Orbital Hydrogen Collector

Orbital Hydrogen Collector (OHC) with docking spacecraft

Orbital Hydrogen Collector (OHC) with docking spacecraft

Deep space missions will require the placement of large quantities of hydrogen in low earth orbit for use as spacecraft propellant. Procuring hydrogen in low earth orbit from the surface of the earth via chemical rocket booster can be relatively expensive.

The Orbital Hydrogen Collector (OHC) offers an alternative method of obtaining hydrogen propellant in low earth orbit. The OHC ‘scoops’ the hydrogen that exists in minute amounts in the near vacuum of the upper atmosphere at altitudes of low earth orbit. This hydrogen propellant can then be accessed by docking spacecraft to the OHC.

FIGURE 1 (not to scale) shows the basic design of an Orbital Hydrogen Collector. The direction of orbit is from right to left, as shown. The ‘flow’ of atmospheric hydrogen is thus from left to right.

ohc 2

Hydrogen molecules enter the scoop (a) and are compressed into higher-pressure gaseous and/or liquid form by the compressor unit (b). The hydrogen is then pumped into storage tanks (c). Spacecraft can access the stored hydrogen by docking with the propellant transfer boom (d).

The collection of atmospheric hydrogen causes the OHC to lose momentum and experience orbital decay. To compensate, the OHC can utilize electric propulsion to provide orbital boost. In the figure, photovoltaic panels (e) provide electric power to engine (f) while propellant is pumped from storage tanks (c) to engine (f).

The operational exhaust velocity of the engine must be higher than orbital velocity, or the engine will not be able to compensate for momentum lost to atmospheric drag. Plasma engines are the logical candidates for OHC propulsion.

At $5000/kg to ship payloads into orbit using expendable rocket boosters, it could cost tens to hundreds of billions of dollars to place into orbit the hydrogen propellant needed for just one human expedition to Mars. Informal calculations indicate that the OHC could collect the same amount of hydrogen in orbit for as little as one percent of that cost.

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The Wizard from Earth, a science fiction novel by S.J. Ryan (aka, Me), available on Amazon as an ebook

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Eye Robot, the Continuing Saga


My original plan for making a robot with visual pattern recognition was to connect a camera to the raspberry pi, and then the raspberry pi to my laptop, and then I would run the raspberry pi ‘headless.’ That means, I would open up a remote terminal program on my laptop to access the raspberry pi’s desktop. The advantages of this are that I wouldn’t need a separate monitor or mouse or keyboard or wi-fi for the pi.

But this turned out to be one hassle after another. It turns out that you can’t configure a pi to be headless unless you first have it ‘headed.’ So you need all that stuff, in order to not need all that stuff. And then I couldn’t get the remote terminal program to work, and I would have to modify several files on the pi that I knew nothing about, let alone how to modify them in the first place . . . .

My second plan was to just do the pattern recognition programming on my laptop. It’s in python, and python is portable, right? So whatever I do on my laptop can be ported over to the pi, even though one is Windows and the other is Linux. Easy as. Nope, the webcam I got for the laptop has a mini-CD disk that clatters in the drive, and I couldn’t get SimpleCV to download at first, and then it wouldn’t work . . . and this got too complicated too.

So then I ended up getting all the peripherals for the pi after all. Today I connected the monitor, only to discover that the power supply that I ordered from Amazon is wrong. I bought the CanaKit power supply, thinking that since it was on the Tontec monitor page, that it was for the Tontec monitor. No, it’s for the raspberry pi, and because people who buy the Tontec monitor also buy the raspberry pi (of course), they also buy the CanaKit power supply for the raspberry pi. And that’s why it ends up on the Tontec monitor page even though it doesn’t connect to it. My fault.

This is what you see in the picture. I still can’t get the thing up and running because I need a power supply for the monitor. That will come next week. I suppose I’m in no hurry.

Anyhow, here are the links for the Tontec monitor and the correct power supply, in case you want to check them out:

Tontec 7″ LCD display screen for raspberry pi

Tontec power supply for the above

Until I get the power supply, I can’t vouch how this stuff works, but you can see the ratings on the Amazon pages.

BTW, I saw a demonstration of the Pixy(cam) Pet robot on Saturday, and it’s a good example of what can be done with robot vision. Here is a Youtube video of the Pixy Pet robot:

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Eye, Robot (Part One)

raspberry pi

pi camera

I’m toying with the idea of a robot that can interact with its environment by pattern recognition. I thought the way to do this was with a raspberry pi computer. So I bought the computer and the pi camera from Maker Shed, and expected that all I would have to do is connect a USB cable to my laptop to begin programming the pi.

Well, not exactly. It turns out that what I need on both the pi and my laptop is a program called VNC, and VNC doesn’t come on the preloaded OS card that I got for the pi. I can download VNC for my laptop easily enough, but it appears that I’ll need a monitor and keyboard connected to the pi in order to download VNC onto it. There may be a way around that, but it looks like I’m about to make a trip to Goodwill for a cheap monitor and keyboard.

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Rocket Ship Freedom free for today (Dec 16)

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Rocket Ship Freedom

This is a YA novel I wrote eight years ago about a single stage to orbit rocket that travels to the Moon. It doesn’t come back, so how the crew gets home is something you’ll have to read the book to find out. If you’re a space buff, you’re probably wondering how an SSTO gets to the Moon in the first place. Again, it’s in the book. Which you can get today for FREE.

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The Wizard from Earth

My science fiction novel, The Wizard from Earth, is available on Amazon Kindle as an eBook. It’s selling for only 99 cents. If you don’t have a Kindle, you can still download the free Kindle Reader software, and read it on your computer and/or smartphone.

Matt was a typical twenty-second century teenager with a supercomputer implanted in his head. He was supposed to be launched toward the star Alpha Centauri, but ended up on another world, lights years and centuries removed from his family.

Carrot was a native of that new world, a mutant of superior strength, senses, and intelligence, alienated from her own family and locked in a deadly struggle with a global empire.

Together they would battle humans, mutants, and super-intelligent AIs in a war for the fate of a new world — and for the survival of humankind.

View: The Wizard from Earth

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Kind of a resume

I’m looking into tutoring again and thought it might be useful to list a few links that illustrate what I’ve done. I may not have done the right stuff, but I have done stuff.

Arduino Park:

Grisbot 2-obstacle course:

Grisbot Follows the Light:

Triac/Reed Switch test:

Ultrasonic distance sensor as toggle switch:

Ultrasonic pinger game:

LED Figurine Illumination

Grisbot with Scratch Obstacle:

ATTiny45 light display:

Grisbot light follow test:

Also, here’s my video work on Modeling Molecules.

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Rocket Ship Freedom available for download

Rocket Ship Freedom

Rocket Ship Freedom is my YA novel about a teenager who gets an internship at a private rocket company and ends up going to the Moon, where he discovers a deadly mystery that threatens the survival of the human species.

Judging by the recent popular movies, the YA genre appears to be dominated by fantasy and dystopia. When science and technology do appear in a story, they often deal with really far out stuff like time travel and parallel worlds. Now, I like that stuff too, but I wondered how come there didn’t seem to be any YA novels that focused on hard technology and an upbeat vision of the future. So I tried to write a story that was scientifically accurate yet also fun and full of adventure.

View Rocket Ship Freedom at Amazon

(By the way, the cover illustration is my very amateur work in Sketchup and has several errors. Can you spot them?)

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Ultrasonic toggle switch

ultrasonic toggle

This is an idea for using an ultrasonic distance sensor (aka ‘pinger’) as a toggle switch. I’ll show it first and then explain:

As the hand approaches, the yellow light comes on to indicate that the switch is in aware mode.

When the hand is close enough, the green light toggles. That is, if it’s off, it goes on. If it’s on, it goes off. The yellow light, having done its duty, goes off.

The yellow light remains off while the hand is retracted to indicate that the aware mode doesn’t activate again until the hand is fully retracted. This is to prevent the ultrasonic equivalent of what is called ‘bounce’ in mechanical switches.

So what are the applications of such a switch? Suppose you have a runaway robot and you’re shouting at it but the background noise is high and so you take out your remote but there’s radio/IR interference too. You could chase after it and slam a mechanical switch on the back, but maybe that is getting too close for safety.

So here’s another solution: simply reach out toward the robot, and when you’re close enough (but still at a safe distance), the pinger detects your hand and deactivates the robot.

A more mundane application would be to turn fans and lights on and off more conveniently.

(In case you’re wondering, I had oatmeal for breakfast.)

Buy at Amazon:

Vivotech Hc-sr04 Arduino Ultrasonic Distance Measuring Sensor Module Good Compatible

Arduino Cookbook

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Debugging Touchless Technology


The comment that I added to the previous post was not the full solution to having a row of touchless buttons, but it set me on the way. A second pinger IS necessary to discriminate against anomalous readings.

In the following video, I turn off the yellow lights but retain a comparison between the distances from the finger to the lower (or ‘green’) pinger and the upper (or ‘yellow’) pinger.

Two comments:

1. There is still some confusion between readings for buttons. This might be corrected by setting the buttons farther apart and increasing the separation of the pingers.

2. You can see the light flicker as the finger hovers over the button. This is the equivalent of ‘bounce’ for a mechanical switch, and the solution is likely to be ‘debounce’ code.

Anyhow, it looks like the best way to use pingers for touchless technology is one pinger per button. That’s where I’m going next.

Available on Amazon:

Vivotech Hc-sr04 Arduino Ultrasonic Distance Measuring Sensor

Arduino Cookbook (2014 edition)

And still trying to sell my stories on Kindle:

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Touchless Technology with ultrasonic distance sensors


The concept behind this circuit design is that you can press buttons without touching them. As your finger lowers to the tabletop, the yellow light will come on, indicating that you are on the correct approach. Farther down, the green light comes on, which activates the button function.

Or so it’s supposed to work. What I find is that when my finger is on the lower level, the upper sensor will still detect its position, which is bad enough, but since it’s measuring at a diagonal, it will measure the distance as greater than it is.


Possible solutions would be to redesign the circuit so that there is a UDS pointing up from each button position. But that would require four sensors rather than two even for this circuit.

Hmm, I wonder how big the ‘spray pattern’ is for the sensor pings. If it’s fairly wide, then the position of the finger could be determined by triangulation.

Available on Amazon:

Vivotech Hc-sr04 Arduino Ultrasonic Distance Measuring Sensor

Arduino Cookbook (2014 edition)

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