RMS OPS – challenge thyself

June 12th, 2009

Some of you must be thinking, “RMS OPS? challenge? he must be joking”…. Well, I’m not 🙂

In this article I want to cover a basic RMS challenge. working the arm without using external views…

Because of the current limitations of SSM2007 this is only possible on mission with the aft window un-blockd. So obviously that “disqualify” all ISS missions. but we are still left with a bunch of fun missions, STS-8, STS-41C, STS-51A, STS-27 and so on. You will also need to know how to operate the arm on UNL/ORB mode, because this is the main mode we will be using.

 

I have chosen STS-31 for this article, So let’s go have fun! 🙂

In order to tackle this challenge we need to divide it up to a few steps.

1. View angles
2. RMS handling and orientation
3. payload Handling.

 

Views

We have already said that we are not going to use external views, so that leaves us with the 3D VC and the 2D panel. and we will need them both. I will describe the work-flow the way I feel comfortable with it might not be the optimum way so in general, YMMV 🙂

RMS Ready to RollI will now make a short “detour” to explain how I work with the RMS (If you are familiar with my way of work or you are just not interested to know 🙂  just click here)

I use X52 joystick with custom profile, I have programmed two of the HAT switches to function as a THC, one HAT switch on the Throttle controls left/right and up/down translations, while a second HAT switch on the stick controls FWD/AFT translations. the stick itself is the RHC, with a twist rudder it’s very similar in operation to the real deal. I of course have the RMS capture & released mapped to the stick (trigger). and I have main view configured on both the stick and throttle to allow some easy access. I can get to the 3D VC, switch position on the 3D VC and access the last 2D panel in a push of a button on the HOTAS system. the system also has a very uncomfortable mouse like device that allows me to make some minor mouse work if I don’t want to let go of the stick.

Another piece of hardware I use only when I want to try stuff like this is my TrackIR (I have the “old” TIR4). In SSM I Don’t like to use it most of the time, but on RMS ops without Ext. views it’s priceless and allows me to move my head around and get a whole new perspective (you’ll see later on what I mean). I can only assume how much fun the Vusix goggles will be – but it’s just too expensive for me.

OK, back to views.

As I said before, we have the 3D cockpit and the 2D panels, each would be used on a different part of the task, but we will transition between them all the time. In real life, the Port Aft position is RMS Operator and the STBD Position is the CDR/PLT position from which the shuttle is flown. so naturally our basic position will be the Port side, where we have the monitor for the CCTV cams and all the RMS readouts.

Because the 3D panel is currently unclickble we will need to preset several settings on the 2D panel first.

RMS RollingWe will need to set the RMS to ORB/UNL mode (because it’s faster, better, more logical then single mode, and because single is unusable in 3D view – pick your favorite “excuse” :)). Next we need to set up the RMS read outs, this is done by rotating the two big gray knobs (which I have no Idea how they are really called) to “wrist roll” and “EE ATT” – because this setting us the single, most important info we need to make a perfect grapple. Then we will need to turn on our cameras and set the MON1 on with cross-hairs. The secret here is to set up the camera that will be most helpful in getting the end-effector to position. Because we have no true 3D view (unless you use the Vusix), we need to cross two diagonal views for a good position. Looking out the back window will give us one, and we need to choose a second view from the 5 cameras we have (A-D and RMS elbow cam). For this mission I will start with the RMS elbow cam zoomed out all the way, adjusted full left, and full down. (because this is the general direction of the grapple point). In this Mission I think that the front STBD camera will also be OK because we are going for the STBD grapple point. so aiming at it will allow us a pretty good line up.

 

 

RMS handling and orientation

Now that we have the initial views set up we can start moving the arm to the grapple position. we are in ORB/UNL, so we start flying the arm to the right position, we need to be aware of the payload, not to hit him, but we also need to keep the arm low enough so that we can see the EE out of the window, here is where the TIR really helps, Just for the fact that you can “crouch down” and catch a bit more out the window. if you do not have a TIR you can also use the STBD position and the center position to help you with the looking around. (just look at the three images below, the EE is “lost” from standard view, “found” with TIR and with standard STBD view). The FF VC view inroduced on SP3.60 allows you the same function as the TIR does, only drawback is that you cannot move the RMS while using it..

EE EE Found with TIREE found - STBD

Main issue here is to keep moving your view, look at the monitor and out the window and get a feeling on where the arm is. if you have a widescreen it’s relatively easy, because you can get both with just a slight change of view angle, on some cases once you set it, it stays there…

Zoom EE camOnce we got the Arm into position it’s time for the grapple, we need to switch the MON1 to the EE wrist Cam with the zoom set for grapple (zoom in until you can’t see the tip of the EE in the camera – as seen on the image on the right).

You can do the final adjustments either on 2D panel or on 3D panel, it’s up to you, both will give you the same info. IMHO (as you can see below), looking out the window at this point helps you remember where do you need to move the arm to get the camera in position, because you can see to where the camera is on the RMS. If you got a grapple on 180 deg wrist roll (like in this case), the FWD/AFT and LEFT/RIGHT are reversed, which can be very confusing. so pick your way and grapple the target. Once there we will start moving the Payload, and this is where it’s getting tricky.

 

Grapple from 3D cockpitEE ATT check from 3D cockpit

 

Payload Handling

Now that he have grappled our target the real challenge begins. On the initial part of the unberthing especially with big cargo (LDEF, HST and pretty much everything we deal with in the missions that allows use to work without External views) will all be done from 2D panel. because the window will be blocked by the cargo, and we will need to switch back and forth between the four PLB cameras (A-D). the secret is to know where your clearance is problematic on every step and adjust the cameras accordingly. So before the initial movement, we will need to identify the problems. they easy way out would be pressing F1. But that is not what we are here for. Initially I will set the cameras to look at each other, something like this diagram.(all four cameras+the estimated FOV of each of them, you can click to enlarge).

Initial cargo estimation - click to Enlarge

HST out of PLBThat gives us a pretty good idea on where we would expect trouble, in this case, both sides and the front of the PLB. The front is even more problematic then you think.. Because when we move the arm up it tends to retract a bit and therefore moving the payload forward. So we’ll adjust the cameras and start motion. initially we want to raise the payload, without moving it. so maintaining the capture EE attitude would be a good idea while fiddling round in FWD/AFT and LEFT/RIGHT motion to keep clearance. Once we cross the “danger line” we can start changing attitude while keeping it clear of PLB walls and floor. at this stage we are still playing around with the cameras, so 2D view is still the place to be (at least most of the time).

 

At some point we would only need one of the aft cameras and the rest we can see out the AFT window – so we’re back to 3D VC from here. Once the payload is clear of the PLB it’s just a matter of getting it into position. while viewing up the top windows.

HST from 3D cockpit

And that’s about it! One more important thing to notice, getting stuff out is easier then getting the same stuff back in (STS-27 and STS-41C Vs STS-32 are fine examples) so practice, practice and practice!

HST Deplyed

No satellites were harmed during the making of this article and all Images are hosted on the image pad

Hope you enjoyed reading this, as much as I had writing it 🙂
Uri

Posted by uri_ba

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