Source for Scale Space Shuttle ET and SRB Nose Cones?

[aerospike]

Year ago I built a 1/100 orbiter and boosted it piggy-backed on a modified Big Bertha. The Bertha had a C6-3 in the usual location but two 13mm A3's mounted on pylons let into two of the fins on the Bertha. I also put a longer nose on it to move the CG fwd. I flew it probably a dozen times and remarkably, never had a failure. It would boost up to about 200-250 ft and I'd get maybe a 15 sec glide out of the orbiter. I wanted more altitude and built another booster that used a D12 and two C6 outboards. I flew it twice in this configuration, both flights boosted the orbiter up to 600-700 ft and I got maybe a 45 sec glide. On the second flight, one of the fins with the outboard C6 mounted onto it broke because I used stock that was a little too thin. George mentioned mounting the Orbiter onto your booster so that it flies at a zero lift angle of attack during boost, that way you only have to deal with the moments created by the engine thrusts and keep that vector close to your CG axis. I did this on my models and just eyeballed what I thought the Orbiter zero lift angle of attack was (maybe 1 or 2 degrees?) and I must have nailed it because I never had any problems with trim during boost.

 

[MaxQ]

Well, while we're on the subject...
Sometimes the best laid plans don't exactly work.

Thrust vectors all figured out.
Still pranged.

And note the ample clear fin area on the Ex tank.......
By far the most beautiful piece of craftsmanship I've ever seen...Rolf really gave Andy Woerner a run for the money , and that is saying quite a bit, given Andy's level of expertise and workmanship.

 

[MaxQ]

This is how it is traditionally done...the single motor in a non scale location.(like the little Estes shuttle stack, and Sheri's Shuttle kit).
Florida University High School....IIRC, Crippen was there for the maiden flight.

Radio control was used for the glide back....and (like Andy's) on the way up.
Succesfully flown.

They even had a team build the scale launch facilty.
This was offered as a limited run kit at one time, not cheap.

 

[MaxQ]

Of course a lot of credit goes to Andy....he did get one to "straighten up and fly right"....with the motors in the scale locations..
Note the fin area on the SRBs showing...bottom right.

 

[georgegassaway]

Well it sounds like piggyback is the way to go if I want to get the orbiter up there. I wonder about a Dyna-soar atop a titan type configuration... Ted

Lots of problems with an orbiter on top like that. First of all, to be stable, it needs huge fins in the back. And even at that, it also needs a lot of noseweight. I’ve done it for a scale Dyna-Soar Titan scaled for a BT-80 (2.6&#8221.

https://homepage.mac.com/georgegassaway/GRP/Scale/X20.htm

To most effectively install noseweight for the Titan rocket, it was put inside the uppermost portion of a BT-20 tube that ran from the adapter up inside of the X-20 (see drawing on web page linked above). Offhand, the Titan and noseweight was many times the mass of the Dyna-Soar (of course the Dyna-Soar was free-flight, no R/C gear. Just too small to be very practical for R/C and no room to install such gear with the BT-20 running up inside of it).

Another issue was the need to make sure the X-20 was dead-straight. Which is sort of easy regarding the wings and fuselage. But, the offset sloped angled nose shape might have produced a little bit of “nose down” canard effect. So, I made it to roll a little bit on the boost. Also, the elevons had to be flat for boost. I solved that by a simple lever attached to the elevons, to push the elevons flat for boost, and let a rubber band pull the elevons up after the Dyna-Soar fell forward off of the BT-20 (after ejection & chute deploy).

Below, some pics of it at NARAM-51 (this year)

Anyway, putting an orbiter on top would just be a very inefficient way to boost a shuttle orbiter. Better to do it as a piggyback, where the booster can be a lot simpler and lighter.

- George Gassaway

 

[dedleytedley]

Thanks for all the good advice George! I really like your Dyna-soar but it does look like an unwieldy model rocket. You've accomplished a great deal with your modeling over the years, judging from your posts. Maybe you should write a book?!? Ted

 

[ben_ullman]

Hey George, while we are on the subject of shuttles,

how hard is it to get one to fly with no fins? If you were to have an orbiter with control surfaces and the motors angled at the right angle would it not sort of fly straight? I have this vision of a 1/20th or so shuttle that flys on sort of moon burning 6000ns M's. Basically lower the thrust just a bit and extend the burn to keep it from being such a jolt.

Is it more or less keeping it stable AFTER the SRBs are burnt? because most of the shuttles I have seen get off the rail fine and then start arcing as they get higher up.

You don't need to type a huge response if you don't want but hey!! I ejoy picking your brain!

Ben

 

[georgegassaway]

Hey George, while we are on the subject of shuttles,

how hard is it to get one to fly with no fins? If you were to have an orbiter with control surfaces and the motors angled at the right angle would it not sort of fly straight? I have this vision of a 1/20th or so shuttle that flys on sort of moon burning 6000ns M's. Basically lower the thrust just a bit and extend the burn to keep it from being such a jolt.

Is it more or less keeping it stable AFTER the SRBs are burnt? because most of the shuttles I have seen get off the rail fine and then start arcing as they get higher up.

It is VERY hard to get it to fly with no fins. Well, it is hard to get it to fly straight with just one fin on each SRB.

The only method that is “easy” is the old Estes shuttle type, with a tube dangling behind each SRB, with big fins on each tube. I even did that with my first two shuttles. One with clear tubing and clear fins, then for the first 1/72 boilerplate with R/C orbiter, simply some BT-5 tubing and fins. Actually at first I had tried the 1/72 model with clear fins on the SRB’s, based on fin area and CG supplied to me by someone who I figured would know even better than I did.... but it was wrong and went unstable. So, the Estes style fins were done to get the project back on track.

In 1988 I tried out one fin on each SRB again. But this time I KNEW that the original CG I had been given was too far aft. So, I did all of my own stability calculations. And since the shuttle is such an incredibly complex thing aerodynamically, I used the old cardboard cut-out method to help me work out a worst-case CP for it when using that size of fin on each SRB. I would not even trust Rocksim today to get that right.

And anyone who does an HPR shuttle, they really need to test fly with a smaller scale very crude shuttle boilerplate first.

I will attach a drawing showing the fins and CG I use. Take note how far forward the CG has to be. That CG is ahead of the glide CG of the orbiter, , so the entire orbiter acts like “tailweight”. At least the orbiter CG is not way far aft of where the shuttle stack CG needs to be, but the orbiter or course has significant mass.

This is why it is key to make *EVERYTHING* lightweight. The far too typical “if it is too heavy then double the power” thinking does not work well here (actually that is never a good excuse for overkill fabrication, but a project like this is makes it more critical than almost any other project type). Take note that the typical CG of the SRB’s are also aft of where the shuttle stack CG needs to be. So, it takes more noseweight in the tip of the ET nose to make the shuttle stable, them ore that the SRB’s weigh. And this is not even considering having any engines in the SRB’s. Engines in SRB’s makes it far worse.

Back to the ET nose, in my model what I ended up with was this. The ET is vac-formed, and hollow, not for the sake of making the ET nose lightweight. Because the ET nose is the one thing that needs the mass. But it is hollow so that as much “needed mass” as possible can be crammed into the nose. In my ultimate shuttle model, proven out in a 1998 boilerplate and 1999 NARAM contest model, it needed zero noseweight. Well, it needed zero “dead” weight” because all of the mass in the ET nose is working mass. The flight computer and batteries are in it. Well, sort of a given, for those. But also, the chute compartment is in the ET nose. And the Chutes and shock cords are stored in the ET nose. And by that I mean 2 chutes and shock cords for the ET nose AND to chutes and shock cords for the main ET also. The only thing inside the ET, aft of the intertank, is a lonesome engine mount tube. The intertank does have something in it, the SRB release mechanism and servo, but everything is built to be as lightweight as possible.

Here are two links about the model:

https://homepage.mac.com/georgegassaway/GRP/Scale/Shuttle-G/shuttlehome.htm

That one has links to lots of info on the 1998 boilerplate and 1999 NARAM contest model, plus some info on the earlier models. There are pics and drawings that document how crammed full the ET nose is,

https://homepage.mac.com/georgegassaway/GRP/Scale/Shuttle-M-CD/ShuttleModel.htm

That one has more info. The link to the “Assembly of NARAM Model” has some “scans” of building the 1999 NARAM model (I did not have a digital camera, so I set parts on a scanner).

The link to Shuttle ET assembly is from when I built a new ET for that model before I flew it at the 2000 WSMC. By then I did have a digital camera. You can get a feeling for how “empty” the ET is (and it was fiberglass, but not heavy HPR-level fiberglass, but instead it was “lighter than an Estes type paper tube” fiberglass). The SRB’s also were lightweight fiberglass.

This message turned out to be too long, so I am splitting it. Since I already attached pics, here is a description:

Stability drawing
1998 Boilerplate configuration layout
1984 boilerplate with Estes-type fins
1998 boilerplate test flight. Note that in this mostly far-side view that only part of one orbiter wing is visible and other wingtip is totally hidden.

 

[georgegassaway]

Continued from above.......


Now, shuttles that have pitched onto their back, no, they do not become “less stable” after liftoff.

EDIT - After posting this, I realized that in a way, a shuttle can seem like it becomes "less stable" as described in the second type of situation below. But I tend to think of that as not being "stable enough" from the start.

Has to be one of two things. One, thrust imbalance. Could be bad thrustline(s) in relation to the 3-D CG (The thrustlines MUST run thru the 3-D CG, and must not cause the model to “crab” sideways thru the air either, but fly dead-straight). Or is clustered with engines also in the orbiter, the orbiter thrust may not be “carrying its load”. Also of course the thrust curve of whatever is in the orbiter engines have to match the other engines or they will be out of sync.

Here is another way to look at it. Imagine the ET and SRB stack alone was stable. And the orbiter was stable. And we will assume all engines ignite and even ignore “crabbing” issues. OK, so you have a “drag race” by launching the ET/SRB stack on pad one, and the orbiter on pad two at 30 feet away. And let’s pretend it is dead calm. If everything has been calculated out with thrust levels and so forth, then both will take off exactly even ,and will fly in formation 30 feet apart, at exactly the same altitude second by second. If the thrust levels (and thrustlines) are not that perfect, where one would pull ahead of the other, then that is why a full stack of the shuttle would pitch nose down or onto its back. If the ET/SRB stack would fly ahead of the orbiter, then a full stack would pitch onto its back.

Two, the model is not 100% stable. It starts off straight, but it begins to pull to one side a bit and once that starts, a higher angle of attack to the air feeds on itself to make it flip unstable. As you probably know, CP is not a constant. The higher the angle of attack, the more that the CP will move forward. So it might be stable at 1 degree angle of attack but totally unstable at 5 degrees angle of attack. This is also complicated by another factor. The SRB’s “blank out” the orbiter’s wings when at a high angle of attack. What do I mean by this? Worst-case, look at the “top” view of a shuttle where you see the top of the orbiter and both SRB’s. Well, actually imagine you are seeing the “far side” of the stack, where the orbiter is on the other side. What do you see of the orbiter? Nothing but the wingtips sticking out past the SRB’s. THAT is what the airflow “sees” worst-case when the angle of attack gets high enough, so in some cases of a high enough angle of attack 80-90% of the orbiter’s contribution to pitch stability (wings) just disappears. That 4th photo Max Q posted in message #32, by that point I guarantee you the orbiter’s wings were blanked out (other than the tips), and probably were well before then.

Well, possibility #3 is a mix of #1 and #2. I mentioned “crab”. If the thrustline or combination of thrustlines do NOT cause the model to fly perfectly straight .,but to “crab” a bit sideways into the air, then that is going to cause an angle of attack to the airflow. A rocket that is stable enough, will pitch over some due to the crab motion, as with weathercocking. And a not-quite-stable enough model will end up getting off to a bad start due to that crabbing action and can feed on itself due to that angle to attack and end up going unstable due to the CP moving more forward from the increased angle of attack. Actually in the case of that model, the thrustlines seem to have been arranged to prevent “crabbing”, but only if all engines ignited and were producing exactly the correct thrust levels moment to moment to be balanced out.

Oh, BTW, also photo #1 posted by Max-Q in message #2, no, those thrustlines were not converging properly. They all needed to intersect in the ET at exactly where the 3-D CG of the full stack was. Of course, that is very difficult to do for practical flight matters, and to do it with the SRB engines would make it look more like a Fliskits “Deuce” exhaust plume than a shuttle. So, a sort of compromise was used there, to hope that the engines in the SRB’s did ignite dead equally and had thrust levels that did not differ too significantly from each other. But in photo #3, it looks like it is tilting to the right a little bit, compared to its smoke plume, as though the right hand SRB engines was producing less thrust than the left one (which is what is going to happen from unequal thrust unless the thrustlines run dead thru the 3-D CG of the full stack)

Also, the two big clear fins on the ET were not doing a lot of good. Because those fins were not that far enough back from the likely CG of the model. Well, they were good for the yaw/roll coupling stability aspect, but were not contributing enough to pitch stability.

And having said all of the above.... how to make a totally finless shuttle model stable? Many years ago I would have said that was not even possible. But a high School Group in Florida got one to fly without fins. Max Q posted a couple of photos in message #33. They must have had an extremely forward CG for it to fly stably. Am even at that I was surprised it was stable in yaw without any yaw/roll coupling problems. One thing of note that they did was that the SRB’s were made out of foam so they were so lightweight that they not only helped with keeping overall mass low and requiring less noseweight, but when they sepped those SRB’s, they were so light they just floated down, with no need for any timers or chutes.

- George Gassaway

https://forums.rocketshoppe.com/attachment.php?attachmentid=17047

 

[ben_ullman]

Well, I do plan to make a boiler plate model in the scale that Jim is making the orbiter. That way I can try the stability and see what works. So what you are saying is the 3 keys to finless flight is: lightweight, motors at the right angles to intersect CG, and even thrust (obtainable with me doing some EX testing). I think I can make that work. With controllable surfaces I think it could help to flightly pitch the model as needed on the way up. It may not do much but anything could help!!

Ben

 

[MaxQ]

Wealth of information here in George's postings.
Bears re-reading.

The two comments that caught my eye.........

<This is why it is key to make *EVERYTHING* lightweight.>

The two large Little Joe scratchbuild scale projects I've done were done in part due to my own desire to explore that region where high power meets lightweight structure, and the rocket survives the flight (plus I just like the look of those rockets).

It certainly doesn't hurt to try and do a project of lightweight materials. It is a little easier on the wallet in any case.

Yeah...we like the wow factor of big motors, sure. However........
The vicious cycle of using more/bigger motors merely for bigger motors sake begins that vicious cycle of needing stronger (read: heavier) building materials and more weight as a result, and then more motor to deal with the additional weight etc. If anything can be taken from traditional NAR competition it is the extent to which those guys can push the envelope to increase performance, w/o resorting to power for power's sake. Which leads to the next statement....

<The far too typical &#8220;if it is too heavy then double the power&#8221; thinking does not work well here (actually that is never a good excuse for overkill fabrication, but a project like this is makes it more critical than almost any other project type).>

I subscribe to an approach where you do some fine tuning and use motor power commensurate with the weight of the structure...and not beyond that.

Particularly when doing scale models...I mean...what's the point?
Speed?

Nothing looks sillier to me than a scale model shooting off like it was a Sprint ABM missile.....unless of course it is a scale model OF a Sprint ABM missile.

Granted...we have to make some compromises since we need some measure of speed to make our primitive model guidance systems...(namely the fins) aerodynamically effective.

Thrust in proportion to the weight, and weight not in excess of what is needed to do the job.

I think that is where Ben was going when he had the thought of toning down the thrust curve when he mentioned a moonburning "M"...

But before he gets there with motors that large, and motors in the scale locations, AND "no fin" area at all...there would be much work to be done.

 

[georgegassaway]

The vicious cycle of using more bigger motors merely for bigger motors sake begins that vicious cycle of needing stronger (read: heavier) building materials and more weight as a result, and then more motor to deal with the additional weight etc.

unfortunately I&#8217;ve seen some projects where first it was built typically HPR-style over-heavy heavy to begin with. And then when they realized the intended motors would be too little for the too-heavy model, then the engine power was doubled, but then that added more weight to the tail so of course it needed more noseweight and......

I mean, you are right that at least some try to build light and then want to use motors so powerful that they have to beef the rocket up. But I&#8217;m afraid the ones that build too heavy from the start far outnumber those who build light from the start and choose the most appropriate motor (actually good motor choice goes hand in hand with these types of things).

For example see that recent thread on the best/biggest V-2. I was almost slamming my head against the keyboard reading that 3 pound 4&#8221; V-2&#8217;s &#8220;flew OK on a G&#8221;, as contrasted to flying an Estes V-2 Maxi on an E15 to the same altitude as a G, or upgrading the Estes V-2 Maxi to fly far better on a G than any 3 pound (or 2 pound) 4&#8221; V-2 could.

Many years back, I built a 7&#8221; diameter Little Joe-II, at 1/22 scale, about 4 feet tall. Without motors, but with noseweight, anyone want to guess what it weighed? And how many N-sec did it need to fly to 800-1000 feet? I will admit that the boilerplate for it was my first Level 1 rocket, in 1991....... but that might not be useful for me to have mentioned that.

Back to motors, it is not just a n-sec thing. It is a thrust versus mass thing, as to how fast it gets going. If a person built a shuttle strong enough to hold up to motors that will jam it into the sky at 400 mph....... why is it boosting at 400 mph? It doesn&#8217;t need to go that fast. Not that it is practical to launch a shuttle really slow either, due to weathercocking issues, but it does not need to be boosting ridiculously fast and as a result to be strong enough to hold up to that ridiculous speed. The kind of lesson learned with Boost Gliders, if the glider is designed for a B4, and you boost it on a B6 and it shreds, the problem was not that the glider was too weak, the problem was putting an engine with a lot more thrust than it needed (or was designed for. There are many contest gliders &#8220;rated&#8221; for B4 engines only which will shred on a B6).

But of course most people do not care about too heavy or efficiency, and that is why we get back to things like the 4 inch diameter 3 pound V-2&#8217;s that &#8220;flies OK on a G&#8221; as opposed to a 1 pound V-2 on an E to the same altitude.

- George Gassaway

 

[MaxQ]

What I'm about to say is only based on my peripheral observations...as I was not an NAR competition guy ...in fact, I've only entered a handful of contests locally since my return to the hobby.

But I am very interested in what they (the NAR competition guys) do in the area of design/construction for competition.
Here is why:

The availability of composite propellants and big composite motors in particular has overshadowed the whole hobby.
Not that that's a bad thing necessarily.

But I look back rather nostalgically on some of those early technical publications where people were trying to squeeze every drop of performance out of the building materials at that time and staying within the limits of rocket model weight and the rather narrow selection of smaller motors then available - just to achieve a Mach flight, or a go a mile high.

There was diligent effort in those days on the part of rocket hobbyists, and some real innovation.

Those propellent limits and overall model weight limits of that day are gone (except for the people still engaged in the traditional NAR competitions)...and that's not a bad thing...it has gotten a lot of people back into the hobby (me for one) and has made a lot of interesting things possible that were not before.
And I have to admit, the reason I got back into the hobby (the first of two BARs for me) was the arrival of the mighty "D" motor, and the subsequent composite propellants. (yes...I have a power junkie gene in me too).

But it was those very limits that made you approach design of a rocket project in an entirely different way than we do now.
That was very apparent to me when I read this thread this week.

It was kinda like deja Vu all over again....reminded me of something, it was around 1983...I was confronted with these very issues...I was attempting to do a space shuttle model myself after seeing Luther Hux do his thing with his airdropped 1/72nd scale shuttle, and after hearing Doug Pratt suggesting someone might be able to launch it with rocket motors...the "BIG"- E-60 at that time.

Folks still want to do it..(geeez...I still want to do it!) and yet the design problem is still the same but the approach is different...enter big motors.

...it seems to me that it has become all too easy these days to just "put a bigger motor in it"....to do what once took real thought and design consideration.
I'm not looking down my nose at the whole big motor aspect of the hobby, it is pretty darn cool.

But asides from the "composite structural materials" part of the hobby (carbon fiber and other stuff like that) ...where strength and light weight are the goal...I think there is a part of the design aspect of the hobby that has just been bypassed entirely these days - an aspect that newcomers won't nescessarily see or experience.
There is a lot of gravitation to the wow factor/big motor part of the hobby.

I'm somewhat predisposed to it myself...probably because we were limited for so many years before Tripoli was formed.
But there is something of those early days when those very limits were in place that has caused a lot of people to think
about design entirely differently, or to be motivated entirely differently.

I'm not for those limits at all in any way...but I think that the design process benefited from the effect those limits imposed.

PS. The weight of that 7 inch Little Joe you did, George?....hmmmmm ( I can only venture a wild guess....2.8 lbs?).

Oh yeah...BTW: I apologize for totally hijacking this thread.

 

[MaxQ]

Well, I do plan to make a boiler plate model in the scale that Jim is making the orbiter. That way I can try the stability and see what works. So what you are saying is the 3 keys to finless flight is: lightweight, motors at the right angles to intersect CG, and even thrust (obtainable with me doing some EX testing). I think I can make that work. With controllable surfaces I think it could help to flightly pitch the model as needed on the way up. It may not do much but anything could help!!

Ben

<3 keys to finless flight is: lightweight, motors at the right angles to intersect CG, and even thrust (obtainable with me doing some EX testing)>.

If by Ex testing you mean ...Ex motors:

Just thought I'd mention that "Even thrust curves" in the motors doesn't necessarily mean Ex at all, unless that is just part of the route you choose to take.

I would think that choosing matching thrust curves within the selection of "commercial" motors that are available, would allow you to concentrate on the structural design part of the task...but then - I know how much you like Ex.

Maybe you can actually achieve matching thrust curves in more than one EX motor at the same time..but it will add to the exercise.

As I read it...going finless - asides from attention to the weight...requires attention to the distribution of that weight and the location of those CGs and CPs will also fit somewhere into this exercise...

I believe that if fins are not going to be there when this thing takes off, then something will have to be there to take the place of them.

IIRC...in three examples I'm aware of, that thing was active RC contol, adequate control surface area to effect that control, and adequate pilot reaction time.

a- the Fla Univ. HS shuttle
b- Andy Woerner's shuttle
c- Rolf's Shuttle over in Germany

I've only seen video of b & c.

Here's the vid of c...

Judge for yourself how fast you'd have to be (hand eye coordination) to get that "stack" back under control.....all the while worrying about what may need to be done with the orbiter glider if something unwanted should occur...like a suden turn towards the ground of the stack at high speed.

https://www.rolfstabroth.de/Hobby/M... Scalemodell/Shuttle Flight/Shuttle Start.wmv

 

[ben_ullman]

dont they make heli gyros? I was thinking someting along those lines to help keep it stable.

What I was reffering to using research was:

I would like the classic white in the SRB and blue in the SSME's. So I could use test data to get them to burn relativally close. Obviously the SSME's will burn longer but if I use BATES config to get it off the ground then the moon burn kicks in for the SSME's it should be relatively close. Thats where the MDRA test stand will come in handy.

I am serious too, if you are making that (1/48th? 1/96th?) Orbiter I would love to make a stack to fly with it. Then use that as a test bed for a larger model.

Ben

 

[luke strawwalker]

unfortunately I’ve seen some projects where first it was built typically HPR-style over-heavy heavy to begin with. And then when they realized the intended motors would be too little for the too-heavy model, then the engine power was doubled, but then that added more weight to the tail so of course it needed more noseweight and......

I mean, you are right that at least some try to build light and then want to use motors so powerful that they have to beef the rocket up. But I’m afraid the ones that build too heavy from the start far outnumber those who build light from the start and choose the most appropriate motor (actually good motor choice goes hand in hand with these types of things).

For example see that recent thread on the best/biggest V-2. I was almost slamming my head against the keyboard reading that 3 pound 4” V-2’s “flew OK on a G”, as contrasted to flying an Estes V-2 Maxi on an E15 to the same altitude as a G, or upgrading the Estes V-2 Maxi to fly far better on a G than any 3 pound (or 2 pound) 4” V-2 could.

Many years back, I built a 7” diameter Little Joe-II, at 1/22 scale, about 4 feet tall. Without motors, but with noseweight, anyone want to guess what it weighed? And how many N-sec did it need to fly to 800-1000 feet? I will admit that the boilerplate for it was my first Level 1 rocket, in 1991....... but that might not be useful for me to have mentioned that.

Back to motors, it is not just a n-sec thing. It is a thrust versus mass thing, as to how fast it gets going. If a person built a shuttle strong enough to hold up to motors that will jam it into the sky at 400 mph....... why is it boosting at 400 mph? It doesn’t need to go that fast. Not that it is practical to launch a shuttle really slow either, due to weathercocking issues, but it does not need to be boosting ridiculously fast and as a result to be strong enough to hold up to that ridiculous speed. The kind of lesson learned with Boost Gliders, if the glider is designed for a B4, and you boost it on a B6 and it shreds, the problem was not that the glider was too weak, the problem was putting an engine with a lot more thrust than it needed (or was designed for. There are many contest gliders “rated” for B4 engines only which will shred on a B6).

But of course most people do not care about too heavy or efficiency, and that is why we get back to things like the 4 inch diameter 3 pound V-2’s that “flies OK on a G” as opposed to a 1 pound V-2 on an E to the same altitude.

- George Gassaway

AMEN and amen, George!!!! I agree WHOLEHEARTEDLY...

At the risk of raising the ire of HPR afficianados (of which I'm an admirer, BTW) I think the capability to just 'shove a bigger motor in' has made a lot of people rather lazy in their optimization of design and building technique... When power was limited, folks had to work to wring the most performance out of the least weight and fixed amount of available power-- just like REAL rocket scientists have to do... figure out how to get the maximum strength out of the materials for the least weight. The ability to shove a bigger motor in just throws all that out the window.

I've seen John Pursley's work-- his ultra-lightweight 1/64 plywood tubes are absolutely amazing... now he's working on some stuff making tubes from Depron cooked to shape in the oven...

I saw the prototype tubes for a model he's building... I won't say what but it's a very popular scale project... and his model, when completed, would be what I'd typically expect to see launched at Black Rock or someplace like that due to the massive HPR engines a model that size would require. He's building it SO light, working from the experience he's gained in making super-lightweight but strong components, so that it will fly on MPR engines... we're talking 2 G's here AT MOST...

I'm sorry, but I don't see the attraction of building rockets strong enough they rival armor-piercing rounds and then shoving the biggest motor you can into them. To me, that's no different than the kids that used to shove C motors into mosquitoes or scouts 'just to see what would happen'... the only difference is the breathtaking expense, and if anything goes wrong, you have an INFINITELY more dangerous object moving at MUCH higher speeds and carrying INCREDIBLY much higher amounts of kinetic energy heading for things and folks you don't want it to, that is precisely designed NOT to break, instead of demolishing itself absorbing it's own impact energy instead of perforating or demolishing what it smacks into...

Sorry, but IMHO, massive overbuilding is NOT real rocketry, no matter how big the motor happens to be... OL JR

 

[Dr.Zooch]

I am looking for either balsa or plastic nose cones for a space shuttle model that will have the external tank based on a BT-60 tube and the SRB's based on BT-20 tubes.

Does anyone know of a source for these nose cones?

Just FYI- The cones used in my kit are from BMS- The SRBs ar BNC20Y and the ET is custom made for me by BMS to a line drawing of the Shuttle ET. When I was designing the kit I just happened to notice that the BNC20Y had almost the same profile as the SRB cones.

 

[MaxQ]

<snip>


Many years back, I built a 7&#8221; diameter Little Joe-II, at 1/22 scale, about 4 feet tall. Without motors, but with noseweight, anyone want to guess what it weighed? And how many N-sec did it need to fly to 800-1000 feet? I will admit that the boilerplate for it was my first Level 1 rocket, in 1991....... but that might not be useful for me to have mentioned that.

<snip>

- George Gassaway

So, George...I'm dying to know...what was the weight (I know what the motors/NS were)....

 

[MaxQ]

dont they make heli gyros? I was thinking someting along those lines to help keep it stable.

What I was reffering to using research was:

I would like the classic white in the SRB and blue in the SSME's. So I could use test data to get them to burn relativally close. Obviously the SSME's will burn longer but if I use BATES config to get it off the ground then the moon burn kicks in for the SSME's it should be relatively close. Thats where the MDRA test stand will come in handy.

I am serious too, if you are making that (1/48th? 1/96th?) Orbiter I would love to make a stack to fly with it. Then use that as a test bed for a larger model.

Ben

Im serious too.

Regarding the Heli gyros, well I flew an RC heli once and that was enough for me.
As for adapting those gyros for a Space Shuttle project...maybe someone is out there doing it....good luck on that one.

As for the R&D on a realistic stack of shuttle with motors in scale locations AND finless....well,,,,if anything,
it will be a boiler plate mock up of the orbiter when it comes to flinging this orbiter up on "stack" with a bunch of motors ....wondering what the outcome might be.

My 1/48th orbiter required a lot of hand carving on blocks of balsa wood and a degree of artistry...(that nose on the "real thing" looks different from each angle when you view it ....really weird to figure out).

So I won't be risking this orbiter for anything but a sure thing (as sure as I can get it - which isn't necessarily a sure thing)

I have delayed finishing and covering this shuttle since I was thinking of making solid male mold copies of both the nose and OMS pods - for pulling vacu form copies later...(I'd rather not have to carve balsa wood blocks again to make new ones in case of an untimely event).

BTW: the yellow ET looking thing is not an Ext. tank...it is my upscale 5.5 " diam. Fatboy for comparison..along with a G-80SU motor, just to put it in perspective.......

 

[ben_ullman]

Im going to come out and tell you, that profile on the nose just doesn't look right Not sure why but it doesn't look right. Maybe its lacking the black and decals. Do like Rolf did (the German guy) he interlocked a vertical and horizontal piece of wood cut to the rough profile. Filled the ares with foam. Finished carving and fiberglassed it. Simple and light!

Ben

 

[MaxQ]

Well there isn't any question that it is missing the black and white decals around the windows, so that's not a maybe....it is.

Will they help the appearance...hmmm.
I think so. I sure hope so...

Yeah...frankly I wasn't real happy with the way it looked either...the nose might need to a tad more pointy, and longer, and the cockpit cabin needs to stick up more.

What was apparent to me when I got photos on line and looked at plans I had - the head on views of a shuttle in many photos look very broad and flat, while from the side view (profile) it has a cockpit area that kinda sticks up, bulbous like.
Seemed almost at cross purposes with itself.
How can the cockpit stick up in a side view in profile and then look so broad and flat in another...when carving I would get one view looking pretty good, then check the other view and try to match that view and it looked better for that but not the other.
I obsessed over that quite awhile.

No plastic model I've seen actually captured that head on view accurately either.
But I think everyone pretty much knows the side view (profile view) intuitively.

As for the construction method, this was built from a set of plans so I wasn't anxious to deviate from the original plans and change the construction method to the cross sectional method Rolf used.
Even with that..., you have to carve it to shape to finish it...basically use some artistic cutting in the right places to fill in the blanks so to speak...although one being from foam,(Rolf's) and the other being from balsa wood (this one).

So in the final analysis I'd be back to where I was either way...carving something to look like a shuttle.

Except I'd be using the two view external templates from the plans - instead of the two piece internal cross sections as you mentioned - to carve to.

Since I'm not entering scale FAI, I'm not going to fret much over it.
Most people know what it is at first glance...just like most people knew that Dan Michaels had an Honest John at Red Glare ....despite the fact that it that looked pretty funny and odd, stretched to the length the way it was.


In the end, it's going to serve my purpose .............
If I have any energy left maybe I'll try the Rolf method you mentioned....what was it to be...1/20th scale? =gasp=


Hey...moderator...think maybe it's time we got booted off poor JRThro's thread? LOL

 

[georgegassaway]

I wrote:
>>>>
Many years back, I built a 7&#8221; diameter Little Joe-II, at 1/22 scale, about 4 feet tall. Without motors, but with noseweight, anyone want to guess what it weighed? And how many N-sec did it need to fly to 800-1000 feet? I will admit that the boilerplate for it was my first Level 1 rocket, in 1991....... but that might not be useful for me to have mentioned that.
<<<<<

So, George...I'm dying to know...what was the weight (I know what the motors/NS were)....

1.75 pounds. 1.5 for the 7&#8221; Little Joe-II, with lightweight fabric chutes, and 4 ounces of clay noseweight in the top of the Escape rocket tube/nose.

A key to the low weight was the body tube. It was styrene plastic .02&#8221; thick. It was sold in sheets of 17&#8221; x 22&#8221;, so the 22&#8221; defined the diameter of 7&#8221; when curled around and joined, and that resulting 7&#8221; diameter therefore defined the scale factor of 1/22.

The main part of the &#8220;capsule&#8221; was also .02&#8221; plastic, with the upper part of it vac-formed. The aft centering ring (with the 7 holes for the engine mounts) was built up from two pieces of 1/32&#8221; plywood with a balsa core in between them, (I think it was 3/16&#8221; light balsa. That took all of the thrustloads). The upper centering ring was just 1/32&#8221; plywood since all it needed to do was to provide alignment for the upper ends of the motor mount tubes (and define the angled thrustlines for the outer 6 motor tube), not share the thrust loads.

It was powered by a G25 and six C6&#8217;s. Yes, G25, not G80. Even if a G80 existed back then, it would have been overkill, as would a G40 (though a G40 would have been a good candidate for flying on just a G with no C6&#8217;s or other clustered motors). Man that G25 was a great motor......

So, with a G25 (120 N-sec) and six C6&#8217;s (9 to 9.5 N-sec), it did nudge into "H" class for total onboard N-sec. I made it in to a bit of a &#8220;trick&#8221; question when I mentioned level 1, because when I flew a boilerplate (built out of poster paper in one night) in May 1991, the G motor alone earned me Level 1 HPR cert because HPR certs were brand new and the procedure was successfully fly a G in order to cert for Level-1 (actually back then it was called H/I cert, and then J/K Cert. Later it was changed to L1 and L2). So, the clustered C6's (or their N-sec) were not needed for the HPR cert, only the G, but I figured to do both the test and HPR cert with one model and one flight

I had built that model with more power in mind. It could have used six D12&#8217;s in place of the C6's (plus the G25). Also, the Aerotech H45 existed back then, and I made it capable on flying on either an H45 by itself or an H45 and six C6&#8217;s. I am not totally sure the fins would have held up to an H45 and six D12&#8217;s (Well, the fins themselves would have held up, but they plugged in for ease of transport so the plug-in method was the weakest link). But I never got a chance to find out, because on its last flight only the six C6&#8217;s lit, the G25 did not. Those six C6&#8217;s had enough thrust, and the model was light enough, to take the model up at least 100 feet, and then it fell down 100 feet, because the ejection charge was from the G25. Ironically I had plans to later add an R/C ejection to it. I believe if it had an R/C ejection on that flight, 100 feet would have been plenty of altitude to fire it, deploy the chutes, and slow down.

As for other aspects of this thread, including shuttle, I&#8217;ll have to get to them later. I visited with friends today, and will be doing the same Friday.

Pics below:
- 1/22 Boilerplate, on G25 and six C6&#8217;s.
- Real model right after it&#8217;s crash.
- The remains of that model. The main &#8220;Joe&#8221; body survived intact, but most of the fins broke off their plug-in attachments. The Apollo parts were smashed. In this pic, for comparison, a Quest MicroMaxx model, and a 1/100 model I made of A-002.

- George Gassaway

 

[MaxQ]

1.75 pounds.

!


That's something........really something.

 

[ben_ullman]

I think its the length. You posted that up close view and it looked ok but could use like another .5" -1" of lengt to make it just right But im not complaining

EDIT!! NOPE! Its the cockpit. It comes down at a gradual angle. I looked at Georges drawings. The cockpit needs to come sort of stright down then move into the nose curve.

for reference: https://homepage.mac.com/georgegassaway/GRP/AOL/NARshuttle/Shuttlesideview.GIF zoom in.

Ben

 

[JRThro]

Hey...moderator...think maybe it's time we got booted off poor JRThro's thread? LOL

MaxQ, I don't mind at all. This is great stuff!
op:

Besides, I found a source for the cones I need. Hopefully they'll be arriving today or tomorrow.

 

[ben_ullman]

MaxQ, I don't mind at all. This is great stuff!
op:

Besides, I found a source for the cones I need. Hopefully they'll be arriving today or tomorrow.

haha Shuttle Smuttle its all the same info

MaxQ you better enjoy carving! I am working on making an AutoCad version of the shuttle, in 1/20th I need to wait till I go back to school to draw a 3D version of the orbiter. I am a little slow with Inventor so it may take me a few weeks.

Ben

 

[MaxQ]

haha Shuttle Smuttle its all the same info

MaxQ you better enjoy carving! I am working on making an AutoCad version of the shuttle, in 1/20th I need to wait till I go back to school to draw a 3D version of the orbiter. I am a little slow with Inventor so it may take me a few weeks.

Ben

Foamcore and foam is cheap....

My time isn't.

 

[ben_ullman]

Foamcore and foam is cheap....

My time isn't.

:roll:

Ben

 

[stantonjtroy]

I too have been poking around with this same idea for a few years now. The problem with the gyros is they slave an actuator servo to a given input ( I flew R/C for a number of years). The only way to get it to work would be to have it slave and stabalize some form of active guidance such as aerodynamic flight surfaces or a gimbaled motor. Possibly guidance vanes in the plume ala V2/Redstone. Perhaps using the control surfaces on the orbiter to control the trajectory on the way up. Given the difference in C/G from the full stack and the orbiter alone, The reactive force created by the inputs would differ between the two configurations. It would take some test flights to figure how everything reacts (and probabily crunch a few boilerplates) but it is doable. One of the engineers I work with has been playing with this very Idea.
FWIW

 

[MaxQ]

I too have been poking around with this same idea for a few years now. The problem with the gyros is they slave an actuator servo to a given input ( I flew R/C for a number of years). The only way to get it to work would be to have it slave and stabalize some form of active guidance such as aerodynamic flight surfaces or a gimbaled motor. Possibly guidance vanes in the plume ala V2/Redstone. Perhaps using the control surfaces on the orbiter to control the trajectory on the way up. Given the difference in C/G from the full stack and the orbiter alone, The reactive force created by the inputs wilol differ between the two configurations. It would take some test flights to figure how everything reacts (and probabily crunch a few boilerplates) but it is doable. One of the engineers I work with has been playing with this very Idea.
FWIW

Well, at least you have described a methodology to adapt them...either for aerodynamic control surfaces or gimballing the motor thrust.

That guy on Ebay selling the shares for his fiberglasssed run of shuttles put it forth with no mentiion of how to adapt it.

I believe there were gimballed motor "finless" rockets featured either in High Power Rocketry or Extreme Rocketry several years ago....