those who don’t want the engine got enough of what they wanted to support each other.

Meanwhile GE/RR is ramping up efforts to reverse this decision, noting, among other things, that the budget numbers that the Pentagon is putting forward on the F136 engine are sketchy at best.

H/t ELP Defens(c)e Blog

Tests Of Alternate JSF Engine Show Higher Thrust

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GE’s F-136 has demonstrated a 15% sea level thrust advantage over the Pratt & Whitney F135 at the USAF’s Arnold Engineering Development Center.

Additionally, GE is saying that they are doing this at lower turbine inlet temperatures, which would imply lower maintenance costs as well as greater upgrade capability:

The intense battle over powering the F-35 Joint Strike Fighter could be heading to new levels following test results that show the General Electric/Rolls-Royce F136 alternate engine has more than 15% thrust margin against specification, significantly exceeding the power of the baseline Pratt & Whitney F135.

The tests at the U.S. Air Force’s Arnold Engineering Development Center (AEDC) in Tullahoma, Tenn., are the first to officially calibrate the combat-rated thrust of a production-representative F136 at sea level conditions. Although the test program is only a matter of days old, it already appears to be showing greater performance margin in afterburner than expected, says the General Electric Rolls-Royce Fighter Engine Team.

I would note that it is likely that, as with the F100/F110 comparison, that the GE engine is somewhat heavier, which would imply that at higher altitudes the P&W engines would provide better performance.

House Calls Obama Veto Threat on JSF Engine

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The House Appropriations defense subcommittee has voted to fund the F136 alternate engine for the JSF (see also here) which runs full face into the implied threat of an Obama veto (SecDef Gates has said that he would recommend a veto, but that is different from Obama himself threatening a veto).

I’m of mixed emotions on this matter.

I think that the F-35 is over priced, behind schedule, and useless for any likely future war, but I remember the history of Pratt & Whitney’s F-100 before GE started competing with them with their F-110 engine, and it was not pretty, so I think that the engine is a good idea.

I think that the Pentagon is worried that any dollars spent on this will drive up the front end costs, making it more likely that the program will be canceled, and they are willing to eat the additional costs of P&W being the soul source on the back end.