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#520
by
robert_d
on 07 Feb, 2012 00:09
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1) Would a notional Delta 4 heavy with a SSME or RS_25e core engine instead of the actual RS-68 increase or reduce payload? Assume the two outboard boosters would still be RS-68 powered. Seems the trade would be higher ISP and slightly lower weight (lighter engine but added apu's) vs the gravity loss of the longer burn time. Any other considerations?
I modeled this, in a crude way, and found that payload to LEO would likely decrease by about 1 tonne, give or take (about a 3.5-4% performance reduction) and by about 0.5 tonnes to GTO (about 5% reduction). About 88 tonnes of propellant would have to be offloaded from the boosters (combined total) to maintain the 1.2 liftoff T/W ratio. That's about 21.5% of the propellant capacity for each booster. The core's better specific impulse would make up much, but not all, of the difference.
- Ed Kyle
Thanks Ed,
To a not-so-knowledgable person, this seems to indicate that the delta 4 heavy is inefficient, in that an imaginary smaller booster with a core powered by an rs-25e would have a similar payload.
Would it be possible to model a two barrel core powered by two rs-25e and tne boosters powered by 2 rs-68's each?
My thought here is that if SLS ia cancelled, we might want a somewhat larger booster that can loft Orion and a significant payload in one launch. And if it isn't already obvious, I wish to preserve a role for the descendants of the SSME.
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#521
by
kevin-rf
on 07 Feb, 2012 00:39
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You do realize that the RS-68 was designed from the ground up with lessons learned in developing the SSME, and is a rightful descendant. One of the main drivers in designing the RS-68 was reducing the manufacturing costs (compared to the SSME). The lower ISP and ablative nozzle are a direct result of that.
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#522
by
edkyle99
on 07 Feb, 2012 01:45
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Thanks Ed,
To a not-so-knowledgable person, this seems to indicate that the delta 4 heavy is inefficient, in that an imaginary smaller booster with a core powered by an rs-25e would have a similar payload.
The idea with Delta IV was to design for minimum cost, using lower-cost gas generator RS-68 engines rather than higher-cost staged combustion engines like RS-25. In addition, RS-68 was designed to be an expendable booster engine while RS-25 was designed to work largely as a reusable, high-altitude sustainer engine for Shuttle.
I don't know what these engines really cost now, but a few years ago we talked about projected RS-68 costs at $20 million versus $70 million for SSME and perhaps $25 million for RS-25. Whatever the truth, and I think it is safe to say that it is not among these numbers, it is clear that RS-25 will cost more than RS-68 despite providing only about 60% as much thrust.
Would it be possible to model a two barrel core powered by two rs-25e and tne boosters powered by 2 rs-68's each?
My thought here is that if SLS ia cancelled, we might want a somewhat larger booster that can loft Orion and a significant payload in one launch. And if it isn't already obvious, I wish to preserve a role for the descendants of the SSME.
You really would only need one more RS-25 on the core, and no additional RS-68 engines, to get full tanks and maximum results. I'll model that in a bit.
But, of course, there are ways to significantly improve Delta IV performance without tossing out its basic propulsion system.
- Ed Kyle
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#523
by
Robotbeat
on 07 Feb, 2012 14:08
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You do realize that the RS-68 was designed from the ground up with lessons learned in developing the SSME, and is a rightful descendant. One of the main drivers in designing the RS-68 was reducing the manufacturing costs (compared to the SSME). The lower ISP and ablative nozzle are a direct result of that.
Precisely.
I find the idea that RS-25 will be roughly the cost of RS-68 laughable.
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#524
by
Antares
on 07 Feb, 2012 16:01
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The old cost numbers don't compare to today's because the SSME contract was supporting a lot of Rocketdyne fixed costs at its facilities, support functions and management. Now the other PWR engines carry those cost burdens.
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#525
by
Robotbeat
on 07 Feb, 2012 16:19
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The old cost numbers don't compare to today's because the SSME contract was supporting a lot of Rocketdyne fixed costs at its facilities, support functions and management. Now the other PWR engines carry those cost burdens.
Well in the case where $30 million is tacked on to any engine to support fixed costs, then yeah, it masks the price differences.
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#526
by
Prober
on 05 Apr, 2012 20:48
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Could the Delta IV be used as a launcher from VAFB to resupply the ISS?
Was thinking of the Orbit the ATV used, with that in mind would it be possible?
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#527
by
Antares
on 05 Apr, 2012 21:03
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It would have to fly a dogleg to get posigrade. It would be a huge performance hit.
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#528
by
Jim
on 05 Apr, 2012 21:40
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Could the Delta IV be used as a launcher from VAFB to resuply the ISS?
Was thinking of the Orbit the ATV used, with that in mind would it be possible?
The orbit ATV used has no bearing on whether spacecraft can launched to the ISS from VAFB
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#529
by
Jim
on 06 Apr, 2012 00:23
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It would have to fly a dogleg to get posigrade. It would be a huge performance hit.
A Delta II took Jason to 66 degrees after deploying TIMED at 74.
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#530
by
kevin-rf
on 06 Apr, 2012 00:49
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Gary Hudson, mentioned in one of the threads that Titan II from Vandenberg to ISS would take a 20% performance hit when he looked at it. Not the Delta IV, and performance will vary.
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#531
by
Prober
on 06 Apr, 2012 02:16
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Could the Delta IV be used as a launcher from VAFB to resuply the ISS?
Was thinking of the Orbit the ATV used, with that in mind would it be possible?
The orbit ATV used has no bearing on whether spacecraft can launched to the ISS from VAFB
Let’s ask this a different way, discount weather etc.
We have two choices using the same launcher the Delta IV.
1) Launch from Alaska
2) Launch from VAFB
Given the same launcher, which site would give max payload (for ISS) per same fuel load etc.
Why?
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#532
by
alexw
on 06 Apr, 2012 06:28
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Could the Delta IV be used as a launcher from VAFB to resuply the ISS?
Was thinking of the Orbit the ATV used, with that in mind would it be possible?
The orbit ATV used has no bearing on whether spacecraft can launched to the ISS from VAFB
Let’s ask this a different way, discount weather etc.
We have two choices using the same launcher the Delta IV.
1) Launch from Alaska
2) Launch from VAFB
Given the same launcher, which site would give max payload (for ISS) per same fuel load etc.
Why?
Question is moot. Can't launch Delta IV from Alaska, because the liquid hydrogen would freeze.
-Alex
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#533
by
kevin-rf
on 06 Apr, 2012 15:23
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Question is moot. Can't launch Delta IV from Alaska, because the liquid hydrogen would freeze.
-Alex
Say what? Oh, I see it's April first...
Another thing is the min. possible launch inclination for Kodiak (ignoring any overflight issues) is 57 degrees, ISS is at 51.6 degrees.
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#534
by
MP99
on 06 Apr, 2012 18:10
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Could the Delta IV be used as a launcher from VAFB to resuply the ISS?
Was thinking of the Orbit the ATV used, with that in mind would it be possible?
The orbit ATV used has no bearing on whether spacecraft can launched to the ISS from VAFB
Let’s ask this a different way, discount weather etc.
We have two choices using the same launcher the Delta IV.
1) Launch from Alaska
2) Launch from VAFB
Given the same launcher, which site would give max payload (for ISS) per same fuel load etc.
Why?
CCAFS (or KSC), presumably.
cheers, Martin
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#535
by
JayP
on 07 Apr, 2012 01:23
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Could the Delta IV be used as a launcher from VAFB to resuply the ISS?
Was thinking of the Orbit the ATV used, with that in mind would it be possible?
The orbit ATV used has no bearing on whether spacecraft can launched to the ISS from VAFB
Let’s ask this a different way, discount weather etc.
We have two choices using the same launcher the Delta IV.
1) Launch from Alaska
2) Launch from VAFB
Given the same launcher, which site would give max payload (for ISS) per same fuel load etc.
Why?
Depends on where in Alaska your launch site is and what you are launching on top of it. If you are launching from somewhere in the aluetians where you can head east without overflying land and can carry an upper stage wiith enough fuel to do the required plane change in orbit, then you could launch a lot more from there than from VAFB.
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#536
by
Prober
on 07 Apr, 2012 20:24
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Could the Delta IV be used as a launcher from VAFB to resuply the ISS?
Was thinking of the Orbit the ATV used, with that in mind would it be possible?
The orbit ATV used has no bearing on whether spacecraft can launched to the ISS from VAFB
Let’s ask this a different way, discount weather etc.
We have two choices using the same launcher the Delta IV.
1) Launch from Alaska
2) Launch from VAFB
Given the same launcher, which site would give max payload (for ISS) per same fuel load etc.
Why?
Depends on where in Alaska your launch site is and what you are launching on top of it. If you are launching from somewhere in the aluetians where you can head east without overflying land and can carry an upper stage wiith enough fuel to do the required plane change in orbit, then you could launch a lot more from there than from VAFB.
Only thought atm of posting of Kodiak. The question however was a general location question, so thx for you info.
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#537
by
DragonRoco
on 10 Jun, 2012 01:13
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How does the delta iv get erected and put in the launch pad as all of the photos I see is when it is less than 50° from the ground?
EDIT- after rereading it some times I mean how does the erector lift the rocket above the posts that stick up. From the photos I have found the posts must go down?
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#538
by
Jim
on 10 Jun, 2012 02:20
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How does the delta iv get erected and put in the launch pad as all of the photos I see is when it is less than 50° from the ground?
EDIT- after rereading it some times I mean how does the erector lift the rocket above the posts that stick up. From the photos I have found the posts must go down?
What are the "posts"?
The rocket is already part way up the erector. The pivot point is several feet below the engine nozzles.
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#539
by
DragonRoco
on 11 Jun, 2012 01:17
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How does the delta iv get erected and put in the launch pad as all of the photos I see is when it is less than 50° from the ground?
EDIT- after rereading it some times I mean how does the erector lift the rocket above the posts that stick up. From the photos I have found the posts must go down?
What are the "posts"?
The rocket is already part way up the erector. The pivot point is several feet below the engine nozzles.
http://www.patrick.af.mil/shared/media/photodb/photos/111011-F-vs513-0025.jpgComputer is not working with me so I will post a link
The posts are the grey things in the bottom right corner.
Also how do they drop the rocket down as in the bottom left of this next photo there seems to be some support does that get taken away or cut off?
http://www.kcet.org/updaily/socal_focus/delta-iv-launch.jpgSorry for so many edits I am still waking up ( I am in Australia)