Quick n Dirty Space Shuttle

[Jeff Lassahn]

I eventually want to build a 1:150 scale Space Shuttle, in the basic style of the old Estes shuttle with an engine in the external tank and the orbiter as a parasite glider. I'm not feeling brave enough to do the work on that without doing some prototyping first, so I'm putting together a quick version with off-the-shelf parts.

As with so many problems, this one can be solved by kit-bashing a Baby Bertha.
So here's a design for a kinda close 1:200 scale shuttle made from a Baby Bertha kit and a few extra bits.

Surprisingly, the only parts that's not close to scale is the shuttle nose, because Estes doesn't have a lot of good BT-50 nose cones. I could have gotten something better in balsa from eRockets probably, but at some point I got stubborn and decided "Only Estes plastic parts, and standard tube sizes"

I'll use this for working out some basic weight and balance issues, making sure the glider release mechanism is solid, and roughing out the aerodynamics of the glider (can I get away with fixed elevator position? can I get away without adding wing dihedral? etc) Then maybe build a better 1:200 orbiter for launch on the same booster, then think about doing the real scale 1:150 version.

 

[BABAR]

Looks cool. Depending on how close your glider rides to the booster, you may be able to put a clip attached to the booster that will hold an elevator on the glider in a neutral position, at separation the elevator is free to shift to up position.

 

[GlenP]

Not sure if either of these fits the size you want, but you could use a foam parasite glider like this maybe

https://www.guillow.com/spaceshuttle.aspx
Or this, if you decorate it right might be close enough

https://estesrockets.com/product/081425-javelin-glider/
You can find some detailed paper templates for the Zooch Shuttle here on TRF and print your own cardstock and balsa sheet orbiter.

 

[tab28682]

The little foam space shuttle from Guillow is about 1/120th scale. Wingspan is a good bit oversize, and scales to about 1/100. Great little glider.

If you went a little bigger with your stack, it would work at 1/120, but would be a D size rocket. I believe George Gassaway worked out a design for a full stack using the foam shuttle.

I have launched a number of them, but never on a shuttle stack. It makes a decent little micro R/C boost glider, with todays very light weigh radio gear.

Here is a link to my thread in rocket gliders showing a sequence of the little shuttle being launched on a non-scale booster of my own design and being flown back via RC. Photo sequence starts at post 16.

https://www.rocketryforum.com/threads/radio-controlling-the-guillows-foam-space-shuttle.120388/

 

[JPalmer621]

Somewhere under card stock rockets is a paper shuttle that is real close to the same size as the Estes shuttle FYI

 

[mjennings]

I'd recommend adopting Dr Zooch's 6 fin set up. I really think that and the off center nose weight in the ET was the secret sauce to that kit that gave it such a stable boost profile compared to the old Estes 4 fin set up.

 

[Jeff Lassahn]

Building in progress.
Using a bunch of Baby Bertha parts, some other standard Estes plastic nose cones, and a bunch of additional body tubes cut to length.


And some balsa and cardstock pieces. 1/8" balsa for the orbiter wings, papered 1/16" balsa for some custom centering rings (can't use the Bertha parts because the motor mount needs to be off center) and some paper shrouds for the SRBs and the ET.


Now to put together the orbiter.
I've been thinking about both the old Estes orbiter design and the Estes Orbital Transport glider. The Estes shuttle has a complicated adjustable elevator, while the orbital transport uses fixed elevators set using a template. It seems from looking around the internet that the shuttle has a reputation for being touchy, while the transport seems quite reliable. Some of this is probably because the transport glider is trimmed for stability -- lots of elevator area, lots of elevator reflex, lots of dihedral angle.

A scale Shuttle can't have very much dihedral because the real vehicle doesn't. This makes me a bit nervous. But there is a lot of elevator area, so slightly nose heavy with a lot of up elevator is probably a good way to go.

So, attaching the elevators, with a fixed angle set by some 1/8" scrap balsa. The right wing is given a slightly higher elevator angle by putting the wing slightly farther back in the jig, to give the glider a tendency to turn right.


I'm not really painting most things but I am giving the glider balsa a primer coat of gesso and some sanding to get rid of the worst of the balsa fuzz. Flying it with bare balsa I'm worried the extra drag will give me a misleading indication of how it performs.

Wimping out, I'm giving the wings just a _little_ dihedral angle.


And here's the finished-ish glider which I'll balance and toss around sometime when it's stopped raining.

 

[Jeff Lassahn]

Today in Stupid OpenRocket Tricks: using a rocket simulator to balance a glider.


We generally want the Center of Gravity of a glider to be just slightly forward of the Center of Lift. That makes the glider stable in pitch, just like putting the CG in front of the CP makes a rocket stable. But it also makes the glider want to nose down, so we need some up elevator to compensate. We generally don't want anywhere near as much stability margin on a glider as we do on a rocket -- it's probably not possible to trim the elevators up enough on a design like this to keep it flying with one caliber of stability.

If the glider wing is relatively thin and has a fairly symmetric airfoil, the center of lift is going to be basically the same as the fin center of pressure as computed by OpenRocket (fins are basically just small symmetric wings, after all). So the overall Center of Pressure in the pitch direction as computed by OpenRocket and the Barrowman equations is a pretty good estimate of the center of lift of the glider, and putting the CG just a little ahead of that is a pretty good starting point for balancing the glider for flight.

For a typical glider, the CP is different in the pitch and yaw directions. Fortunately, for sane glider designs the yaw CP is way farther back than the pitch CP and OpenRocket shows the farther forward of the two. So we can use OR to mess with the pitch CP and count on the yaw CP being OK. If you're doing some kind of odd tailless glider design you may need to be more careful about this stuff.

Anyway, here's a quick model of my orbiter glider. The actual wings are low on the body instead of on the centerline, and this model doesn't represent the up can on the elevator surfaces, but other than that it's pretty accurate.
It says I'm nose heavy and need a couple of grams of tail weight. That turns out to be pretty accurate, I added a bit of clay to the rear until the balance point is about where shown, and a few tosses show that it's gliding OK-ish.

 

[lakeroadster]

Thanks for sharing the S.O.R. tip... much appreciated!

 

[GlenP]

Good use of OR. If you were interested in yaw stability, then just remove wings from the model and use only the vertical stabilizer, maybe?

best to keep weight to a minimum, but if you have to add weight to the tail, then that is a necessary evil. A more efficient design would require moving the wing farther aft on the body or designing the balance point based on the raw materials rather than adding ballast weight, if gliding performance was a primary goal. But no worries, a Shuttle is capable of falling, with style!

 

[Jeff Lassahn]

I've tried removing wings to observe the tail and vice versa, and it's messier than you want it to be. What tends to happen is the axis you don't care about ends up with it's CP very far forward, and since OpenRocket shows the worst case CP it shows the CP up near the nose instead of what you care about.

You can make it work be adding copies of the thing you're experimenting with on the other axis 90 degrees away, so if you're only looking at a pair of wings add them as a 4 wing set. If you're only looking at a vertical stabilizer, add two of them on at 0 degrees and one at 90. That works but it's annoying.

As far as the tail weight goes, it's really driving home how much plastic nose cones weigh. The next version I do will be a more realistic orbiter, with the nose probably carved from balsa which will probably be much better balanced to start.

 

[Jeff Lassahn]

I'm doing final assembly on all the non-orbiter bits today.
Here's the engine mount with fiddly bits of 1/8" dowel to serve as orbiter attachments.

 

[Jeff Lassahn]

And here's everything done.
Booster by itself:


Here's the full stack in "display" configuration without the fin attachments:


And here's the flight configuration with fins:


Now I wait for good weather to see how badly it flies.

 

[Jeff Lassahn]

I just want to say, it feels good to use all the pieces of the Baby Bertha. It seems wrong somehow to brutally kitbash some innocent rocket kit and end up only taking the nose cone and a few odds and ends.

Here's everything that's left over from the Bertha after this thing's built:


I'm sure the centering rings will find a purpose in some future design, and I definitely could have put the retaining hook in this design if I was willing to put up with the extra clutter. Not bad, maybe I'm supposed to throw the decals in a pot an make soup or something...

 

[lakeroadster]

I wonder if this could be built as a tractor motor and thus could fly without the lower fins? Probably be difficult to hide the motors though. What say ye @Daddyisabar

I just want to say, it feels good to use all the pieces of the Baby Bertha. It seems wrong somehow to brutally kitbash some innocent rocket kit and end up only taking the nose cone and a few odds and ends.

Hot Rodding.... The Model Rocketry Chapter!

 

[Daddyisabar]

I wonder if this could be built as a tractor motor and thus could fly without the lower fins? Probably be difficult to hide the motors though. What say ye @Daddyisabar



Hot Rodding.... The Model Rocketry Chapter!

A Shuttle stack is beyond my skill level. I think to keep it looking good the motor needs to be in the back.

 

[Jeff Lassahn]

Not really sure how the whole tractor motor thing would work...

 

[Daddyisabar]

Canted tractor motors can haul things up behind them, harder to implement on a shuttle stack. I would stick with big flame fins.

 

[Jeff Lassahn]

Now I'm thinking we should start a genre of realistic scale model spacecraft being carried away by large dragons:

 

[GlenP]

Looks like when your ship gets captured in Galaga!

 

[Ronz Rocketz]

How old am I that I know what that means...

 

[burkefj]

When I'm checking my gliders for yaw stability all you have to do is make another simulation with the vertical stabilizer the way it would normally be and also with the same size vertical stabilizer 90° to that so you'll have a two fin rocket and you can check that your CP and CG relationships are okay with that design.

I don't like open rocket for determining glide CG I prefer something like bruder wing calc for a horizontal stabilizer less design or an RC aircraft simulator for a normal layout that tells you the mean aerodynamic cord and use a sane percentage of Mac for your CG location. these can allow for more complex wing and tail shapes than you could typically model easily in open rocket

 

[burkefj]

By the way it looks like you've got a lot of positive incedence of the mounted orbiter wing relative to the vertical line of the external tank, that's going to cause you some issues especially with some up elevator on the shuttle if you have that.

 

[Jeff Lassahn]

it looks like you've got a lot of positive incedence of the mounted orbiter wing

The camera angle makes it look worse than it is, but there's definitely some there. I'm trying to decide if it's worth tearing apart the forward orbiter mount to fix it, or if it will "just be fine". With this setup there's always also going to be some wiggle in the mounts, so how it hangs just standing there vs how it hangs under flight conditions are going to be a little different, and I have no idea whether that will also "just be fine" or whether it's going to do weird stuff like chatter itself to pieces.

I don't remember worrying about any of this when I built the old Estes kit. I miss being young and foolish.

There's a big part of me that wants to fly it and watch it do slightly sketchy stuff before trying to make it perfect, hoping to get a better feel for how much of what kinds of slop it's possible to get away with.

 

[burkefj]

I'd make sure there are some supports at the rear and make is parallel to start, I know the new estes shuttle has some issues when the front lug isn't inserted flush and I think John Boren put some addendum or pointed out where you need to check for that, that makes the orbiter have positive incidence as well and makes it arc pretty dramatically from what I've seen in flights.

Frank

The camera angle makes it look worse than it is, but there's definitely some there. I'm trying to decide if it's worth tearing apart the forward orbiter mount to fix it, or if it will "just be fine". With this setup there's always also going to be some wiggle in the mounts, so how it hangs just standing there vs how it hangs under flight conditions are going to be a little different, and I have no idea whether that will also "just be fine" or whether it's going to do weird stuff like chatter itself to pieces.

I don't remember worrying about any of this when I built the old Estes kit. I miss being young and foolish.

There's a big part of me that wants to fly it and watch it do slightly sketchy stuff before trying to make it perfect, hoping to get a better feel for how much of what kinds of slop it's possible to get away with.

 

[JPalmer621]

Just some ramblings on your fins. 1. My friend built his shuttle with fins glued to the back of the ET and added some nose weight. That way they did not hang down so far 2. Paint them like Dr Z and have flame fins. If you get the right angle at lift off for your picture the fins will look like exhaust.

 

[Jeff Lassahn]

This version is the Quick and Dirty test platform, so it's not getting painted. But my vision for the future is flame fins. I've also considered doing the fins in light blue to evoke the look of the original space shuttle patches:
https://cdn.shopify.com/s/files/1/0...pace_shuttle_basic_1024x1024.png?v=1579887891