a reply to: DigginFoTroof
OK, not going to waste my time reading everything, so if I recant something that has already been said, just chalk it up to the fact that every time I
try to explain a similar concept on here, someone gets all bent out of shape because the world doesn't work like they want it to. Not going to go into
a bunch of arguing over that either.
But... you did ask nicely, so here goes a try.
The most difficult aspect of having satellites is launching them and there are many nations that have the capability of doing this and now even
private industry has reached this point.
Launch is only one difficult part of having a satellite. There also must be position control, backups, orientation control, etc. Yes, many nations can
launch satellites, but most only use their launch capacity for government sanctioned operations. The USA is one of the precious few that both can and
will launch a commercial satellite, possibly the only one, and those satellites must meet stringent controls. NASA oversees every aspect of satellite
design and operation.
One exception is the micro-satellites, like the CUBESATs that universities launch. There is still minimal oversight by NASA, but these are given a
little more leeway since they are not for commercial usage and are so small as to not pose a significant safety risk to the public should something go
wrong. Even balloon-mounted equipment is controlled by NASA; one I recently worked on was scrubbed because someone working on altitude control messed
up and it started dipping into the airlanes at night.
My part worked flawlessly. Of course.
Launch is not like calling up a mechanic and scheduling a tune-up. NASA only launches every so often, because of the time needed to build and test a
rocket. You don't just call up and say, "I want a satellite launched next Monday; do you take VISA?." Launches can be scheduled years in advance, and
that in itself means the technology sent into orbit is not the latest and greatest.
The cost of launching is directly related to the size and weight of a satellite (payload), so small and lightweight is not an option but a necessity.
The smallest possible components are used. As an example, the passives (resistors and capacitors) I typically work with here are in the 0805 package
(0.08" x 0.05"). In a pinch, I can go down to 0603, but even that size means a lot more time and tediousness soldering. Satellites can use 01005
packages in their design (0.01" x 0.005") and that means everything has to be fabricated using robotic devices; humans are simply not capable of
working that small. I have never met anyone, regardless of experience and ability, who can go below 0402. To use these tiny parts, the traces on the
circuit boards must be smaller as well (otherwise, there is no real size savings). That increases the cost appreciably.
Another thing to consider is that if your WiFi transceiver goes out, you can unplug it and go to the store to get another one. Not so with satellites.
You can't just call up NASA and say, "I need to replace my satellite. Is my launch still under warranty?" You also can't get a repairman to ride out
and fix it. It's on its own once in orbit. That means it cannot fail prematurely... period. If it does, someone is getting fired (and possibly
blackballed). No, it has to work, as expected, day after day, week after week, year after year. That kind of reliability costs money... a lot of
money. There are three basic grades of electronic components: retail, which is what I use mostly, with something like 99% reliability; military, which
is much more rigorously tested to ensure the parts work correctly every time; and medical, where every individual part is tested. These reliability
guarantees receive a premium price, but in some cases that price is worth it... for example, you do not want the firing control mechanism on a fighter
jet malfunctioning in the middle of an offensive, and you don't want the heart monitor on a loved one failing at the wrong moment. People can die. In
a satellite, that reliability is essential as well, so companies pay the price for it.
On to position and orientation control (GNC)... compressed gasses are not a good solution. You tend to run out of gas pretty regularly. Once out of
gas, there is no way to hook up a compressor and fill the tank. You're done. Most satellites use some sort of motor-driven torque control, since
electricity can be collected from solar cells. That and the associated control systems to maintain attitude are quite expensive; they have to react to
extremely minuscule deviations.
Those solar cells are not like the ones on your roof. They are state-of-the-art, high efficiency, lightweight cells that are specially designed and
built for space application. They also have to be protected from high-energy particles they may contact, so they are encased in a tough, transparent
covering. Now we're talking advanced materials science and more money. I have held several thousand dollars worth of solar panels in my hand, for a
high-altitude balloon, and what I was holding covered less than the 2 square meters you mentioned.
Batteries are lately lithium-based cells. they simply offer the greatest combination of weight, charge density, size, and lifetime. No, not cell phone
or laptop batteries... again, these have to be individually tested and verified to work correctly or the satellite will fail when they do.
Most systems have backups, because if one fails, a backup is the only way to maintain operation. So you're talking about a lot of redundancy, which
uses up space and weight and costs more.
While many communication satellites do use directional antennas, dish antennas are not the design of choice. A dish must be precisely oriented to a
single receiver, placing extra restrictions on attitude control and minimizing the ability of the satellite to communicate with anything else. Dishes
are used in ground based transceivers since they point at the satellite in a known location and only at the satellite, plus their position on terra
firma means its no problem to get the precise alignment. Satellites do not.
Satellites also need to transmit more power since their antennas must cover a wider arc, and must be more sensitive to received power since consumers
demand lower and lower power devices. Low power transmission means the receiver must be more sensitive and that costs money... a LOT of money!
Also, the typical satellite does not operate at the frequencies we are used to here on earth. They can, but it would be a waste of money because the
frequency of the carrier determines the rate at which data can be transmitted. An op-amp that works up to 100 kHz might cost me $0.25... one that
operates at 10 GHz likely costs $100 and up. Even higher, cutting-edge frequencies can get into thousands of dollars for a single chip.
Finally, nothing is off the shelf in a satellite. Every circuit is designed specifically for the tasks it will perform. There is no "Satellites R Us"
Now add in thermal and radiation shielding, increasing the weight again... overall, these satellites are marvels of engineering. And they cost like