Jeff L's unbaked design thread

[jqavins]

And I assume there's a through hole for a launch lug attached to that sleeve over the motor tube?

What's the static margin? It looks pretty small from the picture. Marginal might be OK in this case, since (I think) there'll be basically no body lift.

The body is two hollow hemispheres; where do you get them? 3D print? Cut a ball in half? Or does someone sell a plastic hemisphere nose cone?

Do you mind if - ahem - someone else builds one?

 

[dhbarr]

And I assume there's a through hole for a launch lug attached to that sleeve over the motor tube?

What's the static margin? It looks pretty small from the picture. Marginal might be OK in this case, since (I think) there'll be basically no body lift.

The body is two hollow hemispheres; where do you get them? 3D print? Cut a ball in half? Or does someone sell a plastic hemisphere nose cone?

Do you mind if - ahem - someone else builds one?

Craft store sells hollow split foam spheres.

 

[BABAR]

Rustoleum High Heet Gloss Clear - 2000 deg F...It also comes in Gray, flat Aluminum and Black

I have visions of a thin shell of intact paint with smoldering balsa or body tube underneath. Not doubting the PAINT’S ability to handle the heat, just questioning whether it insulates and protects The surface/substance it is covering.

 

[boatgeek]

It's a 12cm (roughly 5inch) sphere with an 18mm hole in the rear for a motor mount. I'm imagining the top hemisphere separates for recovery. Like this...
View attachment 441655

If anyone builds this, I suggest painting it gold/gold leafing it and naming it "Golden Snitch."

 

[Jeff Lassahn]

And I assume there's a through hole for a launch lug attached to that sleeve over the motor tube?

What's the static margin? It looks pretty small from the picture. Marginal might be OK in this case, since (I think) there'll be basically no body lift.

The body is two hollow hemispheres; where do you get them? 3D print? Cut a ball in half? Or does someone sell a plastic hemisphere nose cone?

Do you mind if - ahem - someone else builds one?

Oh, right. Rockets need launch lugs. Through hole in the sphere is probably the only sensible option here, but it will make lining up the sphere halves when prepping for flight annoying.

Stability margin should be better than OpenRocket predicts -- spheres are actually neutrally stable (CP right in the center) but OpenRocket predicts they're unstable with a CP of +infinity.

I'm thinking the parts come from scrounging at craft stores, etc. Either skim coat a foam sphere or find a plastic one designed as a Christmas ornament or terrarium shell or something. 3D printing is always an option, I guess.

I encourage anyone to build this, with or without Harry Potter Snitch livery (consider adding feather details to the fins for more Snitch styling).

 

[jqavins]

If the lug extends the full length but is attached only to one half then it also serves as an alignment guide. But then one would have to somehow make the recovery rigging assure that the lug lands up. Also, a piece of dowel or rod could be the alignment guide, placed in the lug for prepping and then removed.

 

[BABAR]

Oh, right. Rockets need launch lugs. Through hole in the sphere is probably the only sensible option here, but it will make lining up the sphere halves when prepping for flight annoying.

Stability margin should be better than OpenRocket predicts -- spheres are actually neutrally stable (CP right in the center) but OpenRocket predicts they're unstable with a CP of +infinity.

I'm thinking the parts come from scrounging at craft stores, etc. Either skim coat a foam sphere or find a plastic one designed as a Christmas ornament or terrarium shell or something. 3D printing is always an option, I guess.

I encourage anyone to build this, with or without Harry Potter Snitch livery (consider adding feather details to the fins for more Snitch styling).

If you can line up and build in a tube (like a soda straw) between the two holes for the rod, it really helps in getting the rod through both ends of the lug.

Worked well here.

 

[Jeff Lassahn]

Can the booster stage of a two stage rocket do glide recovery?
An empty motor casing has about the right center of gravity to make a canard glider out of, so I think something like this would work:



The booster alone looks like this, a kind of stubby little airplane. Hopefully it can be trimmed for glide by making small adjustments to the canard wings which won't mess with the full stack too much on ascent.

 

[Nytrunner]

Can the booster stage of a two stage rocket do glide recovery?

If you balance it right, no reason it shouldn't.

Just hve to find the sweetspot where it glides, but the full stack is still stable

 

[neil_w]

Can the booster stage of a two stage rocket do glide recovery?

I have witnessed it, so the answer is "yes". Of course, the time I saw it, it was unintentional: the booster of an Estes Extreme 12 got into a stable glide and went whizzing right past my head. I feel certain that I was the only one who witnessed it.

I don't know how hard it is to *intentionally* get one into a glide, particularly if it's a short stubby booster. I can more easily imagine a gap-staged booster really being designed to be a proper glider.

 

[jqavins]

All I have to say about that is it's a really cool idea and I'd love to see it (as long as I'm not the target).

 

[Jeff Lassahn]

I started playing with booster gliders when I ran across this early shuttle concept:

The drop tank is in the front, which seems like it can solve some stability problems. So since then I've been thinking about space planes with stuff forward of the plane in the stack. I think it would be cool to have a real heavy-lift rocket something like this:

There's a single use fuel tank and some optional payload space in the front, an orbiter with payload and some fuel, and a first stage with glide recovery and vertical landing stap-on boosters. Figure 30 tonnes up to LEO, up to 10 tonnes of return cargo back down, the forward tank can stay attached to the orbiter for the entire mission until just before reentry if you want extra consumables during the mission. Easy-peasy, cheap access to space for everyone in cool looking rocket planes!
What could possibly go wrong?

Or at least tell that as a story and build a fatasy-scale model of it...

 

[BABAR]

Can the booster stage of a two stage rocket do glide recovery?
An empty motor casing has about the right center of gravity to make a canard glider out of, so I think something like this would work:

View attachment 442830

The booster alone looks like this, a kind of stubby little airplane. Hopefully it can be trimmed for glide by making small adjustments to the canard wings which won't mess with the full stack too much on ascent.
View attachment 442829

It has been a goal of mine.

Estes had the black widow and I think centuri hsd tiger shark (may have been same design.) I cloned the tiger shark, couldn't get the booster to glide worth beans.

Edmonds had CiCi2, I did a recent clone, lost the sustainer on first flight, and booster glided into a post and snapped the fuse.

Definitely doable, but I think have a shifting elevator or canard would make booster more likely to glide

Good luck, and post results!

 

[Jeff Lassahn]

In some slightly different world, there was probably a TV show or a movie or something where the writers were really unclear about whether the flying things were supposed to be rockets or jet planes, and the dialog was terrible, and it was all totally ridiculous but also somehow really awesome, and there was a starfighter in it that looks something like this.

 

[jqavins]

Looks somewhat like a colonial viper.

 

[lakeroadster]

I was reading Neil_W's design thread, and I started wondering what a Trek starship would look like if it used Plasma Dart tech for its engines.
View attachment 432498
I'm not really happy with the proportions.

So I get what Neil's "half baked design" thread is meant to mean... but what is an "unbaked design"

View attachment 456814

Just don't get in while the upper motor is running..

 

[jqavins]

[W]hat is an "unbaked design"

I know I've posted some sketches of design notions after exactly zero real consideration of buldability, stability, or performance. That's more "raw dough" than it is a parbaked loaf.

 

[Jeff Lassahn]

More silly Star Trek stuff. Playing around with trying to make something that looks like an actual Trek starship, but still has some chance of being stable. This one needs to cram about 30 grams of weight into the front of the saucer section to fly.

 

[lakeroadster]

That's cool... but it will weather cock like crazy.

No wind... dead calm is your friend on this one.

Might want to put some adhesive foil inside rectangular box to prevent charring?

You know it might fly as a tractor motor design without the nose weight,,, especially with how draggy the design is in the rear. @Daddyisabar ... your thoughts?

 

[jqavins]

I've been mulling some over as well, and my problem is always that the saucer constitutes a giant pair of canards, and we have only the warp nacelles for fins. It seems very challenging.

 

[Ronz Rocketz]

My son is looking for a Millennium Falcon rocket.

 

[Jeff Lassahn]

My son is looking for a Millennium Falcon rocket.

That's brutal -- no place to even try to hide extra fin area.
How do you feel about giant plasma-flame fins:

 

[Ronz Rocketz]

That's brutal -- no place to even try to hide extra fin area.
How do you feel about giant plasma-flame fins:
View attachment 463345

I know right? Do you have an OR/RS agile fir the above? I was thinking it would have a long nose like the tie fighter.

 

[dhbarr]

You know those six vents or whatever on the top aft of the Millennium Falcon? I'd bet if you punched clear tubes all the way through so they stuck out both sides you could get enough drag.

 

[Jeff Lassahn]

A BT-60 based semiscale model of Virgin Galactic SpaceShipTwo looks not too hard, just cutting and gluing some funny shaped balsa fins:

Of course, it's the paint, decals, and various bling that would really make it cool.

 

[BABAR]

fly.

Any chance of flying it backwards? Put the motor in the saucer and the weight in the nacelles?

 

[jqavins]

A BT-60 based semiscale model of Virgin Galactic SpaceShipTwo looks not too hard, just cutting and gluing some funny shaped balsa fins:
View attachment 465554

Looks very cool. I see a potential concern that the fins are so far off to one side. @BABAR likes to say "Symmetry is overrated" and he has lots of successful designs to prove it. I wonder if there any tricks to doing this sort of thing successfully that he might like to pass along.

 

[neil_w]

Looks very cool. I see a potential concern that the fins are so far off to one side. @BABAR likes to say "Symmetry is overrated" and he has lots of successful designs to prove it. I wonder if there any tricks to doing this sort of thing successfully that he might like to pass along.

Yeah, that is *very* asymmetrical, I foresee difficulties in getting it to fly straight. But who knows!

 

[Jeff Lassahn]

Any chance of flying it backwards?

Sadly, not looking likely. It's CP is going to be really far forwards either direction.

 

[BABAR]

Give it to @burkefj , he’ll make a glider out of it!