Explorer I Scale Build

As part of completing the NARTREK SIlver level, I'm undertaking my first scale build, an Explorer I satellite with stage 4 booster.

I'm writing up the build as a series of posts over the next 6-8 weeks on my personal site. The first post went live this afternoon at:

https://www.macmodeler.net/ramblings/2019/7/31/explorer-i-satellite-scale-build-introduction

Mark

 

Here's a dimensioned drawing I found in the Van Allen papers at the U of Iowa online archives.

By the way, the Explorer 1 is a great space modeling project, but it's not considered an allowed subject in NAR Scale, because NAR scale requires the complete rocket as launched, all the way down to the first stage or booster. It *is* allowed in NAR plastic model conversion, though.

Peter Alwa y

 

Thank you Peter.

I am the NAR member Randy Boadway mentioned when you sent these drawings to him earlier this year. These are the plans I have been using for the build.

I will update my post with a correction about scale versus plastic model conversion.

And thank you for all the great work you do.

Mark

 

Hi Peter,

I just read the NAR rules for plastic model conversion. I’m not understanding how the project would be allowed under “plastic model conversion competition.” Rule 56.1 of the code says “The entry must be one that the manufacturer did not produce as a model to be flown; and it must be modified for flight by the competitor.” The build is not a conversion of a manufacturer’s plastic model kit not meant to fly to one that does fly. The build is one where I’m constructing a flyable model rocket version of the Explorer I with stage 4 booster from a combination of 3D parts I’ve designed and standard tubes, motor mounts, etc. to a scale based on the drawings you found.

Either way, the NARTREK Silver level requires a scale or sport scale build and does not appear to include plastic model conversion builds as an option. I’ll pick another rocket for that requirement.

Most importantly, I’m having a blast building this project to “scale.”

Mark

 

OK, *this* project would not be allowed under Plastic Model Conversion, but an Explorer I would be allowed if you based it on the Glencoe kit.

So basically, this is a very fine space modeling project, but not for the NAR Scale contest, the way the rules are written.

 

As I started the project, I purchased the Glencoe Kit, mostly for informational purposes. It's at 1/6 scale so the main airframe is approximately 1 inch in diameter and 13 inches in length. It's a nice kit and includes a stand with a plaque and a JPL decal for the airframe. I can see where it could be a fun build in a NAR plastic model conversion event.

 

Doesnt nartrek just require it to be judged? I never read that as "must be entered into a scale competition"

 

I've posted an overview of the process I'm using for the build at:

https://www.macmodeler.net/ramblings/2019/8/3/explorer-i-satellite-scale-build-overview-of-process

 

Being judged at a NAR competition is an option. All that is required is that the scale model is judged. Here is what NARTREK Silver says:

"Build and successfully fly a scale model from an existing model rocket kit, or construct a scale model from basic parts using scale data obtained from the sources outlined in the accompanying documents. With a second party, make an honest evaluation of your model using the form provided. Alternatively, enter your model in a NAR sanctioned Scale or Sport Scale competition, and have the contest scale judges fill out the certification form. Take a photograph of your model and attach it to the certification sheet after completely filling out the rest of the form. We have included judging sheets for both Scale and Sport Scale judging."

The NARTREK Silver package includes the judging forms for NAR scale and NAR sport scale. I'm inferring, perhaps incorrectly, that means the model must meet all of the requirements of NAR scale or sport scale including the all stages requirement. I've emailed NARTREK to confirm whether I'm correct in my inference.

 

Good news. I heard back from George Scheil of the NARTREK program: "After further review of the Silver packet, we have never required that boosters be included. Should you ever attempt Static or Super Scale, then yes, boosters, and (for SS) launchers are required. Only a tiny number have done either in 40 years."

So, the build will be used for NARTREK Silver after all

 

I've posted a discussion on my iterations to arrive at a scale for the build:

https://www.macmodeler.net/ramblings/2019/8/16/explorer-i-satellite-scale-build-choosing-a-scale

 

As part of figuring out the scale for the project, I moved the body tube reference data at http://www.erockets.biz/body-tube-sizes/ into a spreadsheet. This allowed me to compute relative tube OD's to try and match the ratio of the diameters of the Explorer I. I used Table 2 on page 12 of Alway's The Art of Scale Model Rocketry as a guide.

I asked Randy Boadway if he was okay with me sharing the spreadsheet data, and he was. I cleaned the spreadsheet up and put it in the format Alway used. There are pdf and .csv versions attached. You can open the .csv into your spreadsheet program.

 

A discussion of how the build was modeled in Fusion 360 to generate 3D printed components is now available at:

https://www.macmodeler.net/rambling...-satellite-scale-build-modeling-in-fusion-360

 

I'm getting excited about the build as it's finally taking shape. Here's a photo without fin can mount or launch lugs installed and not all the painting finished (stripes on payload/nose cone) but the other parts dry fitted together. Another post on my blog about the build later this week.

 

Back from vacation. Got the stripes on finally. Now for touch up, add bolts removed back on, flat clear coat, JB Weld the motor retainer on, add parachute and it's ready to go. Weather permitting I hope to have it judged and flown at our Oct. 26th launch. The final posts will hopefully go up around the end of October and early November.

 

Nicely done, sir. Didn't realize how big this rocket was until I read your blog link.
So, 29mm motor mount? What engine have you decided to fly her on?

 

You bringing that to Build Night Tuesday Mark? You've done an impressive job there friend.

 

F67W-4 based on both Rocksim and ThrustCurve. They are saying about 275-300'. This puppy is heavy (~ 1200 g dry weight) and I'm knocking closer to HPR than I had intended. My goal for the first flight involves being judged for NARTREK Silver and then just having a successful up and down flight .

 

Yes. Thank you for the kind words, Phil.

 

I think the stripes look great. I know they were one of your big concerns and I think they look really good.

 

Thanks Zeus-cat!