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#220
by
TrueGrit
on 14 Nov, 2007 17:46
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Thrust and Isp are no the same thing... Thrust is a function of the the chamber pressure setting and chamber/nozzle geometry. Isp is the function of the flowrate required to acheive said chamber pressure. They are both required to determine the performance of an engine. You then need mixture ratio to determine how best size the launch vehicle tanks to the optimal system desing point.
RS-68 actually exceeds the thrust originally proposed, running now at 102% or 663klb sea level thrust. It also has a lower throttled thrust, 57% vs. 60%, for optimal Heavy vehicle performance. Of course these changes and some vehicle structure changes were made to mitigate the engine not acheive the desired Isp. Anyone with a historical perspective will recognize that meeting Isp is the biggest risk to any new engine development, and RS-68 lived up to past expectations. And finally the fundamental design causes of the lower Isp have been investigated since and have resulted in the RS-68A/B developments.
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#221
by
meiza
on 14 Nov, 2007 21:05
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Thanks for the clarification.
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#222
by
Antares
on 15 Nov, 2007 18:59
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I just checked out the new payload planners guide and went over to the Delta Product Sheet.
WOULD SOMEONE AT ULA FIX THE INSULTING GRAPHIC ON THE FRONT NOW THAT YOU'RE ONE BIG HAPPY FAMILY? It gets the Razzie award for most egregious use of PhotoShop in the launch industry. It shows a Delta IV lifting off from Complex 41, not Complex 37. The view would be from the top of the VIF. Plus, the building in the background IS the VIF, not the LC-37 MST. I can't really tell if those are the LC-37 lightning towers, but I'll give the PR department the benefit of the doubt that they didn't use photoshopped versions of the Atlas V MLP Mast.
Sheesh. How insulting to the other half of your company, not to mention your customers.
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#223
by
Nick L.
on 15 Nov, 2007 19:42
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Antares - 15/11/2007 2:59 PM
I just checked out the new payload planners guide and went over to the Delta Product Sheet.
WOULD SOMEONE AT ULA FIX THE INSULTING GRAPHIC ON THE FRONT NOW THAT YOU'RE ONE BIG HAPPY FAMILY? It gets the Razzie award for most egregious use of PhotoShop in the launch industry. It shows a Delta IV lifting off from Complex 41, not Complex 37. The view would be from the top of the VIF. Plus, the building in the background IS the VIF, not the LC-37 MST. I can't really tell if those are the LC-37 lightning towers, but I'll give the PR department the benefit of the doubt that they didn't use photoshopped versions of the Atlas V MLP Mast.
Sheesh. How insulting to the other half of your company, not to mention your customers.
Maybe that's part of the ULA merger. Perhaps they plan to consolidate launch sites soon?
I never noticed that until you pointed it out. It seemed a little weird though...
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#224
by
Antares
on 15 Nov, 2007 21:16
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pad rat - 15/11/2007 3:17 PM
That is the MST, not the VIF (the cruciform panels are an obvious giveaway), and the lightning towers are the SLC-37 towers.
OK. Well, it's still the
back of the MST, which in some ways is even weirder.
Edit: I don't live in Mims, I never see that side.
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#225
by
tnphysics
on 26 Nov, 2007 20:21
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Is it planned to add SRBs to the DIVH (either a mostly-current version or the upgraded version that will fly in 2011)?
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#226
by
Jim
on 26 Nov, 2007 20:30
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tnphysics - 26/11/2007 4:21 PM
Is it planned to add SRBs to the DIVH (either a mostly-current version or the upgraded version that will fly in 2011)?
nope
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#227
by
Skyrocket
on 26 Nov, 2007 20:55
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tnphysics - 26/11/2007 10:21 PM
Is it planned to add SRBs to the DIVH (either a mostly-current version or the upgraded version that will fly in 2011)?
A version with six solid strap ons ist under study, but there are no plans.
This Version would look a little bit strange, as each two solids would be mounted on each of the CBCs - all six on the same side as the other is occupied on the pad by the pad structures. But even this modification would require pad and and non-trivial-vehicle modifications.
See page 265 on
http://www.ulalaunch.com/docs/product_sheet/Delta_IV_Payload_Planners_Guide_2007.pdf
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#228
by
EE Scott
on 28 Nov, 2007 00:50
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Skyrocket - 26/11/2007 4:55 PM
tnphysics - 26/11/2007 10:21 PM
Is it planned to add SRBs to the DIVH (either a mostly-current version or the upgraded version that will fly in 2011)?
A version with six solid strap ons ist under study, but there are no plans.
This Version would look a little bit strange, as each two solids would be mounted on each of the CBCs - all six on the same side as the other is occupied on the pad by the pad structures. But even this modification would require pad and and non-trivial-vehicle modifications.
See page 265 on http://www.ulalaunch.com/docs/product_sheet/Delta_IV_Payload_Planners_Guide_2007.pdf
I would have thought that solids would be the perfect solution if one needs to bump up DIVH payload capacity (for non manrated duty). Obviously someone has done the analysis of the costs/other trade-offs of developing higher performance versions of the RS-68 vs solids/pad alterations, since uprating the RS-68 is going on right now I read. Does there exist any data on costs of these two options?
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#229
by
Jim
on 28 Nov, 2007 00:57
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2 pads would have to be modified. Also uprating the RS-68 is applicable to all the other versions
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#230
by
EE Scott
on 28 Nov, 2007 02:25
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Jim - 27/11/2007 8:57 PM
2 pads would have to be modified. Also uprating the RS-68 is applicable to all the other versions
I will go digging around to see if I can find a figure for development costs of the RS-68B or whatever they are calling it. I forgot about the Vandenberg pad - that obviously makes a difference. Plus additional processing costs would be significant. And now that you make the point about the applicability of the uprated engine to other versions, I could see how perhaps some D4 medium launches might be able to delete a solid compared to the baseline engine, if they were borderline.
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#231
by
Jim
on 28 Nov, 2007 11:23
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D-IV adds SRM's in pairs
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#232
by
Nick L.
on 09 Dec, 2007 04:45
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What are the changed parts that make up the RS-68 upgrade? (injectors, nozzle, etc.) I searched but couldn't find anything. Also, is the upgraded RS-68 a "bolt-on" upgrade for Delta IV, i.e. there aren't significant changes to the vehicle itself?
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#233
by
Jim
on 09 Dec, 2007 11:36
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Nick L. - 9/12/2007 12:45 AM
What are the changed parts that make up the RS-68 upgrade? (injectors, nozzle, etc.) I searched but couldn't find anything. Also, is the upgraded RS-68 a "bolt-on" upgrade for Delta IV, i.e. there aren't significant changes to the vehicle itself?
It wouldn't be on the web. It is ITAR info
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#234
by
Nick L.
on 11 Dec, 2007 22:12
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What do some of the calls in the final countdown mean? Some of them are self explanatory like "hydraulic press at 4000" and "NMEQ report swing arm system ready" but others are more cryptic.
T-120 seconds, "DPA script running"
T-40 seconds, "GE main panel off"
Roughly T-25 seconds, "flight lock in (?)"
Roughly T-10 seconds, "**** deactivated" (can't tell what's been deactivated though because the countdown goes over it)
I've always been curious as to what these phrases mean. If they are proprietary then sorry, but just wondering.
Nick
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#235
by
Antares
on 21 Dec, 2007 05:35
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Jim - 9/12/2007 6:36 AM
Nick L. - 9/12/2007 12:45 AM
What are the changed parts that make up the RS-68 upgrade? (injectors, nozzle, etc.) I searched but couldn't find anything. Also, is the upgraded RS-68 a "bolt-on" upgrade for Delta IV, i.e. there aren't significant changes to the vehicle itself?
It wouldn't be on the web. It is ITAR info
There are AIAA papers on this.
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#236
by
Propforce
on 28 Dec, 2007 04:17
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Antares - 20/12/2007 10:35 PM
Jim - 9/12/2007 6:36 AM
Nick L. - 9/12/2007 12:45 AM
What are the changed parts that make up the RS-68 upgrade? (injectors, nozzle, etc.) I searched but couldn't find anything. Also, is the upgraded RS-68 a "bolt-on" upgrade for Delta IV, i.e. there aren't significant changes to the vehicle itself?
It wouldn't be on the web. It is ITAR info
There are AIAA papers on this.
Ha ha ha... :laugh: :laugh: :laugh: classic !! just classic !! :laugh: :laugh: :laugh:
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#237
by
edkyle99
on 28 Dec, 2007 16:44
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Antares - 21/12/2007 12:35 AM
Jim - 9/12/2007 6:36 AM
Nick L. - 9/12/2007 12:45 AM
What are the changed parts that make up the RS-68 upgrade? (injectors, nozzle, etc.) I searched but couldn't find anything. Also, is the upgraded RS-68 a "bolt-on" upgrade for Delta IV, i.e. there aren't significant changes to the vehicle itself?
It wouldn't be on the web. It is ITAR info
There are AIAA papers on this.
I couldn't find any at AIAA.org. Do you have any paper numbers?
This site,
http://www.spaceref.com/news/viewsr.html?pid=23819mentions that work is underway on RS-68A and RS-68B designs, and that subscale injector testing of a variety of alternative injector designs, performed at MSFC, "benefits the RS-68A and RS-68B engines, as well as the J-2X engine".
My guess is slightly higher thrust and improved ISP provided by slightly revved up turbopumps and/or modified injectors.
- Ed Kyle
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#238
by
TrueGrit
on 28 Dec, 2007 19:45
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120 seconds is when the flight HTPA (Hydraulic Turbine/Pump Assembly) is spun up. Next has to with locking-out specific commands just prior to launch to assure that the system configuration can not change due to an inadvertant command. Flight lock-in is a command used to set the flight computer in ready-to-fly mode. The last one is simply deactivation of parameter alarms as all control is handed-off to the launch computer in the last few seconds.
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#239
by
Propforce
on 28 Dec, 2007 20:57
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edkyle99 - 28/12/2007 9:44 AM
Antares - 21/12/2007 12:35 AM
Jim - 9/12/2007 6:36 AM
Nick L. - 9/12/2007 12:45 AM
What are the changed parts that make up the RS-68 upgrade? (injectors, nozzle, etc.) I searched but couldn't find anything. Also, is the upgraded RS-68 a "bolt-on" upgrade for Delta IV, i.e. there aren't significant changes to the vehicle itself?
It wouldn't be on the web. It is ITAR info
There are AIAA papers on this.
I couldn't find any at AIAA.org. Do you have any paper numbers?
This site,
http://www.spaceref.com/news/viewsr.html?pid=23819
mentions that work is underway on RS-68A and RS-68B designs, and that subscale injector testing of a variety of alternative injector designs, performed at MSFC, "benefits the RS-68A and RS-68B engines, as well as the J-2X engine".
My guess is slightly higher thrust and improved ISP provided by slightly revved up turbopumps and/or modified injectors.
- Ed Kyle
The paper number is AIAA-2007-5833
I'll just make it easy for you to download :laugh:
From the paper
Planned modifications to the current RS-68 are:
1. Increased power level of roughly 6 percent.
2. Main injector changes to improve Isp roughly 2 percent.
3. New bearing material to decrease stress corrosion susceptibility.
4. Redesigned turbopump pump inlets to incorporate tip vortex suppression.
5. Redesigned fuel turbopump second stage blisk to increase robustness.
6. Redesigned gas generator igniter that eliminates potential foreign object debris.
7. Higher reliability oxidizer turbopump bearing chill sensor.
8. Higher reliability hot gas sensor.
9. Redesigned oxidizer turbopump to reduce pre-start and operational helium usage.
10. Modified engine start sequence/configuration to reduce free hydrogen on the pad during engine start.
11. Redesigned ablative nozzle to accommodate the longer-duration Ares V mission profile.
