BalloonSat Extreme

NearSys introduces the BalloonSat Extreme. This is one of the largest BalloonSat flight computers. At its heart is the BASIC Stamp 2 (the BS2pe is recommended), so it is powerful and easy to program.

The flight computer has an eight-channel analog port with 12-bits of resolution for sensors like weather stations. There is a five-channel digital port with connections directly to the BS2 for sensors like Geiger counters. Unlike other BalloonSat flight computers, the BalloonSat Extreme has a GPS Port to allow your BalloonSat to monitor and record GPS reports (like altitude and time). The flight computer can operate three cameras. The cameras can ones with modified shutter buttons or be Canon cameras running the CHDK USB remote program. The flight computer can also control three servos. The servos have a seperate power supply to prevent a bad servo from draining the main power supply.

Part of the BalloonSat Extreme kit is its Control Panel, a seperate printed circuit board. The Control Panel allows you to power up the flight computer without opening the BalloonSat. Two LEDs indicate power is available for the flight computer and the servos. Finally, there is a Commit Pin that allows the BalloonSat to be powered up long before launch. When ready for lift-off, pull the Commit Pin and the flight computer will begin recording data.

The entire kit is only $48. Check it out and its directions and sample code at, http://nearsys.com/catalog/balloonsat/extreme.htm

I'v spent a couple of months perfecting a hovercraft-based robot. My initial goal was to develop a line of robots that behaved like satellites in a weightless environment. They would not move around on wheels (what good are wheels in space?) but navigate around on jets of air (safer than hot rocket exhaust). I discovered though, that air hockey tables can't generate sufficient air flow to lift the robot base. After another year and a half of thinking, I decided to use a hovercraft base in place of the air table. The design I came up with was made possible my resources on the Internet. The toy hovercraft described where just the thing to help me develop the NearSys HoverBot. Unlike traditional robots, the HoverBot accelerates when it drives. Most robots travel at a fixed speed that makes it easier to program navigation goals. The HoverBot roboticist must think about time, acceleration, velocity, and displacement when navigating. Here's an introductory video. You can learn more in my Servo magazine article and can soon purchase a kit from my website, NearSys.com/catalog.

The NearSys HoverBot

I'v spent a couple of months perfecting a hovercraft-based robot. My initial goal was to develop a line of robots that behaved like satellites in a weightless environment. They would not move around on wheels (what good are wheels in space?) but navigate around on jets of air (safer than hot rocket exhaust). I discovered though, that air hockey tables can't generate sufficient air flow to lift the robot base.

After another year and a half of thinking, I decided to use a hovercraft base in place of the air table. The design I came up with was made possible my resources on the Internet. The toy hovercraft described where just the thing to help me develop the NearSys HoverBot.

Unlike traditional robots, the HoverBot accelerates when it drives. Most robots travel at a fixed speed that makes it easier to program navigation goals. The HoverBot roboticist must think about time, acceleration, velocity, and displacement when navigating.

Here's an introductory video. You can learn more in my Servo magazine article and can soon purchase a kit from my website, NearSys.com/catalog.

Test of Geiger Counters

Last week I launched two geiger counters into near space. The mission was for KU aerospace engineering students and I got to send my experiments along in the tracking capsule.

The first geiger counter is the reliable Aware Electronics RM-60. I've flown this geiger counter dozens of times and really love it. It measures everything, alphas, betas, and gammas. Aware has a range of geiger counter products that you'll love. See them at http://www.aw-el.com/

The second geiger counter was built from a kit that's available from Electronics Goldmine. The tube is Russian built and does not include a mica window for alpha particles. Here's the webpage for this product. http://www.goldmine-elec-products.com/prodinfo.asp?number=c6979

The Russian tube is suppose to be pretty sensitive. In my tests, it detects more background radiation. However, I don't have a calibrated source that I can verify that it's actually detecting properly. I have s short video on a test that you can watch on my YouTube channel, www.youtube.com/nearsys.

Below is a chart I produced with data from NearSys-10A. Note how much more radiation the Goldmine geiger counter is detecting.

Normally the RM-60 shows a drop off at 62,000 feet. The driop off doesn't happen until closer to 70,000 feet and it doesn't show up well at all for the Goldmine detector.

So much more to learn!

HoverBot

I finally got the Hoverbot set up with a relay H-Bridge. Unfortunately, one of the relays died. But that still gives me enough to demonstrate this proof of concept.

As you can see, the Hoverbot picks up quite a bit of speed when the drive fans are operating. In this video clip, the fans are on for three seconds and off for one. I've since reduced the lift fan's voltage to 4.5V (from 6V) and reduced the drive fans' voltages to 4.5 volts.

There are two problems to addess. The first is that the Hoverbot has a tendency to steer to the left. Experiments indicate it is due to the counter-clockwise spin of the lift fan. I may have to double up lift fans in a future design.

The second problem is that once the Hoverbot gets into a wobble, it won't come out. In fact, the drive fans are no longer effective in wobble. The HoverBot is going to have to detect this and correct it. Either an extendable foot or being able to shut down the lift fan is going to be required.

Enjoy the video

Clearing Misconceptions About Near Space Missions

I was thinking about these topics earlier this week and thought they ought to be cleared up. So if you'll permit me.

Most people are familiar with the concept that motion is relative. This means that motion to one person looks just the opposite to another person who is not sharing that motion. It's all a matter of your frame of reference.

When we discuss things like the ascent rates and maximum altitudes of a balloon, we really should be discussing these issues in their more accurate frame of reference, that of the balloon. In reality, the balloon is holding still and the earth (along with the atmosphere which is firmly attached to the earth via gravity) is falling. Apparently this occurs because when we put helium into a balloon, we're removing it from the earth and its atmosphere (I'll refer to these as the earth-atmosphere system). When you remove low density material from the earth-atmosphere, you're increasing its average density. Recall that dense objects sink and less dense objects can float. The denser earth-atmosphere now wants to sink. And as long as the filled balloon is firmly attached to the earth's surface (via gravity), like by a person holding the balloon's load line or by tying the load line to a helium bottle, the balloon will hold up the earth. So those of you who are holding the filled balloon before launch, you're really holding the earth-atmosphere up. Think about that next time.

Once the balloon is no longer tied to the earth, the earth-atmosphere falls away. As the earth and its atmosphere fall away, the balloon is surrounded by less and less dense air. The balloon expands as a result. Since the helium is trapped inside the balloon, there are no further changes in the earth-atmosphere's density and it falls away at a constant rate that is dictated by the friction of the air around the balloon. The atmosphere, which remember is firmly attached to the earth, can only slide pass the balloon at a limited rate. Friction is why the earth does not fall away from the balloon infinitely fast. Many of you have no doubt noticed that at some where around 30-40,000 feet, the balloon appears (and let me stress appears) to rise faster. This is the result of the earth-atmosphere slipping around the balloon faster because of changes in air density and balloon size. This is pretty obvious if you recall that the force of friction is based on factors like surface area and density.

At the point where the atmospheric pressure around the balloon is low enough, the balloon bursts and releases its helium back into the atmosphere. This mixing of helium back into the earth-atmosphere system decreases its average density and let's the earth and atmosphere float back up to the balloon. The air rising around the balloon payload makes it tumble (due to turbulence) and inflates the parachute. The mixing of the balloon's helium with the atmosphere occurs very rapidly and therefore, the change in the density of the earth-atmosphere is very fast. This makes the earth-atmosphere begin to rise very quickly. At the earth-atmosphere rises back up to the balloon, the air becomes denser and the parachute creates more drag, slowing the ascent of the earth-atmosphere. Therefore, we see the initial ascent of the earth-atmosphere is very fast at the start, but over time, the ascent rate slows down until the balloon and earth make contact. At that point, the earth-atmosphere system and balloon are back in equilibrium and the motion comes to an end.

Now, since the days of the Greeks, we've known the world is round or spherical. There is no friction between the earth-atmosphere system and outer space. So when you go on a balloon chase, your car tires are pushing the earth and making it rotate the opposite direction. Let me stress, your car is NOT MOVING!! Therefore, it would help if everyone in their cars would travel together and go the same direction. If your chase teams will push the earth in the same direction, you'll rotate the earth in the same direction more quickly and get the earth rotated into the proper alignment with the balloon more efficiently. Therefore, it is imperative that we prevent chase crews from leaving their homes from the opposite direction, as this pushes the earth in another direction at the same time. When one big and heavy chase truck tries to push the earth to the west, the rest of our lighter cars trying to push the earth to the east suffer. I for one do not want to see my gas mileage decrease because of this. So please be polite to everyone else and follow along with the rest of the pack.

This also highlights the importance of using the balloon launch announcements system. There are some weekends with multiple balloon launches. If they are occurring at the same time, our cars are fighting each other to rotate the earth to our proper positions. So be considerate and coordinate your launches with other teams across the country.

Just doing my part to clear things up,
Paul

(Next time I'll explain the relativistic effects of a balloon launch and why the Twin Paradox makes use younger after each balloon flight)

H-Bridge Problem

My HoverBot is grounded. The ducted fans that drive it require nearly 2A, but the TA78080K H-Bridges I'm using have built-in overload protection at 1A. I'd like to use H-Bridges so I can run the fans forwards and backwards. The TA8080's are lightweight and simple to use, so I really like them.

For an interim solution, I'll try using small relays. This won't give the Hoverbot turning ability, but at least it will test the concept until I can replace the H-Bridges.