Search results

MichiganJohn: << I'm working on a two stage project - both stages are 75mm minimum diameter, using a 4-grain motor in the booster (M1297) and 6-grain in stage two (M685). I built a single stage 75mm min diameter (M1350) last year and flew successfully at Airfest - I have good correlation...

Adrian: I re-ran the rocket on RASAero II. I now get: Actual Altitude = 10,136 ft RASAero II Predicted Altitude - Rounded Airfoil = 8,937 ft (-11.83% Error) RASAero II Predicted Altitude - NACA Airfoil = 11,294 ft (+11.42% Error) RASAero II Predicted Altitude - Biconvex Airfoil, 0.02 in...

Adrian: Using the RASAero II .CDX1 file that you posted, and changing the Nozzle Exit Diameter to the actual value of 0.20 in for the F10 motor, thrust is properly varied with altitude, and the existing RASAero II Power-On Delta-CD Models and Boattail Models are used. I'm assuming the...

Thanks Adrian! I'll take a look at it. Wow! An average subsonic CD of approximately 0.225. That's a really low CD. Charles E. (Chuck) Rogers Rogers Aeroscience

Adrian: Great flight! And great flight data! For postflight simulation comparisons, I'd start with using the base diameter of the boattail (the outside diameter of the structure attached to the motor), and use the actual nozzle exit diameter of the motor. This would be like assuming that the...

(A little late to the thread.) Adrian: In RASAero II the nozzle exit diameter is also used to vary thrust with altitude. (It is used for the nozzle exit area for varying thrust with altitude.) So the nozzle exit diameter must be the correct value, to match the thrust curve for the motor, to...

As OzHybrid noted: << The rse file calculation info description for cg calculation says it's based on the change in weight based centrally on the motor length. >> RASAero II uses the same type of model. Loaded, expelling mass as the motor burns, Unloaded (Burnout), the Center of Gravity...

RASAero II is the same. In addition to Rail Guides/Launch Shoes/Launch Lugs, RASAero II also has Protuberance Drag inputs. For the three types of Protuberance Drag: 1) Streamlined - No Base Drag 2) Streamlined - With Base Drag 3) Inclined Flat Plate All are modeled as an increase in the...

In RASAero II there is no re-trimmed increase in angle of attack due to the off-center drag from the Rail Guides or Launch Shoes. In RASAero II the Rail Guide drag and Launch Shoe drag are just added as an increase in the axial force acting on the rocket. Same for the Launch Lug drag...

That is correct. The RASAero II Rail Guide and Launch Shoe models have been calibrated against flight data from multiple rockets, large and small, with large and small (relative to the size of the rocket) Rail Guides and Launch Shoes, at both Subsonic and Supersonic Mach numbers. In particular...

Phrajphogate: << 1. Therorectically, because the flight is not vertical, I would also need to factor in the tilt angle of the rocket by adjusting the gravitational force as well right? (multiplying gravitational force with the cosine of tilt angle) >> That is correct. You'll find it's a...

Some examples of backed-out in-flight CD measurements, compared to RASAero predictions, from the RASAero web site are presented below. They can be found on the RASAero web site on the Comparisons with Flight Data Page ( https://www.rasaero.com/comparisons-flight.htm ). Adrian Adamson flew the...

To All: As part of a 4-week short course I helped teach out of the Air Force Test Pilot School from 2000 through 2005, the students flew Caliber Isp high power rockets with Black Sky AltAcc accelerometers/barometric altimeters. Using the onboard acceleration data and barometric altimeter data...

To All: The 2004 CSXT GoFast flight. Max Mach number was 5.18, burnout Mach number was 4.99. It was the first hypersonic (greater than Mach 5) amateur rocket. The Mach number was based on 3-axis accelerometer data. Using accelerometer data is the standard way to do this. For the flight...

Konrad: It's the parachute opening. The RASAero II parachute model is for a rocket in nearly vertical flight with the parachute opening at apogee, not the rocket under the parachute at Mach 0.5 continuing a parabolic trajectory through apogee (the result of an increased launch angle from...

Joey: Some inputs: 1) Others can confirm, for supersonic rockets my RASAero II software is more accurate than RockSim. For a "yolo" or "bragging rights" flight, if you are not taking any in-flight data, you should run the rocket on the most accurate software, because that is the Mach number...

Adrian: Actually, you're an advanced User. :) For advanced Users like yourself, there are some additional things you can do to model the second (the bottom, the aft closure) boattail on the upper stage. It's basically two separate RASAero II runs; one to match the drag coefficient (CD) and...

Adrian: For having a nested upper stage, see "Adding a Booster Stage with a Nested Upper Stage" section in the RASAero II Users Manual on Pages 39-44. Which I'm sure of course you have looked at, but this is for others reading this thread, who have questions on how to do a nested upper stage...

Konrad: Great to hear from you! I remember when you and I were trying to back out Drag Coefficient (CD) data from your flight data (and data from some other rockets) that the rockets were reaching just over Mach 1, and with the rockets burning out just over Mach 1 that we were having trouble...

Expanding further on the explanations above, obviously it doesn't matter much for a model rocket. It really drives the performance for a nearly 300K ft rocket. As Gerald noted; as your nozzle exit area approaches the base area of the rocket, the difference between power-off CD and Drag and...