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#120
by
edkyle99
on 29 Aug, 2010 04:37
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#121
by
marshal
on 30 Aug, 2010 01:17
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#122
by
kevin-rf
on 30 Aug, 2010 13:44
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#123
by
Antares
on 30 Aug, 2010 14:46
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Lower thrust at the same Isp would entail some minor additional gravity losses, no?
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#124
by
PDJennings
on 30 Aug, 2010 15:43
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Does the reaction engine assembly (REA) tap the same tanks (I assume Hydrazine) as the failed liquid apogee engine system (LAE)? Meaning it will take longer to get to it's final orbit, but will not shorten it's on orbit lifetime?
Lifetime will be shortened because the on board oxidizer cannot be used except for the LAE. If the LAE is completely non-functional, that oxidizer is dead weight.
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#125
by
Space Pete
on 30 Aug, 2010 19:40
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#126
by
butters
on 31 Aug, 2010 02:30
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They're saying that lifetime will not be cut short, but I don't see how that could be, unless they're depending on built-in margins or reducing any planned on-orbit maneuvering capabilities.
Even if the hydrazine storage is shared between the two chemical propulsion systems (best-case scenario), the monopropellant system must have a significantly lower Isp than the bipropellant system.
It will take more time to reach operational status and expend more fuel in doing so. Therefore the useful lifetime must be reduced unless I'm missing something.
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#127
by
Space Pete
on 31 Aug, 2010 20:37
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#128
by
kevin-rf
on 01 Sep, 2010 13:56
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Correct me if I am wrong, but this means more dips than planned through the Van Allen. That means the solar cells will have degraded more than planned... Impacting end of life power availability?
Also, spaceflightnow.com had an article with some very good direct quotes monday.
http://spaceflightnow.com/atlas/av019/100830orbit.htmlMadden says AEHF 1 could reach the desired geosynchronous orbit sometime next summer, 7 to 9 months later than scheduled. But the satellite should have enough residual propellant to operate for its full 14-year mission life.
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#129
by
edkyle99
on 01 Sep, 2010 15:25
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They're saying that lifetime will not be cut short, but I don't see how that could be, unless they're depending on built-in margins or reducing any planned on-orbit maneuvering capabilities.
Even if the hydrazine storage is shared between the two chemical propulsion systems (best-case scenario), the monopropellant system must have a significantly lower Isp than the bipropellant system.
This would be offset to a large degree, I suspect, by use of the Aerojet BPT-4000 Hall Effect Thrusters to provide what looks to be a majority of the Delta-V. BPT-4000 has an ISP greater than 1,900 seconds according to some references.
I agree, however, that this maneuvering seems likely to reduce spacecraft life. It may make it to the "advertised" 14 years, but may not make the hoped for years beyond that minimum spec.
I wonder if they'll be able to dump the now-useless oxidizer before performing the maneuvers. That would be a big help.
Here, BTW, is an interesting script of a press conference statement related to the AEHF problems.
http://www.fiercegovernmentit.com/pages/dave-madden-media-roundtable-opening-statement - Ed Kyle
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#130
by
kevin-rf
on 01 Sep, 2010 17:31
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Thanks Ed
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#131
by
Targeteer
on 02 Sep, 2010 01:28
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Not that I want to defend my Air Force space brethren too much after their slew of program management/oversight disasters, but since the satellite is "based" on the A2100, is the propulsion system (i.e. the failed motor) standard and not a failure of some new, AF-specific modification?
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#132
by
tonngo0
on 02 Sep, 2010 03:36
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Anyone on here has a high resolution picture of the AEHF 1 launch please post.
Thanks
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#133
by
WHAP
on 02 Sep, 2010 21:47
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#134
by
jcm
on 04 Sep, 2010 00:14
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What is the LAE that failed? A lot of A2100 model satellites used AMPAC's Leros 1 LAE, but AMPAC informs me that this one is NOT a Leros 1 (sorry for the text on my site earlier that guessed that it was...)
It doesn't look to be an Aerojet R-4D either, based on the Aerojet press release that touted all their bits on the mission but didn't mention the LAE.
The thrust is quoted as 100 lb (440 N) which seems to rule out the 400N Astrium thruster (unlikely on political grounds anyway).
I don't think Pratt & Whitney Rocketdyne are back in the LAE business?
A possibility is the Northrop Grumman TR-308 engine used for Chandra, or even the engine developed by NRL for MITEX. In any case, it looks like the thruster used is not one of the ones with extensive flight history, unless (quite possible) I'm missing some obvious candidate.
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#135
by
Jim
on 04 Sep, 2010 02:02
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I heard that it might have been a Japanese thruster.
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#136
by
jcm
on 04 Sep, 2010 03:36
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I heard that it might have been a Japanese thruster.
Interesting. That would probably be the IHI 500N thruster used by Orbital on its Star-2 series. That's 112 lb thrust rather than 100lb but I guess that's within the reporting accuracy.
It's flown successfully on 17 Orbital Star 2 satellites.
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#137
by
sdsds
on 04 Sep, 2010 05:29
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I heard that it might have been a Japanese thruster.
Interesting. That would probably be the IHI 500N thruster used by Orbital on its Star-2 series. That's 112 lb thrust rather than 100lb but I guess that's within the reporting accuracy.
It's flown successfully on 17 Orbital Star 2 satellites.
Any of those on Atlas? Is there any chance the launch environment brought out a failure mode not seen on other vehicles?
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#138
by
jcm
on 04 Sep, 2010 14:23
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I heard that it might have been a Japanese thruster.
Interesting. That would probably be the IHI 500N thruster used by Orbital on its Star-2 series. That's 112 lb thrust rather than 100lb but I guess that's within the reporting accuracy.
It's flown successfully on 17 Orbital Star 2 satellites.
Any of those on Atlas? Is there any chance the launch environment brought out a failure mode not seen on other vehicles?
I believe this would be the first Atlas flight with one. Previous flights used Proton, Zenit-3SL, Ariane 5, Soyuz-Fregat.
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#139
by
edkyle99
on 04 Sep, 2010 21:18
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I heard that it might have been a Japanese thruster.
Interesting. That would probably be the IHI 500N thruster used by Orbital on its Star-2 series. That's 112 lb thrust rather than 100lb but I guess that's within the reporting accuracy.
It's flown successfully on 17 Orbital Star 2 satellites.
This, or something like it, might be used by Cygnus as well.
Question. Will IHI, if it is IHI, have to pay any penalties for this loss? (Assuming that it was actually a thruster failure, and not a software or other propulsion system failure.) If the back up plans don't work, the bill would work out to about $2.2 billion.
- Ed Kyle
