RMS Operations

The Remote Manipulator System (RMS) is the robotic arm of the Space Shuttle. It is controlled from the AFT panel. The RMS movement and the End-Effector grapple status are controlled with the RHC\THC controllers. The arm is similar in structure to the Human arm. It has three joints, Shoulder, Elbow and Wrist.

RMS overview - Joints
Diagrams are taken with permission from the SSM2007 Commander's Reference Manual

Each of the Joints has a different range of motion:

Joint Axis range of motion
Shoulder

Pitch
Yaw
-2 to + 145
-180 to +180
Elbow Pitch +2.4 to -161
Wrist


Pitch
Yaw
Roll
+121 to -121
+121 to -121
+447 to -447
Shuttle RMS joint display
RMS Joint Axis
Diagrams are taken with permission from the SSM2007 Commander's Reference Manual

Operating the RMS, grappling objects in the Shuttle payload bay (or floating in Space) and moving the grappled objects at a defined location with the correct attitude constitute one of the more difficult tasks an RMS Mission Specialist needs to learn.

Just as in reality, SSM2007 RMS operations require a similar level of patience and precision and a lot of practice. Performing the easier RMS missions first (such as STS-8) is advisable.

RMS in SSM2007

Controls

In SSM2007, the RHC and THC are simulated by the keyboard in combination with the joystick. In order to actually control the RMS, the AFT controls need to be activated, RMS power turned on and the RMS (always the PORT RMS) should be selected.

RMS switches are all located on the A8 panel. Logically it is divided into three panels. A8U, A8 and A8L.

A8U

The upper most of the three is A8U, it controls the RMS mode (in SSM2007 only ORB/UNL and SINGLE are usable) and the EE mode. It also contains the warning and indication lights, the RMS breaks switch and the Rate of motion indicator.

A8U Panel

A8

The Middle panel of the three, A8, is used to move the arm in SINGLE mode and it has all the indication on the arm's position, attitude and joint angles. During RMS OPS this panel is the most important.

A8 Panel

A8L

The lowest of the three, A8L, contains the power controls over both arms (Port and starboard) it is used to turn the arm on or off and during the RMS/OBSS deployment and stowage.

A8L panel

SPEC 94 Display

In addition to the switches, some more control options are available Via the SPEC 94 Display. On the aft keypad, make sure the mode is SM mode and then enter SPEC 94 PRO.

Keyboard

The controls used are the Numpad keys. the 2,8,4,6,INS and DEL are your RHC, /,*,-,+,9 and 3 are the THC.
RHC/THC

RHC (EE Attitude) THC (Arm Translations)
Pitch NumPad8 / NumPad2 Extend/Retract NumPad + / NumPad -
Roll NumPad4 / NumPad6 shoulder Left/Right NumPad / and NumPad *
Yaw NumPad INS / NumPad DEL Raise/Lower Arm NumPad9 / NumPad3

The “Num Lock” key should be turned on while in the game

Joystick

Attitude control using a joystick is natural. Pitch, Roll are always available. YAW is usable if the joystick has a twist axis, or using the rudder pedal, if available. Throttle if available should be kept in the middle of it's range (explanation below)

Translations with a stick are a bit more complex. To activate translations you hold down the Trigger (button 1 on Joystick) while moving the stick around. Left, Right, Extend and retract are available in this configuration.

Now - Up/Down translations are controlled via the throttle. While holding down the trigger and “increasing” or “decreasing” the throttle the shuttle will translate the arm up and down.

Some users find it easier to use the Stick for Attitude control, and the keyboard for translations.

End-Effector

the actual grappling is done be a snare at the tip of the End-Effactor.

RMS EE snare
RMS End-effector Snare

To close the snare for grappling hit the “ENTER” key on the keyboard numpad.
to open the snare (releasing the cargo) use the “Numpad 5” key.

After a failed attempt to grapple a cargo you must open the snare before re-trying.

The Art of Grappling

Grappling is an Art. Being able to grab and manipulate the Shuttle payload, or capturing an object “floating” in Space, is an imperative skill for completing many of the missions in SSM2007. Without it you cannot fix the Hubble, inspect the Shuttle thermal tiles for damage and assemble and service the International Space Station.

Arm Movement Basics

Currently in SSM2007 the RMS functions in two modes, Single and ORB/UNL

Single Mode

you control the RMS joint by joint from the Aft panel.

Pros: Cons:
* Manipulating the arm is easier to understand
* knowing the correct angles, it is possible to get the arm into place very fast.
* Getting the arm to place Visually is usually much harder. because each joint manipulation require adjustments to other joints.
ORB/UNL (orbiter/Unloaded)

In this mode controlling the arm is not direct like in single mode. here is where the on-board computer kicks in. issues the computer orders on witch direction the arm should be moved, and the shuttle's computers moves the required joints automatically to comply.

ORB/UNL RMS mode
rms-unl.jpg
Original diagram by desktopsimmer
Pros: Cons:
* visually manipulating the RMS is much, much faster this way. * At awkward angles, the RMS is subject to soft stops, which the user must alter the RMS by entering SINGLE mode and moving the arm back towards the poisition it was.
* To position the RMS in awkward location required the use to move other joints to compensate for miss alignment.

Using the RMS in ORB/UNL mode would probably be preferable to most simmers. Just a matter of practice.

RMS ATT/POS

Now you know the how, time for the next big question - where? Whare should the RMS be?

ATTitude/POSition indications on the A8 panel allow us to know where the RMS is positioned. ATT indicates where the selected joint is pointing relative to the Shuttle's tail. The POS indicated where the selected joint is in inches relative to the Payload bay's front wall (cabin's rear wall).

(Image Needed)

Those numbers alone do not give us that much, but the The Official SSM2007 Grapple Cue card gives you the grappling information for stationary targets (not for Free-floating satellites). The Grapple Coordinates are given for the WRIST ROLL joint (which should be chosen).

The Grapple Target

RMS EE and Grapple fixture - Diagram from the SSM2007 Commander's Reference Manual Seen here is an NASA ISSRMS power grapple (which also supplies power and datalink necessary to operate the ISSRMS) and a grapple fixture from SSM2007.

Grapple target - ISSRMS SSM Grapple Fixture
NASA Grapple fixture SSM Grapple Fixture

final alignment of the arm is always done visually. In order to properly align the arm for grapple, NASA has equipped the RMS with a camera on the arm's tip, camera known as the “End-Effector camera”. The camera sits on top of the Snare, the crew then “aims” the camera at a visual target that is part of the payload grapple fixture, as seen in the diagram on the right, taken the SSM2007 Commander's Reference Manual.

The view is displayed on the monitor and overlays a “targeting cross” on the CCTV image. This cross allows the Crew of SSM2007 (i.e. you) to align and judge the correct distance for grappling. Centering the cross is the easy part, distance is a bit more tricky to master. The “secret” is to allow the tips of the cross to sit on the EE target circle as shown here.

SSM EE cam view of Grapple target and visual cues

RMS in the Real-life

Tutorials

rms.txt · Last modified: 2009/07/31 00:42 by uri_ba
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