April 4, 1983: Challenger rises on a long column of solid-rocket exhaust in this photo taken from a chase airplane.
What will be called the smoothest countdown in 20 years is coming to a climax. We’re coming out of the planned T-minus 9 min. hold, and Challenger is coming alive for its maiden launch. It’s April 4, 1983, 1:21 p.m. We’re strapped in, four of us, on the flight deck, the commander and pilot up front, and squeezed behind our two mission specialist. We’re the crew of STS -6, the sixth flight of the space shuttle, designated the “F” crew even before being assigned to the flight, and so we’ve dubbed ourselves “F Troop,” after that 1960s TV comedy. F Troop consists of mission commander Paul Weitz, pilot Bo Bobko, and mission specialists Don Peterson and Dr. Story Musgrave, a medical doctor and long-time EVA (Extra-Vehicular Activity) specialist. We’re strapped in tight, and after delays of more than two months due to engine leaks, finally set to go.
At least we think Mission Specialist Story Musgrave is strapped in. Earlier, he unfastened his straps so he could stretch and said he was having trouble getting strapped in again. We joke with him that in a few minutes we’re going, whether or not you’re strapped in!
Challenger represents a huge stride forward in performance for the Space Transportation System. Weight has been shaved off all the components of the Shuttle stack. The big orange External Tank weights 10,000 less than prior ones. The twin Solid Rocket Boosters that flank it weigh 4,000 lbs. less. Challenger itself is 2,400 lbs. lighter than Columbia. In all, the system has been reduced by about 20,000 lbs. And engine performance has improved. We’ll fire the three Main Engines to 104 percent of the original thrust limit. That’s 488,800 lbs. thrust for each of the liquid-fueled engines versus 470,000 lbs. thrust.
All that translates to a leap in payload weight. We’re carrying about 46,660 lbs. of cargo, more than double what Columbia carried on STS-5. The bulk of that consists of our prime payload, the first Tracking and Data Relay Satellite (TDRSS), the world’s largest privately owned communications satellite (leased to NASA by Space Communications Company, SPACECOM).
The satellite, weighing 4,668 lbs., sports two solar wings measuring 57 ft. long when deployed. The satellite bus houses an array of antennas, the most prominent are two S- and Ku-band dish antennas that will carry the high-rate communications. Gold coated, they are folded like umbrellas at the front of the satellite. When deployed, each is 16 ft. in diameter.
TDRS, built by TRW will serve as a giant switchboard in the sky, relaying communications from as many as 26 satellites and the Shuttle to a ground station at White Sands, New Mexico. This will eliminate the need for many ground stations. With full coverage from multiple TDRS satellites, we will no longer experience the long gaps in communications coverage. At present, the Shuttle is out of the range of ground stations about 80 percent of the time.
To reach geostationary orbit at 22,300 mi. altitude where it will appear to hover over one location on Earth, it will be propelled from low-Earth orbit by the Air Force’s Inertial Upper Stage (IUS). Consisting of two solid-propellant stages, it has flown only once before off an expendable booster. The combined TDRS/IUS weighs about 37,000 lbs.
Besides TDRS, our core objective is to certify Challenger for routine missions. We’ll thoroughly check all of its systems in our relatively short five-day flight. And our mission specialists will conduct the Shuttle’s first spacewalk, postponed from STS-5 due to problems with the EVA suits.
We also have a full array of other experiments aboard, such as the second demonstration flight of the Continuous Flow Electrophoresis System, that separates medical substances in suspension according to their electrical charge. The Monodisperse Latex Reactor, which has also flown before, will produce uniform latex beads. In the payload bay, we’re carry three Getaway Specials (GAS) canisters containing small, inexpensive experiments.
The last minutes drain quickly. At T-minus 7 min, we see the crew access arm swing away. At T-minus 6 min., we throw the switches for the prestart of the Auxiliary Power Units (APUs) that drive Challenger’s hydraulic systems. Less than a minute later, we get the go for APU start. Time to close our helmet visors. Less than 4 min. to go. Challenger goes on internal power. And the Main Engines are swiveled to make sure they are ready to steer the stack. At T-minus 2 min. the are set in launch position.
At T-minus 30 sec. go for auto sequence start. The onboard computers now are in charge of the countdown. At T-minus 6.6 second feel the Main Engines start and build up thrust . . . And zero — bam — the twin solids ignite.
And less than 7 sec. later we’ve cleared the tower. Roll program, and boy, the stack shutters and shakes with the power of those solids. But actually less vibration is less than we’re braced for. At 29 sec., the Main Engines throttle back to 81 percent as we approach Max Q, the point where factors converge to give the maximum air pressure on the vehicle before the atmosphere thins. We hit Max Q 67 sec. into the flight.
Capcom Dick Covey radios, “Challenger, go at throttle up.”
“Roger, go at throttle up.” We’re back at 104 percent thrust.
And Covey radios, “Challenger, Houston. We see you’re slightly depressed.” Meaning our trajectory is slightly low. “No problem,” he adds. We’ve got plenty of engine margin to make up for it.
Two minutes 10 seconds: The SRBs, their job done, are jettisoned with a solid kick and a flash of flame that hurtles crud at the windows. “Good SRB sep.,” we call, “and that was something.”
Covey calls, “Challenger, your first stage performance was nominal.”
With increased velocity and altitude, our options for a safe abort open up. Three minutes into flight, and Houston calls “Two-engine TAL.” Meaning if an engine goes out, we can reach the Trans-Atlantic Landing site at Dakar, West Africa. At 4 min., they call, “Negative return,” meaning we cannot turn around and return to the launch site for a landing. Then we received the call for “two-engine press to MECO.” MECO — Main Engine Cutoff. We can reach orbit even if one engine goes out.
At 5 min. 40 sec., the call that we now can reach Dakar on on a single engine. “Roger, single-engine TAL.”
At 7 min., even better. “Challenger, you’re single-engine press to MECO.’
“Single-engine press, thank you.” We can reach orbit on a single engine.
Just before MECO at 8 min. 20 sec., we hear an alarm for cabin atmosphere, “MECO, we have MECO,” we call.
“Roger, and no problem with your cabin atmosphere.” Just a spurious alarm. We are snugly in orbit — well, almost. We need two burns of the twin Orbital Maneuvering System (OMS) engines in the pods at the rear of the Shuttle to place us in a good orbit. The first comes soon after we discard the big External Tank. The second comes after half an orbit, 43 min. 44 sec. since launch to circularize our orbit at 176 mi.
We have no time to relax, must immediately begin prepare for the deployment of the TDRS, set for 10 hrs. into the mission. We must open the payload bay door, and perform a complex set of steps leading to deployment. When the doors open, we receive a surprise — something looking like a small tree has spouted at the back of the starboard OMS pod. About 300 heat-protection tiles have been replace by insulation blankets of Nomex, which is nylon coated with silicon. A piece appears to have come loose at the back edge. These blankets protect in areas that do not receive high reentry heating, and soon Mission Control concludes the loose corner presents no problem.
The Shuttle checks out fine, ready for work. We can report, “Everything is going tickety-boo so far.”
It’s a race against time to deploy TDRS, as it has limited battery power and thermal tolerance. We raise the satellite to it’s check-out position, angled up 29 degrees from the payload bay. It’s held at the IUS end in a doughnut-shaped cradle that swivels. After a thorough checkout of all its systems, we declare it a clean bird; ready for deploy. We raise the tilt table so that the satellite/ IUS are angled up 58 degrees, the deployment position. We are go.
Deploy, 1,400 mi. east of Rio de Janeiro. We have deploy at 11:32 p.m. EST. The spring release, at just four-tenths of a foot per second, is so smooth, it deceives are eyes. Is it moving? A check of the TV camera trained at the IUS’s engine nozzle shows it sliding smoothly through the doughnut. The satellite, led by its twin golden umbrella antennas folded neatly, sails away without a quiver.
And then it’s time to prepare to sleep. We’ve been up 20 hours. We’re up long enough to hear of the burn of the IUS’s first stage, took place perfectly an hour after deployment. The burn of 2 min. 31 sec. raises the high point of the satellite’s orbit to near-geostationary altitude. A few hours later, while we sleep, a burn of the second stage should circularize TDRS’s orbit up there. Everything appears going perfectly.
Challenger is already a space veteran.