Author Topic: Delta IV Q&A  (Read 243293 times)

Offline tnphysics

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Delta IV Q&A
« on: 08/13/2007 11:08 pm »
What is the actual delta-V split and payload for the Delta IV Heavy? Using astronautix.com numbers, the total delta-V exceeds 10.5 km/s.Also, what would be the payload for a LV consisting of a single CBC and a J-2/J-2X upper stage? I felt that we needed a Q&A thread for the Delta IV.
« Last Edit: 07/11/2008 12:34 am by tnphysics »

Offline meiza

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Re: Delta IV Q&A
« Reply #1 on: 08/13/2007 11:34 pm »
What are the injectors upgrades done for Ares V looking like from Delta IV:s point of view?

Offline Jim

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Re: Delta IV Q&A
« Reply #2 on: 08/13/2007 11:42 pm »
Quote
tnphysics - 13/8/2007  7:08 PM
Also, what would be the payload for a LV consisting of a single CBC and a J-2/J-2X upper stage?

Since no one is working such a vehicle, there is not a good answer

Offline Jim

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Re: Delta IV Q&A
« Reply #3 on: 08/13/2007 11:43 pm »
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meiza - 13/8/2007  7:34 PM

What are the injectors upgrades done for Ares V looking like from Delta IV:s point of view?

The RS-68 upgrades were done for D-IV

Offline meiza

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Re: Delta IV Q&A
« Reply #4 on: 08/13/2007 11:46 pm »
and lemme guess that the performance numbers are ITAR? :)

Offline tnphysics

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Re: Delta IV Q&A
« Reply #5 on: 08/14/2007 12:37 am »
I'm American, PM me if it's an ITAR problem. Both EELV upper stages are too small. The Delta IV's US should be the size of the S-IVB.

Offline Jim

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Re: Delta IV Q&A
« Reply #6 on: 08/14/2007 12:40 am »
it is also propriety

Offline tnphysics

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Re: Delta IV Q&A
« Reply #7 on: 08/14/2007 10:50 am »
All I need to account for is a 1 km/s overperformance when delivering a 25.8 mt payload.

Offline Jim

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Re: Delta IV Q&A
« Reply #8 on: 08/14/2007 11:11 am »
Quote
tnphysics - 13/8/2007  8:37 PM

. Both EELV upper stages are too small. The Delta IV's US should be the size of the S-IVB.

Not for GTO and GSO missions, that's what they were designed for

Offline pippin

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Re: Delta IV Q&A
« Reply #9 on: 08/14/2007 11:50 am »
What's the difference between the RL 10 B 2 engines D IV is using and the ones used on Atlas?

Offline Jim

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Re: Delta IV Q&A
« Reply #10 on: 08/14/2007 11:59 am »
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pippin - 14/8/2007  7:50 AM

What's the difference between the RL 10 B 2 engines D IV is using and the ones used on Atlas?

Extendable nozzle, thrust level, etc.  Many differences

Offline Propforce

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Re: Delta IV Q&A
« Reply #11 on: 08/14/2007 07:04 pm »
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tnphysics - 13/8/2007  4:08 PM

What is the actual delta-V split and payload for the Delta IV Heavy? Using astronautix.com numbers, the total delta-V exceeds 10.5 km/s.Also, what would be the payload for a LV consisting of a single CBC and a J-2/J-2X upper stage?I felt that we needed a Q&A thread for the Delta IV.

Since you're asking a hypothetical question (current D-IV uses RL10B-2 and not J-2/J-2X), you can get a comparable number by taking the existing payload, delta-vee, and B-2's engine Isp, then swap out with the J-2/ J-2X Isp to see what additonal payload gain (if any) can be achieved.  You'll need to run this throughtout the trajectory since the CBC will take a hit on delta-vee because of additional payload weight as well.  I would also allow some gravity delta-vee losses on the vehicle.

You'll then need to substract the additional J-2/J-2X engine weight from that additional payload weight gain.  

Now the fun part is, should you find yourself run out of 2nd stage propellant too early, it's time to re-size the 2nd stage tanks to allow to carry more propellant.  But that would be difficult since you only allow a single CBC and soon we'll run into the thrust limitation of the RS-68!  :laugh:

But don't be discouraged.  Atlas V can't do any better as their initial liftoff thrust-to-weight is already dangerously low.  :bleh:

Offline Propforce

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Re: Delta IV Q&A
« Reply #12 on: 08/14/2007 07:09 pm »
Quote
Jim - 13/8/2007  4:43 PM

Quote
meiza - 13/8/2007  7:34 PM

What are the injectors upgrades done for Ares V looking like from Delta IV:s point of view?

The RS-68 upgrades were done for D-IV

You mean for the Air Force and NASA....

Offline Propforce

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Re: Delta IV Q&A
« Reply #13 on: 08/14/2007 07:11 pm »
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pad rat - 14/8/2007  6:43 AM

"I'm American, PM me if it's an ITAR problem."

How does one prove that assertion on the internet?

Same as "I'm an Iranian student doing a project on ground-to-air missile...."


Offline edkyle99

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Re: Delta IV Q&A
« Reply #14 on: 08/14/2007 07:17 pm »
Quote
tnphysics - 14/8/2007  5:50 AM

All I need to account for is a 1 km/s overperformance when delivering a 25.8 mt payload.

I came up with only about half that much "overperformance" for such a payload, assuming full propellant loading and an extra tonne of "payload" used for adapter hardware, etc. - but still hundreds of meters/second delta-v margin on paper for a big LEO payload.    Calculating Delta IV Heavy is tricky due to all of the throttling up and down during the CBC burns.

I can think of several explanations for the extra delta-v.  One could be that published payload capabilities reflect structural limitations rather than propulsion limits.  There's a lot of discussion in the Planners Guides about payload adapter/payload center of gravity/vibration limits and the like.

Another possibility is that Delta IV dry masses are higher than generally believed.  I think that this is probably true, but I doubt that it accounts for all of the difference.  The strap-on CBCs are heavier than the core CBC, for example, when the nose cones and interstages are included.  

A third explanation is related to the low upper stage thrust - it only produces a 0.19 to 0.36 thrust to weight ratio for this payload mass if full propellant loading is assumed, which means quite a bit of gravity loss to counter during a LEO ascent.  The Delta IV Planners Guide showed a total upper stage burn time of only 912 seconds for a LEO mission, which implies that the upper stage would only carry about 22 tonnes of propellant, 5 tonnes less than its maximum load.  That knocks off about 230 m/s delta-v right there.

A final explanation may be that the Delta IV people are sandbagging a bit, downplaying the real capability that might be available.

 - Ed Kyle

Offline TrueBlueWitt

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Re: Delta IV Q&A
« Reply #15 on: 08/14/2007 07:31 pm »
Quote
edkyle99 - 14/8/2007  3:17 PM

Quote
tnphysics - 14/8/2007  5:50 AM

All I need to account for is a 1 km/s overperformance when delivering a 25.8 mt payload.

I came up with only about half that much "overperformance" for such a payload, assuming full propellant loading and an extra tonne of "payload" used for adapter hardware, etc. - but still hundreds of meters/second delta-v margin on paper for a big LEO payload.    Calculating Delta IV Heavy is tricky due to all of the throttling up and down during the CBC burns.
........

A final explanation may be that the Delta IV people are sandbagging a bit, downplaying the real capability that might be available.

 - Ed Kyle

The better to make it look like you can't loft Orion with it??  

You could probably find out how much margin there was in the US by looking at the demonstration flight where the main's shut down early.. see how deltaV they manage to make up with the US. Wouldn't tell you anything about margin for the core though.

Offline edkyle99

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Re: Delta IV Q&A
« Reply #16 on: 08/14/2007 07:39 pm »
Quote
TrueBlueWitt - 14/8/2007  2:31 PM

Quote
edkyle99 - 14/8/2007  3:17 PM

Quote
tnphysics - 14/8/2007  5:50 AM

All I need to account for is a 1 km/s overperformance when delivering a 25.8 mt payload.

I came up with only about half that much "overperformance" for such a payload, assuming full propellant loading and an extra tonne of "payload" used for adapter hardware, etc. - but still hundreds of meters/second delta-v margin on paper for a big LEO payload.    Calculating Delta IV Heavy is tricky due to all of the throttling up and down during the CBC burns.
........

A final explanation may be that the Delta IV people are sandbagging a bit, downplaying the real capability that might be available.

 - Ed Kyle

The better to make it look like you can't loft Orion with it??  

Nah.  The numbers were in the original Delta IV Planners Guide published in 2000 or so, years before CEV/Orion.

Quote

You could probably find out how much margin there was in the US by looking at the demonstration flight where the main's shut down early.. see how deltaV they manage to make up with the US. Wouldn't tell you anything about margin for the core though.

Yes.  And terrific - there goes my evening!

 - Ed Kyle

Offline Propforce

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Re: Delta IV Q&A
« Reply #17 on: 08/14/2007 07:48 pm »
Quote
edkyle99 - 14/8/2007  12:17 PM

Quote
tnphysics - 14/8/2007  5:50 AM

All I need to account for is a 1 km/s overperformance when delivering a 25.8 mt payload.

I came up with only about half that much "overperformance" for such a payload, assuming full propellant loading and an extra tonne of "payload" used for adapter hardware, etc. - but still hundreds of meters/second delta-v margin on paper for a big LEO payload.    Calculating Delta IV Heavy is tricky due to all of the throttling up and down during the CBC burns.

I can think of several explanations for the extra delta-v.  One could be that published payload capabilities reflect structural limitations rather than propulsion limits.  There's a lot of discussion in the Planners Guides about payload adapter/payload center of gravity/vibration limits and the like.
 - Ed Kyle

What delta-vee were you guys assuming?  What orbit are you trying to get to?

Have you consider possible additional payload FAIRING weight due to a much larger payload?  What size payload (L X D X H)  would constitute a 25.8 mt payload?

Offline edkyle99

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Re: Delta IV Q&A
« Reply #18 on: 08/14/2007 08:17 pm »
Quote
Propforce - 14/8/2007  2:48 PM

Quote
edkyle99 - 14/8/2007  12:17 PM

Quote
tnphysics - 14/8/2007  5:50 AM

All I need to account for is a 1 km/s overperformance when delivering a 25.8 mt payload.

I came up with only about half that much "overperformance" for such a payload, assuming full propellant loading and an extra tonne of "payload" used for adapter hardware, etc. - but still hundreds of meters/second delta-v margin on paper for a big LEO payload.    Calculating Delta IV Heavy is tricky due to all of the throttling up and down during the CBC burns.

I can think of several explanations for the extra delta-v.  One could be that published payload capabilities reflect structural limitations rather than propulsion limits.  There's a lot of discussion in the Planners Guides about payload adapter/payload center of gravity/vibration limits and the like.
 - Ed Kyle

What delta-vee were you guys assuming?  What orbit are you trying to get to?

Have you consider possible additional payload FAIRING weight due to a much larger payload?  What size payload (L X D X H)  would constitute a 25.8 mt payload?

I'm assuming a 5.1 x nearly 23 meter fairing that weighs close to 5 tonnes.  I'm also assuming payload adapter hardware that adds an extra three-quarters of a tonne.  I'm guessing that something in the neighborhood of 9,500 meters/second ideal delta-v would be budgeted for a LEO ascent, which provides a bit of padding for unknowns like gravity losses and covers a variety of inclination assumptions.  I'm remembering my propellant residuals (something like 1%).  I'm guessing a bit when it comes to the CBC throttling and burns, and trying to be conservative with the specific impulse numbers during the first four minutes of flight.  As I mentioned before, I've also gone ahead and offloaded five tonnes of upper stage propellant.

With all of that, I'm still coming up with no less than 9,800 meters/second ideal delta-v, roughly.

 - Ed Kyle

Offline yinzer

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Re: Delta IV Q&A
« Reply #19 on: 08/14/2007 08:34 pm »
The Delta IV upper stage has a very low T/W (0.2) for large LEO missions.  Gravity losses will be much higher than "normal".
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