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I've added load relief to my thrust-vector controller (TVC) and would like to simulate it with some realistic wind data, ideally up to 80 km or higher.

I know wind speed and direction would be measured before launch with Jimspheres or equivalent, and I imagine there must be loads of Jimsphere data collected over the years, maybe for the space shuttle or Saturn V, which have so much public info out there.

I haven't had much luck in my search, so I'm wondering if someone here knows where I could find this?

Huge thanks if you can point me in the right direction!

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  • $\begingroup$ Also, maybe add a link or short explanation of "Jimspheres" are, rather than require every reader to separately google it or know what it is. $\endgroup$
    – uhoh
    May 24, 2021 at 0:35
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    $\begingroup$ @uhoh see space.stackexchange.com/q/52333/6944 $\endgroup$
    – Organic Marble
    May 24, 2021 at 1:29

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Jimspheres don't go anywhere near that high. 60K feet max.

Here's a Jimsphere run from KSC on 6 Jan 2005. Burst altitude 55.8 Kft

Wind speed in feet per second. Y axis is feet with 10K tickmarks.

enter image description here

Wind azimuth in degrees from North. Y axis is feet with 10K tickmarks.

enter image description here

Source: Personal notes.

This paper about the Doppler wind profiler at KSC has some more examples on page 9.

More examples here What are "high altitude winds" and why do they often delay rocket launches?

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    $\begingroup$ Oh wow, this is perfect. Thank you for sharing. This just made my day. $\endgroup$
    – user39728
    May 23, 2021 at 19:21
  • $\begingroup$ Is azimuth measured clockwise (e.g., with East at 90 deg and west at 270 deg)? $\endgroup$
    – user39728
    May 23, 2021 at 19:26
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    $\begingroup$ Yep. Feel free to upvote if this helped you. $\endgroup$
    – Organic Marble
    May 23, 2021 at 19:27
  • $\begingroup$ Now curious about the higher altitudes. At 60,000 ft (~20 km), the rocket would probably be well above the Mach 2.2 velocity threshold at which load relief control would shut down. But air density would still be significant (I think just an order of magnitude smaller than at sea level, if that?), which would be compensated for by the increasing velocity to make aerodynamic forces still... meaningful? In their pre-launch simulations, would they not both with the higher winds, or would they get that data from elsewhere (other probing devices or maybe numerical models of wind speed/direction)? $\endgroup$
    – user39728
    May 23, 2021 at 19:30
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    $\begingroup$ q is negligible by then, so wind is a don't care. space.stackexchange.com/a/49480/6944 $\endgroup$
    – Organic Marble
    May 23, 2021 at 19:41
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The best I can recommend is an atmospheric model maintained by NASA that includes dispersions up and beyond your altitude of interest. The model, GRAM, provides dispersion estimates across the globe. It works well above 60000 ft. However, at altitudes below that it does not capture local terrain effects from mountains and coastlines. To resolve that, NASA and the USAF have used thousands of measurements from balloons and other sources to build Range Reference Atmospheres (RRAs) that they use to verify requirements for launches and landings at a few select places across the United States (such as Kennedy Space Center).

Finding atmospheric data above 250000 ft is difficult. Back in the 1980s, the American space shuttle orbiters began skimming the high altitudes of the atmosphere for thousands of miles during their return to earth. Reviewing the flight data, NASA discovered density shears or "potholes" in the drag accelerometer sensor data that couldn't be attributed to any vehicle attitudes. The flight data ended up being incorporated into the GRAM model dispersions.

You don't need to incorporate the model directly into your simulation -- you can run GRAM stand-alone to generate atmosphere profiles that your simulation then reads.

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  • $\begingroup$ Thank you, Gavin! My interest is piqued. For my simulation I need wind speed and wind azimuth as functions of altitude. Would GRAM generate lookup tables for these variables? $\endgroup$
    – user39728
    May 24, 2021 at 16:56
  • $\begingroup$ Hm, I see the stern warning on the request page that the software is for US-government-authorized purposes only. This is for a personal project, and I'm not about to ask for approval to continue and finish it, so they can keep their GRAM tool. Plus, the request page reads like a consent to be monitored and forfeit my right to privacy. No, I don't need their tools that bad. $\endgroup$
    – user39728
    May 24, 2021 at 17:18

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