History of Stealth

[Wahubna]

With this timeline so far, anyone know what Northrop designs preceded their XST offering?

 

[overscan (PaulMM)]

N-204 (1957) reconnaissance project specifically mentions low radar cross section
N-327 (1974) $100,000 USAF Low Observables Concept Study leading to XST
N-335 (1975) Northrop XST
N-345 (1978) TACIT BLUE

Dates are commencement of program rather than first flight, as we are mixing real aircraft with projects.

 

[quellish]

N-204 (1957) reconnaissance project specifically mentions low radar cross section
N-327 (1974) $100,000 USAF Low Observables Concept Study leading to XST
N-335 (1975) Northrop XST
N-345 (1978) TACIT BLUE

Dates are commencement of program rather than first flight, as we are mixing real aircraft with projects.

Between XST and TACIT BLUE there was Northrop work on TEAL DAWN, which looked at wing-body-tail configurations for cruise missiles, and heavily influenced TACIT BLUE.

John Cashen interview with Peter Westwick, 15 December 2010

CASHEN: All right. After XST—you asked the question, here it is. It was a DARPA program called Teal Dawn, which was a re-look at the intercontinental cruise missile. Northrop back in the '50s had built and fielded an intercontinental cruise missile, and it was called the Snark. This is basically going back and looking at the Snark as a potential weapon for the United States. This time, however, they had to be stealthy. DARPA created a program—this is a different DARPA now. It was not Perko's DARPA, which was tactical technology; it was a strategic technology office of DARPA. And the project was called Teal Dawn. We got a contract, and Boeing got a contract.

Anyway, Teal Dawn made us step back and think about what we'd done on XST and create for the very first time a wing-body-tail all-aspect design. What it was based on was the original Mark 12, the Minuteman reentry vehicle, the ice cream cone, had been studied by the Siegel group at Michigan to the extent that they were convinced it was the ideal radar cross section shape for the reentry application, that you could never do any better than the ice cream cone. It was ideal. And I think it's been proven that way over the decades since then. So, what is the ideal airplane? The ice cream cone's axially symmetric. An airplane can't be axially symmetric. An airplane's got to have wings. That by definition makes it planar. Maybe it's a flat plate, an infinitely thin flat plate. That would be the ideal radar cross section shape for an airplane. You can't make an airplane infinitely thin because you have to put a person and engines in it. So what you do is start out with a flat plate, and you grow above and below that plate the volume necessary to make it into a functional system, and minimize as much as possible the increased RCS due to the addition. But you start out with a flat plate.

CASHEN: They're aligned. Parallel. Parallel planforming we call it. Now, it turns out the design of an airplane historically starts out with a plan view, whether a designer hand draws it or does it on a computer. He starts out with a plan view, and then he starts to grow the third dimension. So the idea of RCS design, Stealth design, of an airplane that starts out with a plan view is consistent with the existing airplane design process. That's the process here at Northrop. It always has been, always will be. Lay out a plan form that you want, because your RCS pattern in azimuth is dominated by the plan form that you've created. And then change it as necessary in creating the real airplane. It's done that way with Tacit Blue—they're all that way. So, we learned that on Teal Dawn, a wing-body-tail cruise missile, and we created our Teal Dawn accordingly.

 

[FighterJock]

First time that I have ever seen anything about Teal Dawn, I take it that there will be no further info, design drawings or even images of the missile?

 

[overscan (PaulMM)]

Northrop's Teal Dawn research led to Tacit Blue and TSSAM. I think you can extrapolate the likely basic shape of their Teal Dawn design.

 

[quellish]

First time that I have ever seen anything about Teal Dawn, I take it that there will be no further info, design drawings or even images of the missile?

Northrop design was super pointy.
Boeing design was different, probably a lot like a Boeing supersonic cruise missile posted in other threads.

You never know, drawings could appear in a few months.

 

[LowObservable]

Bill Bahret provides many insights into the early development of low observables, and mentions at least one previously undisclosed program from the 1960s:

William F. Bahret: The Cold War Aerospace Technology History Project (Interview 1)

William F. Bahret: The Cold War Aerospace Technology History Project (Interview 1)

Squire Brown interviewed William Bahret on August 22, 2006 for the Cold War Aerospace Technologies History Project. In the interview Mr. Bahret discusses his role in the development of military technology during the Cold War.

corescholar.libraries.wright.edu

William F. Bahret: The Cold War Aerospace Technology History Project (Interview 2)

William F. Bahret: The Cold War Aerospace Technology History Project (Interview 2)

Squire Brown interviewed William Bahret, an authority on radar signature, on May 27, 2009 for the Cold War Aerospace Technologies History Project. In the interview Mr. Bahret discusses his role in the development of military technology during the Cold War.

corescholar.libraries.wright.edu

W.F. Bahret, "The beginnings of stealth technology", 1993

https://doi.org/10.1109/7.259548

Very interesting! Just fell down that rabbit-hole myself.... and had a couple of surprises...

 

[Scott Kenny]

Nor a complete list, but...

[...]
Model 151 ARES (1990)

I would not consider the Scaled Composites/Rutan ARES to be a stealth design. It was made to see if a completely composite structure could survive the recoil of the GAU12 25mm cannon.

I am not aware of any mention ever being made about that aircraft being designed with stealth in mind.

 

[quellish]

I would not consider the Scaled Composites/Rutan ARES to be a stealth design. It was made to see if a completely composite structure could survive the recoil of the GAU12 25mm cannon.

I am not aware of any mention ever being made about that aircraft being designed with stealth in mind.

ARES is constructed of fiberglass and Kevlar. It is “transparent” to radar, and I have seen radar diagnostic images that illustrate that the internal metal components of ARES are very visible to radar.

Nonetheless it is listed in at least one place as having made significant contributions to low observables. Why it is on this list is still an open question

 

[overscan (PaulMM)]

ARES is constructed of fiberglass and Kevlar. It is “transparent” to radar, and I have seen radar diagnostic images that illustrate that the internal metal components of ARES are very visible to radar.

Nonetheless it is listed in at least one place as having made significant contributions to low observables. Why it is on this list is still an open question

A negative result is still a contribution?

Just kidding. Its hard to see why its on the list indeed. Radar.... Infrared... Visual.... Acoustic.... not really seeing anything.