Making a boom, before Boom Aerospace - Messing around with breaking mach.

Discussion in 'Hangar Flying' started by nerobro, Nov 3, 2017.

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  1. Nov 6, 2017 #41

    nerobro

    nerobro

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    The engine we're looking at was for a supersonic cruise missile anyway.... At least before they put better materials in it to make it have an appreciable lifespan.

    While "simple" intakes can work on slower planes, they're also working their butts off. A variable geometry intake is "easy-ish" to do, and can be designed to be self correcting. The big benefit there is you get some really serious pressure recovery of the air going into the engine, which would do some really good things for range.

    So... Sonic flight is ok, so long as you're high enough the boom won't reach the ground. I bet, if you could demonstrate the boom was less noisy than say... a C172 at 1500' you'd get permissions opened up all sorts of places.

    HHHmmmmmmmmmmm So were do we find a billionare who's looking to be a millionare so we can publish plans? :)
     
  2. Nov 6, 2017 #42

    Voidhawk9

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    More manageable might be a reasonably priced homebuilt capable of high subsonic mach. The difficult part -as always- is the reasonably priced bit, but should be more manageable and probably ultimately more practical than a supersonic bird - you might actually be able to do it with a prop.
     
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  3. Nov 6, 2017 #43

    12notes

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    Why not use a glider style retractable center wheel? They only move about a foot or less, and are much simpler to implement than standard retracts. The wing drop problem for taxiing could be solved by using a very light duty wing gear, a little more than a roller blade wheel on a stick that folds straight back with little additional support, it doesn't have to withstand a landing, just keep the wing from scraping the ground at low speeds on the ground.

    The U2 used a similar system, except it's wing wheels aren't attached and fall off on takeoff.
     
  4. Nov 6, 2017 #44

    Giggi

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    If I were looking for nothing more than to break the sound barrier on a budget, I'd just go for a rocket. Build a plane with zero air intakes for better aerodynamics, and load the engine with a revolving drum of solid-fuel tubes so the burn can be stopped at a convenient interval. It'd be breaking windows before y'all'd've finished browsing for ten-million-peso turbothingamajigs :shock:
     
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  5. Nov 6, 2017 #45

    pictsidhe

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    Which engine are you looking at?
     
  6. Nov 6, 2017 #46

    pictsidhe

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    Naca TN1032 Looks worth looking at. "(3) The lift distribution of a pointed airfoil travelling point-foremost is relatively unaffected by the compressibility of the air below or above the speed of sound."
     
  7. Nov 6, 2017 #47

    nerobro

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    J85, or CJ610.. ish. But obviously this is all a flight of fancy thing. If you know of an existing engine that might be worthwhile, pipe up!
     
  8. Nov 6, 2017 #48

    Lucrum

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    Not an entirely bad idea
     
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  9. Nov 6, 2017 #49

    Aesquire

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    The DC-8 is the only Airliner other than Concorde and Concordski, that has officially broken the sound barrier.

    In a shallow dive. At full takeoff power. With the trim set nose up and over 25 pounds of pressure on the yokes. With both pilots ready to use the trim to fly in case the elevator became ineffective. They also set several records like weight to altitude.

    Supersonic with a propeller? It's been tried, and if the Government can't do it, it's really expensive. The Republic Thunderscreech tells me I don't want to be nearby when you try. I'm not saying it's impossible. Just darned hard.

    If you build a plane that can do 500 miles an hour, It really belongs on the Beat Strega thread. A more reachable, expensive, crazy goal. ( I enjoy crazy goals )

    Other ideas, like a mini Orion Drive offer the possibility that they'll never hear your sonic boom over the noise of your drive. Neither will you.

    So, I think you're going to need a jet. Forget dropping from a surplus B-29. I can't afford to start 4 Wright engines that size. Forget pure rocket thrust, you'll never get high enough to not break windows with anything much smaller than a V-2. Just a matter of fuel capacity. Rocket boost for a brief trip to the other side of the Sound Barrier would work.

    And, as mentioned before by others, forget variable geometry intakes. The F-16 originally was designed with VG intakes to go over Mach 2, but careful analysis showed the time spent at that speed in combat was tiny, and the weight lost from using a simple intake pays dividends everywhere else in the envelope. More fuel, more ammo, better climb, better transonic maneuvering. The B-1B is another example. They gave up the high mach high altitude portion of the envelope to gain a lot at low level transonic flight. The Rockpile showed the effectiveness of "Booming" an area to keep everyone's head down.

    http://www.supercub.org/forum/showthread.php?26672-B-1-Bomber-fly-by!&
     
  10. Nov 6, 2017 #50

    BoKu

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    I don't really think that'd be a major concern until you get up around M1.6. If you just want to get to 1.1 to say you did, most common aircraft construction materials will probably handle the heat.
     
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  11. Nov 6, 2017 #51

    bmcj

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    OUT OF THE BOX WARNING:

    I wonder if you could reduce wing area by surfing on the shock waves from your prop?
     
  12. Nov 6, 2017 #52

    Topaz

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    Aluminum for sure. Even post-cured composites could handle it for the relatively short periods likely with a homebuilt "SST". Remember, SpaceShipOne was just plain molded carbon-epoxy, not really any different than Bob's gliders. Well, it didn't soar as well... :gig:
     
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  13. Nov 7, 2017 #53

    Aesquire

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    Would Space Ship One's engine be considered a glider sustainer engine since it's not used for take off?

    Btw, I've soared gliders with worse L/D. Better sink rate, though.
     
  14. Nov 7, 2017 #54

    BBerson

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  15. Nov 7, 2017 #55

    Aesquire

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    Ride the shock waves of the prop?

    Inverted Custer Wing.

    It would also focus the noise of your Thunderscreech Jr. towards the ground. Making it louder. A LS 427 cu. Inch automotive crate engine, direct drive, would make perhaps the loudest prop driven home built ever.
     
  16. Nov 7, 2017 #56

    BBerson

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    Garrison said he couldn't really visualize the reason for a shock wave. I think it might help to know that in seemingly still air individual air molecules bounce off each other at the speed of sound (on average). That's what makes it the speed of sound in air.
    So the molecules can't easily move out of the airplanes way at the speed of sound
     
  17. Nov 7, 2017 #57

    Aesquire

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    One day at a shooting range conditions of humidity and light were just right and I spent a while watching the bullets making visible shock waves and the Pradtl-Glauert singularity. Clear as could be. I was amazed I could track supersonic objects like that. The view from behind the shooter was incredible. As a buddy put it, "ah! You could see the donuts". The back side view was of a shiny dot surrounded by a halo of vapor, with radiating circles..... very very rapidly shrinking into targets 100 meters away.

    The Pradtl-Glauert singularity, The Glory, and Sundogs are three phenomenon I've been blessed to see in person.

    Pictures don't do them justice. Sundogs are just luck. I suppose a serious weather nut could try to predict them but it'd be tricky.

    The P-G singularity is often seen at airshows and by plane watchers. I was just amazed to see it so clearly on such a scale.

    A Glory is also a relatively common sight for aviators and mountain climbers. Seeing my shadow on a cloud beside me in a hang glider was inspiring. ( at the legally mandated distance of course, not 50 yards away. ;) )
     
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  18. Nov 7, 2017 #58

    BBerson

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  19. Nov 7, 2017 #59

    nerobro

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    I need to dig through some books to predict weather something like this might actually work on the the cj610.

    I'm "reasonably ok" with this being a mach 0.99 plane that could do mach with a slight dive. Really, so long as it beats an airliner it "has a useful reason for flying". As oposed to being a one time stunt.
     
  20. Nov 7, 2017 #60

    Arthur Brown

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    The issue with beating Strega is that the faster you go the more G's you have to pull round a small pylon circuit. Blackbird was fast but had a turn radius in the order of 100s of miles so it wouldn't have beaten Strega.

    Preping a fast plane project would soon show problems in other areas for example instrument response rate and high speed navigation. Probably you'd have to go for a full cert of airworthiness, in the UK Permit to Fly planes are speed limited. You'd also need full oceanic navigation equipment because there is too little airspace over land that could be flown at boom type speeds. Having full pressurisation for the cabin would be a hassle and almost certainly demand a jet engine with a low pressure take off point and a full set of oxygen for emergencies. Maybe you'd have to carry 3+ VHF sets and likely, to make use of boom speeds an HF set as well

    As long as you can control the engine air inlet velocity and feed it the fuel there should be little problem designing and building an airframe to do Mach 1.2 to 1.5. Getting to Mach 2 starts to approach heating problems needing special metals etc.
     
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