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Build Thread --- 1/200 SD HLV

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JRThro

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... it's not a shuttle that I'm building, but that's as much as I'll say. Except this: It's also not any of the DIRECT variants.
:dark:
Okay, so today, Christmas Day, I actually started building this thing.

Here's what it is:

It's a 1/200 scale model of the Shuttle Derived Heavy Lift Vehicle that was presented to the Augustine Commission on the future of U.S. manned space flight this summer.

It's based on BT-60 tubes for the External Tank and for the cargo carrier, and on BT-20 tubes for the Solid Rocket Boosters.

I used NASA documents that I found online, as well as George Gassaway's FAI shuttle drawing that he posted a link to in the other thread, for dimensional information. Based on actual ET and SRB diameters, the body tubes are between 1/203 and 1/198 scale, so 1/200 is a good choice for lengths, etc.

The nose cones for the ET, SRB's, and cargo carrier, plus the aft SRB skirts and nozzles and the aft dome of the ET, are all balsa parts, which I bought from sandman. The quality of the balsa parts is good, and they are the most expensive parts of the model, since the rest of it is just tubes, motor mount, parachute, etc.
 
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JRThro

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Here are the same pictures of the parts that I already posted in the original thread where I was looking for sources of these parts.

Since these pictures were taken, I shortened the ET tube by about 1/3 of an inch, making it 6.0" long.

PICT0023A.JPG


PICT0024A.JPG


PICT0025A.JPG


PICT0028A.JPG
 

luke strawwalker

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Looking good John...

Where you plan on putting the engine(s) in this thing?? Going for scale locations??

I noticed in the pic that the ET aft dome didn't appear to be drilled for a mount ala most shuttle models...

Later! OL JR :)
 

JRThro

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Looking good John...

Where you plan on putting the engine(s) in this thing?? Going for scale locations??

I noticed in the pic that the ET aft dome didn't appear to be drilled for a mount ala most shuttle models...

Later! OL JR :)
Yeah, the aft dome was left undrilled to allow the option of putting engines in scale locations. But after reading George Gassaway's posts in the original thread, I'm almost certainly going to drill the aft dome for a single 18 mm engine.
 

JRThro

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Here are a couple of side views of the vehicle from the NASA presentation to the Augustine Commission.

Side Views of SD HLV.jpg
 

dwmzmm

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Great job you're doing there, John!!
 

Fred22

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I am fascinated but the subject and I suspect a very high quality build thanks :)
fred
 

JRThro

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The back end of the "sustainer" looks like just a lot of origami work, basically.

If you wreck it just grab another piece of paper!
As it happens, my wife bought a good-sized package of 110 lb. cardstock for a project of hers about a week ago, so I'll at least try going that route.

Otherwise, even if I go with thin sheets of balsa for the back end of the cargo carrier, I'll still use the cardstock to make mockups first.
 

sandman

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As it happens, my wife bought a good-sized package of 110 lb. cardstock for a project of hers about a week ago, so I'll at least try going that route.

Otherwise, even if I go with thin sheets of balsa for the back end of the cargo carrier, I'll still use the cardstock to make mockups first.
That sounds perfect.

Although you may find that the cardstock mockups will look pretty darn good.
 

luke strawwalker

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Yeah, I agree with sandman... cardstock is your friend here, especially on a model like this that's going to tend to get heavy very quickly. Also, the off-center weight is going to be more of an issue with this model than similar sized shuttle models that are being sold, IE the Dr. Zooch kit of the same size. The extra weight of the second cargo carrier nosecone, the weight of the cargo carrier body tube, and the weight of the engine boattail will all tend to get pretty heavy on you compared to the weight of the Zooch orbiter hanging off the side, which is surprisingly light, and most of it's weight is concentrated in the wings and nose very close to the ET, minimizing the stack's CG shift off the ET centerline. Basically, you're going to be installing another body tube and nosecone on the side as the cargo carrier, and it's CG will be essentially along it's own centerline, meaning that it will offset the completed stack's CG more than an equivalent sized shuttle orbiter would. The Dr. Zooch kit makes use of an assymetrically weighted nosecone to keep the stack flying straight and counteract the offset CG caused by the weight of the orbiter on the side of the ET-- I'm betting you'll have to do some experimentation and implement a similar system to prevent corkscrewing flights, simply because of the added mass of the heavier cargo pod compared to the orbiter, as well as it's mass distribution. Basically, every bit of weight in the cargo pod you can save is a good thing, because it will minimize the CG shift of the combined stack.

Another mitigation strategy might be an offset motor mount like the larger Estes Shuttle kit used-- offsetting the motor mount in the ET tube to the orbiter side of the tank to put the thrustline through the combined stack CG. This actually is probably the best way to accomplish correcting the thrust centerline/CG problem, as it minimizes additional weight in the ET nosecone... but shares some of the difficulties of determining the amount of offset and amount of weight required, as you'd still have to determine the necessary offset and if any 'tilt' of the motor mount would be necessary.

To sum up, keeping the weight down is the best thing you can do with a model of this type... it's going to be pretty draggy anyway, and performance is limited with 18 mm motors, unless you plan on installing a 24 mm mount or going with composites...

Later and KUTGW!!! OL JR :)
 

JRThro

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Yeah, I agree with sandman... cardstock is your friend here, especially on a model like this that's going to tend to get heavy very quickly. Also, the off-center weight is going to be more of an issue with this model than similar sized shuttle models that are being sold, IE the Dr. Zooch kit of the same size. The extra weight of the second cargo carrier nosecone, the weight of the cargo carrier body tube, and the weight of the engine boattail will all tend to get pretty heavy on you compared to the weight of the Zooch orbiter hanging off the side, which is surprisingly light, and most of it's weight is concentrated in the wings and nose very close to the ET, minimizing the stack's CG shift off the ET centerline. Basically, you're going to be installing another body tube and nosecone on the side as the cargo carrier, and it's CG will be essentially along it's own centerline, meaning that it will offset the completed stack's CG more than an equivalent sized shuttle orbiter would. The Dr. Zooch kit makes use of an assymetrically weighted nosecone to keep the stack flying straight and counteract the offset CG caused by the weight of the orbiter on the side of the ET-- I'm betting you'll have to do some experimentation and implement a similar system to prevent corkscrewing flights, simply because of the added mass of the heavier cargo pod compared to the orbiter, as well as it's mass distribution. Basically, every bit of weight in the cargo pod you can save is a good thing, because it will minimize the CG shift of the combined stack.

Another mitigation strategy might be an offset motor mount like the larger Estes Shuttle kit used-- offsetting the motor mount in the ET tube to the orbiter side of the tank to put the thrustline through the combined stack CG. This actually is probably the best way to accomplish correcting the thrust centerline/CG problem, as it minimizes additional weight in the ET nosecone... but shares some of the difficulties of determining the amount of offset and amount of weight required, as you'd still have to determine the necessary offset and if any 'tilt' of the motor mount would be necessary.

To sum up, keeping the weight down is the best thing you can do with a model of this type... it's going to be pretty draggy anyway, and performance is limited with 18 mm motors, unless you plan on installing a 24 mm mount or going with composites...

Later and KUTGW!!! OL JR :)
I actually put together a really simple spreadsheet yesterday to calculate what the CG offset will be relative to the ET centerline, based on the weights and locations of the major components of the model: ET, motor mount with motor, cargo carrier, SRB's, and fins and fin holders. I haven't yet weighed the various components, but when I do, it should give me a decent idea of how to offset the motor mount in the aft end of the ET.
 
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georgegassaway

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See message #19 of the “Source for ET & SRB Noses” thread:

http://www.rocketryforum.com/showpost.php?p=60896&postcount=19

Starting with the 6th paragraph that begins with:

“BTW - even with a single engine in the ET, the offset distance is key. The heavier the orbiter weighs compared to the rest of the “stack”, the more the engine mount needs to be offset towards the orbiter.”

That describes the process I’ve used for determining where the 3-D CG was as regards to the engine mount offset. I used that method again recently for the 1/110 shuttle kit prototype.

- George Gassaway
 

JRThro

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“BTW - even with a single engine in the ET, the offset distance is key. The heavier the orbiter weighs compared to the rest of the “stack”, the more the engine mount needs to be offset towards the orbiter.”
Absolutely, George. That's what the spreadsheet will do, once I weigh the various components.

I'm also going to include the weights of the fin units (long BT-5's with fins attached) that will be inserted into the aft ends of the SRB's.

Can you offer any insight into how you arrive at a good length for the fin units, and good fin sizes, on your shuttle stacks? I'd really like this thing to be stable when I launch it. One major difference between this stack and a shuttle stack is the lack of wings on the SD HLV.
 
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JRThro

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I was stressing about how to paint and finish the model (not that things are at that point yet). In reading a few posts by TRF member SpaceAXEplorer, I saw that his signature has a link to his paper/cardstock modeling site at http://axesworld.embarqspace.com. Through that link, I came across Jon Leslie's web site at http://jleslie48.com/, and at that site there is a 1/144-scale model of the SD HLV about halfway down this page of incredible paper space models: http://jleslie48.com/gallery_models_postapollo.html

After downloading the pdf files for that model, I printed them out on plain paper with no scaling and then measured them with a ruler. Given the OD of the BT-60 cargo carrier, the scale of my model at 1/200, and the size of the 1/144 cargo carrier wrap, I then copied the printouts at 76% of full size. Last night, I cut out the cargo carrier wrap, and it looks like it fits perfectly around the BT-60, although it is just a bit too long.

I'll go through a similar process with the wraps for the ET (BT-60) and especially the SRB's (BT-20), which are off in scaling by a percent or two.

There should be wraps for everything except the nose cones on the ET and the cargo carrier. Actually, there *are* wraps for those in the paper model, but it's not clear to me how well they would fit over the balsa cones. So I'll probably paint the cargo carrier nose cone white to match the white wrap, and then see if I can get the ET nose cone wrap to fit well enough, or try to mix paint to match the orange ET wrap and paint the nose cone.

So I want to thank Eric (SpaceAXEplorer). Having the link to your web site in your signature has done a *lot* of good. Thanks!
 

mjennings

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I don't know where it the pictures got to but I saw a version of this that had the Orion capsule on top of the cargo pod.
 

luke strawwalker

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I don't know where it the pictures got to but I saw a version of this that had the Orion capsule on top of the cargo pod.
Yes, that's probably from the Augustine Commission presentation of the SDHLLV that John Shannon did... they proposed using the NSC (Not-Shuttle-C; easier to type) as a manned launcher for lunar capable Orions for exploration missions BEO.

From what I understand, it's doable, but rather risky-- an abort off a stack with an ET and 2 SRB's RIGHT BESIDE THE CAPSULE would severely limit the abort options, since you REALLY don't want to smack into the ET on your way off the stack... that could lead to a REALLY bad day.

Supposedly it CAN be done but it would be WAY more risky than aborting off a DIRECT Jupiter/ NLS/ Ares V classic style inline vehicle...

Later! OL JR :)
 
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