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#160
by
Jim
on 10 Nov, 2007 03:18
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tnphysics - 9/11/2007 9:59 PM
Why is the LH2 tank below the LOX tank, as opposed to the more structurally efficient method of putting the LOX tank on the bottom?
controllability
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#161
by
Analyst
on 10 Nov, 2007 19:18
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Here you can find some very detailed Outer Planets Mission Flagship Study Reports (Cassini class missions to Jupiter/Saturn and their moons). They require a Delta IVH or an Atlas 551. The cost given for the launch service are:
- Delta IVH: $486 million
- Atlas 551: $190 million
The Atlas number is exactly in the New Horizons / Juno range. I am surprised by the Delta IVH, 2.5 times more than Atlas for less than 50% more performance. This is almost the Titan 4B Centaur price class Cassini paid. Any comments.
Analyst
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#162
by
Avron
on 10 Nov, 2007 23:02
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-- >> from the live thread
Jim - 10/11/2007 6:33 PM
This isn't much different than a Titan IV-B Centaur
Jim please confirm - is it closer to a Proton?
Edited by Avron 10/11/2007 6:45 PM
looking for idea in pct..
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#163
by
Jim
on 10 Nov, 2007 23:06
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Lift performance or first stage thrust?
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#164
by
Avron
on 10 Nov, 2007 23:10
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Jim - 10/11/2007 7:06 PM
Lift performance or first stage thrust?
1st stage
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#165
by
Jim
on 10 Nov, 2007 23:23
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1.95 Mlb vs 2.0/2.1 Mlb
DIV Proton
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#166
by
NotGncDude
on 10 Nov, 2007 23:29
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How is that possible, when DIV lifts so much more? Much better mass fraction?
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#167
by
Jim
on 10 Nov, 2007 23:32
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thrust isn' everything
ISP, launch site, mass fraction
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#168
by
edkyle99
on 10 Nov, 2007 23:37
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GncDude - 10/11/2007 6:29 PM
How is that possible, when DIV lifts so much more? Much better mass fraction?
Proton actually has a propellant better mass fraction (much smaller dry mass), but Delta IV uses higher energy propellant. It gets better "gas mileage", in effect, than Proton, so that it can weigh slightly less at lift off. But that propellant, liquid hydrogen fuel and liquid oxygen oxidizer, is less dense than Proton's hypergolic propellants, which means that Delta IV must be physically larger than Proton (and thus weigh much more dry - and cost much more as a result). Delta IV stands about 15 meters taller and measures 15.3 meters across its widest point compared to 7.4 meters for Proton.
- Ed Kyle
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#169
by
NotGncDude
on 10 Nov, 2007 23:49
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I thought 1st stage thrust was closely related to lift off weight, just a fraction above (with some exceptions).
Edit: Oh I see. It's the liftoff weight what depends on ISP, not just mass fraction. Thanks. Darn, gotta got back to those equations.
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#170
by
djellison
on 11 Nov, 2007 08:50
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GncDude - 10/11/2007 12:49 AM
I thought 1st stage thrust was closely related to lift off weight, just a fraction above (with some exceptions).
If you want a really good side-by-side of this not being true - watch the MRO launch and the New Horizons launch side by side. MRO crawls away, New Horizons set's off like a scalded cat.
Doug
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#171
by
gospacex
on 11 Nov, 2007 15:28
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MKremer - 25/9/2007 5:20 PM
As mentioned by others here in different threads, the RS-68 design just takes too much ground support equipment to prep for ignition and through the ignition cycle. To try to add all it needs into an upper stage would add so much mass it would overwhelm any advantages the engine could offer.
I thought that RS-68 is "simpler" than SSME and is cheaper to operate. From the above I learn that it is not completely simple. Can someone give a bit more details where RS-68 stands in comparison to SSME and to, say, RD-180? I mean, how much work/money is needed at the pad to support it?
Another question: it looks counter-intuitive to me that rocket engines, which are designed to withstand huge temperatures and pressures when they operate, are not able to withstand ordinary sea water. It was said several times that first stage engine recovery is not cost efficient because of required cleanup / replacement of parts damaged by sea water. Any more details on what happens to engine which was immersed in sea water for an hour?
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#172
by
edkyle99
on 11 Nov, 2007 16:06
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Analyst - 10/11/2007 2:18 PM
Here you can find some very detailed Outer Planets Mission Flagship Study Reports (Cassini class missions to Jupiter/Saturn and their moons). They require a Delta IVH or an Atlas 551. The cost given for the launch service are:
- Delta IVH: $486 million
- Atlas 551: $190 million
The Atlas number is exactly in the New Horizons / Juno range. I am surprised by the Delta IVH, 2.5 times more than Atlas for less than 50% more performance. This is almost the Titan 4B Centaur price class Cassini paid. Any comments.
Analyst
Wow. It takes one's breath away, doesn't it? I knew it had to be a lot more money than everyone thought, but nearly half a billion dollars?
Scaled with payload capability from the 551 cost, Delta 4H should cost $307 million. $486 million is just outrageous, scandalous even, especially considering that Boeing once listed these at $150 million (!) and that EELV Heavy was sold to the taxpayers as a cost savings compared to Titan 4.
First the EELV scandal. Then the FIA disaster. Now this (although I know that Delta 4 now falls within the United Launch Alliance realm, Boeing developed it). Is Boeing working for, or against, the U.S. government?
- Ed Kyle
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#173
by
Jim
on 11 Nov, 2007 17:10
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gospacex - 11/11/2007 11:28 AM
1. I thought that RS-68 is "simpler" than SSME and is cheaper to operate. From the above I learn that it is not completely simple.
Another question: it looks counter-intuitive to me that rocket engines, which are designed to withstand huge temperatures and pressures when they operate, are not able to withstand ordinary sea water. It was said several times that first stage engine recovery is not cost efficient because of required cleanup / replacement of parts damaged by sea water. Any more details on what happens to engine which was immersed in sea 2. water for an hour?
1. It is simpler and cheaper. It was not designed for airstart and by putting start systems on the ground it made it simpler and less complex. The bulk of the GSE required is a large He tank
2. Plain and simple. Corrosion
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#174
by
gospacex
on 11 Nov, 2007 18:06
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Jim - 11/11/2007 12:10 PM
gospacex - 11/11/2007 11:28 AM
Any more details on what happens to engine which was immersed in sea water for an hour?
Plain and simple. Corrosion
Lots of corrosion after only an hour or two? Can you quantify it?
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#175
by
Jim
on 11 Nov, 2007 18:21
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gospacex - 11/11/2007 2:06 PM
Jim - 11/11/2007 12:10 PM
gospacex - 11/11/2007 11:28 AM
Any more details on what happens to engine which was immersed in sea water for an hour?
Plain and simple. Corrosion
Lots of corrosion after only an hour or two? Can you quantify it?
The engine isn't going to retrieved immediately. The SRB's spend at least a day in the water. Nevertheless, even if it was pulled out after 1 -2 hours, it is going to be disassembled for days or weeks.
It is not just the salt water on the engines, it effects the other components also (avoinics, hydraulics, structure, etc) . It is water impact loads on the structure, components, etc
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#176
by
yinzer
on 11 Nov, 2007 18:22
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edkyle99 - 11/11/2007 9:06 AM
Analyst - 10/11/2007 2:18 PM
Here you can find some very detailed Outer Planets Mission Flagship Study Reports (Cassini class missions to Jupiter/Saturn and their moons). They require a Delta IVH or an Atlas 551. The cost given for the launch service are:
- Delta IVH: $486 million
- Atlas 551: $190 million
The Atlas number is exactly in the New Horizons / Juno range. I am surprised by the Delta IVH, 2.5 times more than Atlas for less than 50% more performance. This is almost the Titan 4B Centaur price class Cassini paid. Any comments.
Analyst
Wow. It takes one's breath away, doesn't it? I knew it had to be a lot more money than everyone thought, but nearly half a billion dollars?
Scaled with payload capability from the 551 cost, Delta 4H should cost $307 million. $486 million is just outrageous, scandalous even, especially considering that Boeing once listed these at $150 million (!) and that EELV Heavy was sold to the taxpayers as a cost savings compared to Titan 4.
First the EELV scandal. Then the FIA disaster. Now this (although I know that Delta 4 now falls within the United Launch Alliance realm, Boeing developed it). Is Boeing working for, or against, the U.S. government?
If the Delta 4H costs almost as much as a Titan 4 Centaur when flying at a much lower flight rate, it is a cost savings of sorts. And you of all people should know that linearly scaling cost with payload weight is completely meaningless. Based strictly on payload weight, the DSP could have flown on an Atlas 521.
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#177
by
Jim
on 11 Nov, 2007 18:34
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Not true. The adapter weighed over 2000 ibs.
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#178
by
Antares
on 11 Nov, 2007 19:14
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gospacex - 11/11/2007 10:28 AM
MKremer - 25/9/2007 5:20 PM
As mentioned by others here in different threads, the RS-68 design just takes too much ground support equipment to prep for ignition and through the ignition cycle. To try to add all it needs into an upper stage would add so much mass it would overwhelm any advantages the engine could offer.
I thought that RS-68 is "simpler" than SSME and is cheaper to operate.
Another question: it looks counter-intuitive to me that rocket engines, which are designed to withstand huge temperatures and pressures when they operate, are not able to withstand ordinary sea water. It was said several times that first stage engine recovery is not cost efficient because of required cleanup / replacement of parts damaged by sea water. Any more details on what happens to engine which was immersed in sea water for an hour?
There's a slight confusion here. RS-68 as currently used requires virtually no maintenance after acceptance. Heck, the Heavy Demo engine covers blew into the river during one of the 2004 hurricanes, and those 3 worked just fine. An air-start RS-68, actually its stage, would not be simple because of the spin-start equipment and new ignition system that would have to be carried along.
As others have said, corrosion is the big problem. Nothing highly electronegative touches any engine in normal use after assembly, AFAIK. Specifically, it's stress corrosion cracking that worries everyone, which is a 3-legged stool. Elevated electrons, electromotive force and an electron transfer medium are required. Well, anything pre-stressed has elevated electrons, so those are all over engines and rockets. As for the other two legs, there are two words: SEA WATER.
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#179
by
Nick L.
on 11 Nov, 2007 19:16
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People are overdramatizing it. This is what happens when you design a vehicle for customers that subsequently disappear. Your costs go up because there are just not enough payloads out there. If they could get customers like Arianespace can and get four or more flights a year then I'll bet the costs go down a LOT.
Also, it costs more because a) there's more raw material cost and b) there are three of them strapped together, aggravating a). If you built an A-V heavy and flew it at D-IVH flight rates it would likely cost about the same and have roughly the same performance.