avi
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Endeavour Launches And Lands At Night – Why?

Sat Mar 08, 2008 1:33 am

On Tuesday space shuttle Endeavour – in mission STS 123 - is about to start a 16 days in space.
The launch is planed to 02:28 and landing – at the moment – is planed to 20:33 (EDT of course).

Since the Colombia disaster NASA launched 8 missions and this one (the 9th) is only the second to launch at night (The Colombia disaster's investigation report recommended a day launch so it will be easy to see foam falling).

More than that, a night launch – which affects the entire mission time line – changes the space station crew daily routine since now they need to swap their days into nights and nights into days.

Is there any specific reason why NASA does it?
Is it possible that since it is a join US-Japan mission NASA needs to take into a count the time in Japan?

Thanks.
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Stitch
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RE: Endeavour Launches And Lands At Night – Why?

Sat Mar 08, 2008 1:42 am

I can only guess the launch window favors a night launch? Or do they need to schedule night launches for certain payload types or weights?
 
avi
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RE: Endeavour Launches And Lands At Night – Why?

Sat Mar 08, 2008 2:23 am



Quoting Stitch (Reply 1):
I can only guess the launch window favors a night launch? Or do they need to schedule night launches for certain payload types or weights?

Thanks.

NASA can launch twice a day to intercept the ISS. The last launch on Feb 7th (only 1 month ago) was at 14:45 so I'm quite sure they can launch at a similar hour.
I don't think it's a payload issue.
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sprout5199
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RE: Endeavour Launches And Lands At Night – Why?

Sat Mar 08, 2008 2:49 am



Quoting Avi (Thread starter):
More than that, a night launch -- which affects the entire mission time line -- changes the space station crew daily routine since now they need to swap their days into nights and nights into days.

??? The "days" only last about 45mins(I think--isn't an orbit 90 minutes?). I don't think that is in the equation.

Quoting Avi (Thread starter):
The Colombia disaster's investigation report recommended a day launch so it will be easy to see foam falling

They have upgraded the radars to "see" if any foam comes off.

Dan in Jupiter
 
Thorny
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RE: Endeavour Launches And Lands At Night – Why?

Sat Mar 08, 2008 5:13 am



Quoting Avi (Thread starter):
Is there any specific reason why NASA does it?

I'm modifying what I wrote here on the subject back in 2006 (STS-121) for this explanation.

The launch time is determined by where the International Space Station is in Earth orbit.

Once a satellite is in orbit, its path is fixed (more or less, more on that in a moment) relative to the stars. The Earth rotates beneath the satellite's orbit. The Space Station is in an orbit angled 51.6 degrees to the equator, meaning the most northerly point in its orbit is at 51.6 deg north lattitude and the most southerly point is 51.6 deg south. The Space Station crosses the equator twice each orbit... once heading north (ascending node) and once heading south (descending node.)

The best time to launch to the Space Station is when the Earth's rotation carries your launch site directly beneath the orbit of the Station. This happens twice a day, 12 hours apart at the equator. At Cape Canaveral, 28.5 deg north of the equator, the two opportunities (ascending node and descending node) are about 6 hours apart, and then its another 18 hours until the next opportunity. Only one of these opportunities is usable from Cape Canaveral... the northward "ascending node". The southward descending node would carry the Shuttle too close to the Florida coast and the population centers of the Bahamas.

Launch Pad 39A passes underneath the orbit of the Space Station at exactly 2:28:10am EDT Tuesday. The Shuttle has enough propellant to maneuver a little to match the Station's orbit. They can launch about five minutes to either side and maneuver "out of plane" back into the Station's orbit. So NASA can launch a Space Shuttle to the International Space Station for only about 10 minutes every day.

Because the Earth is not a perfect sphere (it bulges out a little in the southern hemisphere) a satellite's orbit shifts a little bit with each orbit. This is called precession. So the Space Station passes over Launch Pad 39A about 25 minutes earlier each day. The orbit of the Space Station passes over Launch Pad 39A at 2:28am on Tuesday, but at 2:02am on Wednesday.

The Space Station itself is not flying directly over Launch Pad 39A at that moment. Waiting for such a coincidence would limit launch opportunities to only a few times a year. Instead, the Shuttle goes into the same orbit as the Station and then speeds up or slows down to catch up with the Station. That usually takes two days (the Russians do it the same way with Soyuz and Progress spacecraft.)

Once in orbit, the Shuttle can go higher or lower, flying in a more elliptical orbit than the Station's more or less circular orbit. That means they complete one orbit faster than the Space Station does and they slowly close the distance to the Space Station, a little each orbit.

Landing is roughly the same situation. The Shuttle will be at the International Space Station throughout the mission. When it is ready to come home, they want to fire the engines to bring the Shuttle home during an orbit that passes over Kennedy Space Center. But the Shuttle has those large delta wings that generate a great deal of lift (compared to space capsules, anyway) and the Shuttle can steer up to 1,000 miles to either side of the orbit in order to reach Kennedy Space Center (this is called Crossrange Capability). This in effect means the Shuttle can land on either of two consecutive orbits.

Because the Space Station's (and with it, the Space Shuttle's) orbit precesses 25 minutes every day, the orbit of the Space Station passes over Kennedy Space Center about 6 hours earlier at the end of the mission, on March 26, than it did at launch 16 days earlier on March 11. Landing is scheduled for 8:35pm on March 26. They can try again one orbit later, if necessary, landing at about 10:05pm. They can also shift to the descending node landing opportunity, if desired, although NASA prefers since the Columbia accident to not fly the Shuttle over the continential U.S. enroute to landing, if possible. But with longer and longer missions to the Space Station, precession might shift the landing time to very early in the crew's "day" and NASA might choose to shift to the descending node landing opportunity to have a better-rested crew for the landing (this was the case for STS-120 in October.)
 
sprout5199
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RE: Endeavour Launches And Lands At Night – Why?

Sat Mar 08, 2008 5:18 am



Quoting Thorny (Reply 4):

Very good explanation.  bigthumbsup   bigthumbsup 

Dan in Jupiter
 
avi
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RE: Endeavour Launches And Lands At Night – Why?

Sat Mar 08, 2008 1:45 pm

Thanks Thorny.

I did notice that NASA launches only "ascending node" but I didn't know they are doing it to keep the shuttle away from populated areas.
With this (new) fact in mind, obviously NASA can launch only once a day when the ISS is "around" and the clock doesn't play a role when setting this time.
I guess I didn't notice it in the past because NASA didn't launch 2 missions to the ISS so close one to each other for a very long time.

Quoting Sprout5199 (Reply 3):
??? The "days" only last about 45mins(I think--isn't an orbit 90 minutes?). I don't think that is in the equation.

When I said "day" and "night" I meant the time when they are awake and working and when they are sleeping.
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PC12Fan
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RE: Endeavour Launches And Lands At Night – Why?

Sat Mar 08, 2008 2:32 pm

I think another reason is that - as we all know - the shuttle gets a detailed inspection once in orbit. I don't think it's as much of an issue to actually see the foam fall off when the damage would be spotted anyways.

Quoting Thorny (Reply 4):
Because the Earth is not a perfect sphere (it bulges out a little in the southern hemisphere)

I didn't know that, interesting.
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Thorny
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RE: Endeavour Launches And Lands At Night – Why?

Sat Mar 08, 2008 4:28 pm



Quoting PC12Fan (Reply 7):
I think another reason is that - as we all know - the shuttle gets a detailed inspection once in orbit. I don't think it's as much of an issue to actually see the foam fall off when the damage would be spotted anyways.

Nope. All missions to the ISS use a 2-day rendezvous flight, even Soyuz and Progress. Europe's ATV is planning to use a four or five day rendezvous, if memory serves (on later flights, not for Jules Verne which will take a month for testing.) This is because the ISS is very rarely directly over the launch site at the time the ISS's orbit passes over the launch site. Instead, it usually is a quarter of a world away, and the Shuttle/Soyuz/Progress just play catch-up for two days. (Some Shuttle flight profiles are three days, but this is rare.)

They just squeeze in the inspection in time the crew previously used to prepare for docking, perform other experiments, etc.

Also, with space adaptation syndrome (spacesickness) striking something like half of all people who fly in space, it is useful to have a day or two to get over that before the real work starts at the Space Station.
 
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RE: Endeavour Launches And Lands At Night – Why?

Sat Mar 08, 2008 4:34 pm



Quoting Thorny (Reply 8):

I thought it was now a manditory task after each shuttle launch to inspect the exterior of the shuttle after each launch. Is this not the case?
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Thorny
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RE: Endeavour Launches And Lands At Night – Why?

Sat Mar 08, 2008 4:47 pm



Quoting PC12Fan (Reply 9):
I thought it was now a manditory task after each shuttle launch to inspect the exterior of the shuttle after each launch. Is this not the case?

Yes, but that's not the reason for the night launch or the two-day flight to ISS.
 
connies4ever
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RE: Endeavour Launches And Lands At Night – Why?

Sat Mar 08, 2008 4:56 pm



Quoting Thorny (Reply 4):
Because the Earth is not a perfect sphere (it bulges out a little in the southern hemisphere) a satellite's orbit shifts a little bit with each orbit. This is called precession.

Actually, Thorny, I think what you're referring to is strictly called 'precession of apsides'. There is a brief explanation here: http://en.wikipedia.org/wiki/General_relativity#Precession_of_apsides

Precession per se is usually meant to refer to the 'wobbling' of a body that is rotating about an axis (such as Earth's N-S axis), and that's illustrated here: http://en.wikipedia.org/wiki/Precession . The wobbling can be self-induced or by a torque effect imposed on the body (Moon, Sun, for example).

It's quite true the Earth is not a sphere. It has been referred to as an oblate spheroid, as it's rotation causes the mass nearer the equator to bulge somewhat. But that's not quite right either. Since there is less mass is the southern hemisphere, there is a weaker gravitational field, and hence less force 'holding' the Earth in a near-spherical shape. So it bulges.

One can see the sphere-inducing effect of gravity by looking at the asteroids: the big ones tend to be spheroidal due to their own gravitational field whilst the smaller ones are almost always irregular hunks of rock, gravel, sand, whatever.
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Thorny
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RE: Endeavour Launches And Lands At Night – Why?

Sat Mar 08, 2008 5:46 pm



Quoting Connies4ever (Reply 11):
Actually, Thorny, I think what you're referring to is strictly called 'precession of apsides'. There is a brief explanation here: http://en.wikipedia.org/wiki/General...sides

Yeah, I was trying not to be too technical about it. It's already a bit tough to follow for the layman.
 
PC12Fan
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RE: Endeavour Launches And Lands At Night – Why?

Sat Mar 08, 2008 9:22 pm



Quoting Thorny (Reply 10):
I thought it was now a mandatory task after each shuttle launch to inspect the exterior of the shuttle after each launch. Is this not the case?

Yes, but that's not the reason for the night launch or the two-day flight to ISS.

Ah OK, I got a little confused there as I was referring to the thread starters "necessity" to launch during daylight hours to spot possible foam separation.
Just when I think you've said the stupidest thing ever, you keep talkin'!
 
Thorny
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RE: Endeavour Launches And Lands At Night – Why?

Sat Mar 08, 2008 10:53 pm



Quoting PC12Fan (Reply 13):
Ah OK, I got a little confused there as I was referring to the thread starters "necessity" to launch during daylight hours to spot possible foam separation.

Ah, okay. (These threads are starting to blur together!)

The daylight launch rule was dropped after, I think, two flights without significant foam liberation. That was STS-121 and STS-115, so STS-116 was a night launch.

They still have ET cameras that provide some view during ascent, from ambient light of the SRBs (after the SRBs are gone, the threat from foam liberation is greatly reduced anyway.) And they do have radar capable of spotting things big enough to be a serious concern. That, plus the OBSS boom survey in orbit and the RPM backflip for the ISS cameras provide enough redundancy that they don't require daylight launches anymore.
 
DeltaGuy
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RE: Endeavour Launches And Lands At Night – Why?

Sun Mar 09, 2008 12:27 am



Quoting Thorny (Reply 4):
They can also shift to the descending node landing opportunity, if desired, although NASA prefers since the Columbia accident to not fly the Shuttle over the continential U.S. enroute to landing, if possible.

I would think you'd still want it across the US....imagine if Columbia had broken up over the Atlantic, you'd have hardly found any wreckage.

DeltaGuy
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PC12Fan
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RE: Endeavour Launches And Lands At Night – Why?

Sun Mar 09, 2008 12:55 am



Quoting Thorny (Reply 14):
They still have ET cameras that provide some view during ascent,

I know! That is some of the most incredible launch footage there is IMO. Great stuff! I love the "ring of fire" at the back of the shuttle just before MEC. Very cool!
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halls120
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RE: Endeavour Launches And Lands At Night – Why?

Sun Mar 09, 2008 1:46 am



Quoting Thorny (Reply 12):
Quoting Connies4ever (Reply 11):
Actually, Thorny, I think what you're referring to is strictly called 'precession of apsides'. There is a brief explanation here: http://en.wikipedia.org/wiki/General...sides

Yeah, I was trying not to be too technical about it. It's already a bit tough to follow for the layman.

Your explanation was excellent, and very informative - thanks.
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wingnut767
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RE: Endeavour Launches And Lands At Night – Why?

Sun Mar 09, 2008 2:36 am



Quoting Halls120 (Reply 17):
Quoting Thorny (Reply 12):
Quoting Connies4ever (Reply 11):
Actually, Thorny, I think what you're referring to is strictly called 'precession of apsides'. There is a brief explanation here: http://en.wikipedia.org/wiki/General...sides

Yeah, I was trying not to be too technical about it. It's already a bit tough to follow for the layman.

Your explanation was excellent, and very informative - thanks.

Yeah thanks for the explanation thorny. I want to take my eight year old over for the night launch but Mama does not want him to miss school the next day. We will see who wins this battle. The night launches are an awesome display of light.
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Mir
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RE: Endeavour Launches And Lands At Night – Why?

Sun Mar 09, 2008 8:21 am



Quoting DeltaGuy (Reply 15):
I would think you'd still want it across the US....imagine if Columbia had broken up over the Atlantic, you'd have hardly found any wreckage.

I think the idea is more not to have the wreckage fall on anyone than it is to recover whatever wreckage there is.

Quoting Wingnut767 (Reply 18):
The night launches are an awesome display of light.

They are indeed. I've seen every launch that I've been in Florida for since coming down here in 2006 (116, 117, 118, 120, 122), and I'm definitely not going to miss this one.

-Mir
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checksixx
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RE: Endeavour Launches And Lands At Night – Why?

Sun Mar 09, 2008 2:40 pm



Quoting Connies4ever (Reply 11):
Quoting Thorny (Reply 4):
Because the Earth is not a perfect sphere (it bulges out a little in the southern hemisphere) a satellite's orbit shifts a little bit with each orbit. This is called precession.

Actually, Thorny, I think what you're referring to is strictly called 'precession of apsides'. There is a brief explanation here: http://en.wikipedia.org/wiki/General_relativity#Precession_of_apsides

Precession per se is usually meant to refer to the 'wobbling' of a body that is rotating about an axis (such as Earth's N-S axis), and that's illustrated here: http://en.wikipedia.org/wiki/Precession . The wobbling can be self-induced or by a torque effect imposed on the body (Moon, Sun, for example).

It's quite true the Earth is not a sphere. It has been referred to as an oblate spheroid, as it's rotation causes the mass nearer the equator to bulge somewhat. But that's not quite right either. Since there is less mass is the southern hemisphere, there is a weaker gravitational field, and hence less force 'holding' the Earth in a near-spherical shape. So it bulges.

One can see the sphere-inducing effect of gravity by looking at the asteroids: the big ones tend to be spheroidal due to their own gravitational field whilst the smaller ones are almost always irregular hunks of rock, gravel, sand, whatever.

Actually you both should check out NASA's website for your questions/answers...tends to be a much better source than wiki in reference to what your discussing.
 
connies4ever
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RE: Endeavour Launches And Lands At Night – Why?

Sun Mar 09, 2008 4:34 pm



Quoting Checksixx (Reply 20):
Actually you both should check out NASA's website for your questions/answers...tends to be a much better source than wiki in reference to what your discussing.

Actually, Check, I tend to refer laymen to wiki as it is a reasonable starting point. I could always haul out my Principles of Inertia from grad school and offer up the relevant portions. I'm finding some days that simply going by memory I don't always include enough salient info. Then they can Google if they're interested still.
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