How about a load cell between the motor and airframe plus an accelerometer? That would just leave the changing mass of the fuel to account for. Bill On Tue, Feb 24, 2015 at 2:53 AM, Andrej Vrbec <dmarc-noreply@xxxxxxxxxxxxx> wrote: > Air density was routinely measured in 50's and 60's by a falling sphere > method. See here for example: > http://deepblue.lib.umich.edu/bitstream/handle/2027.42/70398/JAPIAU-27-7-706-1.pdf?sequence=2&isAllowed=y > > Andrej > > ------------------------------ > *From:* "shawn.mchatten@xxxxxxxxxxx" <shawn.mchatten@xxxxxxxxxxx> > *To:* sugpro@xxxxxxxxxxxxx > *Sent:* Monday, February 23, 2015 11:47 PM > *Subject:* [sugpro] Re: Verifying Motor Performance Through Flight Tests > > Hahaha! I think I got it. Although.... do we really need humidity, temp and > pressure or are they all just variables to give us air density which is what > we really want. And if there was some way to measure air density directly > would that not be more helpful. One way to measure viscosity is to drop an > object of "standard" mass and shape through the substance and measure the > rate of descent. So if we flew a rocket to 500m and pitched a 10cm/500g cube > out the side with a 50cm square chute (or whatever other "standard" object we > can make up) and measure it's descent would that not be all the data we need > to measure air resistance directly. It's just a matter of making an easily > repeatable standard. Maybe a tube or sphere instead of cube and streamer > instead of parachute. > > > > > Shawn > > > > On 2015-02-23 16:27, Michael Monteith wrote: > > Com on. Keep up. lol It's really just figuring out what it would > > take to determine motor performance > > through actually flight testing. I do like your idea though. Just > > measure things like temperature, > > humidity, and pressure on the way down so you can correct for air density. > > > > Thanks Shawn > > Michael > > -------------------------------------------- > > On Mon, 2/23/15, shawn.mchatten@xxxxxxxxxxx <shawn.mchatten@xxxxxxxxxxx> > > wrote: > > > > Subject: [sugpro] Re: Verifying Motor Performance Through Flight Tests > > To: sugpro@xxxxxxxxxxxxx > > Date: Monday, February 23, 2015, 3:54 PM > > > > > > Not sure I'm following all this conversation but > > instead of a balloon can you gather data from a parachute > > recovery on the way DOWN instead of on the way up to > > establish air density etc. For that matter are there any > > papers that show air density or viscosity based on a > > specific parachute and mass configuration. If not that would > > be a cool standard to create for the community. > > > > Shawn > > > >