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Civilian Space Launch Imminent

Posted by timothy on from the when-can-we-honeymoon-on-the-moon dept.

rossjudson writes: "Looks like the Civilian Space Exploration Team has gotten clearance from the FAA and the Bureau of Land Management to attempt the first amateur flight into space. That's pretty cool. Maybe one of you space-mathematics types out there can educate us on just what 0-Mach 5 in 15 seconds really means! Is this thing gonna just blow up?"

9 of 53 comments (clear)

  1. about 10 Gs? by renehollan · · Score: 3, Informative

    subject says it all... speed of sound = 1100 f/s, so 5500 f/s in 15 s = 1100 f/s in 3 s = 367 f/s^2. 10 Gs would be 322 f/s^s. Close enuf. Increased accuracy is welcome.

    --
    You could've hired me.
  2. X-Prize? (or was that something else?) by dschuetz · · Score: 4, Interesting

    Wasn't there a prize for the first team to loft 1 kg to 100 km? Would this qualify?

    (no, it wasn't X-prize, that was for bringing people into space and re-launching in, what, a week?)

    Been a while.

    I'm disappointed, though, that they're being asked to keep the exact launch date a secret. If they can't protect a rocket in the middle of the Nevada desert from terrorists (or tourists), then we're all screwed.

    1. Re:X-Prize? (or was that something else?) by mcelrath · · Score: 3, Informative
      The contest you are thinking of is the Cheap Access To Space (CATS) Prize. Unfortunately, that one expired on November 8, 2000 and the money was returned to the investors. As far as I know, no one since has succeeded in acheiving the requirements for the CATS prize. I think these guys will be the first.

      The X-Prize is a $10 million prize to get 3 people to 100km twice within 2 weeks.

      -- Bob

      --
      1^2=1; (-1)^2=1; 1^2=(-1)^2; 1=-1; 1=0.
  3. Here's the numbers... by Spock+the+Baptist · · Score: 3, Informative

    0 to Mach 5 in 15 seconds?

    That's going from 0 mph to 3700 mph, or 0 to 5400 ft/s in a quarter of a minute; assuming 740 mph = Mach 1.

    a = [v(2) - v(1)]/delta t

    a = (5400 ft/s - 0 ft/s)/15 s = 360 ft/s^2
    or about 11gees.

    9 gees is a heavy gee load in air combat maneuvering (dogfighting), so 11 gees is a very heavy gee load. At least over a protracted period.

    --
    "Oh drat these computers, they're so naughty and so complex, I could pinch them." --Marvin the Martian
    1. Re:Here's the numbers... by Louis_Wu · · Score: 4, Interesting
      I'm heading under the bridge, hold this rope and pull me out if the troll gets his hands on me.

      :)

      Part of the reason for using Mach as a reference is that it is so flexible. Many aspects of fluid mechanics depend on knowing if the fluid flow is supersonic or sub-sonic. The behavior of subsonic fluid is fairly familiar to most people, but that changes radically when the flow becomes supersonic. Knowing the flow speed in relation to the shock wave speed (the speed of sound in that fluid) tells you which equations to use, and what to expect. Handy.

      The problem we have here is that we don't care about the fluid mechanics. All we care about is the speed in relation to the ground, and we can't get that easily because the reporter & the PR flack thought that spouting off Mach numbers sounded cooler or more scientific. (My idea of a scientific speed reference in this case would be two-fold: the raw speed number and the velocity vector broken down into components: vertical, North/South, & East/West. But I'm a mechanical engineer, and I want useful information.) We can get a good idea about the bounds of the acceleration involved by using speeds for Mach 1 at various altitudes (10 - 11 gravities as posted already), but a more accurate calc would account for the variation in Mach number with altitude.

      Of course, for a trully rigourous theoretical treatment, what we really want is the mass of the craft, the mass loss rate (fuel burn rate), and whatever measure of the craft's rocket power we can get (it might be the force the rocket produces [which could be a function of time], it might be the power of the rocket [which I think I could translate to a force if I had a few books in front of me], it might be the mean velocity of the rocket's exhaust stream [which I know that I could translate into a force, if I had the proper information about that flow stream]).

      With that {potential} boatload of information, we could apply the modern incarnation of Newton's Second Law, F=d(p)/dt ; force equals the derivative of momentum (p) with respect to time (t). That ends up being F=ma + v*d(m)/dt , the first part being very familiar to anyone who's ever taken physics, the second part much less so. F=ma : force (F) equals mass (m) times acceleration (a). The second term isn't very familiar, because most people don't think of mass changing over time. The classic example of this is a rocket - the topic of today's lecture. {I have no idea why I'm saying so much. Work must be more boring than normal.} F=v*d(m)/dt : force (F) equals velocity (v) times the change in mass (m) over time (t).

      [BTW, all of the "d"s are NOT variables, they are part of the notation of derivatives in calculus. (I was falling asleep during a lecture once, and I wondered why the teacher didn't cancel the extra "d"s from the top and bottom of the equation; then I woke up and almost died laughing at myself.:) ]

      Anyway, the upshot of the math is that if we knew how fast that fuel was being burned [ d(m)/dt ] how fast the craft was traveling at any time (v) and what the mass of the craft was at any time (m), we could back-calculate to get the acceleration. All that work to find out how heavy you'd feel. :)

  4. Missing the big source of error. by MarkusQ · · Score: 5, Funny

    about 10 Gs? ... speed of sound = 1100 f/s, so 5500 f/s in 15 s = 1100 f/s in 3 s = 367 f/s^2. 10 Gs would be 322 f/s^s. Close enuf. Increased accuracy is welcome.

    I think the big source of error in our calculations here will be our uncertanty of the acceleration profile. While constant acceleration is certainly a reasonable solution, it isn't the only possibility. For example, we could have:

    • First second: no accelleration
    • Second second: no accelleration
    • Third second: still no accelleration
    • Fourth second: no accelleration continues
    • Fifth second: dito
    • Sixth second: deep rumbling sound is heard, but no accelleration
    • Seventh second: a very small amount of side-to-side accelleration, but it never amounts to anything
    • Eighth second: rumbling stops; accelleration does not start
    • Ninth second: everything is disturbingly quiet, and quite stationary
    • Tenth second: no accelleration II, the dance mix
    • Eleventh second: a very small amount of upward acceleration is detected, but it is well within the error bars for the instruments
    • Twelfth second: no accelleration, but what might be a hint of smoke
    • Thirteenth second: no accelleration, and that is definitely smoke
    • Fourteenth second: no acceleration, but the smoke is building up nicely
    • Fifteenth second: a great deal of acceleration, accompanied by a lot of smoke and a very, very loud "bang".

    I sure hope this isn't what happens, but it could fit the numbers as well as "constant accelleration at 10.5G +/- a fudge."

    -- MarkusQ

  5. Re:Am I the only one by Myco · · Score: 3, Insightful

    Well, certainly they could spend more money and time to do something flashier than a quick up-and-down. But the purpose of this mission is to make history, to have the first civilian space flight, and that's no mean feat. It's not just so that they can say they did it -- that's a means to an end. It's to open up the door, make people realize it can be done, get other people working on the big, flashy projects. Since the purpose is to get the ball rolling, I think they chose right by doing it quick and simple rather than delaying to add more features to the mission.

    --
    My deviantArt site
  6. I'm one of the leaders of the rocket project. by Eric+Knight · · Score: 3, Informative


    Hi, everyone. I'm glad to join your discussion here.

    I'm one of the leaders of the Civilian Space eXploration Team (CSXT). I head up all of the avionics development of the rocket project you are discussing: http://www.civilianspace.com My specialty is electronics & communications. If I can answer any questions for you, let me know.

    BTW: I see a message thread speculating on the number of g's. We expect a peak of 18 g's just before motor burnout.

    Some other numbers you might find interesting:
    * Motor burnout at 14.2 seconds
    * Mach 5.2 at motor burnout
    * Maximum dynamic pressure (Max Q): 8,500 pounds per square foot (occuring at 13.6 seconds)

    F.Y.I., Since our launch is less than a month away, I'm pretty consumed with pre-launch activities. I may only be able to stop by this forum a couple times per week. I apologize in advance for any tardy replies. ;-) Thanks for your interest in our endeavor!

    -- Eric

  7. Re:Speed of sound w/ altitude... by Eric+Knight · · Score: 3, Informative


    Hi!

    We project 18 Gs just before motor burnout.

    We've been very accurate in calculating (and then confirming) our projections in previous launches. However, I'm not the physics / aerospace guy on the project (so I don't have the wherewithal to provide the calculations). I oversee the electronics & avionics on the rocket.

    Thanks for your interest in our launch!

    Eric Knight
    Project Co-Leader & Avionics Manager
    Civilian Space eXploration Team (CSXT)
    http://www.civilianspace.com