April 11, 1984: Ox von Hoften, left, and Pinky Nelson, on the end of the robot arm, work on the Solar Max satellite berthed in Challenger’s payload bay.

*****

Up and at it, running down the checklists towards EVA — extravehicular activity — on this our sixth flight day, April 11, 1984, of our STS-41C mission to repair the Solar Max satellite.  And it’s finally time for our spacewalkers to make the hands-on repairs.

It’s gonna be tight, packing all the repair work into one spacewalk, but not as tight as you might think.  We’ll save the time compared to the original plan that split the work into two EVAs.  We won’t need to pack up at in the middle of the work and call it a day.  And we’ll save about an hour that we would have waited for Solar Max to power down after capture.  Still, we’re going to be stretched, a spacewalk of seven hours for Pinky Nelson and Ox van Hoften.  That leaves no margin for the unexpected.  We — Bob Crippen, Dick Scobee and T.J. Hart — are orchestrating the effort from Challenger’s flight deck.

At 4:19 a.m., the hatch is open and out the pair swim.  “Looks a lot better out here with the satellite sitting here.”  Sure does! — the satellite held vertically on a support cradle at the rear of the payload bay, just waiting for us.

The pair take their positions for the repair.  Ox will ride on the end of the Remote Manipulator System (RMS) robot arm, secured to the Manipulator Foot Restraint that turns the RMS into a “cherry picker” work platform.  He will conduct the repair tasks during the first half of the spacewalk.  Pinky will assist, floating on his safety line, retrieving equipment from storage boxes strapped to the cradle holding the satellite.  

“This thing is really neat,” Ox says as T.J. Hart, operating the arm from the flight deck, gives him a liftoff.  “OK, here we come Solar Max.”  And just 5 min. into the EVA the repair efforts have commenced.  First up, the big Attitude Control System unit, a 500-lb. (on Earth) module measuring 4 by 4 by 1.5 ft.  It was designed for quick “plug-out/plug-in” replacement.  Ox uses a special-built electric wrench to release the two bolds holding it.  “We’re going . . . real slow and back it out. “

“OK, we’re free . . . OK, go on back,” Ox directs T.J. to back the arm. “It’s a big mother.”  

It’s only taken the duo 5 min. to pull the unit.  And in an hour, 5:23 a.m., they’ve installed the replacement.  They tell Capcom Jerry Ross, “Hey, Jerry all these tools are working just as advertized.”

“Sounds good to us. . .”

“And the view is . . . a little bit unreal.  . . .The moon is just coming up out there — it’s really beautiful. Golly, look at that.”

The spacewalkers install a baffle over the satellite’s X-ray spectrometer to protect it from solar plasma that has been interfering with its detectors.  The task goes super smoothly, too.  Swiftly, at 6:12 a.m.,  they move on to the tough one, the Main Electronics Box of the coronagraph-polarimeter, one of Solar Max’s seven instruments to study the sun.  It wasn’t designed to be replaced.  Ox, riding the “cherry picker” uses a power screwdriver to remove the 11 tiny screws holding the access panel. We enter orbital night, and Ox and Pinky work by floodlight.

“I lost my first screw and I caught it,” Ox says.  

Yet one of the screws does escape.  “There it goes.”

“I guaranteed I’d lose one or two.” 

He installs a temporary hinge on the door to the access panel so that it can swing open like a door and removes the final screws.  “OK, this is the hard part,” Ox says.  “Hey, Jerry, the hinge is on.  . . . All the screws are coming out just great . . .  There is no problem at all.”

By 6:11 a.m., he reports, “The door is coming open.”  He begins disconnecting the wires of the failed unit.  And just 24 min. after opening the door, he reports, “All the connections, all the wires are out.”

By 6:45 a.m., the old main electronic box is out.  “And we are ready to put in another one.”

Capcom Jerry Ross says, “Sounds like it’s about time for Pinky to go to work.”  The duo switches places, with Pinky taking a ride on the Manipulator Foot Restraint to install the new unit, with Ox floating at his side, assisting.  We’re running ahead of schedule.  Pinky uses clips to reattach wire bundles rather than the original screws.  And by 7:22 a.m. in the darkness over Hawaii, he is finishing the repair.  Twenty minutes later the task is done, only taking 1.5 hrs. compared to the 3 hrs. allotted in the timeline.  We are way, way ahead of schedule!  They both ride the robot arm, Pinky locked in the foot restraints and Ox tethered to it, which moves them away from the satellite.

“Two for the price of one.”  The arm takes them to the bottom of the horseshoe support cradle and they start stowing equipment.

At 7:55 a.m., Houston says, “We’d like Pink to go ahead and get some pictures of the solar arrays the top of the spacecraft before we go on to the measurements of the trunnion pin.”

Pinky measures the pin that frustrated his attempts to dock during the first spacewalk.  “. . . There’s a little thermal button on there that’s behind [the trunnion pin].”  It will be determined that, indeed, a fiberglass pin securing the satellite’s insulation blanket, stuck out just enough to prevent docking.

Everyone is sounding very relaxed now that the repairs are complete.  From the flight deck,  “We’ve got Boy George [Pinky] in the foreground and the moon in the background.”

The spacewalkers tease Capcom Jerry Ross, “Jerry, this is no fun at all.  I don’t think you’d like it up here.”

At 8:25 a.m., with plenty of time remaining, the duo moves on to auxiliary tests.  Which means an engineering evaluation of the Manned Maneuvering Unit (MMU) by Ox van Hoften.  Houston says, “Merry Christmas, Ox.”

Ox straps into the backpack, and just before sunrises, releases.  At 9:09 a.m., the payload bay still in the shadows, he says, “OK, I’m ready to fly.”

“Ox is away,” we tell Houston.  He will stay in the payload bay, doing precise engineering maneuvers.  He centers himself in the bay, dips through all three axes, calls “I’m just going to stay inside the bay.

“Yes, you’re in good shape right there,” we tell him.

He jokes, “I don’t want to make Crip anymore nervous than he probably already is.”

“Crip is never nervous.”

“Who’s nervous?” our commander says.

Ox, continuing his maneuvers, says, “This is unbelievably controllable.”

“The MMU is one good flying machine.”

But all good things must end.  He heads for the MMU’s support station at the wall of the bay.  “Enough of this frivolity.”

“I thank you, Mr. Crippen and Houston, for the ride.”

And receive we word that the new attitude control unit on Max is showing a good connection.

“All right, outstanding.  That’s good news,” we say.  And with that, at 10:15 a.m., our spacewalkers return to the airlock.

“Take a bow,” Crip calls to them.  Their spacewalk has clocked in at 7 hrs. 18 min., the longest of the Shuttle program.  Indeed, the longest spacewalk in history other than a moonwalk on Apollo 17 that lasted 19 min. longer.

We’re over the moon with our success.  After detailed checks the next morning, we’ll release the reborn Solar Maximum Satellite.