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Mach 10 X43A Flight Successful

Sector Bug writes "NASA's X43A research aircraft made its third and final flight today, firing its scramjet engine at Mach 10 (7,000 MPH) or close to it, setting a new record. "

77 of 370 comments (clear)

  1. Speed comparison question by Drakonian · · Score: 5, Interesting

    A (possibly stupid) question: How does this compare to the speed of orbital rockets?

    --
    Random is the New Order.
    1. Re:Speed comparison question by Holi · · Score: 4, Informative

      Not even close.

      Hubbles orbital speed is approximately 16,900 miles per hour.

      --
      Sorry, teleporters just kill you and then make a copy. A perfect, soul-less copy.
    2. Re:Speed comparison question by cephyn · · Score: 4, Funny

      MPH? we still use that? I thought maybe in this age of newfangled units, we'd at least get like, .41 times that of the Hubble Telescope, or 34.7 times faster than a lambourghini diablo.

      --
      Moo.
    3. Re:Speed comparison question by Anonymous Coward · · Score: 2, Insightful

      Orbital velocity at an altitude of about 150 miles is about 17000 mph (approx 242 km altitude at 27000 km/hr...checked my memory on howstuffworks), so the rocket was going about 0.41 of orbital velocity. In other words, you have only 17% of the kinetic energy you need to maintain an orbit (since KE=0.5*m*v^2). Unfortunately, you have to reach sufficient velocity to coast to the altitude and speed you ultimately want while there is still enough oxygen around you to make the scramjet work. Interestingly, the geosynchronous orbital velocity is only about 7500 mph, but you have to do more work against gravity to reach that altitude.

    4. Re:Speed comparison question by Kehvarl · · Score: 2, Funny

      What's that come to in migrating swallows?

    5. Re:Speed comparison question by Fnkmaster · · Score: 5, Interesting

      While that is true, this is the first real scramjet implementation. Apparently, people think scramjets will go up to about Mach 15, or over 10,000 miles per hour. While still not low earth orbital velocity, it doesn't have to get there to be useful in getting to orbit.

      If a traditional rocket kicks in at Mach 15 to get the rest of the way to orbit, the savings in launch weight and thus cost from not having to carry all that oxidizer to get up to Mach 15 could still be quite large.

    6. Re:Speed comparison question by Christopher+Thomas · · Score: 3, Informative

      A related question, how does this (and the speed of orbital rockets) compare to the fastest man-made object (whatever that may be)?

      Particle accelerators accelerate anything from electrons and protons to ions close enough to C that the difference is academic.

      For macroscopic objects, I believe compressed-gas guns used for simulating micrometeorite strikes and for producing shockwaves to study things like the metallic hydrogen phase transition accelerate projectiles to tens of km/sec, or larger than but of the same magnitude as orbital velocities.

      Various other types of cannon (the so-called "ram accelerator", used to simulate scramjets, and various flavours of electromagnetic cannon) can also reach projectile speeds in the "greater than but still comparable to orbital" range.

    7. Re:Speed comparison question by frugle · · Score: 4, Interesting

      To allow particle accelerators you need to expand your parameters a bit to include natural objects accelerated by man.

      The fastest "man-made" objects - I would hazard a guess at probes sent from Earth to other planets. Voyager 1 travels at roughly 17.4 km/sec or 38,923 MPH

      This will all be put to shame by the Mini-Magnetospheric Plasma Propulsion system (M2P2) - which if it actually got into production and was launched could overtake Voyager1 (launched in 1977 with a 11 Billion Km head start) in 10 years.

      This M2P2 drive in a nutshell would create a 60 km wide magnetic field filled with plasma behind it, trapping the solar wind and propelling it to a predicted 180,000 mph.

      Let's just hope with all that trapped wind they have enough gaviscon to stop it when it gets where it's going...

      --
      http://www.frugle.co.uk/
    8. Re:Speed comparison question by Total_Wimp · · Score: 4, Interesting

      If a traditional rocket kicks in at Mach 15 to get the rest of the way to orbit, the savings in launch weight and thus cost from not having to carry all that oxidizer to get up to Mach 15 could still be quite large.

      I've heard the idea of using three stages in scramjet orbital launches. The first and third are rockets and the middle is the scramjet. It makes me kind of curious about using chemical propellants, like in a giant howitzer, to propell the scramjet to it's initial speed.

      I couldn't see this doing much for manned flight, but most of what we send up isn't manned anyway. It could also have some pretty kick ass millitary application, say for dramatically increasing the payload of current rocket propelled artillery rounds.

      TW

    9. Re:Speed comparison question by Kehvarl · · Score: 3, Funny

      African or European?

      Yes.

    10. Re:Speed comparison question by Anonymous Coward · · Score: 2, Informative

      Physicists use the metric system, but 16900 mi/h is indeed correct. To clarify this:

      Acceleration of Gravity = Acceleration Centripetal

      ((Gm)/r^2) = (v^2)/r

      G=6.67*10^-11
      m = mass of earth = 5.98*10^24 kg
      r = radius of Hubble from Earth core = 6980000 m

      ((6.67*10^-11)(5.98*10^24))/(6980000^2) = (v^2)/6980000)

      v = 7559.373392 m/s or 16909.83 mi/h

    11. Re:Speed comparison question by foniksonik · · Score: 3, Funny

      At least it doesn't refer to how many Horses equivalent are Powering the damn thing ;-p

      --
      A fool throws a stone into a well and a thousand sages can not remove it.
    12. Re:Speed comparison question by mfago · · Score: 2, Informative


      A related question, how does this (and the speed of orbital rockets) compare to the fastest man-made object (whatever that may be)?


      I thought the fastest man-made object was Pioneer or Viking at around 45k mph. However, a quick Google indicates that Helios supposedly traveled at 150,000 mph.

      I'm positing that the particles in particle accelerators are not "man-made" in this context.

    13. Re:Speed comparison question by Rei · · Score: 3, Interesting

      There's also some other proposals I've seen that use more stages - for example, turbojet->ramjet->scramjet->rocket, so the entire first stage is airbreathing. My favorite for (unmanned!!!) payloads is gun-launch -> scramjet -> rocket. You can to hypersonic velocities in a fraction of a second.

      --
      Nobody pushes buttons like our bunny. Big red buttons with labels that say "IGNITION", apparently.
    14. Re:Speed comparison question by Rei · · Score: 4, Interesting

      IAMAAE, but the reason that they're more economical is that you only need to carry up ~1/9 of your propellant mass during the airbreathing stage. For example, a LH/LOX rocket uses 2 H2 + 1 O2 -> 2 H2O; For molecular weights, H2~=2, O2~=32; thus, the ratio is (32+4)/4 -> 9 times as much mass for the LH/LOX rocket.

      More importantly, however, is the fact that the more mass your craft has, the more energy it takes to accelerate that mass; consequently, craft masses grow geometrically with a given desired increase in delta-V. The net benefit from only needing to carry up your fuel is staggering. Even if you use a hydrocarbon fuel (much denser, which is a very good thing, plus often not cryogenic), you're still going to get at least a 6-fold instantaneous mass difference (which, again, becomes more dramatic as you factor in how much it saves you from having to accelerate propellant).

      Also, they're theoretically simpler, lower maintainance, and less likely to fail because of the reduced number of moving parts. They're just in general Good Things(tm). :)

      --
      Nobody pushes buttons like our bunny. Big red buttons with labels that say "IGNITION", apparently.
    15. Re:Speed comparison question by mintrepublic · · Score: 2, Funny

      Well, it depends on its air-speed velocity while carrying a medium-sized coconut.

    16. Re:Speed comparison question by r_jensen11 · · Score: 2, Funny

      My friends and I have given up on inches, meters, yards, miles, etc, and have substituted them all with yey's. E.g: How big is book? About yey thick. How far away were you? About yey far. How fast did you end up driving? Meh, yey fast.

    17. Re:Speed comparison question by mazarin5 · · Score: 5, Funny

      To allow particle accelerators you need to expand your parameters a bit to include natural objects accelerated by man.

      No no no, you're looking at it all wrong...

      The particle accelerator is a man-made object accelerated to 0.99c.

      You just have to use the electron's frame reference!

      --
      Fnord.
    18. Re:Speed comparison question by the_2nd_coming · · Score: 2, Informative

      ummm.... the difference is 30 years of rocket since, very low oxidizer levels, and the use of some very familiar jet technology.

      --



      I am the Alpha and the Omega-3
    19. Re:Speed comparison question by mrgsd · · Score: 2, Informative

      It's called Kilometres per hour :)

      --
      End Communication.
    20. Re:Speed comparison question by Fnkmaster · · Score: 2, Interesting

      Or rail gun (i.e. electromagnetic propulsion launch) for the first stage. That would be frickin' cool. Rail gun->scramjet->rocket. And as a bonus, we could put Fed Ex out of business with a rail gun->scramjet unmanned terrestrial package delivery system using the same infrastructure.

    21. Re:Speed comparison question by gadget+junkie · · Score: 2, Informative

      "I couldn't see this doing much for manned flight, but most of what we send up isn't manned anyway. It could also have some pretty kick ass millitary application, say for dramatically increasing the payload of current rocket propelled artillery rounds."

      Funnily enough, studies about that go back a long way, circa 1930. dr.Sanger eventually studied a Ramjet powered design, a model of which is in the Deutsches Museum in Munich, Germany. It would have been a cheaper alternative to the Space Shuttle, with a mother vehicle starting from a plain aerodrome and an orbital vehicle piggybacking on it. Basically the mother vehicle is the same concept inferred for the mysterious project Aurore Recce aircraft.

      The military have always been attracted to these concepts, witness the Dynasoar in the late fifties, but the rationale is the same for civilian uses; higher efficiency and flexibility in bringing payloads in low earth orbit or suborbital flight.

      --
      "If a boss demands loyalty, give him integrity. But if he demands integrity, give him loyalty." (John Boyd, 1927-1997)
    22. Re:Speed comparison question by CrimsonAvenger · · Score: 2, Informative
      Yes, you are.

      You run H2 rich fuel mixtures to lower the average molecular weight of your exhaust stream, which increases the exhaust speed for a given combustion temperature. Exhaust speed is proportional to Isp, and high Isp is good.

      I get that figure from the Space Shuttle and Saturn systems. Though I believe that there are some 1:6 ratios out there these days.

      Keep in mind it's a matter of tradeoffs. 1:9 gives you smaller tankage, but lower Isp. Higher fuel:oxidizer ratios increase the size of the fuel/oxidizer tanks, but increase Isp. SO you aim for the "ideal" balance, and we seem to have settled around 1:5 as our ideal point.

      --

      "I do not agree with what you say, but I will defend to the death your right to say it"
  2. With apologies to Marvin by daeley · · Score: 5, Funny

    X43A blurs past the camera. It is silent.

    Marvin: "Where's the kaboom? There was supposed to be an earth-shattering kaboom!"

    EARTH SHATTERING KABOOM!

    Marvin: "At last!"

    --
    I watched C-beams glitter in the dark near the Tannhauser gate.
  3. I guess it is the first 7000MPH post by roman_mir · · Score: 5, Funny

    we shall call it the ludicrous speed.

    1. Re:I guess it is the first 7000MPH post by double-oh+three · · Score: 2, Informative

      To apply Spaceballs retroactivly;

      At the breaking of the 60MPH:

      We shall call it ludicrous speed.

      At the breaking of the sound barrier;

      We shall call it ludicrous speed.

      At the breaking of the speed needed for stable orbitals;

      We shall call it ludicrous speed.

      The point is that we will always be breaking the limits we set now, so to call it ludicrous speed is ok, but the speed will likely be pedestrian in a few years. There's always a speed barrier we'll be breaking.

      --
      "For years, I struggled with reality... but I'm happy to say I finally won out over it." -- Elwood P. Dowd
    2. Re:I guess it is the first 7000MPH post by DarkHelmet · · Score: 2, Funny
      You stole the idea for my post, and I want it back!

      Signed,
      DarkHelmet

      --
      /^[A-Z0-9._%+-]+@[A-Z0-9.-]+\.[A-Z]{2,4}$/i
    3. Re:I guess it is the first 7000MPH post by roman_mir · · Score: 2, Funny

      I guess you should have protected it with a better numeric combination then!

  4. NASA sure has come a long way. by Neil+Blender · · Score: 3, Interesting

    Since their first scramjet, the A-1A, flew at 7 feet per second.

  5. News Delayed by iamlucky13 · · Score: 2, Informative

    Meanwhile, CNN is still reporting the flight as being delayed on the front of their Science and Space page.

    1. Re:News Delayed by That's+Unpossible! · · Score: 3, Funny

      It takes a while for them to catch up because CNN is only operating at Mach 9.

      --
      Ironically, the word ironically is often used incorrectly.
  6. Also last flight of the B-52B mother ship ... by xmas2003 · · Score: 5, Interesting

    The B-52B (tenth off the assembly line) first flew on June 11th, 1955 and among other things, has carried the X-15, Shuttle solid rocket booster, and finally the X-43A (on the same pylon as used by the X-15). Read more about the ol' BUFF at NASA.

    --
    Hulk SMASH Celiac Disease
    1. Re:Also last flight of the B-52B mother ship ... by Wyatt+Earp · · Score: 4, Informative

      It's the last flight of the B-52B mothership, but it is being replaced with an H

      http://www.dfrc.nasa.gov/Gallery/Photo/B-52/HTML /E C03-0258-04.html

      Parts for the engine were becoming rare and costly for the B

  7. Mach by MikeMacK · · Score: 5, Funny
    "Mach Number" was named after the Austrian physicist Ernst Mach.

    I understand he was a very fast guy, much to his wife's chagrin.

  8. Good by Dark+Paladin · · Score: 4, Funny

    Now, when I tell those guys I want my pizza in 30 minutes or less, there is no excuse!

    1. Re:Good by sik0fewl · · Score: 2, Interesting

      Unless, of course, you live on the far side of an airport and they can't get clearance to fly across it. In that case (assuming they had to fly all the way around the world the other way) your pizza would take about 3.5 hours to arrive.

      Still better than some places I've ordered from.

      --
      I remember when legal used to mean lawful, now it means some kind of loophole. - Leo Kessler
  9. Guinness Record by Embedded+Geek · · Score: 3, Funny
    In case you're wondering, it beat its own world record (Mach 6.83, 5000MPH) set back in March.

    By the way (and massively OT), doesn't a "Guinness Record" sound like something you'd like to break yourself, at least if it involved consumption?

    --

    "Prepare for the worst - hope for the best."

    1. Re:Guinness Record by Haydn+Fenton · · Score: 2, Informative

      Highly Off-Topic, but yes..

      The McWhirter twins, IIRC. One (or maybe both) of them were obsessed with quirky facts. Then in 1950 they set up a business together to sell facts to newspapers. Roughly at the same time, the managing director of Guinness had an argument about the fastest bird in Europe but couldn't find any facts on it. Somehow, they ended up in contact with eachother and made the book we know as the Guinness Book of Records. Although they did have certain rules about what would and what wouldn't get put into the book.. no supernatural records (obvious reasons, I guess), no sex records (was to be a family book), no criminal feats (didn't want people doing illegal things to get into the book), and no records like eating the most marshmellows at once (didn't want people to die in the proccess). One died playing tennis, and one was killed by the IRA whilst offering £50,000 for information on terrorists..

  10. Muuuuch better shot for scale... by Anonymous Coward · · Score: 5, Informative

    ...had to hunt for it, but here it is:

    http://spaceflightnow.com/news/n0106/02x43failure/ x43.jpg

  11. Jobs by Anonymous Coward · · Score: 3, Funny

    Steve Jobs invented mach speed.

  12. Re:Someone help me out here. by homb · · Score: 2, Informative

    The rocket gets it up to the minimum speed at which the scramjet can operate: Mach 5-6.

    Then the prototype separates and fires the scramjet to reach Mach 10. It is thought that a scramjet can operate at least until Mach 15.

  13. Let's hope... by HexaByte · · Score: 5, Funny

    Let's hope that this type of engine isn't adopted by commercial arlines. If it were, a flight cross country would take less than an hour, and the flight crew wouldn't have time to get us all drinks and peanuts.

    --
    HexaByte - he's a square and a half!
    1. Re:Let's hope... by corngrower · · Score: 3, Insightful

      I think you've figured out why the airline industry is pushing this technology. They could completely eliminate serving the drinks and peanuts and save beaucoup bucks.

    2. Re:Let's hope... by cplusplus · · Score: 2, Interesting

      My time is worth more than a thimble full of soda and small bag of peanuts :-)

      --
      "False hope is why we'll never run out of natural resources!" - Lewis Black
  14. That 's around 12 000 Km/h by ArcticCelt · · Score: 5, Informative
    That's around 12 000 Km/h for those who use the more civilized metric system.

    (sorry I know this debate is a classic but miles say nothing to me and I guess that many international slashdoters feel the same)

    --

    Yahh, hiii haaaaa! -Major Kong, from Dr. Strangelove
    1. Re:That 's around 12 000 Km/h by clambake · · Score: 2, Funny

      That's around 12 000 Km/h for those who use the more civilized metric system.

      Is that metric hours?

  15. Around the world in 3.4285714285714285714285714285 by Marxist+Hacker+42 · · Score: 2, Informative

    24000 miles at 7000 miles per hour means you'd be home in 3.4285714285714285714285714285714 hours.

    --
    SJW: a person who perceives an injustice, and while correcting it, commits a greater injustice.
  16. Yes but... by wviperw · · Score: 4, Funny

    The important question is, what would Mach 10 be in warp speed?

    --
    Nothing disturbs me more than blind loyalism towards some unrealistic and over-idealistic notion of one's nationality.
    1. Re:Yes but... by otis+wildflower · · Score: 4, Insightful

      TOS Warp or Next Generation Warp?

    2. Re:Yes but... by happyfrogcow · · Score: 5, Funny

      TOS Warp or Next Generation Warp?

      You should win a free slashdot premium subscription for that question.

      Nerd of the Day honors to you!

    3. Re:Yes but... by Galuvian · · Score: 3, Informative

      According to Google, mach 10 = 3.4029 kilometers / second Warp 1 = speed of light = 299,792.458 km/s Therefore Mach 10 is roughly equal to warp .000001

    4. Re:Yes but... by romrom97 · · Score: 2, Funny


      Waaaaaaaaa..... *is hurled off the cliff to the rocks below*

    5. Re:Yes but... by cold+fjord · · Score: 2, Funny

      The important question is, what would Mach 10 be in warp speed?

      Release the docking bay clamps.

      --
      much of left-wing thought is a kind of playing with fire by people who don't even know that fire is hot - George Orwell
    6. Re:Yes but... by Rares+Marian · · Score: 3, Informative

      Um not quite. Warp numbers are exponents so... it would be log 3.4029 in base 299,792.458.

      See each warp re warps the previous one so...

      Now where's my autographed shot of Kirk telling Picard he was out saving the galaxy while his grandfather was in diapers?

      --
      The message on the other side of this sig is false.
  17. You know.. by bludstone · · Score: 3, Insightful

    For all the shit theyve been through, NASA still fucking rocks.

    Kudos to the Alpha geeks.

    We bow.

    --

    no .sig
  18. Re:A loeeson in civics. by Megaslow · · Score: 2, Funny

    You mean like this size?

  19. Re:My SAAB! by theguru · · Score: 2, Funny

    Hopefully, it is one of these and not one of these

  20. More questions... by EmbeddedJanitor · · Score: 2, Interesting
    The scram jet is air breathing. One wonders how much air is available to breath at 110,000 foot. Is there something majic about 110k feet? Is there too little air above this? Is this the altitude limit of jet technology?

    Considering that GPS satellites are something over 20000 km up, 110k feet is only a fraction of a percent of getting there.

    --
    Engineering is the art of compromise.
  21. WRONG by Anonymous Coward · · Score: 5, Informative

    Not even close.

    Hubbles orbital speed is approximately 16,900 miles per hour.


    You are not even close. He was asking about orbital ROCKETS! Not objects in orbit. Orbital rockets are the things that lift the satellites into orbit.

    The space shuttle does not get anywhere near 16,900 mph on lift off. That is the speed it gradually gets to once in orbit, NOT ON LIFT OFF.

    After 60 seconds, the Shuttle has accelerated to Mach 1 (the speed of sound). About one minute later (two minutes into the flight), the solid rockets burn the last of their fuel. By this time the shuttle is over 25 miles high. The now-empty solid rockets are released in order to reduce the weight carried the rest of the way to orbit. [They parachute into the ocean off the Florida coast, and are recovered to be refilled with fuel and used again.]

    After the solid rockets are released, the shuttle is still attached to the external tank and its launch engines are still being fed propellants from the tank. When the shuttle reaches an altitude of about 57 miles, it changes trajectory to fly more horizontally, and pick up speed. In order to achieve orbit, it needs to accelerate to approximately 17,500 mph (~5 miles/sec). Once it reaches this critical speed (about 8-1/2 minutes after lift-off), the shuttle launch engines are shut off, and the shuttle separates from the external tank. The tank re-enters the atmosphere and burns up on re-entry. It is the only part of the Shuttle system that cannot be used again.

    1. Re:WRONG by drinkypoo · · Score: 2, Interesting

      The main tank could be used for something other than being thrown away, but we just jettison them. I'd like to see them taken to the ISS and made into modules, or at least placed in the path of orbital debris.

      --
      "You're right," Fisheye says. "I should have set it on 'whip' or 'chop.'"
  22. Re:Someone help me out here. by richmaine · · Score: 4, Informative

    Please, if you are pretending to supply information, make it at least vaguely close to correct. :-(

    The rocket boosted it all the way up to max speed. The scramjet wasn't even lit at quite the max speed, though close (the research vehicle decelerates slightly in the few seconds after separation from the rocket before the scramjet lights).

    The scramjet *MAYBE* did as well as stopping the deceleration for a few seconds. One of the researchers, who I was talking to as we watched the B52 flyby and landing, said that he thought perhaps they got just a little positive acceleration (i.e. it sped up slightly), but small enough that he couldn't tell for sure from the quick look he took so far.

    But then, that is what was being aimed for.

  23. At Mach 10 by boatboy · · Score: 4, Funny

    So, at Mach 10, can anyone hear you scream?

  24. I'm Not Impressed by nate+nice · · Score: 2, Funny

    It's not like they put it into space, twice in two weeks, for under 10 million dollars.

    --
    "If you are a dreamer, a wisher, a liar, A hope-er, a pray-er, a magic bean buyer ..."
  25. But can it do... by dark-br · · Score: 4, Funny

    ...the Kessel run in under twelve parsecs? ;)

  26. Re:How fast is 7,000 MPH by JohnGrahamCumming · · Score: 4, Insightful

    > Circumference of Earth at equator = 24,900 miles = 3 hours 33min 26 seconds

    Please, if you get a scramjet of your own, take the extra time to go around the earth and fly above sea level! You'll enjoy the trip a whole lot more.

    John.

  27. Some helpful links by UnapprovedThought · · Score: 2, Informative

    The article link doesn't have much in the way of interesting details, so, here are some slightly better links to hopefully raise the signal ratio:

    • http://www.nasa.gov/missions/research/mach10_met eor.html
    • http://www.nasa.gov/missions/research/x43-image- feature.html

    The first one is an article with some details, the second is some artwork that explains the scramjet and the flight path.

    From the looks of it, the scramjet engine doesn't appear to be a very sophisticated device. It's just a funnel that doesn't ignite the fuel until it has already reached supersonic speed.

    The tricky part, if I'm guessing correctly, is building a vehicle that can withstand the 3600 degree heat of flying at Mach 10 in the upper atmosphere. It succeeded, but there was no human pilot inside of this one. I think that will be the next step: to build a craft, as small and light as possible, just to ferry crew into space, leaving cargo payloads to be sent up using a much cheaper but less safety constrained kind of lift capability.

    1. Re:Some helpful links by rebelcool · · Score: 2, Insightful

      Try keeping a flame lit in a 7000 mph wind.

      Its taken decades of design and testing to figure out the geometry of the scramjet so that it actually works.

      --

      -

  28. That's km/h by SysKoll · · Score: 4, Funny
    12000 Km/h is Kelvin times meter per hour. A Kevin is centigrages counted from the absolute zero. For laymen, the association of a temperature with a speed unit is a bit baffling, so let me explain. Km/h is a unit used exclusively to measure the speed reached by those people that run around at high speed while yelling "AAAAARGH! MY UNDERWEAR IS ON FIRE!!!". That's right, the dreaded Underwear Spontaneous Combustion Syndrome, often caused in young guys oogling all these hot chicks in Californian campuses. Witnesses of an USCS occurence generally scramble for water buckets.

    An USCS episode can be dramatic, depending on the Km/h value. At high Km/h values, the victim is running so fast that the bucket carriers cannot catch him. On top of that, the wind of his frantic run vents the fire, which of course burns even hotter, quickening his race. After a certain threshold, the poor guy's genitals burns to a crisp. The critical speed is called "Mach speed" (pronounced Mack), after an early victim.

    So unless you are referring to these sad but uncomon accidents, the metric unit you want to use is km/h, with a small k meaning kilo, not the capital K of Kelvin.

    --

    --
    Mad science! Robots! Underwear! Cute girls! Full comic online! http://www.girlgeniusonline.com/

  29. How is 7,000 mph == Mach 10 at this altitude? by GnuPooh · · Score: 2

    So Mach number is related to air density (speed of sound). At 100,000 ft there's not a lot of air, so while the speed of sound is about 700 mph at sea level, it's not at 100,000 ft. Are they cookin' the books or am I missin' something?

    1. Re:How is 7,000 mph == Mach 10 at this altitude? by GnuPooh · · Score: 2

      I think I got it. From this page: http://www.grc.nasa.gov/WWW/K-12/airplane/sound.ht ml Speed of sound is still 684 mph at 100,000 ft

    2. Re:How is 7,000 mph == Mach 10 at this altitude? by Keitopsis · · Score: 3, Informative

      The speed of sound is approx. sqrt((gamma)RT)
      Assuming Ideal Gas
      Gamma (roughly constant for air (1.4))
      R = Ideal Gas Constant
      T = Absolute Temperature (relates to density, etc)
      (somehow I knew those thermodynamics and aerodynamics courses would pay off someday)

      At 100,000 ft, the temperature is only somewhat lower. This only marginally lowers the speed of sound, but also lowers problems with skin heating at high speed, parasite drag, etc.

      So, no, noone is pulling a fast one. This is an impressive achievement for an air-breathing vehicle. Now if anyone can find an article detailing if they got any positive thrust out of it or if it was all the pegasus booster.

      --Kei

  30. Re:How do they keep the shockwave in place? by Keitopsis · · Score: 2, Informative

    Note that the inlet is built out of the forward body of the vehicle, so the shockwave is still external.
    Its only the portion of the stream that enters the combustion zone that is being propelled, the rest can be reguarded as bypass air.
    Also note the tail of the aircraft is formed to handle post/hyper-sonic exhaust.

    --Kei

  31. Re:How do they keep the shockwave in place? by TigerNut · · Score: 2, Informative

    The guy who designed the SR-71's engines ended up winning one of the most prestigious aviation prizes (no, I can't remember which) for the way that the movable engine inlets ended up being responsible for something like 80% of the thrust produced at high speeds. He later became director of the Lockheed Skunkworks in the era where they produced the F117A.

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    Less is more.

  32. Don't forget the B-70 Valkyrie by Mulletproof · · Score: 2, Informative

    The SR71 uses one of the more complex methods of maintaining high mach travel, but it isn't the only one. The B70 Valkyrie experimental strategic bomber solved the problem using wings that folded down vertically to encompass the shockwave beneath the fusalage and literally ride it. It's supremely ironic that this aircraft can outrun today's B1-b Lancer by a full two times the speed of sound using 1950s technology.

    Some history on this forgotten, stunning piece of aviation engineering.

    --
    You need a FREE iPod Nano
  33. Re:Back in Time? by Bisqwit · · Score: 2

    Speed of sound (~300 m/s) is much lower than the speed of light (~300'000'000 m/s).
    Also, the trick used in Star Trek IV involved the sun somehow (flying behind it or something).

  34. Re:Wasting nearly-Orbital Material by DasBub · · Score: 4, Informative

    "What I don't understand is why you spend so much money in fuel and oxidiser to get the external tank nearly into orbit, then for the additional cost of presumably not very much (in the scheme of things), let the thing fall back to earth and burn up?

    Would it not make more sense to take the tank into orbit and use it for something? It's got to be (at least nearly!) air-tight, why not add it to the Space Station as another module for something? Use it for spare parts - got a leak, hack a suitable sized bit off the old tank and stick it over the hole. Just stack them up in orbit somewhere for raw material to build a interplanetary space ship?"

    You're absolutely correct. Unfortunately, a lot of factors and events have stopped any of these things from happening.

    The ET itself is completely space-worthy. It was designed to operate in space long after reaching orbit. Early plans for space stations and platforms included the ETs since they remain completely useable. What's more, the tanks still have a lot of H2 and O2 left after a launch. So in reality, the shuttle could reach much higher orbits if it _kept_ the ET attached on orbit. This was purposely designed-in, since the original plans for what's now the ISS called for a higher orbit than usual. So any visit to the space station would require one to keep the ET. Even if it was just hanging around LEO, the H2 and O2 in the tank are extremely valuable and are worth leaving in orbit.

    So why don't they do this? Well, they just don't have a reason to anymore...

    First, the shuttle no longer needs access to the higher orbit, since the ISS we have is in a much lower orbit. This was done to accomodate the Russian launch sites. This has crippled a lot of the usefulness of the ISS compared to it's original goals, but that's a whole other post.

    Second, managing the ETs and their contents are more trouble than they're worth. What I mean is that the only immediate usefulness of the H2 and O2 would be for the ISS, but it's just less of a planning headache to have the supplies sent up by Progres than mapping out astronaut time to transfer stuff from the ET through the shuttle to the station (and having to manoeuver with the ET attached). We can say that making orbital warehouses of the tanks and their contents for future missions and projects is a great idea, but it brings up the question of where and how. Do you store them at the ISS, or at some designated point out of the way? If the ISS, you've just added another headache to the crew. If at some other point in space, you have to have station-keeping thrusters to maintain orbit and attitude. NASA has no need for any of these headaches currently.

    Thirdly, the whole idea is moot since the shuttle's death warrant has already been signed. Well, it was signed a long time ago, but suffice it to say that the shuttle isn't going to be around much longer. There's no incentive to change their operations now, so they'll just keep chucking everything away until the program is over.

    It's really quite sad to look back at the past thirty years* of the shuttle and ISS programs and realize how poorly they've been executed and how many opportunities and resources have been squandered needlessly. I have the utmost respect for the engineering teams and all the people who put the shuttles together and made them fly, but the shuttle program really has ruined NASA for decades.

    Blah.

    * - the shuttle fleet has only been flying since '81, but the design work began in the early 70's

  35. rather than leaving a card through the letterbox.. by RMH101 · · Score: 4, Funny

    ...instead you'd have your house, garden and neighbourhood replaced with a huge crater with a squashed packet from amazon in the centre?