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Author
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Topic: Photo of the week 609 (June 25, 2016)
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heng44
Member Posts: 3387
From: Netherlands
Registered: Nov 2001
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posted 06-25-2016 02:50 AM
   
 A Saturn 1B (AS-207, the launch vehicle for Skylab 3) rolls out to launch pad 39B at the Kennedy Space Center on June 11, 1973. The crawler-transporter is nearing the bend, where the crawlerway would continue to the originally planned launch pad 39C. |
capcom
Member Posts: 17
From: staffordshire England
Registered: May 2016
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posted 06-25-2016 03:41 AM
Was this photograph taken from the Mobile Service Structure? |
heng44
Member Posts: 3387
From: Netherlands
Registered: Nov 2001
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posted 06-25-2016 04:03 AM
Yes. |
GACspaceguy
Member Posts: 2476
From: Guyton, GA
Registered: Jan 2006
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posted 06-25-2016 05:59 AM
Great shot! I wish we would have needed Pad C because of an increased launch rate for follow on Saturn launches. |
moorouge
Member Posts: 2454
From: U.K.
Registered: Jul 2009
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posted 06-25-2016 07:26 AM
A nerdy question. Back in God's own country - Wales - they tell the tale of Morgan the Moon who took his rocket to the top of the hill to, as he said, "Get that bit closer."So, how much fuel was saved, i.e. less energy, was required to launch a Saturn 1B into orbit from the top of the milkstool? After all, it was that bit closer! |
NukeGuy
Member Posts: 55
From: Irvine, CA USA
Registered: May 2014
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posted 06-25-2016 08:18 AM
Approximating the reduction in energy required by the difference in potential energy at launch, I calculate the milkstool saved about 2.15E8 Joules. This is based on a milkstool height of 39.4 meters and a Saturn 1b launch mass of 5.6E5 kg.I'll work on translating that into propellant mass but comparing the total energy of the orbital mass in a 150 km circular orbit to 2.15E8 Joules, it's going to be small. |
LM-12
Member Posts: 3208
From: Ontario, Canada
Registered: Oct 2010
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posted 06-25-2016 08:39 AM
Pad 39B sits 7 feet higher above mean sea level than Pad 39A. So, did Apollo 10 save any fuel by launching from Pad B instead of Pad A? |
NukeGuy
Member Posts: 55
From: Irvine, CA USA
Registered: May 2014
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posted 06-25-2016 08:44 AM
Using the energy density of kerosene (46E6J/kg) as an approximation of RP-1 fuel, use of the milkstool saved about 5 kg of propellant. Depending of the mixture ratio, some LOX would also be saved.I would be curious to see if anyone comes up with an answer using a different approach. There are other factors such as the reduced gravitational attraction, increase centrifugal force and lower air density that would increase the amount of propellant saved. I assumed these were negligible. |
NukeGuy
Member Posts: 55
From: Irvine, CA USA
Registered: May 2014
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posted 06-25-2016 09:03 AM
Since pad 39-B is farther from the equator, the 7 foot advantage would be somewhat offset by the reduced tangental velocity of the Earth's rotation relative to that at 39-A.Apollo 10 reached the highest velocity of any of the Apollo missions but I doubt it was due to being launched from pad 39-B. |
NukeGuy
Member Posts: 55
From: Irvine, CA USA
Registered: May 2014
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posted 06-25-2016 09:46 AM
If it is assumed that the S-1B profile is identical to Apollo 7 except for an earlier S-1B stage cutoff then the fuel savings can also be estimated.From "Apollo by the Numbers," Apollo 7 S-1B cutoff at velocity of 7620 fps with fuel and oxidizer usage rates of 1847.6 pps and 4263.6 pps, respectively. The milkstool height of 118 feet would reduce burn time of 0.0155 s at a cutoff velocity of 7620 fps. Thus the savings in fuel and LOX would be about 13 kg and 30 kg, respectively. One source of error is that the propellant/oxidizer usage rates varied during liftoff and the value given by "Apollo By the Numbers" is probably an average. Still, it appears that the propellant saved is about 5-10 kg. |
Tom
Member Posts: 1597
From: New York
Registered: Nov 2000
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posted 06-25-2016 09:50 AM
Wouldn't the different launch azimuths of Apollo 7 and Skylab (2, 3, and 4) affect the cut-off times as well as fuel consumption? |
NukeGuy
Member Posts: 55
From: Irvine, CA USA
Registered: May 2014
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posted 06-25-2016 10:11 AM
I am beating this topic into the ground but my first answer based on the difference in initial potential energy, neglected the efficiency of converting the propellant's chemical energy. So the 5 kg value I came up with would be somewhat closer to the 13 kg value using the alternative method. |
Hart Sastrowardoyo
Member Posts: 3445
From: Toms River, NJ
Registered: Aug 2000
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posted 06-25-2016 10:46 AM
Wasn't the planned 39C pad actually 39A, and when that didn't get built, they switch letters to avoid confusion? |
NukeGuy
Member Posts: 55
From: Irvine, CA USA
Registered: May 2014
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posted 06-25-2016 10:59 AM
Launch azimuths would have an effect as would other factors mentioned previously. Also launch weights. I haven't compared the Skylab launch weights with Apollo 7.The true answer can never be known only estimated ceteris paribus. But estimates based on two alternative methods gave remarkably close results. Both those estimates give propellant savings probably below the range of detection of the installed instrumentation. So the savings were of no practical significance. |
LM-12
Member Posts: 3208
From: Ontario, Canada
Registered: Oct 2010
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posted 06-25-2016 11:28 AM
From Chapter 6 The Cape in "Apollo Expeditions to the Moon", a chapter written by Rocco A. Petrone: We even had a contingency plan for a Pad D in case launchings became more and more frequent.
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cspg
Member Posts: 6210
From: Geneva, Switzerland
Registered: May 2006
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posted 06-25-2016 11:45 AM
quote:
Originally posted by Hart Sastrowardoyo:
Wasn't the planned 39C pad actually 39A, and when that didn't get built, they switch letters to avoid confusion?
From Wikipedia: Launch Complex 39 is composed of three launch pads—39A, 39B and 39C ... Pad C was originally planned but never built for Apollo. It was constructed from January to June 2015 to accommodate small-class vehicles, to be determined." Where is that 39C pad? |
LM-12
Member Posts: 3208
From: Ontario, Canada
Registered: Oct 2010
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posted 06-25-2016 12:09 PM
quote:
Originally posted by Hart Sastrowardoyo:
Wasn't the planned 39C pad actually 39A, and when that didn't get built, they switch letters to avoid confusion?
That is my understanding. The original north to south Pads A, B and C became south to north Pads A and B. |
Robert Pearlman
Editor Posts: 42988
From: Houston, TX
Registered: Nov 1999
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posted 06-25-2016 01:29 PM
quote:
Originally posted by cspg:
Where is that 39C pad?
It is within the perimeter of 39B. quote:
Originally posted by Hart Sastrowardoyo:
Wasn't the planned 39C pad actually 39A, and when that didn't get built, they switch letters to avoid confusion?
There are references to such, but if they are accurate, then they date back to 1962 or earlier. As illustrated here, there were multiple diagrams showing Pad A identified as Pad A as early as March 1963, even though a third pad was still being depicted a year later (even on the cover of LIFE magazine). |
LM-12
Member Posts: 3208
From: Ontario, Canada
Registered: Oct 2010
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posted 06-25-2016 04:26 PM
There is a Cape area map in the Nov 28, 1962 issue of Spaceport News that shows three planned launch pads and maybe two "future tentative & alternate" pads at Complex 39. The map is hard to read, but Pad C appears to be south of Pad B.
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mikej
Member Posts: 481
From: Germantown, WI USA
Registered: Jan 2004
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posted 06-27-2016 06:46 PM
As I note on my LC-39A/B/C/D page to which Robert linked, the pads were orginally numbered in accordance with standard Missile Test Center practice from north to south as pads A, B, and C.They were apparently renamed with Pad A as the south-most pad around January 7, 1963. Reference Moonport: A History of Apollo Launch Facilities and Operations. |
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