X-37B Secret Space Plane To Land Soon 252
Phoghat writes "The highly classified X-37B Space Plane is scheduled to land soon. It was launched from Cape Canaveral in Florida on April 22 atop an Atlas 5 rocket, and the Air Force is still being very secretive on all aspects of the flight. We do know that it's set to touch down at Vandenberg Air Force Base's 15,000-foot runway, originally built for the Space Shuttle program. In many ways, the craft resembles a Shuttle with stubby wings, landing gear and a powerful engine that allows the craft to alter its orbit (much to the dismay of many observers on the ground). Its success has apparently given new life to its predecessor, the X-34, which had been mothballed."
Re:Launched April 22? (Score:1, Informative)
No it's been in space.
Re:Black and White (Score:3, Informative)
Sorry but what do you mean black? Only the bottom looks black to me. It looks like almost the same colors as the shuttle. A lot of the colors are for thermal management and some because that is the color of the material. Almost none of it is "paint" except for some of the id stuff.
paint doesn't tend to do well at those temps.
Re:Black and White (Score:3, Informative)
Try reading before posting next time....
From your answer:
Emmisivity, or the ability of a black body to radiate or re-radiate in some cases, is highly dependent on many variables. Try re-asking the question.
Re:Launched April 22? (Score:2, Informative)
"The X-37B has the requirement to be on-orbit up to 270 days,"
http://spaceflightnow.com/atlas/av012/100225x37arrival/ [spaceflightnow.com] http://en.wikipedia.org/wiki/USA-212 [wikipedia.org]
Re:Taxpayers get shit on.. End black budgets (Score:2, Informative)
Personally, I blame the Vampirates.
Re:Can anyone tell me? (Score:5, Informative)
The direction of that fall is mainly controlled by the forward motion of the craft and the centrifugal effect by that speed allows it to stay in orbit above the atmosphere.
So once you start breaking this forward speed, usually by firing rockets, the gravity starts to win from the centrifugal force and the craft starts to come down.
When you brake carefully the craft will slowly enter the atmosphere and now be slowed down when encountering the high altitude atmosphere, the problem is the speed at that time is still extremely high causing a lot of friction heat.
Would you brake hard with the rockets the craft would fall out of orbit much quicker and enter the denser parts of our atmosphere much sooner causing extreme friction braking and heat, basically the craft would burn up like a meteorite.
So the trick is to brake in a sensible way and have a craft that can withstand the inevitable friction heat long enough to slow down and enter navigable levels of the atmosphere where the wings can take over.
Re:Black and White (Score:5, Informative)
Black items will ABSORB more light. When light (i.e. the energy contained in a photon) is absorbed by a molecule, there are a certain number of likely fates for this energy. Remember, 'what goes up, must come down'
Yes, remember that. Black items will absorb more light, and also radiate exactly that much more heat.
The perfect absorber is also the perfect transmitter. Anything else would be a violation of the first law of thermodynamics, and we can't go around breaking them laws, now can we?
Re:Launched April 22? (Score:3, Informative)
Nope, it hasn't been in the air for seven months - it's been in orbit for seven months. Which isn't particularly noteworthy as far as orbital lifetimes goes.
We've had spy satellites with that capability for over thirty years - and much better ones than this spaceplane can ever be, since they have payloads considerably larger. (Think orders of magnitude.)
Re:Black and White (Score:4, Informative)
Yes, remember that. Black items will absorb more light, and also radiate exactly that much more heat.
Yeah but for a heat shield some heat comes from conduction and that is the same regardless of the albedo of the surface.
Re:Can anyone tell me? (Score:4, Informative)
I was looking at the photos and was thinking about the wing size. "That's because they fly very fast because they re-enter the asmosphere really fast." But then I thought "why do they need to re-enter that fast? Surely they could use the atmosphere to slow themselves down, and enter at a much slower, cooler and more relaxed pace." Then I thought "well maybe the gravity has a fair amount of time to act on the craft before the atmosphere really begins, therefore giving plenty of opportunity for speed, well before a viable way to slow down"
Am I right? Does someone have a better explaination?
Here's a link with the basics: Nasa's Landing 101 [nasa.gov]
When the shuttle de-orbits, it fires it's engines in the opposite direction to it's orbit's travel to slow it's forward velocity, which is several magnitudes faster than ground speed (17239.2MPH for the ISS). At this point, the shuttle's inertia stops counteracting the pull of gravity, and the shuttle starts "Falling", like swinging a bucket full of water around on a string, then slowing down the rotation.
Given that there is no atmosphere at this height, the shuttle can accelerate (at 9.81m/s^2) to speeds well in excess of "terminal velocity" as there is no drag to slow it. It typically hits the atmosphere (80 miles up) after 30 minutes of freefall, travelling at speeds of at least twice the speed of sound.
The orbiter then uses it's aerodynamic profile to control its descent, making a series of sharply banking turns to brake it's speed as it descends through the atmosphere, the friction of the air moving against the underside of the orbiter heating the heatproof ceramic tiles up to white hot.
So, here's the answer to you question is "Because gravity has been pulling them down for half an hour before they even hit the atmosphere". In theory, they could use retro thrusters to brake their descent before they hit the atmosphere (Like the Apollo missions did with their lunar landers), but as that would take immense amounts of fuel (close to that required for blast-off) it would make the orbiter's payload capacity virtually nil. Therefore it is easier for them to take the descent into the atmosphere with the best high-speed aerodynamics they can, using the friction of wind resistance to slough off the excess speed, trading it for heat that can be dealt with as they aerodynamically slow their descent and approach the ground at a safe speed.
Re:I, for one, have childlike faith... (Score:2, Informative)
Re:Offensive (Score:2, Informative)
Tom:
Tell your woman to get her own damned Slashdot account.
That is all.
Please read my slashdot profile [slashdot.org].
Or you could read this article from linuxinsider [linuxinsider.com]:
That is all;--p
-- Barbie
Re:Physics fail (Score:3, Informative)
The emissivity of a material (usually written or e) is the relative ability of its surface to emit energy by radiation. It is the ratio of energy radiated by a particular material to energy radiated by a black body at the same temperature. A true black body would have an = 1 while any real object would have
http://en.wikipedia.org/wiki/Emissivity [wikipedia.org]
Re:Black and White (Score:2, Informative)
Ughhh. Wrong. White paints can rival some of te darkest paints for high emissivity. The critical issue is the alpha to epsilon ratio, or the ratio of absorption to emission. I do this for a living...the black is likely used to minimize reflection. In other words, to remain optically stealthy. That's it. Heck, regular white appliance epoxy comes close to .94 emissivity with only around .20 absorptivity. It's gleaming white, and comes close to fancy black coatings by Lockheed or others. The difference? I can see the mission from 300 miles away after launch with a small celestron telescope with no problem...just look for the large flash. If it were black, I doubt I'd ever find it downrange. Nothing fancy or mysterious about hwy they are doing this. The last thing they want is a mission making Iridium-like flashes all over the place. It's a significant part of the design for a lot of these satellites.
Re:Visibility? (Score:3, Informative)
It's about +3.5 average (2.2 - 4.5) magnitude. It's orbital inclination is 40 degrees making it visible in the twilight sky when conditions are right anywhere between about 45N and 45S latitudes. It's orbital altitude is getting lower and it is maneuvering, both of which make predictions of where to look less precise, but http://www.heavens-above.com has predictions. It travels west to east.
Re:Offensive (Score:2, Informative)
which part of you got offended the most? The 49 yo, the grandmother, the feminist or the c programmer?
I'm thinkin 20 years of programming is going to make anyone a bit touchy.
The person to whom you're responding basically cuts and pastes that same response to most every story. It's bogus - the story didn't include the supposed statement that "offended" them.
I'm beginning to suspect it's a 12-year-old boy that thinks repeatedly posting that same anonymous response is funny.
Re:Offensive (Score:2, Informative)
It also has to with earning power. By the time a man hits 45 or so, he's probably achieved either the best income he will ever have, or at least a lot more than he had at age 20 or 25. Generally he has solidified his standing in his job and community and is successful (or not). Trends should be set to keep him heading in that direction for the rest of his work career.
So now that he has the cash, he wants to acquire the toys he always wanted. Usually this is sports cars, motorcycles, boats, collectibles and memorabilia, and arm candy. All things the man wanted when he was 20-25 but could not afford or obtain.
20-something women aren't looking so deeply at his 401(K) and stock portfolio. The 40-something woman is normally deeply concerned with property resale value and ROI and doing things that perhaps make financial sense but are extremely boring. The man wants to live on the edge. It's part of being male. The woman wants to blunt that edge and make sure nobody runs with the scissors. This increasing incompatibility is what starts to fractures marriages.
A young woman into having fun matches the desires of the middle-age man to have fun and reject the pile of responsibilities set upon him.
I'm in my 40's and making a good living. About age 38, all by itself, a Mazda Miata suddenly started seeming like a reasonable transportation solution. Previously I had ridiculed that kind of car purchased by a friend during his midlife. I did not go buy that car. My existing boring car is fine. But I have ramped up buying collectibles because I want them and my income supports it.
There is no wife telling me not to and I'd absolutely bristle at the idea of such a thing. So finding a wife my own age is simply impossible. I'm not going to surrender who I am for such a thing. Not now.
That said, I haven't had any luck with the younger arm candy. Oh well.