Thursday, October 08, 2009

Rocket weight inflation

Egads, the as-built weight of the Raygun Gothic HoJo is sitting at a whopping 35 oz without motors.  I weighed all the 'major' parts before assembly but it appears that I left something out (like the epoxy, shock cord, etc.).  So, I updated the over-rides and reran the RockSim model.  It says the HoJo is stable and a -5 delay is almost perfect.  Referencing the handy thrust-to-weight chart on ROL InfoCentral, the loaded weight of 36.5 oz falls about 3/5's of the way between 'safe' and 'marginal'. Close enough for me - I'm going with the RockSim (sim details below).  I am sure glad I didn't add 4 oz of copper to the cone!

Engine selection
[D12-5, D12-5, D12-5, D12-5]

Launch guide data:
Launch guide length: 36.0000 In.
Velocity at launch guide departure: 37.7346 ft/s
The launch guide was cleared at : 0.295 Seconds
User specified minimum velocity for stable flight: 43.9993 ft/s
Minimum velocity for stable flight reached at: 49.7764 In.

Max data values:
Maximum acceleration:Vertical (y): 307.442 Ft./s/sHorizontal (x): 0.062 Ft./s/sMagnitude: 307.442 Ft./s/s
Maximum velocity:Vertical (y): 140.7451 ft/s, Horizontal (x): 0.2066 ft/s, Magnitude: 140.7470 ft/s
Maximum range from launch site: 3.94934 Ft.
Maximum altitude: 411.24016 Ft.

Engine ejection charge data:
Using a delay time of : 5.000 Seconds
Velocity: 29.0245 ft/s
Altitude: 397.69685 Ft.

Recovery system data
P: Parachute Deployed at : 6.651 Seconds
Velocity at deployment: 29.0245 ft/s
Altitude at deployment: 397.69685 Ft.
Range at deployment: -3.94934 Ft.

Time data
Time to burnout: 1.651 Sec.
Time to apogee: 5.729 Sec.
Optimal ejection delay: 4.077 Sec.

Landing data
Successful landing
Time to landing: 26.918 Sec.
Range at landing: -1.12456
Velocity at landing: Vertical: -19.4417 ft/s , Horizontal: 0.0813 ft/s , Magnitude: 19.4419 ft/s