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Thread: LM Blast Crater

  1. #1
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    I was wondering about the whole blast crater idea.

    Has anyone ever pointed out to the HBs that the lift off thrust of the Saturn V was 7.5 million pounds and it didn't leave a blast crater or are do they produce of some their usual unscientific ideas?

    <font size=-1>[ This Message was edited by: jrkeller on 2002-04-23 14:06 ]</font>

  2. #2
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    I'd imagine one answer would be 'what Saturn V' ' [img]/phpBB/images/smiles/icon_smile.gif[/img]

  3. #3
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    Well, even if they'd acknowledge that there WAS a Saturn V, they'd probably argue that the launch pad was some specially engineered material that would withstand the "millions of degrees" and "gazillions of tons of pressure" that everyone knows are characteristics of rocket exhaust. [img]/phpBB/images/smiles/icon_smile.gif[/img]

  4. #4
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    Isn't one of Percy's arguments that the F-1 engines concealed smaller engines? Don't know how it would have gotten off of the ground if had smaller engines.

  5. #5
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    hallow shell? I mean they werent going to the moon anyway, didnt need all that propellant, they were just going 'out of sight' and then to the north pole...

    I guess the only problem was they were tracked not only by telemetry, but you can see a rocket pretty well using binoculars etc...

    oh well [img]/phpBB/images/smiles/icon_smile.gif[/img]

  6. #6
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    If Percy's claim is that there were small engines inside the F-1s, he obviously never looked at the footage that shows the firing of the F-1 during launch. It would be very easy to correlate the back ground in these films with what is in the long range photos, etc.,

    Again, the Moon Hoax theory gets worse.

  7. #7
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    He has in fact looked at the F-1 firing footage, and he claims the dark appearance of the plume means they were not really firing at appropriate capacity. Of course Percy doesn't realize, or else doesn't acknowledge, that he's seeing footage from DACs mounted on the MLP and running at something like 200 fps. That limits your exposure. He wants to compare the plume to still photos taken from afar.

    Clearly David Percy knows nothing significant about the physics of rocket propulsion. He is still at the point of claiming the LM descent engine must have been firing at 10,000 lbf because they wouldn't have specified a more powerful engine than necessary. He can't seem to do the computations necessary to show that you hover on 2,800 lbf or so, and that you simply can't hover at 10,000 lbf.

    Both he and Bill Kaysing seem to think 10,000 lbf is some whopping huge engine. The V2 produced something like 160,000 lbf, and even most jet engines produce more than that.

  8. #8
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    Last night on British TV was a prog about the Harrier Jump Jet. I've captured some frames to point out a few things...

    [img]http://photos.msn.co.uk/imageserver/image.aspx?Image=*EtEZjHm6coQiDslBu2m29xQQcGLMtbVE ly8S4RziufYrN1Lxk7niWC9HwrXY4EtCouY2nJLfMZPo*m8Ynm KZdI7NDtgmhuBWzUX4iAcKLpcrfYN0MPZH3mM6z0uDvsL[/img]

    This is the deck of an aircraft carrier underneath a hovering Harrier, developing 24,000lb of thrust (maybe a little less, because that's max rating. However, the engine is at a high throttle setting when hovering).

    [img]http://photos.msn.co.uk/imageserver/image.aspx?Image=*EtEZjHm6coQiDslBu2m29xQQcGLMtbVn 2xUsNeqA*rD9xMWWiEgcYjf8eQk6lZHmpKE2ZACcox06AJ1MFp opiwgpyCGZqSsT9bD5gZ!RhuqqT2Y3UDmxGK80tenEgnl[/img]

    [img]http://photos.msn.co.uk/imageserver/image.aspx?Image=*EtEZjHm6coQiDslBu2m29xQQcGLMtbVa 09jFxKeMhREboxr82MI5OvZcpDjn6zokOpYQBRJUyfFV*C1XYQ !lBXIERRpi3mOTmli7YDzVTRgHEysb8XO1qljfgY7JqRh[/img]

    [img]http://photos.msn.co.uk/imageserver/image.aspx?Image=*EtEZjHm6coQiDslBu2m29xQQcGLMtbVP 7iJnf6HczjgCB85TNR*FWSbd0pv5A9rEOc3EAcV5E0SecGXCDY V7NL3O6H40ZQ7mDshNx9tG5EARpaVOSPY2t8K410qc*2O[/img]

    This is the sequence of the landing. Note a) no big nasty flames coming out from underneath and b) no great disturbance from the searing heat of the exhaust.

    [img]http://photos.msn.co.uk/imageserver/image.aspx?Image=*EtEZjHm6coQiDslBu2m29xQQcGLMtbVQ HzvaeInkYlBCNOYp92aU2Hto!C92qYtDC4Js6iEhLtWvPCkoP3 C13VmvvQKm9iqWqqyRaXFbFZW0WGhu2tnJYPpe6tH6hDI[/img]

    [img]http://photos.msn.co.uk/imageserver/image.aspx?Image=*EtEZjHm6coQiDslBu2m29xQQcGLMtbVx XeWe!pOQCpNlR7JXtktHktk76FfZ0VeR5Ou7XhKDHofFzYMwDi co4WrJkw6Tctf7TbDSpIyWEW5!BSKZTA18ViSpp6*8zVi[/img]

    [img]http://photos.msn.co.uk/imageserver/image.aspx?Image=*EtEZjHm6coQiDslBu2m29xQQcGLMtbV4 RJTxC4tpJIOGuIEmb6vD4PinkrL2H!a0ngp07dX8gH1i1!DswT HC9KDed5HXX1Z!JQeG8cWe3YtVe067AOicvK!KkLCgFQ5[/img]

    This is a flyby sequence in hover mode, before the aircraft comes in sideways to land. This high thrust machine is less than 100ft over water, yet I can't see any disurbance on the surface of the sea whatsoever.

    [img]http://photo.msn.s8.com/MS8zLzAvMS8xMDMwLzE1NS8zMi9xWXdfaHE5R2pfd2FVWVVFSE 81cWFB/d84962cb2658c14e609ff3a2cd566671/clbk=*EtEZjHm6coQiDslBu2m29xQQcGLMtbVbERIGCdLzeY!q AtwHsj*Z5rl0i*BMW84gNrHbHk8gsg$/jpg.jpg[/img]

    This is a Harrier just hovering. Nothing is visible coming out the bottom, the film makers are not being blown off their feet, and the camera equipment is not being melted. And this craft produces more thrust per each of it's four nozzles than the LM engine did on final descent.

  9. #9
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    Well, of course, a Harrier is not an LM, and the deck of a carrier is not the lunar surface. There's no layer of dust to blow around, and the landing surface is steel, not rock.

    Now, land a Harrier on a dusty, rocky desert surface and you'll see... no crater.

  10. #10
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    Actually, I believe that the (copied! copied from our noble British design!) Russian jump jets used to set fire to the decks of their carriers. Perhaps that's why they never went to the Moon?

  11. #11
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    Or, they built their flight decks out of papier-mache...?

  12. #12
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    Hey Johnwits:

    Ahem...The Harrier isn't sucha good example. [img]/phpBB/images/smiles/icon_wink.gif[/img] I was at the Oshkosh fly-in some years ago when they had a Harrier demo. They landed it on the grass 'cuz the jet blast would (thermally) crack the concrete runway.

    The grass landing was something you had to survive to believe. We were about 100 yards away and we were catching grass, dirt, pebbles, worms, paper trash, younameit. It left a burnt creater about one harrier in diameter & about a foot deep.

  13. #13
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    Was there something wrong with the runway? Was it new and therefore not fully cured? Runways are very thick, and are exposed to close proximity jet wash every time an airplane takes off or lands. It seems very odd that they would prohibit a Harrier landing on the basis of thermal stress.

  14. #14
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    What about that experimental Delta Clipper then? It was a single-staged controlled lift vehicle designed to fly in the Earth's atmosphere in the same way the lunar landers did on the moon. I don't recall seeing any big craters under that thing, and I'm sure it had a much greater thrust than the LM.

    http://www.hq.nasa.gov/office/pao/Hi...x-33/dc-xa.htm



  15. #15
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    On 2002-04-25 01:59, JayUtah wrote:
    Was there something wrong with the runway? Was it new and therefore not fully cured? Runways are very thick, and are exposed to close proximity jet wash every time an airplane takes off or lands. It seems very odd that they would prohibit a Harrier landing on the basis of thermal stress.
    I don't have all of the details. That is just the explanation we were given by the announcer for verticle manuvers being done over grass. I would think thermal stress would be a possibility however, as the regular jet wash you mention is tangental to the concrete and the Harrier perpendicular. You get more heat soak from a vertical jet wash hovering to land/takeoff. Who knows? I have not studied it at all so all of this could be urban folk lore. [img]/phpBB/images/smiles/icon_smile.gif[/img]

  16. #16
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    Yes, I suppose there would be enough difference between the concentrated perpedicular wash from a Harrier and the more tangential, transitory wash from a departing or arriving airliner. BTW, the wash is pretty direct with the aircraft pitches upward to take off, or when it deploys its thrust reversers, but since it's moving across the surface at 150 knots or more, I doubt the effect is significant. And since the Harrier would only heat a certain small area, there's the problem of a thermal gradient and expansion ratios. It might crack when it cools.

    Put another way, runways may be temperature-hardy, but they're also very expensive. If there were the slightest chance it would crack, I'd have the Harrier land on the grass.

  17. #17
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    On 2002-04-25 12:31, Russ wrote:
    I don't have all of the details. That is just the explanation we were given by the announcer for verticle manuvers being done over grass. I would think thermal stress would be a possibility however, as the regular jet wash you mention is tangental to the concrete and the Harrier perpendicular. You get more heat soak from a vertical jet wash hovering to land/takeoff. Who knows? I have not studied it at all so all of this could be urban folk lore. [img]/phpBB/images/smiles/icon_smile.gif[/img]
    If it was at Oshkosh they don't allow VTOL aircraft on the runways because of all the crud they tend to leave scattered about. FOD is a very serious matter with all of the vintage and jet aircraft flying during the daily airshows during AirVenture.

  18. #18
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    FOD is actually a big threat to VTOL aircraft too.

    I seem to recall, from the depths of my memory, that the Harrier scenes in True Lies for which an actual Harrier was used required the crew to do the Navy-style clean sweep of the area.

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    FOD? Another TLA I don't know. [img]/phpBB/images/smiles/icon_wink.gif[/img]

  20. #20
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    On 2002-04-26 01:32, Peter B wrote:
    FOD? Another TLA I don't know. [img]/phpBB/images/smiles/icon_wink.gif[/img]
    Sorry. "Foreign Object Damage" [img]/phpBB/images/smiles/icon_smile.gif[/img] As bad as it can be for jet aircraft it's even worse for some of the irreplaceable vintage types at the Oshkosh airshow.

  21. #21
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    And from Russ's anecdote it sounds like the spectators were used as shields to protect the aircraft from flying debris. [img]/phpBB/images/smiles/icon_smile.gif[/img]

  22. #22
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    In response to the post of dealing with the thrust of the Saturn V rocket on the launch pad. If you don't know this already you might find this interesting. Yes an F1 engine was rated at 1.5 million pounds of thrust and clustered in a group of 5 that would equal 7.5 Million pounds of thrust. There was great concern of "melting the concrete". The solution to this (which is still used to this day on shuttle launches)is a sound suppression system which is used to reduce the vibration created by the sound and to help prevent the launch pad from becomming to hot. About 15 seconds before launch they start pumping water onto the blast deflector. By the time of liftoff a couple million (not sure of the exact number)
    gallons of water have ben dumped on the blast area. Most if not all of this water is turned to steam from the intense heat.
    Intresting fact. The Space Shuttle produces just over 7.5 million pounds of thrust. 3.3 million from each SRB and each main engine is rated at 415,000 pounds of thrust. As for the people wondering if small engines were plased in the F1 on the Saturn, give me a break. Do you realize the engineering problems not to mention weight considerations of trying to do that. If they had wanted to use more smaller engines they would have used them. They would have not "hidden" them in a F1 engine bell. Believe me. I have a real Saturn V less than 5 miles from my house that I can get plenty of reference photos for anyone in question.

    Just because some don't want to
    believe the truth dosen't mean
    it isn't the truth.

    Prox

  23. #23
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    The water has a double role. It absorbs the tremendous heat by a phase change to steam. But more importantly, it absorbs the tremendous acoustic energy of the rocket exhaust. A little known fact of payload design is that the acoustic loading is what's going to kill your payload, not heat or g-forces. The water keeps the shocks waves produced by the exhaust from slapping back off the hard surfaces and damaging the rocket, the launch pad, or the payload. Even so, the F-1 plume consumed about 3/4 inch of the plume deflector surface.

    Propulsion engineers drool over the Rocketdyne F-1 the way car enthusiasts drool over a '67 Mustang convertible. There is so much interest in its development, specifications, and operation that to claim it was just a big farce is tantamount to psychosis. The principles of rocket engine design are no mystery, and the appropriate features of the F-1 are well known and easily measured on the surviving specimens.

  24. #24
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    Amen to that.
    We used to tour Marshall Space Flight Center. They would take us out to the test area where in the 60's they tested the first stage of the Saturn V. It was cooled in the same manner as the launchpads at Kennedy. I believe they said there was 81 thousand holes in the blast deflector that water was pumped through. There are a couple of tanks close to the stand that held a couple million gallons of water.
    Sure wish I could have been in that block house the day they test fired the complete first stage.

  25. #25
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    There's an F1 on display at the Space Museum in Alamogordo, NM; the beauty of the thing is that it's lying there on its side utterly unattended and you can climb all over it...with adult supervision and a good insurance policy and I didn't tell you about this either. It is almost worth a trip to the outback for this experience if you're a confirmed rocket-freak. If you are, it will break your heart even as you clamber.

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