Why can't amateur rockets reach space on an O motor?

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I think a well designed O motor in a "traditional rocket" (no boosted darts or two stages) is capable of 100-150K. That being said I've rarely seen high performance rockets in that size. The mentality seems for those big EX minimum diameters that if you want to go higher, just use a bigger motor, which is a little disappointing. Design smarter, not bigger!

Alex
 
Are our recovery systems really that much heavier than the payload in a sounding rocket? They aren't just going up for giggles (like we are!), they have instrumentation packages.
 
enderw88 said:
Are our recovery systems really that much heavier than the payload in a sounding rocket? They aren't just going up for giggles (like we are!), they have instrumentation packages.
Click to expand...

Instrumentation can be really small. Loki Darts carried basically chaff. Even with actual electronics, they can easily be made much smaller than the volume required for a parachute and deployment system.
 
DizWolf said:
nasa:
_38804205_flagap300.jpg


us:
Ape-man-with-bone-from-Stanley-Kubricks-2001-A-Space-Odyssey.jpg
Click to expand...


hahahahahahahahahahahahahahahahah

Hey Dave,,,,,,,,,,
Das a cheap shot man............
And I for one resemble dat remark.....................

hahahahahahahahahaha

Teddy
 
Aksrockets said:
I think a well designed O motor in a "traditional rocket" (no boosted darts or two stages) is capable of 100-150K. That being said I've rarely seen high performance rockets in that size. The mentality seems for those big EX minimum diameters that if you want to go higher, just use a bigger motor, which is a little disappointing. Design smarter, not bigger!

Alex
Click to expand...

I agree with this, but having worked on a couple of projects like this I've learned that an amateur cannot easily manage the scope required to get to such performance. There is so much time, money and energy required that the optimizing metric, at some point, shifts from wringing every last foot out of the design, to having it "just work". On smaller projects it is easy to push the absolute limits because the there is much less time and materials invested, and you can have it rebuilt in a month or two. On larger projects, rather than take risks which could sacrifice years of work, it becomes easier to just add more propellant and run a more conservative design.

I don't think there is any major technical knowledge we lack, it's just we don't have resources to commit to it.
 
Ethan said:
I agree with this, but having worked on a couple of projects like this I've learned that an amateur cannot easily manage the scope required to get to such performance. There is so much time, money and energy required that the optimizing metric, at some point, shifts from wringing every last foot out of the design, to having it "just work". On smaller projects it is easy to push the absolute limits because the there is much less time and materials invested, and you can have it rebuilt in a month or two. On larger projects, rather than take risks which could sacrifice years of work, it becomes easier to just add more propellant and run a more conservative design.

I don't think there is any major technical knowledge we lack, it's just we don't have resources to commit to it.
Click to expand...

I guess that is why the only successful attempt in the past needed a relatively large team of people.
 
enderw88 said:
Are our recovery systems really that much heavier than the payload in a sounding rocket? They aren't just going up for giggles (like we are!), they have instrumentation packages.
Click to expand...

Yes, we are heavier recovery wise. Many sounding rockets do not recover anything other than payload- the rest come screaming down with recovery gear.
 
I have read the comments but I don't think it's time to give up yet.

Lots have done it before and not all of them experts. There are ways around different issues that can be worked around. Take for instance recovery. We have recovery to prevent accidents upon return to earth. There are other options. Up here in Canada we have something called lots and lots of uninhabited land. Worst you could do is start a forest fire but we already have a few on the go. Or, launch to land at sea, why not. (And with the paperwork required to launch there's time for your design approval).

Andrew
 
Aksrockets said:
I think a well designed O motor in a "traditional rocket" (no boosted darts or two stages) is capable of 100-150K. That being said I've rarely seen high performance rockets in that size. The mentality seems for those big EX minimum diameters that if you want to go higher, just use a bigger motor, which is a little disappointing. Design smarter, not bigger!

Alex
Click to expand...

100-150k ft is only 30-50% of the way to the recognized boundary of space. So design smarter and bigger?
 
ali8bongo said:
I guess that is why the only successful attempt in the past needed a relatively large team of people.
Click to expand...

Exactly. Their goal was to make space, and they had the foresight to recognize that it would be more easily achieved by using a conservative design and off the shelf materials. Rockets magazine April 2012 has a good article written by Derek Deville about the CSXT motor design. His "Qu8k" article also gives a good illustration of how performance is often traded off for simplicity and reliability.
 
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jmattingly13 said:
Two letters: delta v. As Reinhard and Mark K indicated, Isp and mass fractions play a pretty big role in that. Rockets need a certain amount of delta v just to get off the surface and up to 100km. The small mass fractions (ie - mostly not propellant) and the poor Isp of solids makes achieving those high delta v's difficult.
Click to expand...

DeltaV is almost irrelevant especially considering its normal usage; we are talking about altitude not orbital insertion. Interesting to note: many altitude shots aim to limiting velocity to mitigate drag losses especially in the early phase of the flight. I'm confused by the mass fraction and ISP comments. Sea level ISP is not painfully less than most boost liquids and density ISP (and 250+s solid propellant is no mystery), a relevant metric in gravity well flights, is even more so. One of the major advantages of solids is that the mass fraction is incredibly high...

Ethan said:
I agree with this, but having worked on a couple of projects like this I've learned that an amateur cannot easily manage the scope required to get to such performance. There is so much time, money and energy required that the optimizing metric, at some point, shifts from wringing every last foot out of the design, to having it "just work". On smaller projects it is easy to push the absolute limits because the there is much less time and materials invested, and you can have it rebuilt in a month or two. On larger projects, rather than take risks which could sacrifice years of work, it becomes easier to just add more propellant and run a more conservative design.

I don't think there is any major technical knowledge we lack, it's just we don't have resources to commit to it.
Click to expand...

Does it really take that much money to do a bunch of simulations and mathematics to design out mass? No. Mostly its just some creative thought and iteration with plenty of conservatism to make it reliable (like 2x instead of 25x). Do I need a 1400lb quick-link when I could use a knot? Do I need a 4 foot parachute bay when I could fit everything in 6 inches? Do I really need a 20 foot parachute with 3 miles of harness and 3 deployment events for that matter? Can I lay up a carbon fincan that weighs 2 lbs or should I use a weaker, Al can that has 400 bolts coming out of it at every angle that weighs 5?
 
I didn't do an exhaustive study, but according to RASAero, if you could stuff a CTI O8000 motor into a weightless 161mm diameter rocket with 1/16" fins then you might be able to break 150k.

That may or may not be even remotely accurate, but I suspect you'd have to stuff an O motor into a VERY small package to get a low enough drag coefficient to make it to 300k feet. You'd need a specific impulse that was (literally) unbelievably high.
 
The problem is O8000 burns way too quickly. What you want is an O1000, relatively speaking. Get it up to about M1.4 (perhaps a lot lower than that) and then slowly accelerate from there over a long period of time. Dual thrust could be good for this. Increasing the burn time will drastically improve the altitude. If you can make the same total impulse motor burn out at, say, 15 seconds instead of 4 seconds, you might find you get near double the altitude.

In the O range, penalty for being over optimal mass is approximately 1Kft/lb. Mass is less of a driving factor than the total impulse robbed dealing with drag rather than converted to altitude. You want to keep the drag low when down in the higher density air. As the drag drops at higher altitude one can go for more speed as then it is worth having the speed.

Gerald

PS - Splitting the full O into a 2 stage configuration would be better of course, as would a boosted dart.
 
A 13.5lb 4" MD 2-stage with N5800 => O3400 with 1/8" fins sims to around 300K ft if you launch from Balls (4000ft above sea level) but gets really marginal on the stability of the sustainer at high mach.
The other problem is that you're hitting M4.5 at 35K feet (and that's after allowing for the optimal coast between stages) which is also marginal on composites.

If we had high ISP slow burn engines to play with for the sustainer it gets easier.
 
wfcook said:
I didn't do an exhaustive study, but according to RASAero, if you could stuff a CTI O8000 motor into a weightless 161mm diameter rocket with 1/16" fins then you might be able to break 150k.
Click to expand...

Ah yes, but Wildman has not yet released his line of minimum diameter rockets with the new Unobtainium body tube and fins. :D
 
Zebedee said:
A 13.5lb 4" MD 2-stage with N5800 => O3400 with 1/8" fins sims to around 300K ft if you launch from Balls (4000ft above sea level) but gets really marginal on the stability of the sustainer at high mach.
The other problem is that you're hitting M4.5 at 35K feet (and that's after allowing for the optimal coast between stages) which is also marginal on composites.

If we had high ISP slow burn engines to play with for the sustainer it gets easier.
Click to expand...

I can't wait for the build report!
 
Ravenex said:
I can't wait for the build report!
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The sustainer I used is actually my plan for a level 3 rocket so you just might see the top half of it. Probably won't have 1/8 fins though - more like 0.2 once the T2T is done.
 
butalane said:
DeltaV is almost irrelevant especially considering its normal usage; we are talking about altitude not orbital insertion. Interesting to note: many altitude shots aim to limiting velocity to mitigate drag losses especially in the early phase of the flight. I'm confused by the mass fraction and ISP comments. Sea level ISP is not painfully less than most boost liquids and density ISP (and 250+s solid propellant is no mystery), a relevant metric in gravity well flights, is even more so. One of the major advantages of solids is that the mass fraction is incredibly high...
Click to expand...

I disagree with your notion that delta v is irrelevant. While I agree you are not using it to compute orbital maneuvers, it is still a relevant metric of how much energy is required to launch the rocket. In fact, delta v is used in space launch and there are drag, steering, etc. penalties that are applied that obvious depend on how you operate within the atmosphere. It was pointed out earlier that hobby solids have an Isp closer to 212s than 250s, so most liquid engines end up having Isp's 50-100s higher than our solids, which is huge. Mass fraction is independent of propellant composition, rather it is a function of propellant mass and structural/payload mass. Since propellant doesn't dominate the masses of our rockets (well, I guess I don't know what you launch, but I have a sneaky suspicion...) and it tends to make up over 80% of orbital launch vehicles, I'm going to stick with my previous assertions on mass fractions, too.
 
jmattingly13 said:
Since propellant doesn't dominate the masses of our rockets (well, I guess I don't know what you launch, but I have a sneaky suspicion...) and it tends to make up over 80% of orbital launch vehicles, I'm going to stick with my previous assertions on mass fractions, too.
Click to expand...

https://www.rocketryforum.com/showthread.php?42436-4-quot-Min-Diameter-Rocket
https://www.rocketryforum.com/showthread.php?58793-Honey-Badger-2-Build-Thread-and-Flight-to-57k!
https://www.rocketryforum.com/showthread.php?66948-MLP-(HB2-1)-Rocket-Flight-to-63k-ft-M3-9

:D
 
MClark said:
If you want to make a Loki type rocket it would be single use but then nearly all high flying ones are.
The flight hardware would not be too bad as there are no casting or liner tubes, just short insulators at the ends.
The big cost would be the great long mandrill but it would be reused if the configuration stays the same.

As said above recovery weight is the performance killer. In the dart it no issue but a chute on the booster is wasted energy in getting to space. Since the goal is just to get there and not have a real payload like the Loki carried a smaller, meaning lighter, dart can be used. The 1 3/8 dart is ballpark 11 pounds, if a 7/8" dart could hold the required electronics there is 5 pounds that can be budgeted to booster recovery. So if a full O is used it may make it.

M
Click to expand...
This. But you have to execute. Harder than it sounds when dealing with that level of performance/engineering.
 
Now you have all the reasons that it can't be done. Get lotsa bucks and do it. You might want to try breaking the altitude records one motor at a time, starting with G. Maybe every other motor. Learning, experience.
 
I think that with an O motor it would be achievable but a lot of work and detailed planning would be required, however I think a P motor with a reasonable amount of work could be realistically achieved. I think that anything higher than a P would be a bit excessive.
 
jmattingly13 said:
100-150k ft is only 30-50% of the way to the recognized boundary of space. So design smarter and bigger?
Click to expand...

The point is one can achieve the edge of space with a well design rocket with an O motor. The only O motor I find capabale of that is the O-3400 from CTI.
 
ali8bongo said:
Hi
I have been doing research on sounding rockets used in the 60s and I found three of specific interest: Skua2, Petrel 1 and the INTA 100. All of them reached an apogee of 100Km using AP based propellants that provided less than 25KN of thrust. They used old technology, steel construction, have similar empty weights to what can be achieved today while using AP fuel which is readily available in O motor form. As O motors can provide anywhere between 20 and 40KN then surely a 40KN motor rocket if well designed could easily reach 100KM, yet I see very few O motor flights achieving an apogee of over 90,000ft. Why is this? Thanks :)
Click to expand...
The physics of rocket flight has not changed over the past century so I knew something wasn't right.

All 3 rockets you referenced are 2-stage rockets. In each case, the first stage use several fast burn, high thrust motors to get the rocket up to speed, and the second stage has a single lower thrust long burn motor to get it to altitude.

For example, the Petrel 1 first stage was powered by 3 Chick motors with a total thrust of 60 kN for 0.2 s = 12 kNs (N-impulse motor) followed by the second stage motor powered by a 4.5 kN thrust for 30 s = 135 kNS (Q impulse motor). Total Impulse ~ 80% Q which is way more than an O and a 2-stage to boot!

https://www.astronautix.com/lvs/petrel1.htm https://www.astronautix.com/engines/chick.htm

https://www.sat-net.com/serra/skupe_e.htm

The 3 rockets you reference are a effectively a hybrid of a short-burn, high-thrust SuperLoki booster coupled to a long-burn, low-thrust Arcas sustainer.

The fast-burn booster allows for the use of a much shorter launcher than the Arcas launcher. The same principle is used in all tube-launched shoulder-fired tactical missiles today.

Bob
 
enderw88 said:
Are our recovery systems really that much heavier than the payload in a sounding rocket? They aren't just going up for giggles (like we are!), they have instrumentation packages.
Click to expand...

We launched an Improved Orion sounding rocket and it went to ~99km. The rocket that had launched previously was very similar and also used an Improved Orion motor but that one included a recovery system. If I remember right that one topped out at ~60 km. When you run on the limits of things like this a small amount of weight can change the performance by quite a bit. Granted the recovery systems for these rockets have to be pretty serious since they come back into the denser part of the atmosphere at over mach 3.

The Super Loki dart that was mentioned before uses 2024 aluminum for the motor case if I remember right which is several times more expensive than the 6061 we use. It also would heat up enough during launch that it would glow. So it was pretty much on the limits of how thin they could make the case, and its maximum temperatures it could withstand. Also the Super Loki still didn't make it to official space, and the motor was also a P class if I recall correctly.

ali8bongo said:
Hi
I have been doing research on sounding rockets used in the 60s and I found three of specific interest: Skua2, Petrel 1 and the INTA 100. All of them reached an apogee of 100Km using AP based propellants that provided less than 25KN of thrust. They used old technology, steel construction, have similar empty weights to what can be achieved today while using AP fuel which is readily available in O motor form. As O motors can provide anywhere between 20 and 40KN then surely a 40KN motor rocket if well designed could easily reach 100KM, yet I see very few O motor flights achieving an apogee of over 90,000ft. Why is this? Thanks :)
Click to expand...

So these sounding rocket motors are generally quite a different beast than what we are used to. Many come from old surface to air missiles, and the construction costs for them are substantially higher than what people get them for. The steel they use in the cases definitely isn't the mild steel we are used to. Typically they use things like Iconel or other Nickel superalloy steels, since they can withstand temperatures up to 1600 degrees F and still keep most of their strength properties, while the 6061 we use in our motor cases loses most of its strength at over 500 degrees.

So if you build an O motor with a sliver thin margin of safety, don't have a recovery system, and use exotic materials in everything to keep the weight down, you might have a chance of getting close to space on a single O motor. You probably won't be able to have any payload on that rocket as well. Also add some of the spicier ingredients that are used to boost the isp over what we get will help as well. Though the spice usually makes the propellant a 1.1 explosive instead of the 1.3 we use, so your permitting will be much more fun.

DizWolf said:
The overall impulse may be the same, but the burn times typically are not. The Arcas, for example, was an endburning motor. Lots of heat, and expensive (and in some places asbestos) materials to deal with that heat. I've yet to find much info on the actual propellant, but I've heard there were other magic tricks in there, not just a simple endburning AP casting.

Almost all hobby motors have a relatively fast burn time.
Click to expand...

Check out a book called "Small sounding rockets: A historical review of meteorological systems 1955 to 1973" It has the propellant formula for the ARCAS if I remember correctly as well as design drawings for it and the super loki and other small sounding rockets. It's not the HTPB stuff we use. Also the ARCAS is a wire-burner not exactly an end burner.
 
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