Overheard
Space Cadets
Who will be the next Marc Garneau?
Since the Canadian Space Agency launched its third national astronaut recruitment campaign a year ago, a shrinking pool of scientists, engineers, and doctors have been run through a series of medical exams, interviews, and aptitude tests. This May, only the top two individuals will be named to the CSA’s astronaut corps. To find out what it takes, The Walrus listened in on one of the candidates’ most challenging assignments: learning to operate Canadarm2-like robotics.
Errors found in the 1986 film Space Camp
As posted by imdb.com user tpaladino
- Kids would never be allowed to board a fully loaded shuttle, much less during a static engine test. never.
- If there were fully loaded space suits on board, then why not use oxygen from them to get the extra hour they needed to make the reentry window? One suit has enough for one person to last 8 hours. IT would give seven people at least an hour. And there were two suits, so that’s almost two hours per person right there. Problem solved.
- Going to retrieve oxygen tanks from a half-built space station would be completely impossible for them without navigational support and close coordination from mission control. How did they know where it was?
- You can’t adjust the size of a spacesuit to fit a child using a belt.
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Instructor: As I am, sitting behind the hand controllers, these frames match exactly my body frame.
Candidate 1: And this relates to the internal frame of reference of the latching end effector?
Instructor: Yes.
Candidate 1: In other words, if I want to move along positive X with the lee I am going to push the translational hand controller forward.
Instructor: Yes, that is correct.
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Candidate 2: So if I rotate and then I want to move forward, X is away from me?
Instructor: In the internal command frame, X is always forward.
Candidate 2: Right, but if I rotated the arm?
Instructor: You have to imagine yourself upside down.
Candidate 2: Okay.
Instructor: So if I made this motion, what would that be?
Candidate 2: That is pitching positive.
Instructor: Yes, because my nose is moving up.
Candidate 2: That’s what I was getting at. The frame does not stay fixed in space as I rotate around.
Instructor: Your internal frame stays fixed, like I said, with respect to the lee.
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Candidate 1: You’ll tell us whether we are in the internal frame giving command inputs, or whether we’re making command inputs with respect to the external frame?
Instructor: And which external frame. We only have one internal frame, but there are many external frames, so we’ll have to specify frame 1, frame 2, et cetera.
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Instructor: What do I do now? I’ll ask candidate 3.
Candidate 3: We are going to have to do a positive Z, so down on the translational hand controller, and then we are going to need to pitch up, so pull the rotational hand controller back.
Instructor: Exactly. Do we all agree with that?
Candidate 1: I understood the pitch, because the dot is down, which means that your end effector is angled like this; you have to pitch up. But I’m not sure I understand the green crosshairs.
Instructor: I like that question, and I’m glad you asked it.
Candidate 1: To me, the green crosshairs suggest the End Effector is too low. Not only is it too low, but it’s pitched down, so that I need to actually move the green crosshairs up.
Candidate 3: If this is purely a translational problem and it’s getting all sorted out, where would that white dot be? Will it be right in the middle?
Instructor: Like the other example we used, it will be right in the middle, slightly high. Candidate 4 wants to say something.
Candidate 4: If you’re using an external frame and you command the rotation, does the centre of the rotation of the end effector—
Instructor: It’s not the camera but the centre of the plane that is flush with the end of the lee.
Candidate 4: Is that for the external frame?
Instructor: Both external and internal. We said that.
Candidate 4: It’s still around this point?
Instructor: For all command frames, this is the centre of rotation.
Candidate 4: Got it.
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Candidate 4: I’m lined up, looking straight down.
Instructor: You’re pretty much looking at it.
Candidate 4: But I think I am like this a little bit.
Instructor: Either you’re like this a little bit, or like this a little bit.
Candidate 4: Okay, I must be translated to the right, so I need to move to the left a little bit.
Instructor: What does the white dot tell you?
Candidate 4: That I am looking straight down.
Instructor: It’s a little bit left, actually. But it doesn’t matter. I mean, it’s never a one-axis misalignment.
Candidate 4: So I need to yaw left and translate left.
Instructor: Well, you want to at least translate left, because it seems that you are misaligned like that, but it is a combination of yaw and translation.
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Instructor: Can we start with the answers? I will start with candidate 5. Internal.
Candidate 5: It’s going to be a roll, and if you go clockwise… sorry, that’s going to be negative.
Instructor: From here to there. From here… to there.
Candidate 5: Okay, yup, that’s a positive roll.
Instructor: Do we agree with a positive roll, tilt right? Correct. Let’s go with candidate 3 for frame 1.
Candidate 3: Since, again, they’re aligned, it’s going to be the same input—for positive roll.
Instructor: Same thing—a positive roll, tilt right. Candidate 6 for frame 2.
Candidate 6: Now it’s essentially a yaw, a positive yaw, and we are going to twist straight.
Instructor: Do we agree with positive yaw, twist straight?
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Instructor: Candidate 3, frame 2, please.
Candidate 3: Frame 2 is a negative yaw, so that would be a twist to the left.
Instructor: Do we agree with negative yaw, twist left?
Candidate 2: How was the camera again?
Instructor: Like that. This is how I determine my rotation. I start like this and rotate like that.
Candidate 2: Yup.
Instructor: So what does that give you?
Candidate 2: Well, if I’m lying on my back and I want to rotate it like that, that’s a roll.
Instructor: That’s a rotation to your left.
Candidate 2: Oh, sorry, yup. I understand now that’s a yaw. Yeah, I got it now.
Instructor: We agree with negative yaw?
Candidate 2: Yes.
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Instructor: Let’s start with candidate 3, then, for internal.
Candidate 3: We have a positive pitch and a positive yaw, so that is going to be back and twist to the right.
Instructor: Is that right? Do we agree?
Candidate 2: I have a hard time between roll and yaw with these ones.
Instructor: I’m glad you’re asking this now. We are not moving in the roll. It’s a combination of this rotation and that. So although it looks like the roll axis is moving, we’re not rotating around that axis.
Candidate 2: Oh, yeah.
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Candidate 5: Frame 2 should be a negative yaw and a positive roll.
Instructor: That is the correct answer. And what does that mean for hand control input?
Candidate 5: It’s going to be a twist left and a tilt right.
Instructor: Twist left, tilt right, simultaneously.
Candidate 5: Does the rotational hand controller allow simultaneous input?
Instructor: Yes, it does. Negative yaw. And we want this motion.
Candidate 5: That’s the roll, the positive roll.
Instructor: Excellent! One last case, and then we’re done.
