Paper Rocket

By Nathan | January 17, 2011
Mercury Redstone card model

Mercury Redstone card model

A while ago I did a couple little paper models of some Futurama characters which were a lot of fun. Recently I've been waiting to see a space shuttle launch with @spacekate and after visiting so many museums and NASA facilities I really wanted a model of a rocket.

The think about models is they are pretty boring unless you build them yourself. After the success of the Futurama figures I thought I would look and see what paper models there are for space. It turns out there are quite a lot. So many that there are whole forums based around it. Kate recently wrote a great overview of some of the choices in paper spacecraft.

Building the Rocket

I wanted to do a kind of build log but I was so excited by actually building the thing that I didn't bother to take any pictures of the process. I will say that it was hard. Some of the pieces are only fractions of a millimeter wide at points. I didn't even think one could cut and fold anything so tiny. As it turns out as long as you have patience and a steady hand those details are not as impossible as it might seem.

Mercury Redstone instrumentation unit

Mercury Redstone instrumentation unit with antennas and other detail

The escape tower on the rocket

The escape tower on the rocket

Learning Lessons

Launch table and base detail

LOX and fuel fill and vent detail along with the launch table.

One really nice thing that I found out is making models is a great way to learn about how the rockets work. After spending 2 hours making a hydrogen peroxide fill plate, I will forever remember where that is on a Mercury Redstone and that the engines used H2O2 to run the fuel pumps. I learned about the umbilical fairings and the surprisingly low tech straps on the hold down ring under the capsule. I'm beginning to think that this is my favorite rocket. But that will change as soon as I build the next one!

The particular model I built can be found here: http://www.cardinspace.com/content/view/10/8/lang,en/

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Near Earth Asteroid Lamp at Science Hack Day SF

By Nathan | November 24, 2010

This past weekend I was at science hack day in Palo Alto. A normal hack day is when a bunch of people get together and try to build something—usually a program, but can be something physical like electronics too—in 24 hours. Science hack day is a 24 hack day for making things for science—whether it be a program to crunch large datasets from particle accelerators, or a robot with a spectrograph attached. This was the second science hack day, the first was in London this summer and was a big success.

Since Palo Alto is way closer to me than London I jumped at the opportunity to participate. I had only one problem, I didn't know what to work on. Luckily the event's organizer and fellow space enthusiast Ariel Waldman had come up with a fantastic idea and was looking for help. Her idea was to make a lamp that would light up whenever a near earth asteroid went by. So I came down to the Bay area with a teensy and a box of electronics and got to work.

Design

We started with a cheap IKEA lamp but I didn't have the right relays to turn the bulb on and off so I decided to take it apart and replace the bulb with LED's. That way I could turn the lights on and off with the microcontroller. I went a step further and used three color LED's. I glued a bunch of LED's to a translucent plastic cup and glued some more cups together to make a lamp shade.

Cups and LED's and glue

Cup Hack © Jeremy Keith

Then I wired each color of the LEDs to a switching transistor to turn them on and off and wired that to the teensy. I got a ton of help soldering from my friend Kate. The actual building of the lamp only took a few hours. I spent a lot of my time talking to all the other interesting people at the hack day.

Case Study for Open and Accessible NASA Data

Once the LED's were wired to the teensy I could now trigger the lamp over USB. Now all I had to do was figure out when an asteroid has passed by the earth. NASA's JPL provides plenty of information about near earth objects including a page with all the past and upcoming passes. In general NASA is committed to open data. They have all kinds of pages like this. The problem is while I can go to the page and look at it, the data isn't 'machine readable'. What would be better is there to be an API that I could hook into that could automatically let a program know what asteroids are passing and when.

Luckly for the lamp, someone has already done this. Sort of. @lowflyingrocks is a twitter account that has been set up by Tom Taylor to scrape the data off the JPL site and update @lowflyingrocks every time there is a pass. Twitter, unlike random JPL webpages, does have an API. So I wrote a python script to read the @lowflyingrocks stream and send a signal to the teensy to flash the lights.

Near Earth Asteroid Lamp from Nathan Bergey on Vimeo.

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Fun with Real Time Data

By Nathan | August 7, 2010

I've been working on bits and pieces of a project to be able to record and view data in near real time for the last few months. It's one of those things where each layer has its own set of challenges and is written in its own language. But I finally put all the pieces together this week.

I used what hardware I had laying around, which turned out to be an arduino and a light dependent resistor (LDR). The light dependent resistor is exactly what it sounds like, a resistor that changes resistance depending on how much light shines on it. This effectively makes it a light sensor. I attached the LDR and a resistor to one of the analog pins on the arduino and wrote some code on the chip to read the value or the LDR and report it when asked over serial/usb.

my arduino

An off the shelf arduino with a 'ProtoShield' from sparkfun. On the breadboard is the LDR (red oval shaped thing) and a resistor.

Then I wrote a script in python to ask the arduino how much light the LDR was reading and take the answer and dump it in a database. I scheduled the script (with cron of course!) to run every 2 minutes. Then I wrote a webpage in php that read the last 36 hours of data in the database and drew a graph of it.

an example graph from the LDR

In a snapshot of the webpage you can see how the light in my room changes in the course of the day (bigger numbers are brighter). Also notice the period around midnight when I turned on my room light before I went to bed.

If by now you're wondering “why?”, because it's fun. And also it's practice. I would like to get more interesting sensors; I already have some temperature sensors in the mail. It's been hot recently and I've often wondered just how hot it gets in my room, perhaps in comparison to how hot it is outside. But there are many more options, cloud sensors, power consumption, wind speed, sound, the list goes on. Now I have the infrastructure in place, all I have to do is think about what kind of data I would like to see.

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Successful Launch!

By Nathan | July 3, 2010

In my last post I talked about building a rocket. This past weekend I actually flew it! I went out to the middle of nowhere in Eastern Oregon for Oregon Rocketry's “Summer Skies” launch. My plan was to launch with an H motor and then a J to get my level 1 and level 2 TRA certifications. I was also there to help Portland State Aerospace Society launch their much larger rocket. Both rockets were a success, though each with their own caveat. Regardless I had a blast!

Setting up

The night before I prepared my rocket, getting the chute folded and all the parts put into place. I also calculated the stability using OpenRocket and decided to add some weight to the nose to offset all the weight of all the epoxy in the tail.

Rocket and its components laid out.

The rocket and its components laid out.

Then it was off to Brothers Oregon, or at least some empty piece of desert nearby. I discovered upon arriving that the different altitude/temperature/humidity/something had changed the nosecone fit. I ended up spending an hour sanding it down so it fit better. But after that all I had to do was load the first engine and fly!

All loaded and ready to go

All loaded and ready to go

On the pad waiting to launch

On the pad waiting to launch.

Liftoff!

Liftoff!

Safe back on the ground

Safe back on the ground.

The first flight was nearly perfect! My delay charge was a little too long and so the chute opened a little after apogee. But otherwise it was did exactly what it should have done: go up about 1000 feet and land a little ways away unharmed. Level 1 achieved!

I'm pretty happy that it flew well!

I'm pretty happy that it flew well!

Level 2

Level 2 requires taking a test and flying a rocket on a larger motor. The test was no problem, but a larger motor means bigger forces, more speed and more things that can go wrong. After checking over my rocket I decided that it was still in prime condition so I loaded up the larger J335 motor (75 lbs of thrust for 2 seconds) and flew it again. This time the rocket would go to an altitude of about 3000 feet.

Liftoff for level 2 flight

Liftoff for the second time in a day!

The takeoff was beautiful! If you're wondering, the launch rail was tilted to compensate for wind. 10 seconds later I was expecting to see a chute, but for the second time it was late! In fact a bunch of people that day had the same problem. We are beginning to suspect that some our motor delays were mislabeled. At any rate the chute did open and I could see it come down in binoculars.

Falling on drogue.

Falling on drogue.

But when I got to it (this time it came down over half a mile away) I found out that the top had “zippered”. What happened is that the since the chute didn't open at apogee the rocket started to fall and had picket up so much speed that when the chute opened the chord yanked the cardboard body tube around and cut into it.

Oh no!

Oh no!

Oh well, it turns out that it's still flyable, all I have to do is trim the tube a little. And because it's still flyable I still got my level 2 certification!

PSAS

By this point I was pretty tired so I called it a night. Unfortunately there was a full moon that night so there wasn't much to see star-wise. Someone brought a telescope and we looked at Saturn which was beautiful. The next morning everyone got up and worked on the main even: Portland State Aerospace Society's LV2c rocket. Equipped with cameras, flight computers, an electronic roll control system and a massive N2000 motor this 70 pound behemoth blasted 15,700 feet into the air. A lot more info can be found on their launch data page. Here is a video of the launch from about a mile away on a nearby hill:

More Rockets

I plan to continue working with PSAS and hopefully launch another big rocket in September in Black Rock Desert, Nevada. Until then I work on understanding the complex interaction between roll control canards and rear fins, which turned out to be more problematic than anticipated (on PSAS's rocket). I don't know if I'll fix up and fly mine again. Maybe someday.

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Rocket Build Log

By Nathan | May 21, 2010

Until the weather turned ugly I was planning on flying a rocket big enough to get level 1 and level 2 TRA certification this weekend. While it looks like I will have to hold off until next month, I can at least share a short build log.

The rocket is a kit from Giant-leap rocketry. It comes with a nose cone, body tube, motor retainer and centering rings, and fins all cut out and ready to assemble. It also comes with a parachute and shock cord, Kevlar wadding, and launch lugs. In other words it comes with everything except fuel, epoxy, and patience.

The kit the way it arrived.

The kit the way it arrived.

Unfortunately, for reasons that are too complicated to explain here, I was not able to take photographs of the first few steps. So I pick up after having put the motor retainer and centering rings in the base of the tube and tacking the fins in with a little bit of epoxy. The next step is to really glue the fins in. And I mean really glue them in.

Epoxy everywhere

Epoxy everywhere

This involves adding thick epoxy fillets to each fin interface. The outside is actually the least important in terms of strength, but a sharp transition is bad for aerodynamics. So I added a fillet made of epoxy mixed with millions of micro-balloons—microscopic, vacuum-filled plastic spheres. This keeps the mixture light, but add lots of volume.

Masking around a fillet that is ready to be poured.

Masking around a fillet that is ready to be poured.

A finished fillet.

A finished fillet.

The next step is to put the final centering ring in the base. I used JB weld instead of standard epoxy because this part can get very hot from rocket exhaust. Most epoxies are destroyed by heat, so be sure to use something heat tolerant.

The bottom centering ring.

The bottom centering ring.

After that construction is pretty much complete. All that's left to do is paint. I started with a couple of coats of primer followed by three coats of flat white.

Ready to paint

Ready to paint

Flat white

Finished coat of white paint

Then I did some personalizing. I channeled a Mercury Redstone and added some test pattern checkerboards in black. I also painted the nose cone black at this point.

Masked for black paint

Masked for black paint

All that was left was to add the launch lugs and add some stickers.

The finished rocket

The finished rocket

When I go to launch I'll slide the motor in and stuff the parachute and wadding in the top. Then hopefully it'll fly straight up 3,000 feet! I will follow up with a post with pictures, and possibly even a video of the launch—which at the moment looks like will happen the last weekend in June.

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