From how far away could the Challenger explosion be seen?April 7, 2012 5:27 PM   Subscribe

From how far away could the Challenger explosion be seen? (Did you see it? Where were you?)
posted by avocet to Science & Nature (15 answers total) 5 users marked this as a favorite

There is footage taken from around Jacksonville or St. Augustine, about a hundred miles away, but I can't find it on youtube right now.
posted by ROU_Xenophobe at 5:45 PM on April 7, 2012

The wikipedia page for the accident gives the main breakup altitude as 48,000 feet. The back of the envelope calculation for distance-to-the-horizon at 48,000 feet (given here) is around 268 miles. That would be the hypotenuse (is that the right term?) of a cone with a pretty damn big base, confounded a bit by the earth not being flat. Conceivably, anyone in that circle could have seen it, and it might not take much* to draw that circle on a Google map.

* he said, leaving this an exercise to the reader. I pulled this basically out of my arse and welcome any and all corrections by the more math-inclined.

posted by jquinby at 5:50 PM on April 7, 2012 [1 favorite]

Kids from my school saw it in Gulf Stream, Florida. (We would all go out to the field to watch the shuttle launches.)
posted by Comrade_robot at 5:52 PM on April 7, 2012

I saw it from the play yard of my Montessori school in Holiday, FL. That's on the other coast, about 150 miles away I'd guess. I have very vivid memories of the explosion and of one of the teachers crying out and trying to cover the eyes of a few of my fellow students.
posted by alas at 6:30 PM on April 7, 2012

Seen from Gainesville, Fl. About 160 miles away.
posted by Ochre,Hugh at 7:10 PM on April 7, 2012

I saw it in Lake Mary, FL, about 70 miles away.
posted by judith at 7:42 PM on April 7, 2012

alas: Interesting that you could see the launch from that distance. But as for teachers covering students' eyes, are you sure your memory is accurate? I ask simply because in the footage I've seen of the explosion, it's not necessarily clear what's happening at first. Even many TV commentators, who were watching magnified images of the shuttle as it ascended, thought at first that they were just seeing the SRBs separate. I would be extremely surprised if laypeople, watching from over a hundred miles away, were able to immediately understand that the shuttle had exploded.
posted by Artifice_Eternity at 10:54 PM on April 7, 2012

Assuming you’re asking for a theoretical answer, we’ve got to delve into the math just a little bit. Here’s my back-of-the-envelope work:

Imagine a triangle that connects the viewer, the shuttle, and the center of the earth. Imagine the shuttle and the center of the earth are fixed points, but the viewer can be anywhere on the surface of the earth. For most points on the earth, the line between the viewer and the shuttle will intersect the surface of the earth, meaning that the earth will obstruct the view of the shuttle. We will call these points outside of the viewable area. Therefore when the viewer is the furthest away she can be without an obstructed view, the line connecting the shuttle and the viewer will be perpendicular to the line between the viewer and the center of the earth. If this doesn’t make sense, draw this on a piece of paper and you’ll see why this is true. (One side note: this is assuming that the point of view is at the surface of the earth. This simplification will have negligible effect.)

Because we have a triangle with a perpendicular intersection (i.e. a right angle), Pythagoras give us the answer. The hypotenuse is the radius of the earth (6378.1 km) plus the height of the shuttle at breakup (15 km) is 6393.1 km. The known leg is just the radius of the of the earth. So 6393.1^2=(x^2)+ (6378.1^2) -> x=sqrt((6393.1^2)- (6378.1^2)) -> x=437.68 km, or about 272 miles.

(Second side note: This doesn’t consider refraction. Refraction actually extends the viewable area because the arc is concave towards the earth.)

This of course is variable based on size of object, weather conditions, eyesight of viewer, and mechanical aids (e.g. binoculars.) But about 300 miles should be pretty close to the theoretical limit when the shuttle was at that height.
posted by ochenk at 11:28 PM on April 7, 2012 [1 favorite]

But as for teachers covering students' eyes, are you sure your memory is accurate?

The Challenger disaster has, in fact, been used as an example of how fallible (or malleable) human memory can be.

In a study conducted the week of the disaster, subjects wrote down where they were, what they were doing, and how they found out about the Challenger explosion. They then answered the same questions 9 months later. A quarter of the subjects provided at least one inconsistent answer; for example, they thought they saw the explosion on TV when in fact someone had called and told them. Surprisingly, they were nearly as confident in these incorrect memories as they were in their correct memories.

I have a similar perspective on my 9/11 memories -- my friend who called me insists it was after the second plane hit, I insist we saw it together, while both on the phone. (We both agree we were on the phone together when the first tower fell, though, and the sound of her involuntary wail is to this day one of the most chilling things I've ever heard.)

I would be extremely surprised if laypeople, watching from over a hundred miles away, were able to immediately understand that the shuttle had exploded.

For comparison, here is a rare amateur video, taken from Winter Haven, FL (70 miles away). These lay launch watchers are concerned almost immediately but unsure what has happened until one of them goes inside his house to hear news reports and comes back out to say "It exploded!"

I would estimate that the visual size on the standard YouTube screen is about how it would appear to someone at 150 miles. (It's also quite possible that the teachers had a radio running and could hear the news commentary or the infamous words, "Obviously a major malfunction.")

Even many TV commentators, who were watching magnified images of the shuttle as it ascended, thought at first that they were just seeing the SRBs separate.

Interestingly, I suspect it is actually more possible to understand quickly what happened seeing the "master shot" viewpoint rather than the close-up. The amateur video lets you see the brightness of the "explosion" as the external tank broke up and vented its payload, which then ignited. The traditional media view was the Cape tracking cameras, which had an almost straight-up aft view, and while they show the "explosion"/breakup it's very easy to be distracted by the still-firing SRBs and think that's the orbiter itself. Sadly, nobody realized that the crew compartment was one of the largest of the plumes falling quickly out of frame. Post-Challenger there were more video options, and post-Columbia even more, although few were live. Still, it's remarkable that the lay observers could tell that the launch plume was brighter than usual, reflecting the venting SSME fuel from the ET that was igniting as it left the bottom of the tank.

This, by the way, is a second amateur video, taken at the Orlando Airport, about 40 miles away.
posted by dhartung at 2:56 AM on April 8, 2012 [8 favorites]

I saw it in Ozona, Fl which is west of Tampa by a bit. I will never forget it.
posted by PorcineWithMe at 6:34 AM on April 8, 2012

I was in Port St. Lucie, FL at my kindergarten playground. About 85 miles away.
posted by bluefly at 9:25 AM on April 8, 2012

My (now deceased) grandmother claimed to have seen it from a plane. She had been visiting my uncle, who worked at the Cape, and was flying back to NY. I think she described what she saw as a really bright flash, but she didn't know what it was until later.
posted by DiscourseMarker at 9:35 AM on April 8, 2012

I saw it from the big flight dynamics control room at Goddard. GSFC is backup to Johnson for any manned launch, and I'd just moved over to the software side so I didn't actually have to be there, was just hanging out. Our system (a pair of mainframes) did orbit determination and also used telemetry to generate displays which showed position during orbit (those sine waves on the world map) but during launch, showed big velocity, altidude, and flight-path-angle curves on a big graph, which all essentially flat-lined after T+72 seconds. They were projected up on big screens either side of the main TV feed from the Cape. I was part of the operational launch team there between '82 and '85, best job I ever had, in some ways, but that day I was glad I didn't have to stick around, went back to the office off-site, were nobody was working, instead all in the meeting room, watching the TV coverage. Later that evening, back home, I pick up the phone and my buddy's deep voice said "You did it."
posted by Rash at 3:41 PM on April 8, 2012 [1 favorite]

I would be extremely surprised if laypeople, watching from over a hundred miles away, were able to immediately understand that the shuttle had exploded.

We (high school students) definitely knew something was wrong. At that point we'd watched the shuttle take off 50 times - this looked very very different, and it was clear something unusual had happened, so we ran inside to the school library to watch the news.
posted by judith at 7:51 PM on April 8, 2012 [1 favorite]

My experience was the same as judith's. We were very young, but we had grown up watching shuttle launches and this one looked different. I remember someone in the class asking the teacher why there were so many fires, and she didn't know. Then, a few days later, someone came to our class to discuss what we had seen (and felt) and what had really happened.
posted by bluefly at 10:13 AM on April 9, 2012

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