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NASA Science

Shuttle Reentry Over the Continental US 139

Posted by kdawson
from the boom-boom dept.
TheOtherChimeraTwin notes that the shuttle Discovery will land at Kennedy Space Center on Monday morning at 8:48 EDT. The craft will make a rare "descending node" overflight of the continental US en route to landing in Florida. Here are maps of the shuttle's path if is lands on orbit 222 as planned, or on the next orbit. Spaceweather.com says: "...it takes the shuttle about 35 minutes to traverse the path shown... Observers in the northwestern USA will see the shuttle shortly after 5 am PDT blazing like a meteoric fireball through the dawn sky. As Discovery makes its way east, it will enter daylight and fade into the bright blue background. If you can't see the shuttle, however, you might be able to hear it. The shuttle produces a sonic double-boom that reaches the ground about a minute and a half after passing overhead."
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Shuttle Reentry Over the Continental US

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  • by BitZtream (692029) on Sunday April 18, 2010 @06:56PM (#31891124)

    Its supposed to catch as much air as possible, thats how it slows down from Mach 22 to 250 knots in 35 minutes.

  • by Anonymous Coward on Sunday April 18, 2010 @07:00PM (#31891156)

    Orbital mechanics determines the speed required to be in orbit. It is fairly simple physics and about 17,000 MPH for all objects.

    Landing implies a ZERO speed relative to the rotation of the Earth at the landing sight.

    You need to get the vehicle from 17,000 MPH to zero. There are many ways to accomplish that, but many less if you want to reuse the vehicle and want the people inside not to fry or wait for the last second to "stop." Within these limitations and thousands of others for weight, payload sizes, number of people, some political issues, the shuttle was designed to use air friction to slow it down. They actually fly in S-turns to both slow it and release some of the built up heat to the atmosphere. It is a controller burning of the protective tiles, when it all works.

    Being more aerodynamic would mean the shuttle wouldn't slow down enough to land safely.

    Being less aerodynamic would probably mean it would need to weigh SIGNIFICANTLY more to handle the added stress placed on the vehicle.

    BTW, Mach number only has meaning with their is atmosphere since it is related to the local speed of sound that the vehicle is flying/falling through. In space, there is no Mach number and it changes as you fly though different atmospheric conditions.

    The Space Shuttles are about the size of a DC-10 intercontinental aircraft holding over 250 passengers and glides to a landing. There is only 1 chance to land it where you want it. If you miss the runway, I doubt the vehicle will be usable again. $4B gone each ... or $25M for a museum.

  • by Moraelin (679338) on Sunday April 18, 2010 @07:15PM (#31891256) Journal

    1. Well, during re-entry it's not entering nose-first, but belly-first, so the wings basically like air brakes more than like wings. I'm not sure if making it more aerodynamic for flight like an aircraft would actually be an impediment there. It would still have the aerodynamics of a parachute when re-entering belly-first anyway.

    2. Well, "glide" is technically accurate, but maybe painting a slightly wrong image for the layman. That thing is losing altitude (falling) at 50m/s (about 110mph or 180 km/h) even in its best glide phase. And it's glide-to-drag ratio is more comparable to a parachute, and I don't mean paraglider, than to an aircraft even at touchdown, during earlier phases let's just say it's got about half as much lift/drag as a squirrel ;)

    The angle of descent at touchdown is actually 20 degrees, which doesn't sound like too steep, but it's about 7 times steeper than a commercial airliner landing. By comparison to just about any fixed wing aircraft, it's not akin landing an anvil or the proverbial lead duck ;)

    Not saying it's a bad thing, since it does have a _lot_ of altitude and speed to shed, and it's obviously doing a good job at thazt. More like just saying, for the benefit of whoever needs that kind of clarification, that it never actually acts that much like a normal glider, not even on the very last part. Or at least not like a glider you'd want to pilot for fun. All it can do is fall, and quite rapidly at that, just in a more controlled manner. It's a shape to do just one thing: fall down from 340,000m or so (about a million feet) to the ground without going *SPLAT* on touchdown. While techically there is some gliding involved, I think the best description of its role for the layman is more like "rigid parachute" than "glider."

  • by colinnwn (677715) on Sunday April 18, 2010 @08:36PM (#31891770)
    I've seen reentry across Austin (and not the time it broke up smarty pants). Have you ever seen the ISS or a satellite crossing the sky? It looked kinda like that. The shuttle was a bright dot streaking across the horizon very fast, a good 3 times faster than a commercial plane, and left a contrail that hung in the air for a while. Contrail is a misnomer since it stands for condensation trail. What it really is leaving is a trail of ionized gas and ablated material off the orbiter. A minute later I heard a faint sonic double boom.

    At the distance you are at, it will be lower, meaning you will have less range you can see it over, so I'd imagine it will still appear to be going very fast (and it will be fast). I think it should be just above supersonic, so you should hear the boom. I doubt it will still be leaving a contrail. I don't think you'll be able to miss it.
  • by v1 (525388) on Sunday April 18, 2010 @09:08PM (#31891934) Homepage Journal

    Yep here it is, orbital calculator [nasa.gov]. Punch in your zip code and tell it to show you pass 222 of the shuttle. It will give a set of times. (in eastern standard time)

    My set peaks at 10 deg above the horizon, so ya, probably not going to happen. Maybe if I went out in the country, but it'd be so far away, that's a shame. I'd like to say "maybe next time", but that's not likely... :(

  • by Orgasmatron (8103) on Sunday April 18, 2010 @10:03PM (#31892236)

    It isn't. A retrograde landing at KSC would come in from the Atlantic Ocean.

    An orbit requires two things, altitude and transverse velocity. There are no shortcuts for altitude, so we have to do it entirely the hard way, with rockets. On the other hand, everything on the surface of the earth (not counting the poles) has transverse velocity already, because the earth is turning. This gift of velocity is towards the east, and is related to the launch site's latitude, greater at the equator, less at the poles. This is one of the two reasons why we nearly always launch to the east. Anyone know the second reason?

    When we launch to the east to take advantage of this gift, we call that a prograde orbit. Launching into a retrograde orbit requires burning fuel for 100% of the required transversal, plus enough to overcome the initial eastward velocity from the launch site.

    A southward launch from California can be used for a polar orbit, but I don't think the shuttle has ever actually done it. I think the Air Force insisted that the shuttle be capable of this mission, which would be a single-orbit spy flight over the Soviet Union.

  • by Criliric (879949) <Shane.belaire@gmail.com> on Monday April 19, 2010 @02:11AM (#31893414)
    mach 22 = 45 014 740.2 furlongs per fortnight 250 knots = 773 323.789 furlongs per fortnight :)
  • Negative on 222 (Score:3, Informative)

    by Lost Race (681080) on Monday April 19, 2010 @07:42AM (#31894638)
    Just watched the shuttle pass over Seattle without re-entry on orbit 222, closely followed by ISS. Next pass will be well past sunrise (6:57).
  • by TheOtherChimeraTwin (697085) on Monday April 19, 2010 @08:11AM (#31894856)
    The landing has been postponed until Tuesday (at least) due to rain. Check SpaceWeather [spaceweather.com] for updates.
  • by Anonymous Coward on Monday April 19, 2010 @08:13AM (#31894872)

    Adding to this, what I'm not sure the OP well above realizes is... well, a couple of things.

    1) Technically, ALL descents start while the vessel is facing retrograde. ;) (Sorry, just being a jerk.)
    2) Orbital planes can take many shapes on a mercator projection of a map, from a flat line (at the equator) to a sine wave, to what appears to be a pair of tangental lines (north-to-south). This particular plane is an abnormally radical "sine wave" when looking at a mercator map projection, and technically is coming in over the northwest instead of the west, as probably has already been said elsewhere. This is to avoid any particularly expensive orbit normal/anti-normal maneuvers to change the orbital node.

    Anybody who would like a better hands-on understanding would do well to jump on trying Orbiter Space Flight Sim. ;)

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