|Quoting SLCPilot (Reply 19):|
Can the ISS be thought of as a two dimensional structure in terms of layout? And is there a graphic available to make sense of Thorny's description?
No. There are modules attached on all three axes.
When you see a photograph or illustration of the International Space Station, the end to which the Space Shuttle docks is the forward end. That's the direction the Station is travelling in orbit.
At the rear is Russia's Zvezda module. This is a control and propulsion module. At its aft end are two rocket engines and a docking port for visiting Soyuz or Progress spacecraft. The engines have a finite lifetime, so Russia generally uses them sparingly, preferring to use the engines of the attached Progress to raise the Station's orbit from time to time. The Zvezda engines can't be fired while a Progress or Soyuz is docked there. At the other end of Zvezda is a "node" with three docking ports, one facing forward, one facing upward and one downward.
The upward port on Zvezda is unoccupied. It was to support the Russia Power Platform, a set of solar arrays on a mast standing upward. Those arrays were cancelled after the Columbia accident.
The downward port on Zvezda is occupied by Pirs, Russia's small airlock module. Pirs has a hatch for spacewalking cosmonauts on one side. The lower end of Pirs is a docking port for visiting Soyuz spacecraft. Russia plans to attach a large laboratory module here in 2009. This module will also have a Soyuz/Progress docking port. Pirs may be relocated to the upward port on Zvezda at that time.
Attached to the forward port of Zvezda is Zarya, the Functional Cargo Block (FGB in Russian) which contains crew living quarters, storage areas, and propellant tanks. Zarya was paid for by NASA (through Boeing) but built by Russia. Zarya was the first element of the Space Station launched into orbit, in November 1998.
The forward end of Zarya also has a node with three docking ports, one forward, one up and one down.
The upward port is unoccupied.
The downward port is a docking port for Soyuz spacecraft, since during crew rotations two Soyuz must be docked at the same time. The Space Shuttle will attach a Russian docking module, somewhat like Pirs, here in 2009 or 2010.
The forward port of Zarya is attached to the U.S. Node 1 "Unity" module, by way of a tunnel called a Pressurized Mating Adapter (PMA-2 in this case) which bridges between the large, square hatches on the U.S. side of the Space Station and the smaller, circular hatches of the Russian elements.
Unity has six ports: one upward, one downward, one portside, one starboard, one forward and one aft.
The aft port is occupied by PMA-2 and attached to Zarya.
The upward port on Unity is occupied by the Z1 module, a mostly unpressurized unit which houses the Station's four giant Control Moment Gyroscopes (for attitude control) as well as its High Gain Antenna.
The downward port is vacant. This is where the large Multipurpose Logistics Modules are docked after carried to the Space Station by visiting Shuttles.
The portside (left-facing) port was occupied by PMA-3, a third, spare docking tunnel for visiting Shuttles until a few weeks ago, when it was moved to a temporary berth on Z1, clearing that port to be a temporary berth for the upcoming Node 2.
The starboard port is occupied by Quest, the U.S. airlock module from which astronauts take spacewalks.
The forward port on Unity is occupied by the U.S. Laboratory Module "Destiny", the primary U.S. laboratory and control center.
The forward end of Destiny has another hatch, to which is attached PMA-1, the docking tunnel used by visiting Space Shuttles (which use Russian-built hardware, hence the needed for the hatch-diameter-changing PMA.)
Mounted on struts atop Destiny is the U.S. Integrated Truss Structure, centered on Destiny and utlimately to span 310 feet, running to port and starboard. The Truss contains batteries, solar panels and heat radiators, as well as various support hardware.
-120 Discovery will deliver Node 2 "Harmony", a slightly longer sister of Node 1 "Unity". It too has six docking ports... up, down, port, starboard, forward and aft. Node 2 will eventually by attached to the forward end of the Destiny U.S. Lab module, where PMA-1 is now. Because the Space Shuttle Discovery will be docked to PMA-1, the crew cannot immediately attach Node 2 in its final position. Node 2 will temporarily be berthed to the portside docking port of Node 1 (where it can receive keep-alive power) until Discovery departs. Then the Space Station crew will disconnect PMA-1 from Destiny and install it to the forward end of Node 2. Then Node 2, with PMA-1 attached, will be installed on the forward end of Destiny. (This will all take place in the month between Discovery's STS
-120 and Atlantis's STS
Europe's laboratory module "Columbus" will be attached to Node 2's starboard docking port on STS
Japan's "Kibo" laboratory complex (it has three distinct elements) will be berthed to Node 2's portside docking port in 2008.
Node 2's upward port was to be occupied by the Centrifuge Accomodation Module, which was unfotunately cancelled after the Columbia accident.
The Shuttle's Multipurpose Logistics Module (MPLM) will be attached to the downward-facing port of Node 2 while Shuttles are present. It is likely one MPLM will be modified with improved micrometeoroid shielding and will be permanently berthed here to serve as a storage facility after the Shuttle's retirement in 2010.
PMA-3 will be berthed to the downward port on Node 1 "Unity" after Node 2 is installed, since that port will no longer be used by Shuttle-borne MPLMs.
A third Node is due for launch in 2010. It will be berthed to the downward facing port on Node 1. PMA-3 will be relocated to its forward end, where it may someday be used by visiting Orion or commercial spacecraft. Node 3 will contain life support hardware and sleeping berths, as well as a large, multi-windowed observation deck called the Cupola.