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Virtual Earth Exposes Nuclear Sub's Secret
NewsCloud alerts us to a story a few months old that has been getting a lot of play recently. A Seattle blogger, Dan Twohig, was browsing in Microsoft's Virtual Earth when he accidentally came across a photo of a nuclear sub in dry-dock. Its propeller is clearly visible — this was a major no-no on the part of someone at the Bangor Sub Base. The designs of such stealth propellers have been secret for decades. Twohig blogged about the find and linked to the Virtual Earth photo on July 2. The debate about security vs. Net-accessible aerial photography has been building ever since. The story was picked up on military.china.com on Aug. 17 — poetic justice for the Chinese sub photo that had embarrassed them a month before. On Aug. 20 the Navy Times published the article that most mainstream media have picked up in their more recent coverage. Twohig's blog is the best source to follow the ongoing debate. No one has asked Microsoft, Google, or anyone else to blur the photo in question. Kind of late now.
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Tell the truth and you won't have so much to remember.
Is this really so secret nowdays?
I think I remeber that the thechnology to make these kind of silent propellers where sold by a norweigan company to a KGB front in the early 1980:s. As I recall, it was a major scandal when the news brooke.
As I have understod it, most soviet nuclear subs had these improved propellers since late 80's and that most of the eastern block started to get access to the same technology.
Most western submarines has had these kind of silent props for years and I belive that most submarine nowdays have one.
You could try to track the Swedish HMS Gotland with passive hydrophone and see how far that takes you, for instance... she insn't even a NATO sub but she is more silent than even the american SSN subs.
Why three?
I am not a fluid dynamicist. But: To increase thrust at a certain RPM, it seems that you can either (1) increase the diameter of the propeller, or (2) increase the number of blades. The problem with increasing the diameter is that the velocity at the tips increases, which leads to effects like cavitation (which, besides being very noisy, damages propellers). So what you do is increase the number of blades.
Prop-driven airplanes produced near the end of WWII had many-blade propellers for this reason as well: They wanted a lot of thrust, but, if they made the blades any longer, then the tips would have been supersonic. (I think I got this factoid from the History Channel.)
My guess is that a quiet high-thrust propeller would spin slowly and have many, very wide and heavily-curved blades. Let's see if somebody who knows more agrees.
Coordinates are +47 43' 39.58", -122 42' 55.83" for the base (this can be plugged into Google Earth.)
The location of the snapshot is of the dry-dock at 4744'36.08"N, 12243'48.51"W.
This link may or may not work: http://maps.live.com/default.aspx?v=2&cp=ryqjnb4s5 7d5&style=o&lvl=2&tilt=-90&dir=0&alt=-1000&scene=1 0352732&encType=1
There's no propeller visible in the Google Earth imagery. All you can see is that there's what might be a sub; it's quite blurry. The Windows Live imagery shows a blurry whirly instrument of death; looks like a bunch of boomerangs.
Honestly, it's stupid. Half the shit that's classified, is just classified to impress. For example, the top speed of various US air craft carriers. Like that can't be figured out by a foreign government...? Like our *propeller technology* is that much more advanced, and other nation's subs haven't figured out what it sounds like? C'mon.
Please help metamoderate.
I served for a long time.
And I was exposed to all branches for long periods of time. You will not find a less gay friendly place than the Navy. Even the Marines are more tolerant. It's because of the hollywood archetyping of the navy as gay that the navy has had such a buildup of anger about it. The 1993 DADT policy greatly increased the problem, and violence against gays has increased by about an exponent from 1993-1999 (no idea of the exact recent statistic, but it has increased greatly up to today)
Gays int he military are usually quite good. dedicated to serve in spite of additional hassle. The Brits have been open for a while, and they are, man for man, extremely effective. I'm not implying that there is some kind of problem with gayness in the military.
But this is typical trash propaganda. Sounds ludicrously paranoid, but the fact is that there is an effort to portray soldiers as feminine weakling children or sociopathic monsters. You'll find most gays in the Army. You'll find the fewest in the Navy.
Actually, the majority of the images you see when zoomed in on Google Earth and Google Maps, as well as Microsoft Virtual Earth, are from aeriel photography. i.e. taken from planes. Check with Google if you don't believe me.
Commercially available satellite imagery does not have the resolution to show you a photo of your house from orbit. Images used by the 'intelligence' communitity and the military have higher resolution, but not at the magnification that they'd like you to think they have.
The secret bit of these propellors is what materials they are made of, how precisely they curve, and to what tolerance they are engineered. The big problem with propellors is that they tend to suffer from cavitation at high speed, where the sudden change in pressure causes bubbles to form and collapse. Apart from being rather noisy, referred to as "singing" (which is a bad thing for a stealthy submarine trying to make a fast getaway) it also causees damage to the blades (much like desert sand on engine turbine blades).
The purpose of having an odd number of blades is no secret - it is to reduce vibration. As the submarine travels through the water it leaves a wake behind it. Above the submarine there is less water pressure than below - so having two blades above and below at the same time is a bad thing. The more blades, the less vibration, but propellors are more efficient with fewer blades. You will see speedboat propellors with three or four blades, and fishing boats can have propellors with only two blades.
There is also the problem that having different metals in close proximity in a salt water environment, can lead to an electrolysis effect where the metals and water act as a kind of battery. Lots of technical papers on Propellor design
"The most frequent cure for a singing propeller is the popular "anti-singing edge". This is a chamfer applied to the trailing-edge to promote separation of the vortices."
Vintage computer adverts: http://www.vintageadbrowser.com/computers-and-software-ads
K changed my original post but I put a close up of the liveearth propeller image here. I agree the U.S. govt doesn't care about it at this point or MSFT would have blurred it.
...Or increase the pitch of the propeller. Many Naval vessels use CRP or CPP (Controllable Reversible Pitch or Controllable pitch propellers)
Source
Also read about the low amount of use China's submarine fleet gets, and the inexperience they have: Source
This basically amounts to China having never actually used their submarines as a nuclear deterrent, and since they have no ICBMs that can reach the US they have no nuclear deterrent against the US and a comparatively very limited navy. (Report)
The media loves to hype up China's military spending, but if you think China's grounded 1980's built subs, or the speculated five new Jin-class (Type 094) subs, are going to make the US Navy "ineffective", or if you think aircraft carriers (the most expensive ships of all) are just for intimidating small nations, then you're a few warheads short of a nuclear power.
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That's actually an excellent answer. There is an article about precisely that subject here: http://www.aerospaceweb.org/question/propulsion/q0 039.shtml
One thing the article doesn't point out is that increasing the solidity of the propeller disc can have it's own consequences, and there is generally an optimum solidity (depending on various other factors) which results in the highest efficiency.
A deep unwavering belief is a sure sign you're missing something...
Research into making more efficient and quieter propellers was conducted from the mid-70s to the mid-80s, because of the greater fuel efficiency of propellor-driven aircraft in light of the Arab oil embargo. This research led to the development of the 'propfan', a turboprop engine with wider, swept-back propeller blades. The Advanced Turboprop Project at NASA's Lewis Research Center's developed engine and propeller designs that would spark a resurgence of the turboprop era, but socio-economic factors -- primarily driven by a reduction in fuel costs, reducing the perception of any need for immediate and radical fuel conservation -- kept the new designs from making more than a peripheral entry to the aviation market. Many modern turboprop aircraft use propellers incorporating advances developed by the ATP, and the research contributed to the development of the high-bypass turbofan jet engines used in most modern airliners, but there was no significant return to the use of turboprop aircraft in commercial aviation. Research has continued, with some engine designs becoming more exotic, as in this image or this one, but commercial applications of the research continue to use ducted fan designs, such as the newest UHB (ultra-high bypass) turbofan designs. The designs produced by this research, however, bear sufficient similarities to the screw design in the satellite photo that it is clear that the same overall design considerations apply, subject to the differences in density, viscosity, and compressibility of the driving medium in each design case.
Okay - so I'll comment as a ten year Navy veteran (with Sub time) and as an MS Virtual Earth employee.
On the actual propeller, some of the comments above are accurate with respect to design, power, speed and cavitation issues. If it's covered by Wikipedia, then it must be true! There has always been a policy to cover the propeller whenever the boat was pulled out of the water - it's part of the secret sauce behind our submarine stealth. Not showing it in public only makes sense, but this picture from the air could have been taken by anyone flying a private plane. Shame on the Navy for not covering it, but then again, there's more to the engineering behind it than a picture could ever show.
Talk of satellite imagery and Government intervention is an interesting topic of the day, however. For one thing, the image was not taken by satellite, but rather by airplane using a unique capability for oblique imagery. In Virtual Earth, you can view the same area at 2 zoom levels and 4 compass points. The imagery comes from Pictometry, and MS uses the term "Bird's Eye" to depict areas in which it is available. It's pretty incredible imagery, truly raising the quality bar over systems using only satellite imagery.
Note that Microsoft does not manage satellite or aerial providers - we only take the imagery in, enhance it, tile it and then provide it to our customers in the form of an API. The organizations that provide the imagery have been in business for years capturing images of the earth and selling them to commercial and government organizations. If anyone should be on point to discuss the appropriate image capture time and location, these would be the organizations to do so. Since I do not work for one of these organizations, I will abstain from commenting on their data capture policies. Perhaps they have a Slashdot reader who would like to comment!
So what is Microsoft's position on this issue? A quick search (http://search.live.com/results.aspx?q=justin+osme r+submarine+propeller) yields the following statement on Navy Times from Justin Osmer of the MS Virtual Earth product team:
At the end of the day, several commenters here and elsewhere have used the term "get used to it", referring to the fact that we're losing our privacy and anonymity every day via cameras in the sky and search engines on earth... Perhaps this is true, but then again, maybe it's exactly what we need at this point in our civilization.
"Ducted propulsion" on a navy demonstrator vehicle...
...is this a secret?
We apologise for the fault in this post. Those responsible have been sacked. -- Signed RICHARD M. NIXON
The movie Das Boot starts with the statistic that of the 40,000 German sailors who served on U-Boats in WWII, 30,000 of them died.
meh
I know Derek (from online, for years, but not in real life), and he's been there and done that.
The general shape is not news; it's the same general shape as on a bunch of US attack sub prop pictures which have been public for 10+ years.
The photo reveals the blade advance ratio for that particular prop design, though, which is useful to adversaries, and is different than the attack sub props.
As far as I know, and I have a naval architecture degree and have followed sub and naval ship design reasonably well for 30+ years, enough details to determine blade advance ratio on Ohio SSBN props have never been public. It was widely known that they were skew / scythe props. But "It's of that general type" and "Oh, look, that's what speed it's designed for" are two different things. A smart hydrodynamicist or naval architect can use that and tell roughly how fast an Ohio can reasonably be expected to go at top end speed, and things about how much cavitation noise it will make accellerating in a sprint. Also, it can help map propellor RPM to speed.
It's important, and the blade advance angle there is very different than the previously widely known ones on attack sub props, and that will tell bad guys something.
DRM 'manages access' in the same way that a prison 'manages freedom'
An Australian Collins class sub has also had a confirmed kill against a US carrier.
Did they change the ROE for your war games after this? (In order to make it much harder for the sub)
They've done this for the US vs AU exercises, now the exercise starts with full ASW assets deployed, and a visual fix on the sub (It must be at periscope depth)
Propellers are obsolete for submarines, pump-jet propulsors are used now. The US Navy first used them on the Seawolf class, the next class of missile sub is certain to get them. The sub in the picture is an Ohio class, the first of which was commissioned in 1981 - hardly cutting edge technology these days.
The worst that photo will do is give potential enemies a better idea of an old sub's capabilities, not allow them to build a sub that's as quiet as the latest US subs.
It's never too late to have a happy childhood.
By the way, that design of the propellers won't exactly work for Russian subs, either. You try an exact copy of the propeller and it could adversely affect the handling of the Russian Akula, Sierra and Oscar class submarines; in short, each submarine type requires its own unique propeller design. And this design definitely does not work with the type of ducted propellers that are starting to appear on the very latest submarine designs (The US Seawolf class submarine uses them, and I believe the new Virginia class submarine will use ducted propellers, too).
This is basically the case and you can prove it by looking at any modern airliner. A modern high-bypass turbofan jet engine is really just a turbine-driven ducted propellor, and the propellor geometry is much like what you describe, with a whole ton of blades spinning at a reasonable speed.
You have a pretty much completely wrong idea of jet engines. The blades spin very quickly at thousands of RPM's - in fact the tips of the blades are barely subsonic in speed. They are subjected to such high rotational forces that a small crack in the the blades could cause catastrophic failure (i.e. destruction of the engine as the blade tears apart and rips through anything in it's path).
Also the blades are not used to provide thrust as a jet engine used direct thrust. Instead, they are used to compress air prior to combustion and to power said compression. The blades in the front of a jet engine are there to compress air to get more air into the engine. When combined with jet fuel and ignited, this air expands and the expansion of the air provides the thrust. The expanding air also happens to turn the "turbo" blades near the exhaust that drive the previously mentioned compressor blades as well as powering generators for the electrical and hydraulic needs of the plane.