" A plane that can take off horizontally, burning atmospheric air while accelerating and climbing, which then switches to using its own on-board oxygen in order to reach orbit makes a lot of sense."

Until you look at the physics/economics. Extracting oxygen from the atmosphere isn't free. It shows up as drag, which requires more fuel to overcome. The liquid oxygen in a rocket's propellant tank has already had kinetic energy added to it. The oxygen you get from the atmosphere is at a much lower energy state, so you have to add energy to it. This makes high-speed airbreathers very difficult.

The "massive amounts of oxygen" you are saving are actually quite cheap. Liquid oxygen is one of the cheapest fluids you can buy. Cheaper than bottled water. The idea that it's going to be cheaper to manufacture it in flight than on the ground is inherently flawed. What you save in LOX, you lose in additional fuel. Moreover, the fuel needed to make these schemes work is not hydrocarbon (cheap) but liquid hydrogen (expensive). The structures needed to contain LH2 are also expensive, due to the low propellant density. These factors make airbreathing a non-starter.

"I reckon the "real" purpose of the program is to develop a mach-10 air-breathing aircraft"

Certainly not. Hypersonic airbreathers are extremely difficult, and there's an enormous difference between cruise missions (airliners) and acceleration missions (space launch). Airbreathers tend to perform well at a specific velocity (cruise speed) while rockets must perform well over a wide range of speeds.

Jess Sponable knows that, have seen what happened in the X-30 NASP program, and will not go down that route.

Even SpaceX does not use rad-hard components because of the expensive.

Well, some people think that global monitoring of crop patterns, rainfall, land usage, climactic shifts, etc. is useful science.

If you don't, that's okay.

You need to do some research. NASA just successfully launched two PhoneSat satellites this year, which use Arduino as part of a watchdog circuit. They plan on flying more in the future.

Planet Labs was founded by two of the lead engineers who built PhoneSat. The founders of Nanosatisfi worked at NASA Ames, where PhoneSat was built, and EADS Astrium, a major satellite manufacturer.

Just because something appears in a parts catalog doesn't mean it's available for overnight shipping. You'll find that out if you actually try to order them.

The fact that someone is doing something differently than you would doesn't necessarily mean they are stupid or know less than you do. They may have good reasons for what they are doing, because they spent more time thinking about the problem than you did composing your Slashdot flame. Not to mention building actual hardware and testing it. If you believe you can do better, great -- build your own satellite.

"Nowhere do I see mention of these arduinos being special, radiation-hardened versions. Nowhere, is there mention about extended temperature range, vibration, etc. These are all important if the mission is expected to succeed." Most small satellites do not use radiation-hardened components. Rad-hard chips provide 1/10 the power at 10 times the price, and thet aren't available when you need them. Generally, they're made to order with long lead times. It's generally easier to add a watchdog circuit to reboot the computer when it crashes due to a radiation event. Even the laptops aboard ISS are not rad-hard. In higher orbits and interplanetary space, radiation levels are higher and rad hardening becomes a bigger concern. Even there, techniques like spot shielding can reduce the number of components that need to be hardened. You might want to consider the possibility that maybe, perhaps, people who have built and operated satellites professionally for organizations such as NASA are not idiots and have some idea what they are doing.

Not legally.