From another forum:

The difference was, five of the astronauts were “professional” astronauts, two were essentially “guests” or filling seats for various purposes… Greg Jarvis had won a contest at his shuttle contractor company “Hughes” to win a flight on a shuttle as a “payload specialist” (which was basically a “slot” NASA created to allow people to fly on the shuttle with minimal training or responsibilities on a mission, IOW fill in seats with people to create “goodwill” and garner more support for the agency). Unfortunately for Greg Jarvis, he was bumped from an earlier flight to make room for “more important” people like Senator Jake Garn of Utah (a major shuttle contractor state where Morton-Thiokol, the SRB solid propellant manufacturer, was located) and Representative Bill Nelson, who also flew on a prior shuttle flight, purely for the purpose to gain support for the shuttle program and NASA funding in Congress.

Others, like Christa McAuliffe, where flown simply as PR stunts. Interest in NASA and support for spaceflight efforts were seriously flagging in the general public and gubmint which frankly had much bigger fish to fry, and NASA was anxious to stir up public support and gain attention and excitement about the space program. Flying a “dump truck” to space wasn’t particularly exciting, particularly with no station to go to at that time and mostly “make work” and experiments “peeing in jars and looking at stars” to do once they WERE in space… So NASA’s PR machine dreamed up the “teacher in space” program to increase visibility and support. Along with it they dreamed up the “reporter in space” and “artist in space” program to fly reporters and ultimately artists in space to better connect with a largely disinterested public. Christa McAuliffe was selected from thousands of candidates largely on her gender, appearance, and charismatic personality… in short, because she’d make good
PR on TV while “teaching a class from space” via TV downlink from the orbiter. It wasn’t exactly coincidental that they timed the mission to coincide with the Presidential State of the Union address either, despite NASA’s assertions to the contrary after Challenger was lost. It might not have been a “priority” but it was DEFINITELY a consideration.

At any rate, the other five members of the crew, being professional astronauts, were well versed in the limitations and hazards of the shuttle system, and accepted those risks as part of their chosen profession as astronauts, particularly the commanders and pilots, but the mission specialists (which were largely scientists, doctors, and various other highly trained specialist astronauts) who were professional full-time astronauts were knowledgeable (to varying degrees) of the shuttle’s problems and accepted those risks as astronauts. The “payload specialists”, particularly those selected for “free rides” and as PR stunts like Christa McAuliffe, were mostly unaware of the shuttle system’s problems. Most of what they knew of the shuttle program was the carefully crafted PR NASA had created around the shuttle program, that it was a perfectly safe “airliner to space” providing “cheap, routine access to space”. NASA had carefully groomed the appearance of the shuttle program to minimiz
e the problems and overstate the successes and capabilities of the shuttle system. To a disinterested public and non-savvy outsider unfamiliar with the specific technological problems the shuttle program had demonstrated on previous flights and programmatically overall, virtually everybody not intimately involved in the program believed the NASA PR. When the world’s foremost space administration, who had taken us to the Moon, said their vehicle was safe and efficient, virtually everyone just took it on faith and believed it. Remember that this was before the current era of massive distrust of government, back when most (certainly not all) people had a basic level of trust and faith in their government, not like now (and perhaps the revelations after Challenger were in some small way part of the beginning of the massive erosion in the public’s trust and faith in their government that has become the “norm” nowadays… might be an interesting topic of research). At any rate, such
“single mission” minimally trained ‘astronauts’ like Greg Jarvis and Christa McAuliffe would have had little/no “inside information” on the shuttle hardware and program problems and would have been operating mostly ‘blind’ other than the general safety training and mission-specific training they would have required to fly the mission. They certainly didn’t get the “full picture” from the management, training personnel, or full-time astronaut flight crews. Such subjects were basically taboo and weren’t openly discussed; no more than they had been in the lead-up to the Apollo 1 fire– the crew KNEW the capsule and program had ENORMOUS and SERIOUS problems, but even Gus Grissom had said that if he refused to fly it it would be the end of his career, and so he just had to do the best he could and “hope for the best”, and accept the risks. So it was in the shuttle-era astronaut corps, particularly pre-Challenger.

What was MORE dangerous was, NASA itself had come to believe it’s own PR, as had large segments (if not most) of the astronaut corps itself. NASA had had several “close calls” and “near misses” in previous flights, in particular with eroded O-rings and burned SRB cases that had fate been slightly different WOULD have resulted in the loss of those prior missions and crews… BUT NASA management took the position that “since nothing bad HAS happened, nothing bad CAN happen” because of those issues, created band-aid approach “mission rules” or “launch constraints” to address the problems seen (most of which NASA also capriciously “waived” when they interefered with the launch schedule or other mission parameters) which basically were totally inadequate and didn’t address let alone solve the underlying issues that had caused those malfunctions on previous flights… hence when an SRB casing was returned from the ocean with a hole burned through the O-ring area big enough to put a man’s
head through on a previous flight, and investigation revealed the O-rings sealed poorly the colder it got, since it was 53 degrees the day of that launch, NASA simply issued a “launch constraint” that the SRB O-rings should be above 53 degrees at launch– which of course they waived whenever it suited them, as it did with Challenger. NASA had come to believe the shuttle was an “airliner to space” providing “cheap, routine access to space” and that it could be operated like an airliner, instead of the experimental and extremely complicated and technologically brittle system that it was. There was also enormous pressure to meet the over-inflated expectations and cost savings that NASA itself had created for the shuttle system in selling it to the Congress and various presidential administrations over the years prior to the shuttle even flying, hence the enormous pressure to launch and “keep to the schedule” to “prove” the shuttle was what NASA *said* it was and had presented it as.

Christa McAuliffe’s flight on Challenger was to just be a beginning. The second “teacher in space” (McAuliffe’s backup) stuck it out in the astronaut office for years until NASA finally was willing to try again and rewarded her for her tenacity in waiting it out with a shuttle flight. NASA had intended to trot out a number of “*whatever* in space” astronauts to drum up support and increase public interest and excitement and support for the shuttle program… the next up was the “reporter in space”, which long time space beat reporter Jay Barbree was intensively training for (and nearly killed himself jogging on the beach to get into better shape to be in the front-runners for the reporter-in-space astronaut slot, when he collapsed of cardiac arrest on a Florida beach and luckily for him, was seen and gotten prompt medical aid and was hospitalized for and recovered from). The “reporter in space” program was basically in its infancy when Challenger pulled the plug on all those PR st
unts– the “artist in space” program which was to follow it never got off the drawing board, basically, and all discussion of other such programs like the “everyday man in space” selected from the general public was promptly dropped and never heard from again in the wake of Challenger. Had Challenger NOT happened, NASA would SURELY have gone full steam ahead on these other PR stunt projects to drum up public interest and prop up flagging support for the shuttle program. It’s also CERTAIN that eventually one of the shuttles WOULD have suffered Challenger’s fate, it was only a matter of time, not “if” but “when”.

Indeed the “lessons learned” from Challenger were sadly repeated 17 years later with the loss of Columbia and its crew… again a shuttle and crew was lost to a problem which was well known and had been amply demonstrated by a number of near misses and close calls that could have destroyed previous flights, and if it had not happened to Columbia it’s almost certain it would have happened to another shuttle at some point, and it was SHEER LUCK that it had not happened previously, or that the damage incurred when it HAD happened on prior flights had not been sufficient to destroy the vehicle on those flights, just like Challenger.