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Rubr_Duky

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I'm learning new CAD software, and in the process am putting to use the experience to develop a model that I started on a long time ago. Maybe after finishing this design, I will have a job that will provide the extra funds needed to build it.

Anyway.

A Delta II is available in several configurations:

The one I am trying to model is a 7952H for the Mer-B launch. 7925 and 7925-H are exactly the same, with the exception of the larger, and longer GEM 46 (9) boosters instead of the standard GEM 40 boosters. The GEM 46s are also longer than the 40" boosters by 1.7 meters (about 48"). The H version is only available with 9 boosters.

Delta II Configuration scheme:
7 - indicates the use of the RS-27A engine, and GEMs from ATK
9 - indicates the number of boosters (3, 4 or 9)
2 - Is the Aerojet AJ10-118K 2nd stage engine
5 - is the third stage engine (0 - none, 0H - none, Heavy with GEM 46, 5 - Star-48B Solid Motor, 5H - Star-48B with GEM 46, 6 - Star-37FM solid motor)

and then there's a designation for the fairing used:

-9.5 - 9.5' x 27.8' metal fairing. (The one with ribs on it)
-10 - 10' x 29.1' composite fairing. Smoother, kinda bullet-shaped.
-10L - 10' x 30.4' composite fairing. Similar to the 10, but a little more blunt tip, and a bit longer.

I know all about the configurations.

Here's what I don't understand.

Looking at the photo below, the first stage tanks are divided by that white, ribbed ring around the middle of the rocket body referred to as the 'middle body'. The boosters are attached at the very bottom of the boat-tail section, and also at the top of the straight-section of the booster, just prior to what we would call the nose cone. On both top and bottom, they have ejector springs, that push the booster away from the rocket body. On the bottom, if you look at close-up photos, there are little pads (spherical protrusions, actually) for the springs to rest against that are either mounted to, or an integral part of the bottom plate of the boat tail. Up on the top, in-line with the booster attach points, there are metal plates that are bonded to what appears to be the skin of the rocket body, though it always seems to have a different texture, and a bit more thickness than the rocket body. Each of these pads has two locations for springs to rest against, so there are 9, one between each of the boosters.

If you look at a Delta II without the boosters attached, your eye divides it into more sections than exist, which is natural, but again, referencing the photo below, you have from bottom to top: Boat tail, Oxidizer tank, Center Body section, Fuel tank, and interstage.

What is it that the boosters actually mount to? There isn't any additional structure, or electronics to release them? More to the point, does it not differ between a vehicle destined to become a 7925 (like MER-A) and one that is to be a 7925H (like MER-B)?

I've looked at hundreds if not thousands of photos, and haven't been able to come up with a side-by-side comparison of the naked Delta II rockets without boosters for the two configurations, or at least from similar prospective and showing this detail.

Can anyone offer some help with this?



The MER rovers were both launched with the same configuration - 7925-9.5. Except Spirit (MER-A) was launched with GEM-40's, and Opportunity (MER-B) was launched in the H configuration, with the GEM-46's.

From photographs, I can't tell the difference in the rocket itself (naked, without the boosters) like you'd think you should be able to, considering that both types of boosters, (GEM-40 and GEM-46) both connect to the Delta body in the same place in relation to the Booster (remember, one is about 48" longer than the other) not the Delta body. So, on the upper booster attach point, you would expect to see a difference of about 48". I think this should be noticeable in most photos, given that it's at least half the diameter of the body.

Here is as close as I can get to a side-by-side photo of MER-A and MER-B.


Notice the 'middle-body', the white ring just above the boosters. Now, notice the difference in distance (despite difference in perspective) from the top of the boosters to the bottom of the 'middle body'?

In the vehicle-processing photos that I have, the two Delta bodies are indiscernable from each other (with the exception of the rover logo, which is not always visible) by the location of the upper booster mounts.

With upper booster mounting points 48" apart, it can't be in the same place!

I see no reference to this in ROTW, nor any other source that I have found, so any help would be appreciated.

Thanks,

RD
:D
 

Delta-IV

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I'll talk to my buddies down the street next week, I wasn't here yet when the rovers were launched.
 

mikec

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Notice the 'middle-body', the white ring just above the boosters. Now, notice the difference in distance (despite difference in perspective) from the top of the boosters to the bottom of the 'middle body'?
I worked on MER, but only very peripherally. (I was lucky enough to stick my head into the fairing door on pad 17A during launch prep for MCO on a 7425.) I do know that the 7925H required longer cork insulation panels on the surface of the booster to shield it from heat from the solids, and that keeping these panels from falling off was a bit of a challenge and led to some launch delays IIRC.

I think you may be being misled by the position of the Rocketcam pod, which appears to farther aft (closer to the center body section) on vehicle 299 (MER-B). AFAIK, the only other difference between the two boosters is the location of the forward hardpoint for the solids. But I'm not sure when in the flow these are put on.
 

Rubr_Duky

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I worked on MER, but only very peripherally. (I was lucky enough to stick my head into the fairing door on pad 17A during launch prep for MCO on a 7425.) I do know that the 7925H required longer cork insulation panels on the surface of the booster to shield it from heat from the solids, and that keeping these panels from falling off was a bit of a challenge and led to some launch delays IIRC.

I think you may be being misled by the position of the Rocketcam pod, which appears to farther aft (closer to the center body section) on vehicle 299 (MER-B). AFAIK, the only other difference between the two boosters is the location of the forward hardpoint for the solids. But I'm not sure when in the flow these are put on.
I think you're nailing down what I'm talking about.

That matte-textured section around the forward hard points for the boosters... that's cork? How is the forward hard point for the boosters attached? What is it attached to?

It would make sense if these were simply surface-mounted on the oxidizer section of the rocket body, maybe there's some structure inside sufficient to distribute the load, I'd just think that there's more to it than a surface-mount capture device, though it is very possible that the booster's ejection (now that I think about it) control is mounted in or routed through the boat tail, to the booster, up the wire trough that's on the booster, and then plugged into this surface-mount device.

So then, the location of this matte-textured section would be dependent upon the desired location of the upper hard-point for the boosters, and the rocket would have to be structured differently from a non H version from the get-go.

Thank you both for your help.
 

AlphaSigOU

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If I remember correctly the mounting mechanism for the top of the boosters is quite a bit different from the older Castor IV-A steel-cased boosters and early GEM-40s. They may have been modified for the newer GEM-40s aand GEM 46s Unfortunately, I don't have scale data for the new mountings.
 
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