Active Recovery

[JoeG]

Saw the "pull pins" thread start to evolve into something else and thought this might be a good time, since I have a question or two, to start a new thread on active recovery.

It seems to me that active recovery has been defined the same way by NAR and TRA. The NAR goes to great lengths to explain the collaborative effort here.

https://www.nar.org/2006/07/definition_of_active_recovery.php

However, it looks as if the application by each organization is different. I am seeing TRA saying that any vehicle over a full J must have active recovery while NAR seems to be stating that only certification flights have these restrictions. The only time the NAR uses the term “Active recovery” is in their certification section. At least that I found.

In addition, the member must use an active recovery system for their certification attempt, which usually includes parachute recovery; details of these recovery methods are described in the Definition of Active Recovery.

While in the NAR high power safety code:

12. Recovery System. I will use a recovery system such as a parachute in my rocket so that all parts of my rocket return safely and undamaged and can be flown again, and I will use only flame-resistant or fireproof recovery system wadding in my rocket.

No mention of “active” recovery here. If a saucer returns safely, as I saw many do this past week at LDRS, is that “as a parachute”?

If so, the only time a person needs to use active recovery of a saucer is on their cert flight. TRA doesn't allow “Odd rocs” for cert flight anyway. If that is not the interpretation. Since the NAR didn't apply any power limititation to their rules there are a lot of snitches out there that will need to have chutes installed to be compliant with the new code.

I don't care one way or the other. Honestly. It just seems that even when the two organizations get together they end up in different places. Just curious as to how everyone else is reading this.

 

[cwbullet]

I would say a saucer has a built in rcovery system. I sure hope that is the case. I like saucers.

 

[bobkrech]

IIRC the reason why both NAR and TRA agreed to require active recovery for certification flights was that most rockets being flown are not saucers, and they felt that certifying with a saucer did not demonstrate the prerequisite conventional recovery skills which are required in most rocket flights.

Rocket going up rarely cause any problems. It's the down part that can be dicey. A rocket descending under full main at descent rate around 15 fps can be seen before ground impact and thus can be avoided by some one on the ground. Even if one should be so unfortunate as to be hit by a rocket under full main, the event is not likely to kill the person. On the other hand, a rocket on a ballistic descent is hard to see and could impact an individual before they could react and move, and there is a good chance that the individual would suffer a severe injury or even be killed.

It is easy to design a small saucer so that the aerodynamic drag after burn out will be sufficient to produce a terminal velocity in the 15-20 fps range. Saucer weight generally increases as the cube of the diameter while the drag increases as the square of the diameter, so as the saucer gets larger and is built stronger to handle larger motors, the terminal velocity increases and the kinetic energy of the vehicle on recovery increases as the product of the mass multiplied by the square of the velocity so at some level you need an active mechanism to lower the terminal velocity and energy to an acceptable level.

TRA has defined that level as a K-impulse limit where as NAR leaves it to the flier to insure that the recovery velocity will be safe. Both methods should produce the same results provided than due diligence has been used to simulate the rocket flight prior to lift-off.

Bob

 

[cwbullet]

Hopefully NAR does not put a K limit in place. Then again, if safety is the issue, maybe the change is a good thing.

 

[CarVac]

I do think it is a good idea. After all, on a K-sized saucer, there is easily enough room for a chute.

 

[cwbullet]

Now I have to figure how to retro fit my saucer for a parachute. Maybe I will fly it with commercial motors at NAR launches and build another.

 

[CarVac]

Try rear ejection.

 

[cwbullet]

I will on my New build. It won't work on the rebuild.