Jonfliesgoats

Has anyone had a chance to compare Galileo to GPS and GLONASS? Any significant diffferences in terms of satellite acquisition?

Cute

I wonder if a system of inflateable modules would make the craft look like a bunch grapes merged with trusses and antennae?

To be fair to NASA, they are subject to the whims of the American electorate and politics.

Lots of water in Ceres! http://www.space.com/35052-water-everywhere-on-dwarf-planet-ceres.html

Agreed, PB666. Economics killed the DC-7 as jets became more sustainable. People are knocking the motor more than the airframe (get it? Knocking the motor! I amuse me!). That said, extracting more power from reciprocating engines lead to increasing complexity in props and other devices. By the time you have have turbo-supercharged, with umpteen or tens of cylinders, hydromechamical controllers for auto-mixture, waste gates, and other things you have a pretty complicated piece of gear with lots of points for failure. Honestly, I am amazed we didn't see more troubles with fires, uncontained supercharger failures, etc. I repeat myself, though. Also, along the lines of the DC-7 getting a bad wrap, other prop liners with more successful reputations fell out of the first-world market around the same time. Constellations and Stratoliners were off long-haul routes only a short time later. Short-haul recips, like Convair 440s, lasted a while longer until turboprops made it onto the scene with decent reliability. The C-46, which came out some years earlier, had some pretty bad teething problems associated with fires and en electromechanical propeller system. We did work through those problems until the C-46 was relatively safe and reliable. So timing is certainly a factor. Was production of reciprocating airliners ended early? I don't know. You mention some of the cost and teething problems associated with the DC8 and 707. At the time it was obvious, due to power and thrust loading, that jet power was the future. You can extract more thrust from an engine weighing only a fraction of the equivalent reciprocating engine AND the jet engines liked high altitudes better than similar props. So getting an early start pushing your next generation of plane makes some sense, considering the difficulty in setting up production lines, etc. What wasn't obvious was the maintenance reliability and safety of jets at the time. Only a few years earlier the DeHavilland Comet was crashing. It would have been reasonable, considering the high temperatures and stresses involved in turbine engines, to expect some more catastrophic events from, what was then, a technology new to the commercial market. So a decision to keep making propliners would not have been unreasonable. Early jets after the Comet did pretty well, it turns out. Yeah, there were noise and pollution issues. The ability to load more people and bags onto these planes drastically reduced the cost per seat per nautical mile, however. D.C.-8s stopped flying for UPS not ten years ago. The last D.C.-9 stopped flying for Delta only two years ago while MD80s and 90s keep flying. 727s and other craft can still be found on freight ramps and in the third world. Sadly, Convair's 880 never quite made it and the company eventually disappeared. The only 880 I can find is in Graceland, only a few miles from where I type now. Reciprocating engines aren't dumb. We got a lot of know-how from making complicated reciprocating motors during the Second World War and Postwar years. The huge, complicated messes of systems that made for very high performance reciprocating engines, contra-rotating propellers, and elaborate control systems display a lot of brilliance in solving problems. Perhaps, when electric props are the norm, people will say similar things about the reduction gear boxes and accessory systems associated with turboprops?

Great reference regarding the DC-7! There are DC-6s flying in Alaska to this day, but DC-7s are quietly collecting dust and mouldering in Cotonou and N'djamena. They are relics of the JCA airlift into Biafra from the late 60s. Here's a link to the constellations parked at São Tomé from the airlift. They were more reliable than DC-7s, but faced similar economic pressure from simpler jets with higher thrust and power loadings. These planes still have the fish in their tails from JCA. The DC-7s and 6s rotting in nearby airports were likely left over from the airlift, but I can prove their heritage. Still, you see them rotting at the corners of W. African airfields along with BAC 1-11s, a handful of Tridents and growing numbers of 727s.

Chemistry is awesome! Our understanding of itty-bitty physics grew from and involves chemistry. Chemistry drives at the nature of what and who we are.

It's actually hard to find a well-produced video about the axiom of choice. Here's a decent presentation by a TA at Cornell. He has a thick, Indian accent but his presentation is accessible to the lay person.

Concrete is awesome! Roman architecture wouldnt be as cool without it! Scented candles are part of modern, human mating rites. Go chemistry!

Another piece of information related to this has to do with TCAS/ACAS. in a previous life, we mounted some extra devices on a plane that was going to be shipped overseas. The TCAS on the plane got some weird interference that caused azimuth information to go wonky while range to targets displayed remained normal. Eventually a new location for the TCAS antenna had to be found and the system recertified. What was eye-opening about this was the number of blind spots that exist in most TCAS systems. Even after recertification a target would disappear off TCAS entirely when we flew into a certain position and reappears when we gently turned a few degrees another way. Also degradation of antennae can exist without causing any fault messaging in a lot of the systems, as we found out by pulling components and testing them. So a lot of what we read about regarding the necessity for visual vigilance still remains. There are ICAO-defined standards that these systems have to meet to make certification, but even a system that passes certification and meets design requirements will have a lot of inherent weaknesses. The simpler a particular system is designed, the fewer hidey-holes unknown weaknessses have to exist. Weaknesses that are known and appreciated can be handled with different procedures, complimentary equipment etc. In trying to hang a new lump of stuff off a production airplane, the team I was on wound up chasing these technical rabbits throughout an airplane's avionics and electrical system. KISS is really important.

Great input, Green Baron! Aviation pulled heavily from maritime and naval techniques and procedures. This is why we have the conventions regarding navigation lights, passing, right of way, etc. With regard to constant bearing, depending on where/what you learn, we don't really teach constant bearing as a means of judging WHETHER a collision is a risk. Aircraft nearby can and do maneuver onto collision courses and away from them. We do, however, teach that a thorough and deliberate visual scan is important because the greatest hazards don't always jump out at the pilot with relative motion. Also, with regard to your experience flying props, it is valuable experience and you have as much unique insight into observations made as anyone. Humility is admirable, and qualifying your experience is good for information. This said, the chest thumping that remains rampant in aviation is something that stops people from sharing ideas and harms us. Your input is as valuable as anyone else's. Even in a video game forum, we are better off with your viewpoints shared than otherwise.

Here are some goofy and some pretty wise suggestions from U of Maryland: http://spacecraft.ssl.umd.edu/akins_laws.html

Here's a video about infinity and reality presented by someone more eloquent and concise than I am. Enjoy!

Here's that archive: http://www.utdallas.edu/library/specialcollections/hac/cataam/

The original Strela (SA-7) would roll its entire airframe in flight and maneuver only about a single axis. That was a pretty simple solution to the problem of packing enough guidance and attitude control into a man-portable SAM. The sights of the first Strelas were aligned with the launch tubes. This meant an operator had to superelevate their launcher (or engage a target more than thirtyish degrees above the horizon) or else the missile would splat into the ground in front of you before it's boost motor could ignite. So it took a little bit of training to use this system well. There were/are issues regarding the thermal salt batteries used for seekers, too. The Blowpipe took a lot of training. Later versions solved this problem by tilting the sight so the launch tube was automatically super-elevated in any engagement. On a related note, In the West we tend to think our effort to push Stingers and Blowpipe missiles into Afghanistan during the Soviet War in the 80s was the first time MANPADS had a strategic impact. This is an artifact of Western transparency and pop culture. In the final days of the Vietnam conflict HUMINT and other sources reported strange new weapons being smuggled into South Vietnam. During the final drive by the North Vietnamese into the South, SA-7s made an appearance and were responsible for shooting down a South Vietnamese AC-119. There were other engagements with these weapons in the quiet wars in Laos and Cambodia. My point is that new weapons technologies cross borders and are used much quickly than we generally believe. There's a really good archive preserved at the University of Texas at Dallas for interested parties. Here is an article regarding some field engineering on these systems: http://armamentresearch.com/improvised-manpads-batteries-employed-in-syria/

As I move into earlyish middle age, I find sticking my nose where it doesn't belong usually pays big dividends. If you chase strange leads down, you wind up studying and working in some really unique niches. Also, chemistry is far from boring. If you want to do something "expeditionary"with chemistry, I am sure there are ways.

There have been unmanned helicopters for a while. There was even a Kaman UAV that worked a few logistics missions in Afghanistan. This is one of Boeing's takes on unmanned helicopters. http://www.boeing.com/defense/unmanned-little-bird-h-6u/

I wonder if this will usher in a new, modular, satellite system? The ability to remove and replace components without a manned EVA is pretty neat.

The evolution of self-guidance systems has really been fascinating, It's really interesting to learn how different engineering teams tackled similar challenges, especially before solid state electronics became viable. There are really useful tactical applications of this wonky knowledge too. In real life a lot of this knowledge regarding modern systems can't be discussed here. Legacy systems, some of whose details make it into popular games and books are fair game. Optimizing warheads for specific applications is another fascinating design challenge too.

https://warisboring.com/nasa-just-ordered-a-robot-that-can-repair-satellites-in-orbit-44027c3f7e1a#.frb9h7smj

I should have searched. Curse my lazy thumbs!

You know, this is why I am always impressed with folks that pull stuff off like this. There are some pretty neat solutions in IRCM and IRCCM too.

This uses a quote from Wikipedia; not from any AFTTP, etc. Pilots learn that two aircraft on a collision course have no apparent motion in the cockpit. So planes that appear to be moving aren't going to hit you without a course change, while stuff that will hit you will appear fixed or nearly fixed, blending in with cultural lighting, stars, etc. This is why deliberate visual scanning still remains important. The same principal is used to automatically compute appropriate lead in some Air to Air missiles. Rather than use an eleaborate lead computing algorithm that depends on a processor and rapid communication to relevant servos, some missiles make course adjustments by change in relative bearing to target rather than relative bearing itself. Pretty neat, eh? This is why you should hug an engineer! (Engineers hate hugs, though.) "The Sidewinder is not guided on the actual position recorded by the detector, but on the change in position since the last sighting. So if the target remained at 5 degrees left between two rotations of the mirror, the electronics would not output any signal to the control system. Consider a missile fired at right angles to its target; if the missile is flying at the same speed as the target, it should "lead" it by 45 degrees, flying to an impact point far in front of where the target was when it was fired. If the missile is traveling four times the speed of the target, it should follow an angle about 11 degrees in front. In either case, the missile should keep that angle all the way to interception, which means that the angle that the target makes against the detector is constant. It was this constant angle that the Sidewinder attempted to maintain. This "proportional pursuit" system is very easy to implement, yet it offers high-performance lead calculation almost for free and can respond to changes in the target's flight path,[7] which is much more efficient and makes the missile "lead" the target."

Speaking of armor in movies, it's all wrong, especially for women. Surface to Air and Air to Air missiles are always in a boost phase and never in a ballistic phase in the movies. You always have nice trails of flame and vapor to look for rather than scanning visually for a nearly invisible rod traveling toward you at Mach 3. I know the ballistic phases of these missiles are less spectacular for film, but it's all wrong. These things are still dangerous after their motors burn out. Also, missiles in the movies rarely spin. Many man-portable systems roll and corkscrew in flight.