Alien Anomalies

ICEMAN · Senior Member

RE: Why does it take nearly 2 days to reach the ISS ?

Mark Anthony · Member

http://esamultimedia.esa.int/docs/issedukit/en/html/t010605r1.html

According to ESA:

How does the ISS stay in orbit?

The ISS has to be carried into orbit with the help of a rocket. To reach and to remain in orbit, the ISS needs a certain speed.

The speed needed to remain in orbit depends on the distance from the Earth. If the speed is too slow, the spacecraft will fall back on Earth. If the speed is too high, the spacecraft will be “shot” into outer space.

To generate speed, you need to apply a force to accelerate the spacecraft. If the force applied is not strong enough, the Earth’s force (gravity) will pull the spacecraft down to Earth. If the force applied is too strong, the Earth’s gravity forces will not be powerful enough to keep the spacecraft in orbit.

Here's an interesting forum discussing the time from launch to rendezvous with ISS.

http://www.airliners.net/aviation-forums/military/read.main/84880/

qmantoo · Teaching the truth

I understood that if you fired a rocket on a mass, then you would have to fire another rocket in the opposite direction to stop the mass from just keeping on going. What is to stop the ISS moving to a higher orbit with this rocket firing?

I can appreciate the falling back to Earth part due to normal attraction. All near Earth orbiting spacecraft eventually fall back to Earth but if you push something in space, then it just keeps on going.... doesn't it?

ICEMAN · Senior Member

HOUSTON — The international space station has been literally falling out of the sky, according to NASA tracking data obtained by MSNBC.com. Under the inexorable decay of air drag, its orbital path around Earth has slipped down to 207 miles (332 kilometers), the lowest average altitude in the nine-year life of the project.

A small rocket engine on a docked cargo ship is being fired this week to boost the orbit by a small amount. But since the orbit is continually dropping at about 300 feet (90 meters) per day, the boost will be eaten up by the effects of air drag within several weeks.

Humanoid · Veteran Member

qmantoo wrote:
(...)
Do you have any idea what they do for the rest of the 13-15 days? Delivery of water and provisions for a few people on the ISS seems to take place rather often. Apparently you can get tons of stuff into the shuttle's cargo hold and I read somewhere that they take up some fresh stuff too.

Do you remember the list of shuttle missions I gave you? You could've easily found out the answer yourself in there.

For example STS-134 (16/05/2011) lasted for 15 days, 18 hours.

Here's what they did: ISS assembly flight ULF6, ELC 3, Alpha Magnetic Spectrometer

STS-134 Mission Timeline

qmantoo · Teaching the truth

Ok, thank you for explaining.
So now I have to wonder how they catch up the Moon which has a much larger orbit and they can manage to calculate the angle to get there in 4 days without missing it. Anyway, I wont worry my small brain about that as it does not reach to astro-thinga-mebobs, which is probably why I dont understand all these things.

Do you have any idea what they do for the rest of the 13-15 days? Delivery of water and provisions for a few people on the ISS seems to take place rather often. Apparently you can get tons of stuff into the shuttle's cargo hold and I read somewhere that they take up some fresh stuff too.

Humanoid · Veteran Member

qmantoo wrote:
(....) I really dont think they have to take 2 or 3 days to get matched up with the ISS's speed, etc.
What in the world (or space) can they be doing all that time?

Quoted from source

Quoting Avi (Thread starter):
Is there any specific reason why NASA does it?

I'm modifying what I wrote here on the subject back in 2006 (STS-121) for this explanation.

The launch time is determined by where the International Space Station is in Earth orbit.

Once a satellite is in orbit, its path is fixed (more or less, more on that in a moment) relative to the stars. The Earth rotates beneath the satellite's orbit. The Space Station is in an orbit angled 51.6 degrees to the equator, meaning the most northerly point in its orbit is at 51.6 deg north lattitude and the most southerly point is 51.6 deg south. The Space Station crosses the equator twice each orbit... once heading north (ascending node) and once heading south (descending node.)

The best time to launch to the Space Station is when the Earth's rotation carries your launch site directly beneath the orbit of the Station. This happens twice a day, 12 hours apart at the equator. At Cape Canaveral, 28.5 deg north of the equator, the two opportunities (ascending node and descending node) are about 6 hours apart, and then its another 18 hours until the next opportunity. Only one of these opportunities is usable from Cape Canaveral... the northward "ascending node". The southward descending node would carry the Shuttle too close to the Florida coast and the population centers of the Bahamas.

Launch Pad 39A passes underneath the orbit of the Space Station at exactly 2:28:10am EDT Tuesday. The Shuttle has enough propellant to maneuver a little to match the Station's orbit. They can launch about five minutes to either side and maneuver "out of plane" back into the Station's orbit. So NASA can launch a Space Shuttle to the International Space Station for only about 10 minutes every day.

Because the Earth is not a perfect sphere (it bulges out a little in the southern hemisphere) a satellite's orbit shifts a little bit with each orbit. This is called precession. So the Space Station passes over Launch Pad 39A about 25 minutes earlier each day. The orbit of the Space Station passes over Launch Pad 39A at 2:28am on Tuesday, but at 2:02am on Wednesday.

The Space Station itself is not flying directly over Launch Pad 39A at that moment. Waiting for such a coincidence would limit launch opportunities to only a few times a year. Instead, the Shuttle goes into the same orbit as the Station and then speeds up or slows down to catch up with the Station. That usually takes two days (the Russians do it the same way with Soyuz and Progress spacecraft.)

Once in orbit, the Shuttle can go higher or lower, flying in a more elliptical orbit than the Station's more or less circular orbit. That means they complete one orbit faster than the Space Station does and they slowly close the distance to the Space Station, a little each orbit.

Landing is roughly the same situation. The Shuttle will be at the International Space Station throughout the mission. When it is ready to come home, they want to fire the engines to bring the Shuttle home during an orbit that passes over Kennedy Space Center. But the Shuttle has those large delta wings that generate a great deal of lift (compared to space capsules, anyway) and the Shuttle can steer up to 1,000 miles to either side of the orbit in order to reach Kennedy Space Center (this is called Crossrange Capability). This in effect means the Shuttle can land on either of two consecutive orbits.

Because the Space Station's (and with it, the Space Shuttle's) orbit precesses 25 minutes every day, the orbit of the Space Station passes over Kennedy Space Center about 6 hours earlier at the end of the mission, on March 26, than it did at launch 16 days earlier on March 11. Landing is scheduled for 8:35pm on March 26. They can try again one orbit later, if necessary, landing at about 10:05pm. They can also shift to the descending node landing opportunity, if desired, although NASA prefers since the Columbia accident to not fly the Shuttle over the continential U.S. enroute to landing, if possible. But with longer and longer missions to the Space Station, precession might shift the landing time to very early in the crew's "day" and NASA might choose to shift to the descending node landing opportunity to have a better-rested crew for the landing (this was the case for STS-120 in October.)

-End of quote-

qmantoo · Teaching the truth

OK, from that list, it seems that they nearly all take 9days plus. Some even take up to 15 days. I really dont think they have to take 2 or 3 days to get matched up with the ISS's speed, etc.

What in the world (or space) can they be doing all that time?

Humanoid · Veteran Member

qmantoo wrote:
Maybe someone can answer this for me.....
The trio will spend almost two days in the cramped Soyuz capsule before docking with the space station, where they will remain until mid-November

Well I reckon they need about 2-3 days to match orbits/trajectory and then rendezvous.

qmantoo wrote:
And... if anyone can, maybe they can tell me why the shuttle spends 11 days in orbit each mission too please?

List of space shuttle missions.

gbull · Veteran Member

not sure qman,

maybe it is to zero in on it? speed, etc?

i read that they just launched a sat that went out to the moon in 11 hrs.

as to the shuttle, they must have stuff to do and only so much food, (i'm being simple about it.)

they circle the earth in what, 1 1/2hrs? so it's not like they have a 11 day window or anything to get back.

qmantoo · Teaching the truth

Maybe someone can answer this for me.....

Article here

A Russian spacecraft blasted off from southern Kazakhstan in the early darkness of Wednesday morning to take a three-man crew to the International Space Station.

Russian cosmonaut Sergei Volkov, NASA's Michael Fossum, and Satoshi Furukawa of Japan roared into the night sky from the desolate but balmy Kazakh Steppe early Wednesday.

Furukawa held a thumbs-up as the rocket charged into low orbit at speeds approaching 14,000 miles per hour, and a soft toy began to float, indicating zero gravity.

"We feel just great," Volkov said in answer to a question from mission control outside Moscow.

The trio will spend almost two days in the cramped Soyuz capsule before docking with the space station, where they will remain until mid-November.

And... if anyone can, maybe they can tell me why the shuttle spends 11 days in orbit each mission too please?