[NRVR-Members] Input requested on two stage build project

Weeks, Thomas t.weeks at vt.edu
Wed Mar 3 10:17:04 CST 2021

Just realized.. you were talking about 2000 GRAMS.. not G forces... ;)

Yeah.. small, fast rockets can outfly the field. We've seen min-diameter Hs "disappear" off the pad and never return.  Even if you don't break our waiver's ceiling (8kft for research launcehs), you'll likely lose tracking and never see it again.  If this is expected, using a tracker (RF transmitter with directional "finder") is recommended.

Again.. if we see your Pre-Flight Data Capture form.. you'll get feedback and recommendations as a part of that approval process. :)

Send us some build pics too! Everyone loves to see people's build process. :)


From: Weeks, Thomas <t.weeks at vt.edu>
Sent: Wednesday, March 3, 2021 10:59 AM
To: nrvr-members at server2.nrvr.org <nrvr-members at server2.nrvr.org>
Subject: Re: Input requested on two stage build project

To answer your first question (about the safety protocol).. YES.. TRA pyro and staged ignition requirements (and general "best practice") is to have a built in (externally accessible) power-disarm switch so that there is no power going to either your pyro or sustainer ignition circuitry until the rocket is loaded and in the upright position on the pad.   This is strictly enforced at our launces and if you don't accommodate this requirement, you will not be allowed to fly. If you want to see some examples (w/schematics), just

Your mention of G ratings doesn't seem practical (anything over a couple hundred Gs are impact level events and becomes destructive, both mechanically and aerodynamically).. and you'll probably never exceed more than 100Gs at any of your flights (with us at Kentland).

As for submitting designs.. all student and new flyer launches are required to submit a pre-flight Data Capture form like this:

So that will help us find any "weird issues" that would make a launch unsafe.

Any other design questions.. feel free to post photos & questions here.. or talk to your prof(s) and us about setting up a design review (for larger projects).

Hope that helps.


From: Michael Czernicki <mikebpd221 at yahoo.com>
Sent: Wednesday, March 3, 2021 9:10 AM
To: nrvr-members at server2.nrvr.org <nrvr-members at server2.nrvr.org>
Subject: Input requested on two stage build project

I’m working on a two stage project and have run into a question I wanted to get some feedback on while I’m still in the conceptual phase.  Does our group have a safety protocol on sustainer ignition in two stage rockets?  Electronics in the budget range I have can do either a timed ignition with inhibition based on orientation axis or minimum altitude/velocity.  The build scope is a 2.2” airframe, not exceeding 2000g so there’s not a ton of room to build in.  I’m planning on keeping the flight profile under 3000’ altitude with H to F motors.  Anything bigger risks outflying the field.

Forum opinions on this question are pretty wide but seem more directed at mitigating failures in much larger rockets than what I’m proposing.  Closer to home input seems like a better idea than “the internet said so”.

I appreciate the feedback and I’m more than willing to bring plans and pieces to the next event if that helps.  Look forward to flying soon.

Mike Czernicki

Sent from my iPhone

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