How do the astronauts do spacewalks when the ISS is orbiting around at 17,000mph? Can you do that with a moving vehicle?
Inertia is a thing, you know. The astronauts are in the same inertial frame of reference as the ISS. Thus, as the ISS is orbiting at 17,000mph the astronauts are doing the same speed, inside it. As space is almost friction-less (no air resistance to slow you down), when they step outside the ISS, they are still doing the same speed as they were inside it.
Thus, their relative speeds remain the same.
Imagine a passenger train moving at 100 mph. You and all the other passengers sitting in it and you are all moving at 100 mph.
If the train was operating in a frictionless environment (like space) if you stepped off the train you'd still be doing 100 mph (until you experienced some form of friction).
If you are on the same train and you walked from the back to the front of it, your speed to all the other passengers would appear to be 5 mph. This is because you are all in the same inertial frame of reference.
However, to a stationary outside observer, your speed would be your the train's speed plus your walking speed: 100 mph + 5 mph = 105 mph.
If you walked from the front to the back of the train, against the direction of travel, your speed to the other passengers would again appear to be 5 mph.
However, to our stationary observer your speed would appear to be 95 mph. This is because you are moving against the direction of travel so you minus your speed form the train's speed: 100 mph - 5 mph = 95 mph.
The ISS is more than 15 years old, how come there are no maintenance activity of the thousands of seals, airlocks and such? The astronauts should be covered in grease rushing to keep up and do maintenance. Even Aircraft have more maintenance...hundreds and thousands of parts need to be replaced...how come the ISS doesn't (especially without an atomsphere)?
Firstly, there is continual maintenance on the ISS. Those spacewalks you referenced earlier in your question, those are generally for maintenance.
A brief google search on the term 'iss airlock maintenance' turns up tens of thousands of articles, press releases, fact sheets and videos on this topic.
In fact, there's an entire wiki page dedicated to ISS maintenance. It seems like you should be doing some of this leg work your self.
There is a lot of maintenance on internal hatches and the like. Like the external maintenance, it's a continual thing. ISS has routine maintenance that is centrally planned by mission control. Crew members include maintenance activities as a part of their daily duties.
As to the second part of your question. Space is simultaneously a very harsh and a very benign environment for mechanical systems. Exterior hatches and the like are exposed to the radiation and heating/cooling cycle, which is very tough on them. Internal hatches are kept at a standard pressure, at a standard temperature in an almost vibrationless environment with quite low humidity. This is an almost ideal situation for long life for mechanical systems.
In contrast, aircraft are subject to continual vibration, acceleration/deceleration, changing environmental conditions, 60-80 degree celcius temperature cycles and lots of other abuse through their operational lives (which are generally 24-28 years long). Everything an aircraft does subjects the airframe, engines and other systems to stress. Take-off, landing, climb, descent and cruising flight all have their individual stresses and strains.
Operating in a vacuum vs operating in an atmosphere require very, very different engineering solutions and maintenance requirements.
How does the ISS produce oxygen? Yes it uses water. How does it produce water then? No system can produce 100% effiency so they are losing massive amounts of water. Where does it come from?
Off the top of my head, ISS has three different oxygen generation systems, two of which use electrolysis via water and one of which uses sodium/lithium hydrochlorate. Plus, there are back up oxygen cylinders and maybe some other solid oxygen generation systems as well. There are at least two oxygen recycling systems I can think off.
ISS typically operates with a six month reserve supply of oxygen and water and is resupplied frequently (six resupply missions have reached the ISS this year alone). For example, the July 2015 resupply mission included 106 pounds of oxygen and 926 pounds of water, making up better than 25% of its total payload. The most recent mission included 110 pounds of oxygen and 990 pounds of water.
ISS doesn't produce its own water, it imports it. It does recycle water though. Waste water, including urine, is used in the oxygen generation systems.
I can barely get satellite TV sometimes. How come there is constant communications from the ISS especially when they are on the other side of the world?
The ISS has multiple communications systems. There are couple of UFH radios (plus a Ham radio) and S-band and Ku band satellite relays for direct ground-space comms. Plus it has priority tasking on two high geosynchronous orbit communications satellites - one Russian, one US.
You have to deal with interference from the atmosphere and magnetosphere. ISS doesn't have to deal with the former and has reduced interference from the latter.
