skunk-works-digest Thursday, May 14 1998 Volume 07 : Number 027 Index of this digest by subject: *************************************************** Re: skunk-works-digest V7 #26 OT: Listowner need help again... Re: Kinda off topic GPS question Re: Kinda off topic GPS question RE: Kinda off topic GPS question Shock Wave Thickness Re: Kinda off topic GPS question area 51 story Re: It's Offiical [none] Re[2]: It's Offiical Re: Shock Wave Thickness Re: Shock Wave Thickness Re: Re[2]: It's Offiical 3 - 2 - 1 - Test Away! *************************************************** ---------------------------------------------------------------------- Date: Sun, 03 May 1998 12:45:14 -0400 From: Don Hackett Subject: Re: skunk-works-digest V7 #26 What happened to Skunk-works-digest V7 #25? Never got it, after a longish silence, and it is not in the archives. ------------------------------ Date: Sun, 03 May 1998 16:57:06 GMT From: georgek@netwrx1.com (George R. Kasica) Subject: OT: Listowner need help again... Hello: Hate to be asking this again, but I seem to have misplacedyet ANOTHER digest here...V7 #25 is not in the archives and I would really appreciate it if someone could send a copy here for posting. Your slightly recently addled and confused listowner, ===[George R. Kasica]=== +1 414 541 8579 Skunk-Works ListOwner +1 800 816 2568 FAX http://www.netwrx1.com West Allis, WI USA georgek@netwrx1.com Digest Issues at: http://www.netwrx1.com/skunk-works ------------------------------ Date: Sun, 3 May 1998 15:29:35 -0500 (CDT) From: John Szalay Subject: Re: Kinda off topic GPS question At 08:18 AM 5/3/98 -0400, you wrote: >I just figured many on this list may be able to answer questions about >GPS >What kind of accuracy is possible with todays military and/or civilian >GPS receivers? >(I think by accuracy I mean radius of true position) > IIRC: Military units are 3 meters, and civilian versions out of the box are 1500 ft accuracy. HOWEVER by using a beacon with a GPS, civilian versions can get close to the 3 meter setting. the beacon is rather expensive but if you want the accuracy for survey or such, you need it. I find the 1500 ft is more than enough for our uses. we have a low cost model , the Eagle Explorer, $145-$175 if you shop around. >Are there any brands of commercially available GPS receivers 'better' >than others, and why? It appears that most "serious" users favor the Garmin unit, a good place to get information, is the sci.geo.satellite-nav newsgroup, drop in and read the posts, but remember opinions expressed there come from many different folks just as here, opinions may vary .... Another piece of advise on GPS, and it is displayed on our GPS unit everytime its powered up... DO NOT RELY ON THIS PRODUCT AS YOUR PRIMARY SOURCE OF NAVIGATION. GPS is subject to politics. ------------------------------ Date: Sun, 03 May 1998 20:16:34 -0600 From: Lee Subject: Re: Kinda off topic GPS question At 02:29 PM 5/3/98 , you wrote: > IIRC: Military units are 3 meters, and civilian versions out of the >box are 1500 ft accuracy. I hope you meant to say 150 ft. Most articles I have read on the error budget suggest that in the worst case your actual position will be within 50 meters of the displayed position in excess of 95% of the time. By letting the unit average a position, you can get much closer. I believe that the error budget limits a unit to 3-5 meters before the SA (Selective Availability) error in introduced. I have a Garmin unit and I have to admit it is a fun toy :) Lee __ __ _ __ _ - ~~ l ~-_ http://www.wasatch.com/~racer @~~ ------+--------~----____ Ex-Naval Aviation, 3 time Utah Karting @==/~_~\===|=~======|===/~_~\~~-, Champion, Still a kid at heart. \ ( (_) ) \_______| ( (_) )__ , 1987 Fiero GT Burgundy Red, CS >~~\___/~~~~~~~~~~~~~~~~\___/~ ICQ 2403935 ------------------------------ Date: Mon, 4 May 1998 08:27:08 -0700 From: "Erik Hoel" Subject: RE: Kinda off topic GPS question Lee (racing2win@uswest.net) wrote on May 03, 1998 7:17 PM: ... chop ... > I hope you meant to say 150 ft. Most articles I have read on the error > budget suggest that in the worst case your actual position > will be within > 50 meters of the displayed position in excess of 95% of the time. By > letting the unit average a position, you can get much closer. > I believe > that the error budget limits a unit to 3-5 meters before the > SA (Selective > Availability) error in introduced. > > I have a Garmin unit and I have to admit it is a fun toy :) Vanilla GPS with SA scrambling results in accuracy on the order of 100 meters. Using differential GPS with a base station between 110-215 miles away, you can easily get approximately 2 meter accuracy. For a layman's discussion of GPS, try the following article from Byte ("How Accurate is GPS"): http://www.byte.com/art/9602/sec14/art16.htm Interesting note from the Byte article - apparently during Desert Storm, there were not enough military GPS receivers. The obvious work around was to turn off the SA scrambling, thus allowing more readily available civilian receivers to function much more effectively. Erik - -- Erik Hoel mailto:ehoel@esri.com Environmental Systems Research Institute http://www.esri.com 380 New York Street 909-793-2853 (x1-1548) tel Redlands, CA 92373-8100 909-307-3067 fax ------------------------------ Date: Mon, 4 May 1998 08:49:34 -0700 (PDT) From: David Lednicer Subject: Shock Wave Thickness > Since the list is slow, I have a non-skunky question. For those > whom are into fluids dynamics: There is any paper publish regarding of > how to calculate the thickness of a shock wave? A shockwave is inifinitismally thin. An observer is either on one side of it or the other. There is no way for the observer to not be on one side or the other. - ------------------------------------------------------------------- David Lednicer | "Applied Computational Fluid Dynamics" Analytical Methods, Inc. | email: dave@amiwest.com 2133 152nd Ave NE | tel: (425) 643-9090 Redmond, WA 98052 USA | fax: (425) 746-1299 ------------------------------ Date: Mon, 04 May 1998 13:45:38 -0400 From: Drew Subject: Re: Kinda off topic GPS question Thanks to all who responded. WOW, there is a whole bunch to learn about GPS. I am looking at the Garmin 12XL. Thanks again, Drew ------------------------------ Date: Mon, 4 May 1998 22:57:48 +0100 (BST) From: "A.S.Foster" Subject: area 51 story The person who typed that story must be mad as no body would believe it (as in the general populus of this planet). THE ONLY THING THAT WILL MAKE PEOPLE BELIEVE IS UNDISPUTABLE EVIDENCE. OTHERWISE STORIES LIKE THIS MAKE THE PUBLIC BELIEVE THAT UFOS ARE JUST FANTASIES OF THOSE WITH OVERACTIVE MINDS . - ---------------------- asf197@soton.ac.uk ------------------------------ Date: Mon, 4 May 1998 23:46:49 EDT From: Xelex Subject: Re: It's Offiical Too bad about the SR-71 being retired. Again. Even though it is over 30 years old, its performance is still unmatched by any operational aircraft: Cruising Speed: Mach 3.2 Average Max Altitude: 75,000 to 85,000 ft. Max. Altitude: 92,000 ft. (at a gross weight of 60,000 lbs) Flight operations of the NASA SR-71A are only funded through FY 1998 to complete the Linear Aerospike SR-71 Experiment (LASRE). Peter W. Merlin ------------------------------ Date: Mon, 4 May 1998 21:16:45 -0700 From: "Roff Johannson" Subject: [none] unsubscribe skunkworks-l end ------------------------------ Date: Tue, 05 May 98 13:50:32 -0500 From: gregweigold@pmsc.com Subject: Re[2]: It's Offiical Gee, you mean the NASP won't be operational before then? :-) As long as they don't cut the airframes up, I guess they might be resurrected again, but then they ought to rename them Phoenix!! Greg W. ______________________________ Reply Separator _________________________________ Subject: Re: It's Offiical Author: at INTERNET Date: 5/4/98 11:46 PM Too bad about the SR-71 being retired. Again. Even though it is over 30 years old, its performance is still unmatched by any operational aircraft: Cruising Speed: Mach 3.2 Average Max Altitude: 75,000 to 85,000 ft. Max. Altitude: 92,000 ft. (at a gross weight of 60,000 lbs) Flight operations of the NASA SR-71A are only funded through FY 1998 to complete the Linear Aerospike SR-71 Experiment (LASRE). Peter W. Merlin ------------------------------ Date: Tue, 5 May 1998 11:25:44 -0700 From: Larry Smith Subject: Re: Shock Wave Thickness >> Since the list is slow, I have a non-skunky question. For those >> whom are into fluids dynamics: There is any paper publish regarding of >> how to calculate the thickness of a shock wave? > A shockwave is inifinitismally thin. An observer is either on one >side of it or the other. There is no way for the observer to not be on >one side or the other. While watching tests run this weekend on a new chip model, I decided to pull some books out and see if there was some information on Su Wei-Jen's question. I recalled reading some stuff about shock wave thickness while reading some of John D. Anderson's excellent books on fluid dramatics. I was able to quickly find one little tidbit in Anderson's latest "Introduction to Flight" book. He mentions that shocks have a thickness on the order of 10**-4 cm - as David asserts, these things are essentially inifinitesmally thin as far as most fluid dynamics are concerned). However, I suddenly recalled a neat Space Shuttle video I saw where they showed one big honking (technical term) shock attached to somewhere in the nose of the Shuttle soon after they hit the atmosphere during reentry. If I recall correctly, I think it was in the cockpit area. Although there was of coarse no reference scale, this shock looked quite thick. Much thicker than 10**-4 cm. So obviously, the flow regime has something to do with it. Anderson, in his intro book to Fluid Dynamics, was really talking about the normal flow regimes one encounters in aerospace engineering. The Shuttle on the other hand was immersed in a high altitude (low density) high temperature flow. And there was obviously a difference in the shock widths. So, continuing to run this down ... . I have another book in my collection entitled "Gasdynamic Discontinuities", by Wallace D. Hayes, published as Volume 3 of the Princeton Aeronautical Paperback series, in 1960, by Princeton University. This book has some interesting insights on shock waves. It states: "Gasdynamic discontinuities are not discontinuities in the strict sense. A shock has a finite thickness across which the physical properties change continuously. ... If thermodynamic equilibrium is disturbed, a characteristic time must elapse before equilibrium can be approximately reestablished. This times the velocity of the fluid defines the characteristic distance, which is of the order of the mean free path [between molecular collisions], or better. If the physical and chemical changes occurring in the discontinuity are sufficiently slow so that the thickness of the discontinuity is large, compared with this characteristic distance, the concept of thermodynamic quasi equilibrium may be considered to apply." Now in Anderson's "Hypersonic and High Temperature Gas Dynamics", he goes into some interesting discussion regarding the mean free path between the collision of air molecules. The mean free path between the collision of air molecules, down here where we all live and breath is around 2.2 * 10**-7 ft, or around .73 * 10**-5 cm. It's interesting to compare that with the average shock thickness of 10**-4 cm from Anderson's "Introduction to Flight" book looking for the 1 or more mean free paths mentioned from the Princeton book. Clearly there is room inside the shock for many (namely 10) mean free paths. Anderson also mentions at the very high altitude of over 300,000 ft, the mean free path between the collision of air molecules is on the order of 1 ft! So not only would we expect shocks to be thicker at that altitude, which explains what I saw on the Shuttle video, but Anderson mentions you could feel the strike of each air molecule if you stuck your arm out at that altitude. So, when you're flying your open high altitude saiplane at 300,000 ft, and stick your arm out to signal a turn, you'll feel each of the air molecules hitting your hand! Larry ------------------------------ Date: Tue, 05 May 1998 12:09:27 -0700 From: patrick Subject: Re: Shock Wave Thickness Alright Wei-Jen, no more questions. At least not the kind Larry can answer! patrick@e-z.net ------------------------------ Date: Thu, 07 May 98 04:52:28 GMT From: betnal@ns.net Subject: Re: Re[2]: It's Offiical On 5/5/98 11:50AM, in message <9805058943.AA894390952@cc.pmsc.com>, gregweigold@pmsc.com wrote: > Gee, you mean the NASP won't be operational before then? :-) > > As long as they don't cut the airframes up, I guess they might be > resurrected again, but then they ought to rename them Phoenix!! > > Greg W. > > > ______________________________ Reply Separator _________________________________ > Subject: Re: It's Offiical > Author: at INTERNET > Date: 5/4/98 11:46 PM > > To keep them from being resurrected is why they're being sent to DM. To make it > too expensive. Plus, the cutting gear is there. ------------------------------ Date: Thu, 14 May 1998 16:20:25 -0700 From: patrick Subject: 3 - 2 - 1 - Test Away! 980661. Air Force Space Command reworking how it gets to space by Tech. Sgt. Timothy Hoffman Air Force Space Command Public Affairs PETERSON AIR FORCE BASE, Colo. (AFNS) -- Air Force Space Command will reduce government launch costs by 25 to 50 percent by transitioning most of its space launch activities to the commercial sector by 2004. "Our core competencies are concentrated in operating in space, not in getting to space," said Brig. Gen. Robert C. Hinson, director of operations for AFSPC. "We operate satellites, provide missile warning, monitor space weather, ensure global communications and navigation, and track space debris -- and integrate it all with the warfighter and other agencies who need it. "Launch is vital to getting these systems on orbit and our launch wings do a great job. But even today, civilian contractors possess the manning and technical expertise for launch processing and execution," said Hinson. The major migration of the space launch mission from the military to civilian contractors is made possible by an evolution of new thinking on how the command approaches space launch operations and the economic benefits of the rapidly expanding commercial space sector. "We are now concentrating on gaining insight with our launch contractors rather than providing oversight," said Hinson. "We have blue-suit maintenance people who never touch a wrench, operations people who never launch a booster -- in a time of declining manpower, we feel this is not the most efficient use of our highly trained people." So instead of telling contractors how to do something, now the command will only ensure the final product -- a launch vehicle and its payload - -- is on time and ready to go. "All we want is insight to the process that says: 'You, Mr./Ms. Contractor, have done everything you claimed to do for us to have a successful mission. You have taken into consideration and provided safety, security and infrastructure protection, so collectively we can have a successful launch,'" said Hinson. "AFSPC will continue to demand a focus on safety, security and resource protection regardless of the type of system being launched at Vandenberg Air Force Base, Calif. and Cape Canaveral Air Station, Fla.," added Hinson. "Collectively, AFSPC and the launch contractors remain very serious about our attention to these areas and protection of local communities adjacent to these national ranges." The general sees launch bases or spaceports running very similar to the way commercial airports are today. Each contractor will have an area or launch complex it builds, maintains and launches from -- just like an airline's own terminal at a major airport. Contractors will be responsible for all the operations and maintenance costs associated with their activity. "This will relieve the Air Force of a tremendous O&M (operations and maintenance) bill and free up thousands of government man-hours. Combined, we are talking about millions of dollars," Hinson said. Another driving factor in saving the Air Force money is the sheer volume of commercial space activity. In the 50s, 60s, 70s and most of the 80s, the military and government agencies accounted for more than 90 percent of all launch activity. This year, according to Hinson, approximately 48 percent of all space launches will be for commercial corporations. The commercial competition, greater number of launches, and improved technology have all combined to lower the cost of getting to space. "As our heritage systems (intercontinental ballistic missile-based launch vehicles like the Titan, Atlas and Delta) are phased out, and as the Evolved Expendable Launch Vehicles come online, we eventually expect to see up to a 50-percent savings in the cost of getting to space." Both versions of the EELV, one made by Boeing and one by Lockheed Martin, are expected to be operational by 2002. They will launch both military and civilian satellites. The money saved by these initiatives is needed to address a major problem for the command -- rapidly aging ground stations. "We have a huge need for money to upgrade and maintain those ground systems that support our satellites," said Hinson. "As the scope of our mission broadens and we bring new systems like SBIRS (Space-Based Infrared System) on line and upgrade existing satellite constellations like GPS (Global Positioning System) we have to continue to upgrade the ground systems that control and communicate with those satellites. "We need this end-to-end systems architect so we can meet the needs of the warfighters in the field. We, AFSPC, need to be the focal point for the operation and funding of these systems so that all U.S. forces and our allies have access to the critical resources and information delivered from space," explained Hinson. "Again, a lot of this will be made possible by reducing the cost of getting to space." The vast and rapidly approaching changes coming to the launch business will affect a lot of military people -- this hasn't been lost on the command's leadership. "Everyone will have a job," said Hinson. "There will still be some semblance of launch squadrons that will provide insight and coordination with the contractors. There will be jobs at both ranges on the East and West Coasts. This command also has a large requirement for people to operate and fly satellites and work in the ICBM force." The general was quick to point out that the transition will take place over several years. By 1999, both the 30th Space Wing at Vandenberg AFB, Calif. and the 45th SW at Patrick AFB, Fla., will be down to one launch squadron each, consisting of several flights. "Then as the EELV comes on line in 2002, we will have to use some of those folks to transition to the new system. We are currently working to define specific tasks we want the EELV flight to take on. "At the same time, the contractors will be transitioning from the Atlas, Delta and Titan programs to their own versions of the EELV. We will need a squadron structure to handle this; then we will downsize out of those systems sometime in the 2003 to 2004 timeframe," said Hinson. Other military missions at Vandenberg and Patrick are expected to remain intact. Vandenberg will continue as the main training base for satellite and ICBM specialists, maintain its follow-on test and evaluation launches of ICBM systems and continue operating the Western Range. Patrick will run the Eastern Range, support NASA, and continue to support the Navy's sea-launched ballistic missile test program. Both bases are expecting to see a surge in commercial launch activity. "The command's people are the key to this successful transition," Hinson said. "In concert with the civil and commercial interest, these efforts will enable us to transfer investments to do things in space rather than paying the huge costs to get there." (Courtesy of AFSPC News Service) ------------------------------ End of skunk-works-digest V7 #27 ******************************** To subscribe to skunk-works-digest, send the command: subscribe in the body of a message to "skunk-works-digest-request@netwrx1.com". If you want to subscribe something other than the account the mail is coming from, such as a local redistribution list, then append that address to the "subscribe" command; for example, to subscribe "local-skunk-works": subscribe local-skunk-works@your.domain.net To unsubscribe, send mail to the same address, with the command: unsubscribe in the body. Administrative requests, problems, and other non-list mail can be sent to georgek@netwrx1.com. A non-digest (direct mail) version of this list is also available; to subscribe to that instead, replace all instances of "skunk-works-digest" in the commands above with "skunk-works". Back issues are available for viewing by a www interface located at: http://www.netwrx1.com/skunk-works If you have any questions or problems please contact me at: georgek@netwrx1.com Thanks, George R. Kasica Listowner