J record attempt using Loki J1026

[kjhambrick]

No worries, take your time, Adrian.

Biz before fun

-- kjh( but every time I see that you've posted something new, I get all excited about studying your flight analysis )

EDIT: p.s. I REALLY DO apprecialte that you sent me that new 38mm Av-Bay before you went off to the launch ...

 

[Adrian A]

Sunday at Mile High Mayhem had lots of sun and low wind. I completed repairs and upgrades to my rocket that I renamed "persist" on Saturday afternoon, prepped into the evening, and Sunday morning I headed back to the launch site bright and early.

I got a nice straight boost, and the GPS lock came back about 13 seconds before apogee:


View attachment 20240602_084653~3.mp4






Closeup of the boost:


The rocket left the 12' tower at about 225 feet per second (153 mph). Speed at motor burnout was right about 3000 feet/second, or Mach 2.66. The rocket was rolling 4.5 revs/second at that point, which I'm pretty happy with, considering the speed and the small diameter of the airframe.

It's not very obvious but most of these plots show both Blue Raven altimeters superimposed on top of each other. The top one is solid and the bottom one has a dashed line.
Here's a closeup of the accelerations during the coast:



Most of the X and Y axis accelerations are just from the Blue Ravens not being perfectly aligned with the axis of the rocket, and some is centripetal acceleration. The Blue Raven can be launched in any orientation and the on-board calculations compensate but it's convenient to have the axes aligned with the rocket so that the raw data like this is meaningful.

 

[Adrian A]

Here is what the flight path looked like in Google Earth:


The GPS lost lock for a few seconds and had some spurious location data right at first a due to the high speed and high acceleration, but it got the lock back about 13 seconds before apogee.

Here's the Cd vs velocity data from this flight and the previous day's flight on the same rocket and same motor case:


Some nice photos of the launch, taken by George Barnes:




Great timing this time.

And the landing, which was without a scratch:

 

[Adrian A]

Here are the GPS and low rate data files from the flight:

 

[Adrian A]

Let's see if I can upload the high rate data files:

 

[kjhambrick]

Let's see if I can upload the high rate data files:

The High Rate file for your bottom Blue Raven looks good, as do both Low Rate Files and the GPS file.

Can I ask, what was your launch site temperature, more-or-less ?

Thanks for the files Adrian !

-- kjh

 

[Adrian A]

The High Rate file for your bottom Blue Raven looks good, as do both Low Rate Files and the GPS file.

Can I ask, what was your launch site temperature, more-or-less ?

Thanks for the files Adrian !

-- kjh

Maybe the 70s I think.

 

[kjhambrick]

Thanks Adrian.

Open Meteo data for the Featherweight GPS ( UTC Time, lat, lon ) = ( Jun 02 2024 14:47:17.099 UTC, 40.88669000, -104.63799000 ) = ~66 F looks to be in the ballpark then ...

Dumped file is attached.

-- kjh

 

[kjhambrick]

Wow !

The progressive acceleration -vs- time profile just now hit me.

Closeup of the boost:

Your Plot from Blue Raven High Rate Data:

Compared to the Loki 38-1200 J-1026-LC from ThrustCurve.org > Loki J-1026-LC

Interesting difference between the profiles from the test stand -vs- in flight from a mile-high launch site and accelerating 80 -to- 100 Gs !

Kool stuff !

Thanks again, Adrian.

-- kjh

 

[Adrian A]

Wow !

The progressive acceleration -vs- time profile just now hit me.


Interesting difference between the profiles from the test stand -vs- in flight from a mile-high launch site and accelerating 80 -to- 100 Gs !

Kool stuff !

Thanks again, Adrian.

-- kjh

With constant thrust, the acceleration goes up because the rocket is getting significantly lighter during the burn.

The liftoff mass was 1615 grams and the recovered mass was 1026. The empty mass was 439 grams.

About 3/4 of the liftoff mass was motor, and about 36% of the liftoff mass was propellant.

 

[kjhambrick]

With constant thrust, the acceleration goes up because the rocket is getting significantly lighter during the burn.

The liftoff mass was 1615 grams and the recovered mass was 1026. The empty mass was 439 grams.

About 3/4 of the liftoff mass was motor, and about 36% of the liftoff mass was propellant.

Dooh !

Of course !

I've never seen accelerometer data from a flight with such a high propellant mass fraction.

Nor have I ever seen accelerometer data for velocities so high.

Eyeballing your plots and a ittle q&d arithmetic:


Initial Acceleration: 735 m/sec^2 ........ about 75 G
Inital Mass ........: 1.615 Kg

Final Acceleration .: 981 m/sec^2 ........ about 100 G
Final Mass .........: 1.026 Kg

Drag Acceleration ..: -176 m/sec^2 ........ about -18 G
Coast Mass .........: 1.026 Kg

So to convert acceleration to Thrust at liftoff and burnout and Drag at burnout:

Thrust at liftoff .....: 1187 N ........ = 735 m/s^2 * 1.615 Kg
Net Thrust at burnout .: 1005 N ........ = 981 m/s^2 * 1.026 Kg
Drag at burnout .......: -181 N ........ = -176 m/s^2 * 1.026 Kg

But the Thrust at Burnout is reduced by Drag at Burnout

Thrust at Burnout -minus- Drag at burnout gives:

Motor Thrust at Burnout: 1186 N ........ vs 1187 N at liftoff !

And compared to ThrustCurve.org > Loki J-1026-CT Data:



TLAR.

Wow ! It is a beautiful thing when your can see Newton's Laws at work in a flying rocket

Thanks for opening my eyes to a new realm of rocketry, Adrian ( aka high propellant mass flights ).

-- kjh

EDIT: tried to fix alignment ( I give up )