What Are Our Motors "Missing"?

[deandome]

I've been looking over pretty much all of the missiles in US History (!!) to look for build ideas & just for fun: https://www.designation-systems.net/dusrm/index.html

In doing so, I see that a lot of small rockets...new & old, no bigger & even smaller than what we launch...were/are hitting 30-50 MILES in altitude pretty regularly. The Arcas only weighed 75 lbs & it took 10 lb. payloads to 32 miles. Look at this modern one, the whole thing weighs 65 pounds & it hits 50 miles :eyepop: https://www.designation-systems.net/dusrm/n-11.html

That begs the question...what the hull is in those propellants that we don't have in ours? I thought that our ACP stuff was pretty much military grade, or at least very close to it. But I remember that guy who hit the 'record' of about 100K feet several years ago...his rocket weighed HUNDREDS of pounds, and it could only go 1/2 as high as an Arcas.

I could see how maybe the 'recipe' for current propellants might have some secret goodies, but I'd think we'd be able to match what, say, the Arcas used.

What gives?

 

[shreadvector]

The high power rockets you are bemoaning are built out of non-aerospace materials and use re-loadable motors for the most part. Recovering the casing and re-using it means a thicker wall and heavier motor. And the rockets are often built like a civil engineer designed them, not an aerospace engineer.

Aerospace vehicles are not usually made from parts obtained at Home Depot.

 

[patelldp]

A couple things:

• Thousands or millions in Research and Development
• Access to state of the art materials and fabrication
• No regulations on materials or processes, as well as expendable parts with a large area for (intentional) crash landings.
• Smart people that optimize every little bit of these things
• Did I mention a lot of money?

 

[mikec]

Look at this modern one, the whole thing weighs 65 pounds & it hits 50 miles :eyepop: https://www.designation-systems.net/dusrm/n-11.html

The dart gets to 50 miles. The booster has 52500 N-s total impulse (that's a P motor) and the dart weighs 6 kg max. Total mass is 29 kg. The booster has no recovery gear and is obviously single-use.

I'm fairly sure that this could easily be duplicated by amateurs, but building stuff that deliberately lawn-darts is kinda outside of the rules.

 

[r1dermon]

just looking at the booster compared with a cessaroni O motor...a few differences are...


(without knowing the darts booster motor specifications)

the booster is much longer than an O motor casing, which is 31.6" long, as opposed to the darts 10ft+ booster length.

(the booster on the dart would fall into a small O range for impulse, based on 11,692x2.1 seconds of burn time.

the cessaroni O casing is 161mm, while the darts booster is 4", only 101mm wide.

these systems are optimized from tip to tail to do a specific application. the nozzle geometry was likely optimized for that specific application, to attain the maximum efficiency out of every ounce of thrust.

the motors which are commercially built are not optimized for one single application, rather, they are suitable for many different applications.

looking at some members record attempts using mid power, and small high power motors, it's safe to say that, with skill and time, you can get some impressive results using the materials available on the internet, and the commercially available and certified motors.

i'd guess the biggest difference between hobbyist vehicles is in the R&D department. because while you may spend a lot of time designing your rocket, the people that designed the dart, did it for a paycheck, spent weeks or months on it, and had a team of other professionals working on the same project. this is what will always separate a hobby apparatus, from a professional one.

 

[troj]

The government can also use much more energetic goodies in their propellants than we do in ours. Remember, they're spending your money, so cost isn't as much an issue.

My guess is they also tend to do things like "airframe is the motor case" and case-bonded propellants.

-Kevin

 

[cjl]

A large part of the difference is that they do not waste any mass or space on a recovery system. The motors really aren't significantly better, they just don't have to worry about the safety aspects as much. In addition, many amateur rockets really aren't as aerodynamic as they could be.

 

[r1dermon]

A large part of the difference is that they do not waste any mass or space on a recovery system. The motors really aren't significantly better, they just don't have to worry about the safety aspects as much. In addition, many amateur rockets really aren't as aerodynamic as they could be.

not countering the argument...just wondering...

it'd be interesting to see how much the avionics, electrical equipment, test equipment...etc...all the onboard "goodies" weigh on one of these vehicles...in comparison with a similar mass amateur rocket equipped with a recovery system.

 

[JDcluster]

The ARCAS is a minimum diameter rocket, most of it's mass was of the propellant.
https://www.astronautix.com/lvs/arcas.htm

It was also launched from a breech in some configurations.
https://www.designation-systems.net/dusrm/n-6.html

It's booster had 7,800lbs of thrust for 2 sec then an upper stage burn time of 29 sec and you'll get 32miles.

If you can mass produce 86% solid propellant your rockets would fly higher also.

JD

 

[MClark]

The motors we use have heavy cases.
The Super Loki the case is about 25% of the motor.
See, https://www.ahpra.org/34.bmp (I scanned this entire book)
In normal hobby type motors the case is 50% and propellant 50%.
There is no reason motors can not be made light, just that they are going to be single use.

Mark

 

[deandome]

The SUPER Arcas was breech launched & had a booster (and hit 62 miles).

The 'regular' one was one stage, 4.3" diameter x 7' tall rocket launched from a resting position, and it hit 32 miles. Total weight was 65 lbs, and given a 10lb payload & guessing at least 10-20 lbs for the airframe & electronics, the propellant weight was probby about 30-40 lbs.

Compare to the 'record' flight of Ky Michelson's team...they hit 50 miles, but it was a FIVE-HUNDRED POUND rocket!! Then there was this one: https://www.amusingplanet.com/2011/10/amateur-rocket-launch-reaches-121000.html

It is constructed of aluminum, and lots of record attempts are being made w/aluminum and/or carbon fiber, not 'Home Depot' stuff.

No...there are some fundamental differences in the propellants here, and I don't think that the recipe for, say, the Arcas' propellant is top secret or anything.

I kinda thought our stuff was near the max 'energy density', or at least 80% or so of what the top stuff has...but I'm thinking it's not even 50% of what they were using in the 1960s.

Am I wrong?

People

The ARCAS is a minimum diameter rocket, most of it's mass was of the propellant.
https://www.astronautix.com/lvs/arcas.htm

It was also launched from a breech in some configurations.
https://www.designation-systems.net/dusrm/n-6.html

It's booster had 7,800lbs of thrust for 2 sec then an upper stage burn time of 29 sec and you'll get 32miles.

If you can mass produce 86% solid propellant your rockets would fly higher also.

JD

 

[shreadvector]

Yes, you are wrong.

The High Power Rockets are not engineered by Aerospace Engineers.

Just because they use aluminum, does not mean they use it wisely. Or that they even use or have access to the correct alloys.

That is why most of these missiles and rockets are ITAR items. Google that term if you need to.

The SUPER Arcas was breech launched & had a booster (and hit 62 miles).

The 'regular' one was one stage, 4.3" diameter x 7' tall rocket launched from a resting position, and it hit 32 miles. Total weight was 65 lbs, and given a 10lb payload & guessing at least 10-20 lbs for the airframe & electronics, the propellant weight was probby about 30-40 lbs.

Compare to the 'record' flight of Ky Michelson's team...they hit 50 miles, but it was a FIVE-HUNDRED POUND rocket!! Then there was this one: https://www.amusingplanet.com/2011/10/amateur-rocket-launch-reaches-121000.html

It is constructed of aluminum, and lots of record attempts are being made w/aluminum and/or carbon fiber, not 'Home Depot' stuff.

No...there are some fundamental differences in the propellants here, and I don't think that the recipe for, say, the Arcas' propellant is top secret or anything.

I kinda thought our stuff was near the max 'energy density', or at least 80% or so of what the top stuff has...but I'm thinking it's not even 50% of what they were using in the 1960s.

Am I wrong?

People

 

[deandome]

There's one launch from about 5-6 years ago where a real sophisticated homebuilt alum rocket hit about 98K' (it had a conical nose, beautifully machined everything...help me out here!). Anyways...they poured & cast, I believe, over 100 lbs of propellant directly into the booster's airframe, which is what the military/research rockets do.

Again, the Arcas was only a 4.3" diameter, 7' tall rocket weighing 64 lbs...that'd be considered TINY for one of our level 3 rockets. Arcas were cheap, low-tech stuff compared to 'real' missiles of the time.

The motors we use have heavy cases.
The Super Loki the case is about 25% of the motor.
See, https://www.ahpra.org/34.bmp (I scanned this entire book)
In normal hobby type motors the case is 50% and propellant 50%.
There is no reason motors can not be made light, just that they are going to be single use.

Mark

 

[ClayD]

yeah.. you should do some google searches on sounding rockets and missile propellants.
(you wont find the formulas) but most of them are NOT HTPB based... if they are they have a ~forumula~ we dont typicaly use or allow in hobby motors.

https://www.roxelgroup.com/images/products/roxel_products.pdf

Some of the HTPB propellants that are simillar, are used for longer burn durations i would think... (where you dont want 40kns in 2 seconds... but 9)

 

[deandome]

I'm now mostly interested in the Arcas in comparison to our stuff...1959 technology, designed to be super CHEAP (not state of the art), using a STEEL booster airframe with an end-burning motor kicking out 300 lb thrust for 30 seconds, giving a total-impulse of 9000 lb/seconds.

I got that here (you all WILL dig this!), pgs 14-19: https://www.dtic.mil/cgi-bin/GetTRDoc?Location=U2&doc=GetTRDoc.pdf&AD=AD0458308

This is the breech-launch version, which was hitting 300,000 feet, the same rocket hit about 200,000' launched normally. Oh, it did indeed have a sophisticated recovery system for the payload.

I don't think we could come CLOSE to that altitude using our propellants in a 64 lb. EXP rocket with a one piece alum airframe/casing. Many of the top hobbyists are indeed aeronautical engineers/rocket scientists. And I didn't think there are any limitations to what people are 'allowed' to use at EXP launches ala LDRS, BALLS, etc.

But that is indeed the crux of my question...you're saying these propellants ARE different. Great...how are they different? Why are they different? I'm sure they're much "more different" now, but were they really using stuff FIFTY years ago that was 2-3x 'hotter'* than what we have now? (* "total impulse per-pound").

I'd LOVE to hear from Gary and/or Mr. Cesaroni tell me/us what the differences are, and if/why we're prohibited from using certain formulations (that aren't any more toxic/dangerous than ACP...just more powerful).

 

[MClark]

This book
https://www.amazon.com/dp/0967410606/?tag=skimlinks_replacement-20
is a must have for anyone interested in sounding rockets.

 

[Reinhard]

Even the regular ARCAS was launched from a "Closed-Breech Launcher with Auxillary Gas Generator". Sounds more like a cannon to me. Competition fliers use a similar, but simpler technique (piston launcher) to maximize altitude.
The motor is remarkable: 4.5" diameter, 43KNs, 29s burntime (~P1500). One of the more interesting features is the apparently really well working insulation - asbestos filled phenolic resin. Good luck finding a supplier for that these days. However, this enabled the really long burn time in an end burning configuration. A side effect of this is the maximized volumetric loading of the motor.
The propellant has a high, but not an outlandish ISP: 230s (CTI E75: 242s IIRC). The propellant has to be naturally fast, or otherwise combined with some tricks like embedded wires to achieve ~1500N in an 4.5" end burner. As a rough guestimate it is about 3.5 times as fast as AT W9, which delivers about 350N in an endburning 98mm motor.
The casing is made of steel, which allows for a lighter motor despite its higher density because of its high weight specific tensile strength *1). Steel doesn't loose strength as fast as aluminum when it is heated up.
Combined with the launcher, this made for an interesting flight profile: initially high acceleration (~125g) followed by a long an gentle sustained phase. Burn out was at about 50kft, at around 3000fps.
Only the payload was recovered, which decreases the size of the recovery system.

A frangible version of the ARCAS was investigated, with a fiberglass casing. Even this worked with the extreme long burn time, which makes me wonder what kind of resin was used. The frangible version used high explosives, to destroy the booster some time after payload separation to ensure only "harmless" debris was coming down. Interestingly it appears that even with 60s era radar they were able to follow the debris cloud of an mostly fiberglass rocket (metallic paint?).

A host of information can be found at www.dtic.mil - 644 search results for ARCAS alone. Be prepared to spend lots of time reading the reports.
https://www.dtic.mil/dtic/tr/fulltext/u2/437681.pdf
https://www.dtic.mil/dtic/tr/fulltext/u2/630932.pdf (big file, loads slow)


Reinhard

*1) Aluminum is usually a good material for lightweight construction if the geometries are adapted accordingly but in certain cases, like pressure vessels and cables, pretty much the only thing that is interesting is tensile strength per weight. Steel is quite good in this regard.

Edit: I type to slow, you've already found half of the content of my posting.

 

[cjl]

yeah.. you should do some google searches on sounding rockets and missile propellants.
(you wont find the formulas) but most of them are NOT HTPB based... if they are they have a ~forumula~ we dont typicaly use or allow in hobby motors.

https://www.roxelgroup.com/images/products/roxel_products.pdf

Some of the HTPB propellants that are simillar, are used for longer burn durations i would think... (where you dont want 40kns in 2 seconds... but 9)

That's true that many missiles do not use APCP, but most of the non-AP based propellants are actually worse than APCP in performance. Missiles use them mainly for their low smoke output, since that is a rather important factor when you are using a missile in a fight. You don't want a smoke trail leading back to where you are. However, APCP/HTPB propellants are really quite good in efficiency, and only fall behind high energy composite propellants among the current crop of solid fuels (which are used in things like modern ICBMs). As stated above, the biggest factor is the mass ratio. Our motors and rockets in general don't have a very good mass ratio, and even the best probably don't exceed 50-60% (I have an N5800 altitude rocket on the drawing board for example, and even with as much weight shaved off as I dare, it's looking like it'll be about 45-50% propellant mass fraction, which isn't very good compared to many sounding rockets). For comparison, the Arcas had 42 pounds of propellant in a 65 pound rocket, a mass fraction of 65%, and it only had a very slightly larger cross section than my rocket will (since mine is a 4 inch minimum diameter). Having 15% better mass fraction, similar cross sectional area, and a bit more than twice the total impulse does a LOT for performance.

 

[deandome]

All good points...thanks.

But as someone said, our masses are bigger mostly because of reloadable motor hardware. But the record-setting hobby launches (particularly that one I can't friggen recall/link to from about 2005 AAARRGH) don't all bother with that; they pour EXP mixes right into the airframe (or a liner that's lighter than reloadable hardware).

That's true that many missiles do not use APCP, but most of the non-AP based propellants are actually worse than APCP in performance. Missiles use them mainly for their low smoke output, since that is a rather important factor when you are using a missile in a fight. You don't want a smoke trail leading back to where you are. However, APCP/HTPB propellants are really quite good in efficiency, and only fall behind high energy composite propellants among the current crop of solid fuels (which are used in things like modern ICBMs). As stated above, the biggest factor is the mass ratio. Our motors and rockets in general don't have a very good mass ratio, and even the best probably don't exceed 50-60% (I have an N5800 altitude rocket on the drawing board for example, and even with as much weight shaved off as I dare, it's looking like it'll be about 45-50% propellant mass fraction, which isn't very good compared to many sounding rockets. For comparison, the Arcas had 42 pounds of propellant in a 65 pound rocket, a mass fraction of 65%, and it only had a very slightly larger cross section than my rocket will (since mine is a 4 inch minimum diameter). Having 15% better mass fraction, similar cross sectional area, and a bit more than twice the total impulse does a LOT for performance.

 

[MClark]

I see no reason a Loki could not be made.

At my old job we made Super Loki and Viper 3A motors. There was nothing exotic or mysterious about the materials or methods. It was state of the art in 1948 or so. All the drawing are available, it would have to be reformulated to use HTPB because the right polysulfide polymer is no longer made. I have all the casting tooling for Loki, Super Loki and Viper 3A so that would not be a problem, I would consider loaning to some one that had a clue of what they were doing.

One of the issues with hobby HPR motors is they all have short burn times, it used to be you could get 20 second burn motors but now days 5 seconds is considered long. Back when I fired some H & I motors for Kosdon that were long burn, up to 40 seconds. I used Estes type tube and nose cones to make the airframes lighter. They were tube launched and boosted out of the tube by a black powder charge. We had fairly good success but did have one exciting half minute landshark. No altitude data as at that time there was no small light electronics, used time fuse. We did get a near apogee ejections so we were getting the performance we had expected. IIRC we were hitting about 12k with an H motor. Frank had not tried to reduce the weight of the motors yet, we went on to do something else.

I believe a 30 second burn motor using a very light case and airframe could be made with out resorting to exotic/expensive technology. It may not go 50 miles but it would go higher than existing HPR.

Mark

 

[Reinhard]

But the record-setting hobby launches (particularly that one I can't friggen recall/link to from about 2005 AAARRGH) don't all bother with that; they pour EXP mixes right into the airframe (or a liner that's lighter than reloadable hardware).

Are you refering to the CSXT space shot in 2004?
https://ddeville.com/derek/CSXT.htm

Or Gene Nowaczyk's flight to 93k in 2006?
https://www.aeroconsystems.com/Gene_Nowaczyk_Balls2006/balls2006.html

Both of these rockets went the high mass fraction, high ballistic coefficient (for hobby standards) route. The high mass fraction keeps the gravity losses small, the high ballistic coefficient the aerodynamic ones.
This automatically results in relatively big rocket but is somewhat of an brute force method for reaching high altitudes.

Reinhard

 

[deandome]

...Or Gene Nowaczyk's flight to 93k in 2006?
https://www.aeroconsystems.com/Gene_Nowaczyk_Balls2006/balls2006.html
Reinhard

DING DING DING....we have a winner! THANK YOU!!!

That's interesting stuff & what I was getting to; 'our' top performing rockets are really big, but I don't think 'we' have the ability to create a 9' tall, 4.3" diam. 64 lb. rocket with 42 lbs of OUR propellant(s) in a single-use configuration that can hit 32 miles w/a 10 lb payload (or even come close). And I don't think the airframe weight is the reason.

 

[daveyfire]

And I don't think the airframe weight is the reason.

You should take the advice of Mark. And Chris. And Fred. They're right. High tech energetic additives don't buy much in the way of specific impulse - they're there for things like plume signature and burning rate control. If you don't believe them, take this into the research section and I'll be happy to run all the equilibrium calculations you want to see with all sorts of strange, novel additives that we had in the 60s and that we've come up with today.

The difference between a hobby rocket and an Arcas is engineering. An example is Derek's Qu8k rocket and the very similar airframe constructed by the USC group -- Qu8k, built with a 0.25" wall aluminum airframe and an aluminum/graphite nozzle went 120,000 feet. USC's rocket, built with a 0.100" wall carbon fiber airframe, honeycomb fins, a composite nozzle, and a skosh more propellant should go to over 370,000 feet (if it holds together). The vehicles are physically the same size and nearly identical in fin design and nose contour. The only difference is weight.

 

[mikec]

That's interesting stuff & what I was getting to; 'our' top performing rockets are really big, but I don't think 'we' have the ability to create a 9' tall, 4.3" diam. 64 lb. rocket with 42 lbs of OUR propellant(s) in a single-use configuration that can hit 32 miles w/a 10 lb payload (or even come close). And I don't think the airframe weight is the reason.

Have you done the math on the Super Loki boosted dart and the needed Isp and mass fraction of its booster, or is this just idle speculation on your part?

Suppose the booster all-up mass is 23 kg and its mass fraction is 0.9, so 20.7 kg of propellant for 52500 N-s total impulse. That's an Isp of 20.7*9.81/52500 = 259 s. That's high but not absurdly so -- the Isp of Aerotech White Lightning is about 220, IIRC.

 

[deandome]

Simple questions:

1) Could a well heeled, experienced hobbyist create a 1:1 scale model of the Arcas where the airframe/motor liner weighs as much/less than that of the original Arcas? I think the answer is yes, ala the CF/honeycomb/etc. build you mention below. I think they could go much lighter, in fact, than the 15-20 lbs of the old airframe. BTW, I'm not so sure about cjl's statement that a 64 lb arcas had 42 lb of propellant; it had a 10 lb payload, a bunch of insulation, recovery gear, electronics...so the bare STEEL airframe would have to weigh less than 10 lbs...a tall order in a cheap, 1959 rocket.

2) Would said 1:1 scale, 64 lb total-weight clone hit 32 miles with 42 lbs of one of our current propellants?

I don't think so...thus this thread.

You should take the advice of Mark. And Chris. And Fred. They're right. High tech energetic additives don't buy much in the way of specific impulse - they're there for things like plume signature and burning rate control. If you don't believe them, take this into the research section and I'll be happy to run all the equilibrium calculations you want to see with all sorts of strange, novel additives that we had in the 60s and that we've come up with today.

The difference between a hobby rocket and an Arcas is engineering. An example is Derek's Qu8k rocket and the very similar airframe constructed by the USC group -- Qu8k, built with a 0.25" wall aluminum airframe and an aluminum/graphite nozzle went 120,000 feet. USC's rocket, built with a 0.100" wall carbon fiber airframe, honeycomb fins, a composite nozzle, and a skosh more propellant should go to over 370,000 feet (if it holds together). The vehicles are physically the same size and nearly identical in fin design and nose contour. The only difference is weight.

 

[cjl]

Simple questions:

1) Could a well heeled, experienced hobbyist create a 1:1 scale model of the Arcas where the airframe/motor liner weighs as much/less than that of the original Arcas? I think the answer is yes, ala the CF/honeycomb/etc. build you mention below. I think they could go much lighter, in fact, than the 15-20 lbs of the old airframe. BTW, I'm not so sure about cjl's statement that a 64 lb arcas had 42 lb of propellant; it had a 10 lb payload, a bunch of insulation, recovery gear, electronics...so the bare STEEL airframe would have to weigh less than 10 lbs...a tall order in a cheap, 1959 rocket.

2) Would said 1:1 scale, 64 lb total-weight clone hit 32 miles with 42 lbs of one of our current propellants?

I don't think so...thus this thread.

The 42 pound figure comes from a simple calculation, assuming the total impulse and specific impulse values given earlier in the thread. It also sounds about right for a high performance, minimum diameter rocket with no recovery system. Steel isn't necessarily all that heavy if it is used correctly. Yes, it's more dense than aluminum, butt it's also much stronger, so less of it can be used for the same strength.

 

[MClark]

Dave,
Did you write this?
https://www.tdkpropulsion.com/wp-content/uploads/2010/06/WireLitReview.pdf
Or are there other David Reese'

 

[MClark]

Suppose the booster all-up mass is 23 kg and its mass fraction is 0.9, so 20.7 kg of propellant for 52500 N-s total impulse. That's an Isp of 20.7*9.81/52500 = 259 s. That's high but not absurdly so -- the Isp of Aerotech White Lightning is about 220, IIRC.

ISP of Super Loki propellant is 232.
I have the book on them.

 

[Adrian A]

The altitude at which the peak velocity gets done also makes a huge difference. As long as you can get past 30-40k, or better yet, 50-60kft, before the rocket is going really fast, much of the drag loss can be eliminated, allowing even small rockets to work. Check out this graph of the added altitude provided by the 38mm J rocket that went to 22kft when launched at 5400 feet. That same rocket to get to a total altitude over 100,000 feet ASL if launched from 40kft. I think an M-J 100 kft shot would be pretty cool, and I think it's definitely feasible.

https://www.rocketryplanet.com/foru...ghlight=raven+adrian+featherweight#post188032

I wonder if it's possible to get to the space boundary altitude without exceeding O total impulse (class-3 waiver territory)

 

[Lentamental]

Just started work on a project at the University of Vermont to launch a 2 stage rocket from a weather balloon, which should in theory reach the 100km (or 120km depending on who you talk to) line of "space". The preliminary back of the envelope calculations in OpenRocket show something as small as an L staged to a J could get to space. As Adrian is saying, it makes a huge difference where you are going "fast". Traveling 5000ft/sec up at 300,000' and the air resistance is negligible.

We'll probably end up going for something a little bigger than L to J, just to make sure we really do make it to space, but you'd be surprised how easy it is without having to worry about air resistance.