- This topic has 55 replies, 13 voices, and was last updated 16 years, 11 months ago by
Warren B. Musselman.
Warren B. Musselman.-
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Doug Gerrard
Let’s do the Math 😀
9000 ft / 30 ft/sec on a streamer is 300 seconds or 0.08333 hours
3 miles / 0.08333 hours is 36 mph wind speed.
I don’t remember the wind being that fast but it’s possible. 🙄 Of course these are averages, you mileage may vary…
Doug
James Russell
10 to 15mph is what I would have guessed, it was picking up when he launched.
James Russell
First, my question – was this rocket really found 3 miles away (per the original post over in lost and found?) If it was indeed that far away, how does a rocket that goes to 8K (or 9K or even 10K) land 15,000′ feet downrange when it was under a streamer? Either it went a LOT higher, allowing it to land way over there, or it took off on a pretty wicked tangent (meaning it wouldn’t have gotten nearly as high). I would say mathematically it is pretty much impossible to go to 8K and land 3 miles away with a smallish streamer.
John I looked at the map and it looks like it was about 1.5 miles from the launch site.
I also think the waiver is 2 miles but goes up to 3 with the 35k but lets see what Joe says, he has the waiver.
Adrian
James,
The Parrot altimeters, like all barometric altimeters, measure pressure. The Parrot does so very accurately. I know it’s accurate because I checked it against an accurate pressure reference gauge. I paid extra to have that reference gauge calibrated against a NIST-referenced standard, and that calibration report verified it is accurate within 0.2%. When I checked the Parrot against that calibrated reference gauge after the flight, the Parrot agreed with the pressure gauge within 0.3%. (the Parrot was low).
Parrot altimeters report pressure when you download the data. There is a formula that everyone uses to convert pressure to altitude, and that’s what the spreadsheet does when you plug in the Parrot’s data. There’s no adjustment, no tweaking, no scaling of the pressure data. I do use the data “straight off”, and that’s what I reported.
It turns out that there are more accurate ways to convert pressure data to altitude data than the standard atmosphere equation that everyone uses, (using soundings from weather balloons and/or correcting for ambient temperature that’s different than what is assumed in the standard atmosphere model), and I provide a way to do that, also in the analysis template. But that’s not been the standard practice for what constitutes a record and so I’m not planning to report that altitude as the record. I’d like to see everyone use the most accurate methods to convert pressure to altitude, but until then, we’re stuck with a standard method that is inaccurate except in the coldest of flying conditions.
I have provided a Parrot to fly with several other altimeters and a GPS on Ken Biba’s flight that was supposed to go over 40,000 feet. I expect that the Parrot altimeter’s pressure readings, when converted to altitude using balloon soundings, will provide a better match to the GPS data than the other altimeters that Ken is flying. But I haven’t heard back from Ken to find out if he did that flight. I have flown a Parrot in the same av-bay as another altimeter (I think a MAWD), in one of John Wilke’s flights, and the Parrot reported a higher altitude. After that flight, I also checked that Parrot against my reference source and found that the Parrot I used matched the pressure reference gauge to within a few tenths of a percent. Therefore, John’s other altimeter was less accurate than the Parrot was, or my reference gauge is off.
John,
From Mike’s description of where he found this shot, I marked the location on a Google map:
http://maps.google.com/maps/ms?msa=0&msid=114868309855736157763.0004589a9594c47b95e9eIf the link doesn’t work, you can find the map by searching on “outboard booster” when you’re in Google Maps.
If I interpreted Mike’s description correctly, the rocket landed about 1.3 miles from the pad.Adrian
But why not shut up all the critics and just fly you rocket with another altimeter? If you can set an altitude record with the parrot, why not do it with another altimeter?
I can fit a Parrot and a Beeline transmitter in 2.1 inches of 24mm coupler tube, and I generally design my rockets to take advantage of that. No other altimeters that I know of, that have been approved for records, can fit in that space. The only other record-approved altimeter that would come close to fitting is the Alt15k, but it wouldn’t work because it doesn’t do deployments. Motor ejection delays are never long enough for record-attempt birds.
That being said, the two rockets I used to break records were actually designed for other applications. The one that I used for the F record (“Barack-it”) was designed for G80s without an extension, and the rocket Mike found was designed to be a booster that overlapped half of the sustainer motor. So both of them had some extra room in the airframe when they flew. Barack-it is mostly lost now, but the G record booster could fly again. I’m not sure that’s how I want to spend my last G37, however. Maybe next year I’ll go for the F record again with a rocket optimized around an F10 and another altimeter. Then I’ll cut it down and try to raise the bar with a Parrot. I’m pretty sure the F record can be set over 8500 feet with a Parrot. With the extra mass and length of another altimeter, it would be something lower, but I’m not sure how much yet.
Anonymous
Let’s do the Math 😀
9000 ft / 30 ft/sec on a streamer is 300 seconds or 0.08333 hours
3 miles / 0.08333 hours is 36 mph wind speed.
I don’t remember the wind being that fast but it’s possible. 🙄 Of course these are averages, you mileage may vary…
Doug
At the risk of wandering a bit off the topic, while your math is correct Doug, there is still a flaw in the logic above. The ROCKET would have to be moving 36mph in your equation, which would mean the winds would have to be significantly higher. A piece of tissue may move equal to the wind, but not a rocket. Also most rockets will fall more than 30fps under a streamer.
Again, if the rocket landed closer then all this math is N/A anyway. My point is that it would take more than 36mph winds to move a rocket that far.
MikeS
iflyrockets wrote:First, my question – was this rocket really found 3 miles away (per the original post over in lost and found?)___________________________________________________________
That was My statement. (3 miles) Stated before
looking at a map.I stand corrected.
According to the math others have put forward.
And looking at the map. Each square = 1 mile.My visiual judgment on distance is in error.
The place I have pointed out as the rocket location is correct. Give
or take a few yards.Warren B. Musselman
I’m not 100% sure about the AAO during the 20K waiver, but I do know it was 5m radius when the call-in to 35K is active. I would expect it is 3m radius and not diameter.
Personally, from all that Adrian has written about the Parrot and what I know of his engineering skills, I suspect his is a more accurate baro altimeter than the run of the mill. After a long conversation with Jim Amos about the Standard Atmosphere Model some time back, I’m well aware of the need for temperature compensation and most manufacturers do some form of it, but not to ambient temperature, just to a fixed “guess” of what the pressure curve should be like at 70 degrees F or thereabouts. Robert DeHate’s altimeters are specifically excluded from all contest use by TRA because he does none whatsoever. Adrian’s Parrot provides a means to post-process the data to the actual ambient temperature. In addition, it also has accelerometer data that can be used to validate the barometric data.
The big issue is it isn’t direct reading so it can be read at the launch table by the LCO and witnesses and that the data has to be downloaded before anyone can get any altitude out of it. Perhaps a direct read-out with the downloaded data able to provide correction or enhancement of the data based on post-processing. Even better, perhaps all that processing can go on in the device including temperature compensation to the actual ambient temperature.
James – what you’re saying about having to use a Tripoli certified and owned altimeter is the one that makes the most sense although it also is going to make for a logistical nightmare for Tripoli.
Warren
James Russell
James – what you’re saying about having to use a Tripoli certified and owned altimeter is the one that makes the most sense although it also is going to make for a logistical nightmare for Tripoli.
Warren
They do not think so do to the number of submitions, they figured maybe 12 units or so and will publish the mounting or size so that you will be ready for it and then once you get it you mount it or through it in and fly it and then ship it back.
Warren B. Musselman
Well I can see at least 4 people in NCR who have their eyes on altitude records who would want one within the next couple months… John Wilke, Adrian, Chad and myself… and probably more.
I would assume TRA would have all these altimeters calibrated to NIST traceable standards and that they would have to be a recording altimeter. Given that aviation baro-altimeters are in the $4000 price bracket, in part due to the calibration process, this might open a small market for highly accurate and individually calibrated altimeters. They should probably also have 3 axis accelerometers and an air temp sensor as well and would want the altimeter returned with all data intact onboard so proper data evaluation could be made – sounds like a Parrot to me.
I do agree that a manufacturer flying his or her own altimeter is a conflict of interest when attempting altitude records.
W
Doug Gerrard
James Russell
Adrian
Anonymous
MikeS
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