Launch Pad SA-2 Guideline

[blakbird]

Well, it's not exactly a review at this point, but I did build two of these from the Plan Pak, and I've posted lots of photos of the construction below. An actual review will take me a long time since there's a lot to say about construction, especially since you have to make most of the parts yourself!

Construction Photos

I've launched one of them so far, and all of the complex staging actually worked! I've got some videos and a photo of the flight below.

Launch Video

FYI, this is a two stage with a 3xD12 cluster in the booster and 1xD12 in the sustainer. Each motor is different. A D12-0 thrusts against a piston attached to a micro switch. When this motor ejects itself, it completes a circuit through a mini-phono plug to the 9V battery and arming switch in the upper stage, which fires the upper stage. After the D12-5 in the upper stage is away, a D12-3 in the booster which has a long tube attached to it ejects the booster parachute. The booster chute is protected from engine blast by a tethered plywood panel. Finally, the third D12 is simply plugged and ejects. Like I said, amazing it all worked!

Eric Albrecht

 

[Stymye]

great job,nice!
I have the rim 2stage plan pak and have debated on using this system or going with a timer,,,from your perspective does the
piston switch mechanism look like it will hold up to repeated launchings?is it tricky to do maintenence on?

thanks in advance

 

[blakbird]

There's really nothing about the switch system that will "wear out". But there's absolutely no access to it after construction, so make a good solder joint. The problem with a timer is that it starts to arc over right away when the motors burn out, so you need to get that upper stage lit immediately. The D12-0 does that nicely. You could certainly save a lot of complexity with the timer, especially since you wouldn't need the phono plug between stages. If you build it per plans, bring a little electrical tester and verify 9.6V at the ignition leads with the switch armed and the motor removed. When you pop a motor in the lower stage, it should drop to 0V.

Eric

 

[Stymye]

ok I watched your video , I see what you mean about staging right away,indeed that could be tricky with a timer...thanks Eric

 

[blakbird]

Another SA-2 fan. There is a kit available,

I've looked at that one and would like to get it. It is quite a bit smaller. Mine is 52", diameter from 3.5" to 2.6". Mine is also two-stage with a 3 motor cluster in the booster. But the other one would be a lot easier to prep!

And how does yours compare to this model?

Those are some great SA-2 photos! In terms of scale detail, I think the Launch Pad plans do a good job. The Scalekits kit doesn't have a "gap" in the booster, and doesn't have an exhaust cone like the Launch Pad plans do.

Eric

 

[eugenefl]

Wow, that is one intricate MPR rocket! Nice work! Looks great and it's nice to see that it functioned properly.