What does 3.6 million pounds of thrust look like?

By Phil Plait | September 17, 2009 2:39 pm

It looks like this:

That was the full up test of the Ares-1 solid rocket motor from last week. Last I heard, everything went pretty well. Now all we need to do is figure out if NASA will have a rocket to put it in.

CATEGORIZED UNDER: Cool stuff, NASA
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Comments (79)

  1. Phillip M

    That was awesome, hopefully, NASA will have the funding needed to develop it into a serviceable motor for human space flight.

  2. Richard

    That’s an impressive display. Imagine how much more powerful that explosion could have been had the fuel been diluted to homeopathic levels!

  3. Brandon

    In case you haven’t seen it yet, here is the time lapse video of the Ares 1-X being stacked. The first part is the final check out and preparations of the segments in high bay 4 of the VAB. The second part is the actual stacking process on the mobile launch platform modified for the Ares 1-X rocket taking place in high bay 3 of the VAB. Modal testing has been complete and the analysis is being carried out now. Whether we go with this configuration or not, it sure will be cool to watch it launch. However, it will only have 4 SRB segments (unlike the video you just watched). Enjoy

    http://www.youtube.com/watch?v=qaU201HEzx4

  4. Kevin F.

    “Well I don’t know, Phil. What DOES 3.6 million pounds of thrust look like?”

  5. How different is that engine from the Space Shuttle SRB? From what I’m reading, it’s essentially an SRB with an extra segment.

  6. andy

    What’s that in proper units?

  7. 5. andy Says:
    September 17th, 2009 at 3:04 pm
    What’s that in proper units?

    A bit over 16 meganewtons.

  8. Alex

    Is anyone else wondering what the Mythbusters would do if they had one?

  9. Chris

    Toasterhead – it has some modified grain geometry and a different nozzle so that it provides a slightly different thrust curve while remaining within operational pressure limits. It’s fairly close to a shuttle SRB with an extra segment, but it definitely has some changes.

  10. Brian T.

    Alex:

    I imagine they’d have the most epic weenie roast this world has ever seen.

  11. Okay, so how many of these would you have to line up and burn to shift the Earth off its access and send it plummeting into the sun?

    BTW, question for you gearhead types… If, as the narrator said, steel boils at the temperature produced by this rocket motor, what exactly is the nozzle made out of? I’m thinking my mom’s fruitcake.

  12. Roger D. Parish

    An impressive column of smoke from that motor! How toxic are the exhaust fumes? I don’t think I would want to be downwind of that test!

  13. markm

    @andy Says: What’s that in proper units?

    Approximately 62,800 ’68 Chevy Camaro SS , with the big block V8.

  14. I linked to this during the VAAS conference at NRAO last weekend.
    Awesome!
    Dr. Kathryn Thornton was talking about her trip to repair the Hubble, and the future of spaceflight.
    Or maybe it was during Dr. Bob O’Connell’s talk about the most recent Hubble repair mission.

  15. Bernd

    kuhnigget: Forget it. Won’t work. The momentum dissipates in the atmosphere.

    You would need *huge* boosters with exhaust plumes reaching into space.

  16. whatever

    @ kuhnigget
    Nozzle Materials: D6AC steel for fixed housing with throat and forward exit cone housings. aluminum for nose inlet and aft exit cone housing.
    http://www.astronautix.com/engines/srb.htm

  17. Sili

    In the interest of equal opportunity:

    “That’s what he said!”

  18. what exactly is the nozzle made out of

    Likely ceramic composites. I bet Phil knows.

  19. @11. kuhnigget

    Quick Google search answers your question. Was curious myself. Source linked to my name.

    “Nozzle Materials

    Structural materials are applied generally according to the maximum operating temperature to which they will be exposed.

    Up to 500 °F, the most used materials are aluminum alloys and fiberglass-resin composites, both of which have high-strength-to-weight ratios, are light in weight, easily fabricated, have good corrosion resistance, and are reasonable in cost. High strength steels are used when major considerations are high strength in thin sections, or operation at the higher end of the temperature range.

    Between 500 °and 1,900 °F-, the higher temperature iron, iron-nickel, nickel, cobalt, and iron-nickel-cobalt chromium base super alloys are used.

    Above 1,900 F, alloys of refractory metals (capable of resisting high heat without cracking, melting or crumbling) such as molybdenum, columbium, tantalum, and tungsten provide high strength to approximately 4,500 °F. Above 4,500 °F, about the only structural materials available are graphite and pyrolytic graphic. “

  20. Telarian

    @kuhnigget: While I have no idea what the nozzles are made of, there are substances that can withstand significantly more heat than steel. Various ceramics are particularly good at the job. Hence their use in the shuttle heat shield.

    @Roger: I believe that is mostly dust kicked up from the earth. The narrator actually mentions the dust at one point.

  21. 6. andy Says: “What’s that in proper units?”

    About 16 MN (mega Newtons).

    Burning for 120 seconds give a total impulse of 1.9 x 10^9 NS (Newton seconds). If you’re into model rocketry, that would be a NAR code of “AD.” In fact, it’s 40% of the way to an “AE.”

    – Jack

  22. 12. Roger D. Parish Says: “An impressive column of smoke from that motor! How toxic are the exhaust fumes? I don’t think I would want to be downwind of that test!”

    It’s pretty nasty. Assuming it’s close to the same propellant mix as the Shuttle SRB’s (polybutadiene rubber and ammonium perchlorate) the exhaust has a significant amount of hydrochloric acid in it. That plus the tons (literally) of particulates that you don’t want to be breathing.

    There’s a reason Thiokol is located in Utah. In fact, it’s directly across the road from Golden Spike National Monument. I always thought that a great combination of two of my hobbies!

    – Jack

  23. Wow that was quite impressive!!

    Imagine all the strength required in the structure to hold the rocket in place during that test! It wouldn’t be very pretty if it were to break up and start flying off everywhere!

  24. Patrick

    For some reason, at first glance, I read that as “3.6 million tons” and nearly did a spit-take.

  25. Dwatney

    I was looking to see if Mr. Bill was strapped to the device in the path of the exhaust. “OH, NO!!!”

  26. @ Bernd:

    Memo to self: cancel plans for world domination and blackmail. bwuh-ha-ha..ahem…ha :(

  27. I say we take it on over to the Bonneville Salt Flats and set a *real* land speed record!

  28. Brian

    Combining elements of andy’s and kuhnigget’s posts, and free associating from that starting point, I believe the proper units of thrust could be restated as:

    16 megaFIGnewtons!

  29. gopher65

    Richard #2 made me laugh:).

  30. StevoR

    Awesome! 8)

    Now that was D-R-A-M-A-T-I-C!!!

    So good to watch something happening with this new rocket! 😀

    I love seeing this & I can’t wait to see more happen and watch Ares & Orion being ‘Go’ for a full launch – & a manned one.

    Thanks BA.

  31. Owen

    For all my desire to be able to go into space (not that it’s likely to happen)… the thought of actually strapping yourself to the top of that thing? It gives one pause. Astronauts man — respect.

  32. Grizzly

    Okay, I’m impressed.

    But can someone give me low-down as to why this is better than the Direct 3.0 Launcher?

  33. Spectroscope

    That Ares I rocket booster test sure looked great! I defy anyone to look at that and not feel a sense of hope, pride and “yes we can” spirit! :-)

    @ 27. Dennis Says:

    I say we take it on over to the Bonneville Salt Flats and set a *real* land speed record!

    Or an airspeed or all-time one.

    The speed to beat – the highest speed ever flown by humans – is 39,897 km/h (11.08 km/s or 24,791 mph) set on May 26, 1969 by the crew of Apollo 10 (Gene Cernan, Tom Stafford & John Young) on their return from the dress rehearsal of the Lunar landing.

    Mind you, I’m not quite sure how the Ares I solid booster compares with the power of the Saturn V first stage or even if it beats the Shuttle’s SRBs on which it’s based.

    Plus, of course, the Voyager s and New Horizons and a few other spaceprobes have gone faster still.

    Still it’d be a fun thing to try! 😉

    (Trying to imagine that long booster with wheels and a h-u-g-e wing in order to provide the necessary downforce to *keep* it on the ground.)

  34. Petrolonfire

    @ 32. Grizzly Says:

    Okay, I’m impressed. But can someone give me low-down as to why this is better than the Direct 3.0 Launcher?

    Well, for starters because we’ve actually built and test fired this Ares I booster now while the Direct 3.0 one is still just an idea on the drawing board isn’t it? 😉

    (Or is it? I dunno, I haven’t heard of that 3.0 one much if at all before.)

    Wicked thought of the day : If you had a person standing directly behind those rocket engines when they were test fired it just how far away would that person – or his blackened mortal remains end up? >;-D

    Any mathematicans here care to answer? 😉

  35. Joseph

    @ kuhnigget: in reference to shifting a planet with a motor; this has been addressed in a couple of sci-fi’s I have read as well as a sci-fi comic strip online called Schlock’s Mercenary. Best bet is to create a double ended fission powered rocket motor.

    One end points down at the planet and keeps the whole thing hovering over it while the other end sticks out into space and acts as the drive component. Works best with a gas giant as it uses the atmosphere as fuel.

    Best bet if you want to continue to live on the planet is to use gravitational billiards to toss the habitat planet into orbit around a gas giant then use the whole thing as a massive space ship.

  36. Bob

    Since it was mentioned, and since BA has devoted all of two posts to Constellation since this budget issue came up, here is a video of the House Science Committee’s review of the Augustine Panel:
    http://science.edgeboss.net/wmedia/science/scitech09/091509.wvx

  37. Petrolonfire

    @ 10. Brian T. Says:

    Alex: I imagine they’d have the most epic weenie roast this world has ever seen.

    Given what the word weenie is sometimes slang for, all I can say is … OWWWW! 😮

  38. When I first saw the title I thought, how did you get a picture of me.

  39. Bob (#36) do you have issues with how I cover topics on my blog?

  40. 33. Spectroscope Says: “I’m not quite sure how the Ares I solid booster compares with the power of the Saturn V first stage or even if it beats the Shuttle’s SRBs on which it’s based.”

    It’s about half of the Saturn V first stage, which was 7.5 million lb (33 mega Newtons) but that used five F1’s rated at 1.5 million each (6.7 MN), so this is about 2 1/2 times more thrust than the F1 (still the largest liquid engine ever flown).

    The Shuttle SRB’s are about 2.8 million lbs (12.5 MN), so you can see this is a significant increase. I didn’t catch what the diameter of this unit was, but the Shuttle SRB is 120″ (305 cm) in diameter.

    – Jack

  41. Bob

    Just improving the content of the blog. The committee is extremely supportive of an increase for NASA’s budget.

  42. Wonderful video, but… how can 22 million horsepower (as stated in the voiceover) be 3.6 million pounds of thrust? That’s only about 1/6 pound per horse. Can someone please explain?

  43. A test firing of their new rocket! Lies I tell you! They positioned the rocket horizontally to decrease the earth’s rate of rotation! It’s all a giant conspiracy to make us work longer hours!

  44. sleepneed

    @8 Alex. Heh I thought the exact same thing. I also wish they could use this one to test the “Rocket Powered Car” Myth. I’m sure this could give them the distance they are looking for before it spats against the mountain!

  45. themos

    Thrust must be (mass rate)x(exhaust speed). I am guessing that a reasonable definition of power in this case is (rate of kinetic energy imparted) which would be (thrust)*(exhaust speed)/2. 22 million horsepower is 16.3 GWatts. that would give (exhaust speed)/2 = 16300/16 = call it 1000. exhaust speed is then 2km/sec which would give a mass rate of 8000 kg/sec.

  46. Adam English

    Alex- In an internal combustion engine the exhaust gasses create a protective barrier while leaving that keeps your cylinder sleeves and exhaust ports from being damaged by the heat, it creates an “envelope” that carries out the gasses. I can only imagine some similar force is at work here. Just a guess, though.

  47. T.E.L.

    Mike Torr Said:

    “That’s only about 1/6 pound per horse. Can someone please explain?”

    They’re very small horses, Shetland ponies in fact.

  48. How do they start one of those rockets, anyhow? I’m imagining like a really big version of one of those old Estes ignitors.

  49. Toasterhead: There is what is essentially a downward facing flamethrower in the top segment to ignite the combustion chamber. The estes engines (while being pretty much the same fuel) are small, and lighting a small bit of them and letting the flame propagate is fine. In something so big you need to get quite a bit more of it going all at once.

    Questions on “what materials?: the nozzle is ablative, meaning it decomposes during the burn to absorb heat/become part of the exhaust rather than allow that thermal energy to transfer to the structural parts of the nozzle. That’s a common theme in substantial rocket engines.

    What’s different? 5 segments instead of 4, different nozzle size, different nozzle extension (engine bell part), different gimbaling system, different fuel grain core shape.

    Hope that was helpful :)

  50. Combining Richard’s (#2) and kuhnigget’s (#26) comments, we could have a new supervillian. A Dr. Evil-type who tries to blackmail nations using homeopathically diluted rocket fuel in his bombs. Dr. Woo?

  51. I can’t help but think what my plant would be fined for flaring that much smoke

  52. Grand Lunar

    Impressive experiement, I have to say, even though I’m not exactly a fan of the Ares 1 (I used to be, though).

    I wonder just how many more of those rockets would be needed to alter Earth’s rotation?

    “But can someone give me low-down as to why this is better than the Direct 3.0 Launcher?”

    Like someone else said, Direct 3.0 is only on paper.
    Believe me, I wish it WAS reality.

    If NASA is going to choose another launch system, though, it’s likely to be the side-mount launcher.

  53. T.E.L.

    Grand Lunar Said:

    “I wonder just how many more of those rockets would be needed to alter Earth’s rotation?”

    You only need one, if you don’t need it altered very much.

  54. I was bummed when this test was cancelled a couple of weeks ago. The fanfare was huge. When NASA TV covered it again it I was lucky enough to catch it becuase it was literally about 5 minutes of coverage.

    No matter how many times I see these things fire the power is just mind boggling.

    I watched a good bit of that hearing the other day. The resounding message was lack of funding. To the tune of $3 billion. As one congressman said, paraphrased, ‘We can give AIG 150 billion but can’t give NASA 3 billion?’ 😛

  55. 49. Spiv Says:
    September 18th, 2009 at 7:35 am

    Toasterhead: There is what is essentially a downward facing flamethrower in the top segment to ignite the combustion chamber.

    You had me at “downward facing flamethrower.” :)

  56. cameron

    Man, humans can do cool things.

  57. T.E.L.

    Lewis,

    There’s some subtlety that needs to be take into account. The AIG bailout was to forestall an economic meltdown of Biblical proportions that needed addressing right then & there. The wisdom of that bailout is debatable after the fact, but NASA wasn’t and isn’t teetering on the edge of dissolution and threatening to spread the ripples of its collapse throughout the Country. NASA’s short budget is debated perennially, which all by itself means that it’s perennially a priority of low-urgency.

  58. Charles Boyer

    “The AIG bailout was to forestall an economic meltdown of Biblical proportions that needed addressing right then & there.”

    Maybe so, but we as American taxpayers also helped pay AIG’s bonuses this year. Moreover, if AIG was the only firm that we helped it would be one thing. The list is far longer than AIG.

    Lewis’s point remains salient in my mind. Investing in NASA is also investing in America’s economic future.

  59. T.E.L.

    Charles Boyer Says:

    “…we as American taxpayers also helped pay AIG’s bonuses this year.”

    That must be why I said “The wisdom of that bailout is debatable after the fact…”

    “Moreover, if AIG was the only firm that we helped it would be one thing. The list is far longer than AIG.”

    The list is long because the economy is large and hyperconnected, and the culture of management these days is shortsighted, simplistic. It may be various company managements’ own faults that their businesses crashed, but placing blame doesn’t keep them solvent and save millions of jobs and mortgages.

    “Lewis’s point remains salient in my mind. Investing in NASA is also investing in America’s economic future.”

    I never said it wasn’t. But you know what? Emergency bailouts are also investments in the Country’s future, just like treating a bleeding gash is an investment in being alive tomorrow instead of dead this evening.

    If you want space travel to be a major player in the economy of the future, then it’s time for NASA to call a moratorium on manned flights and put everything it has into making it much more affordable to get payloads to low orbit. Once there you’re most of the way to escape velocity anyway (escape velocity is just orbital velocity x sqrt[2]). But until that happens, it’ll NEVER be profitable enough to support itself.

  60. I think the Earth is spinning a little faster now. Or slower, depending on which way the exhaust was pointing.

  61. Phil, here is a recent op/ed published in The Space Review written by John Jurist, ‘Taming the fire: the Ares 1 first stage development test‘. He is a biophysicist who works primarily in aerospace medicine. Given the reaction from a number of members of Congress to the Augustine report summary, I would say that the Constellation program is here to stay and that NASA will likely be getting a boost in funding. At this point it would require an legislative act of Congress to dissolve the Constellation program.

  62. Bryan Feir

    @artbot:

    Well, El Niño alters the rotational rate of the Earth. So did the Boxing Day Tsunami. Measurably, in both cases. Granted, the Boxing Day Tsunami (or, more correctly, the preceding subduction which altered the moment of inertia of the planet by moving dense rock closer to the rotational axis) only changed the length of a day by about 3µs, so saying that it’s measurable is more a statement on how sensitive our measuring tools are than on how much the speed changed.

    I used to work in VLBI, so I knew people who worked with the IERS.

  63. 49. Spiv Says: “Toasterhead: There is what is essentially a downward facing flamethrower in the top segment to ignite the combustion chamber. The Estes engines (while being pretty much the same fuel) are small, and lighting a small bit of them and letting the flame propagate is fine. In something so big you need to get quite a bit more of it going all at once.”

    Well, not quite. The “Estes engines” are black powder, which burns quite nicely at atmospheric pressure. That means you can light one end of the propellant grain (near the nozzle, naturally) and it will happily burn from the bottom to the top. These motors (the one in this test, the SRB’s on the Space Shuttle, the SRM’s on the Titans and the larger motors used in the rocket hobby) use something called “APCP” (Ammonium Perchlorate Composite Propellant). This propellant, a mixture of a synthetic rubber fuel and ammonium perchlorate oxidizer, needs to be pressurized in order to burn. If you were to light a slug of this material in the air it would just smoke and sputter with an ugly yellow flame and lots of black smoke.

    This means that APCP motors have to be ignited from the top with a big hole running down the center of the grain to the nozzle. When the top of the grain is started by the ignitor (which I’ll get to in a second), the resulting pressure pulse travels down the central core towards the nozzle, pressurizing the core and letting the whole inner surface start quite rapidly.

    If you were to try and ignite an APCP motor from the bottom, the first pressure pulse would vent directly out the nozzle, depressurizing the core and causing the combustion to essentially stop. This is called a “chuff” in the hobby. Generally, the flame doesn’t go completely out, but slowly creeps up the core creating more gas which raises the combustion rate enough to regain flight pressure. Sometimes it takes several “chuffing” cycles to get the whole core to ignite. In the hobby, the ignitors used are not that different from the Estes style ignitors, except that they have to be long enough to reach all the way to the top of the grain. That’s any where from a couple of inches to several feet at the larger end of the hobby. Instead of a phosphorous compound at the tip like used on the Estes “Solar” ignitors, most APCP ignitors use a magnesium based material.

    Naturally, something more sophisticated is needed for the big boys. I’m not familiar with the design of this Ares motor, but in the Shuttle SRB’s, the ignitor assembly is a four stage device where an electrically actuated “squib” ignites some very fast burning material that is used to ignite a not-so-small rocket motor that has 11 nozzles (this is the “flamethrower” that Spiv mentions). Each of the nozzles is trained on one of the 11 slots molded into the top half of the top motor segment. The huge surface area of these slots (each one is about 5 feet long by 3 feet deep by 4″ wide) generates the volume of gas necessary to pressurize the core very quickly. The slot arrangement also provides a big spike in the thrust for the first few seconds, which helps get the vehicle off the pad more quickly.

    – Jack

  64. FriendlyPrimate

    Depending on the direction they pointed that thing, they just changed the length of a day!!! Wonder if that means I get to go home early today.

  65. Charles Boyer

    Here’s what 7.5 Million pounds (34.02 MN) looks like when it was tested.

    http://www.youtube.com/watch?v=f3sVuFjJlp4

    Your new booster is a mere bottle rocket. (I kid)

  66. 62. Jack Hagerty Says:
    September 18th, 2009 at 1:09 pm

    This means that APCP motors have to be ignited from the top with a big hole running down the center of the grain to the nozzle. When the top of the grain is started by the ignitor (which I’ll get to in a second), the resulting pressure pulse travels down the central core towards the nozzle, pressurizing the core and letting the whole inner surface start quite rapidly.

    Oh way cool. Thank you for the detail!

    But if it burns from the inside out, how is it that they can regulate the thrust to throttle down at max-q and back up again?

    I’d always thought these burned from the bottom up and the manufacturers contoured the propellant so it was thinner in the throttle-down periods, but now I see that this was a false assumption…

  67. 64. toasterhead Says: “Oh way cool. Thank you for the detail!”

    You’re welcome.

    > But if it burns from the inside out, how is it that they can regulate the thrust
    > to throttle down at max-q and back up again?

    They can’t. That’s the job of the SSME’s (Space Shuttle Main Engines) on the orbiter itself. Once you light the solids, you’re going whether you like it or not! They burn to completion and there’s nothing that can be done to change that short of a total “thrust termination” (which is a destruct maneuver where they open up the motor casings with pyrotechnic zip cord and let the propellant go out). That’s why they always start the SSME’s first and let them go through a self-check for a few seconds before lighting the solids.

    > I’d always thought these burned from the bottom up and the manufacturers
    > contoured the propellant so it was thinner in the throttle-down periods, but
    > now I see that this was a false assumption…

    Well, not too false. Grain geometry is a real art, and there are all sorts of funny shapes that they cast propellant in for exactly the reason you state. It’s the only way to play with the thrust-time curve, although it’s not variable once you’ve made the mold. It’s literally cast in place. A good example is the one I mentioned with the slotted top segment helping shove the vehicle off the pad quickly before settling down to a sustained thrust level.

    The core in the Shuttle SRB is not a straight cylinder but a very slender cone frustum. It starts at about 6′ (2 meters) in diameter at the bottom of the first segment and tapers to about 4′ (1.3 m) by midway through the top segment. It then narrows down rapidly to about 2′ (.8 m) to form the base of the slots I mentioned before. This is done to help keep the thrust even during the burn. A straight cylindrical core has a thrust level that rises continuously during the burn because the surface area increases as the flame front chews its way to the wall. In the Shuttle SRB there’s only about 2′ of propellant wall at the base and 3′ at the top. The surface area does keep increasing until the propellant at the base of the grain reaches the casing wall. After that it’s a pretty continuous area as the bottom of the grain moves forward.

    Incidentally, This is what did Challenger in. You’ve all seen the video of the flame impinging on the ET, but the reason there was no flame at liftoff is that the 1-2 segment joint was covered in propellant. After the bottom of the grain had moved forward of the joint the gasses were free to move through the defect in the O-ring, which, unfortunately, happened to be aimed in the direction of the ET.

    – Jack

  68. 64. FriendlyPrimate Says: “Depending on the direction they pointed that thing, they just changed the length of a day!!! Wonder if that means I get to go home early today.”

    Sorry, but I think you’ll have to stay later. From the shadows on that video, it looks like the business end of that motor was pointing roughly east. That means it slowed the rotation down a little, lengthening the day.

    – Jack

  69. Torbjörn Larsson, OM

    But if it burns from the inside out, how is it that they can regulate the thrust to throttle down at max-q and back up again?

    “The solid rocket motor thrust profile is tailored to reduce thrust during the maximum dynamic pressure region; the propellant begins as a star profile, which progressively burns away to a circular profile, the latter having a lower surface area, and thus providing a thrust reduction. [Wikipedia “Space Shuttle Solid Rocket Booster”]”

    “The propellant mixture in each SRB motor consists of an ammonium perchlorate (oxidizer, 69.6 percent by weight), aluminum (fuel, 16 percent), iron oxide (a catalyst, 0.4 percent), a polymer (a binder that holds the mixture together, 12.04 percent), and an epoxy curing agent (1.96 percent). The propellant is an 11-point star- shaped perforation in the forward motor segment and a double- truncated- cone perforation in each of the aft segments and aft closure. This configuration provides high thrust at ignition and then reduces the thrust by approximately a third 50 seconds after lift-off to prevent overstressing the vehicle during maximum dynamic pressure. [NASA]”

    Why thrust raises again (confirmed by the thrust profile graphic) they don’t say. But the burn area increases, so gas production would too.

  70. Torbjörn Larsson, OM

    Oops, didn’t update so I missed Jack Hagerty’s expert comment.

    Well, at least I got the later thrust increase right.

  71. 70. Torbjörn Larsson, OM Says: “Oops, didn’t update so I missed Jack Hagerty’s expert comment.”

    Hey, no problem. We can never have too much information (unless it’s about Phil’s tattoo).

    That’s a good description, especially the propellant mix. I didn’t go into that because my posts were getting too long already. That mix is basically what AeroTech sells as “White Lightning” propellant, so called because of its brilliant white flame. Generally speaking, the polymer that Wiki calls the “binder” is considered the fuel, and the aluminum powder as an “augmenter” or “burn enhancer.” There are versions of APCP that don’t have the aluminum and have an almost invisible pale blue flame (AeroTech “Blue Thunder”).

    The only problem I have with their grain description is that it’s not a “star.” There are true star shaped grains where the groove features come to a point. The ones at the top of the SRB’s are square-bottomed slots that taper from about 4″ wide at the top to 3″ at the bottom (closest to the casing).

    I know all this because I’ve actually crawled through an SRB top segment at Thiokol. I was bidding on a job to do automated inspection of the grain after casting using a robotic camera on a crane as part of the post-Challenger improvements. The unit I was crawling in was an engineering test article that differed from a real flight article by not having any AP in it. So all of the dimensions I’ve been quoting have come from my actually measuring them with a tape. They may have changed since the early ’90s, but probably not much.

    BTW, we lost the bid to a Canadian company. I’ve always wanted to go back and see what the inspection tool they use looks like!

    – Jack

  72. Michael Kingsford Gray

    Arggh!!
    Pounds, Horsepower(!), degrees Fahrenheit!
    This is the 21st & half century NASA.

  73. marcello

    don’t know why, but i find it exhilarating!
    i mean, i was actually giggling while watching the video

    M

  74. davem

    I’m beginning to think that these moon-landing deniers are on to something. No one who still uses Fahrenheit, pounds and horsepower could ever have got to the moon. They were history in my engineering classes 40 years ago.

    Meantime, can anyone explain to me the mangling of the English language by NASA commentators? The engineers never turn something on, they ‘activate’ it, or ‘commit’ it. The test is ‘go’, never ‘on’. You always ‘have ignition’ rather than the ‘rocket has ignited’. You don’t hear any of that on an Ariane Launch.

  75. Nelson

    I was wonder how much of the rocket was made in China( or non-us), including the test equipment and computers.

    I know in Canada, all we make is beer and gas!

  76. Thanks Jack! I hadn’t realized estes motors were just gunpowder based. I guess it’s just the bigger toy motors that they use APCP in. Guess the estes ones are just the same as the stuff we made as kids (with ‘adult’ supervision, of course).

  77. 76. Spiv Says: “Jack! I hadn’t realized Estes motors were just gunpowder based. I guess it’s just the bigger toy motors that they use APCP in. ”

    You’re welcome, and I’d be careful what you’re calling a “toy.” At the big end of the hobby (“M” and up) the motors put out 1,000 lbs (5,000 N) of thrust or more for 10 seconds. That’s serious.

    For anyone still reading this thread, I found a short video (only 30 seconds) that is just incredible. It’s the nozzle camera view of the booster ignition taken at some incredible frame rate. This thing is looking right up the nozzle at the top of the grain (shooting into a mirror, obviously).

    http://www.youtube.com/watch?v=mN048TcTjto&NR=1

    The first thing you see is the ignitor motor lighting up the 12 slots (one more than the Shuttle’s SRB) at the top of the grain. The view is quickly obscured by the smoke from the propellant catching as it’s pushed towards the nozzle. The flame front moves faster than the smoke, though, so by the time the smoke reaches the nozzle, the combustion flame is pushing through it right into the camera!

    It was really cosmic. It reminded me of the early universe. First the Big Bang lights everything off and it’s really bright. Then everything goes dark for a period until fusion catches and lights everything up again.

    I think I’ve been reading this blog too long…

  78. Daboke

    3.6 million pounds of thrust looks like an environmental disaster. Perchlorate is an endocrine disrupter, more specifically, thyroid disrupter. Parts per billion in a young one’s food will have deleterious effects. Using perchlorate in huge quantities will be an environmental disaster. The unburned perchlorate and the toxic byproducts will fall on farmland leading to agony for many creatures, possibly including you. This is not cool! That white plume is toxic!

    Oh, by the way, NASA was successful in polluting a large swath of Florida this morning with the launch of the Ares I-X rocket.

    Daboke

  79. Daboke – You do, of course, have peer reviewed studies to support everything you claim, right?

    1) Perchlorates are not emitted by the motor. They’re burned to make the exhaust gas which consists of a lot of carbon compounds and some hydrochloric acid. There are also particulates in the form of aluminium oxides.

    2) There is no farmland anywhere near the Thiokol testing grounds. Not downwind for 100 miles or more. That’s why it’s located where it is! Most of that white plume (90+%) is dust kicked up by the exhaust.

    3) You do have any studies showing the effects on that “large swath” of Florida? KSC is, by design, on the very edge of the peninsula and the rockets head out over the water, which is also downwind. Between the Shuttle and the Air Force Titans, they’ve been putting a lot of these motors out that direction for decades. Do you have evidence of any damage? I didn’t think so. Remember, these things rise very quickly and most of the aerosols never make it back down to the ground, at least not for a very long time. They are dispersed and diluted to levels below even your ability to measure them.

    – Jack

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