60,000feet in 60seconds; MD N5800; Cesaroni Challenge

[Adrian A]

Thanks, Reinhard. My calculations show close to the same results as yours, with the exception of the N4800 and the M1590, which I calculated to have 1557 and 1874 m/sec respectively. I'm using the Isp provided on thrustcurve.org, and taking the final mass as the initial mass - the propellant mass, because those are available on thrustcurve. (Jeroen makes a good point that the real final mass will be a little different) Would you mind checking those? I'm curious if I'm missing something.

 

[butalane]

I meant that the Isp figures provided are based on the mass of the fuel alone, so the Isp will stay the same even if the case mass goes up. I was trying to explain why Isp alone doesn't tell you everything you need to know about the overall performance and efficiency, and I was doing a poor job of it.



Thinking about this some more, I think the best way to explain why the N5800 is "special" is just to use the rocket equation to show what delta-V the motor could provide on its own. Delta velocity = Isp* G * ln (Mfinal/Minitial). G is just the gravitational constant, 9.8 m/sec^2 if you're working in SI units. You can plug in motor data from thrustcurve for any motor and this equation will tell you what the burnout velocity would be if your airframe didn't weigh anything or have any drag.

For comparison:
N5800 2095 m/sec Isp: 228
N1100 1814 m/sec Isp: 210
N4800 1557 m/sec Isp: 197
G80 1481 m/sec Isp: 223
I600 1408 m/sec Isp: 186
G115 859 m/sec Isp: 229

I'm curious now if there are any motors on thrustcurve that have a higher delta-V. I doubt it but I haven't searched comprehensively.

Gotcha.

I did a quick analysis - holding mass_total the same while varying mass_propellant (and subsequently increasing Isp). It seems that a lower Isp (Mr ->1) gives you a higher deltav capability but, and I think this was the point of your initial post, the higher Isp and M_burnout had higher momentum.

 

[bobkrech]

I meant that the Isp figures provided are based on the mass of the fuel alone, so the Isp will stay the same even if the case mass goes up. I was trying to explain why Isp alone doesn't tell you everything you need to know about the overall performance and efficiency, and I was doing a poor job of it.



Thinking about this some more, I think the best way to explain why the N5800 is "special" is just to use the rocket equation to show what delta-V the motor could provide on its own. Delta velocity = Isp* G * ln (Mfinal/Minitial). G is just the gravitational constant, 9.8 m/sec^2 if you're working in SI units. You can plug in motor data from thrustcurve for any motor and this equation will tell you what the burnout velocity would be if your airframe didn't weigh anything or have any drag.

For comparison:
N5800 2095 m/sec Isp: 228
N1100 1814 m/sec Isp: 210
N4800 1557 m/sec Isp: 197
G80 1481 m/sec Isp: 223
I600 1408 m/sec Isp: 186
G115 859 m/sec Isp: 229

I'm curious now if there are any motors on thrustcurve that have a higher delta-V. I doubt it but I haven't searched comprehensively.

Thanks, Reinhard. My calculations show close to the same results as yours, with the exception of the N4800 and the M1590, which I calculated to have 1557 and 1874 m/sec respectively. I'm using the Isp provided on thrustcurve.org, and taking the final mass as the initial mass - the propellant mass, because those are available on thrustcurve. (Jeroen makes a good point that the real final mass will be a little different) Would you mind checking those? I'm curious if I'm missing something.

Gotcha.

I did a quick analysis - holding mass_total the same while varying mass_propellant (and subsequently increasing Isp). It seems that a lower Isp (Mr ->1) gives you a higher deltav capability but, and I think this was the point of your initial post, the higher Isp and M_burnout had higher momentum.

These numbers are nice but relatively meaningly in the ground launch scenerio.

1. The delta velocities only apply in space where the only force is inertia.
2. Real rockets have an airframe and payload mass that significantly reduce the Mfinal/Minitial ratio. It looks like the calculated delta velocity values presented only consider the rocket motor casing and the propellant which is not realistic.
3. Real rockets launched from the ground also have a gravity loss = mg
4. Real rockets operating in the atmosphere also have drag losses = 1/2 Cd A rho V^2 where rho is the atmospheric density.
5. Real rockets launched from the ground and through the atmosphere will not come near those velocities, and furthermore
6. The maximum velocity that any rocket can reach in the atmosphere is = sqrt(2(T-mg))/(Cd A rho)), not the delta V value obtained from a rocket operating in a force free environment.
7. Mach 4 is the absolute best that a perfectly constructed minimum weight 4" MD N5800 rocket could obtain which is ~1325 m/s and Mach 3.4 is probably wnat most 4" MD N5800 rockets might reach which is ~1150 m/s.
8. You will loose a minimum 770 m/s to rocket mass, gravity and drag in the best case, and more typically 940 m/s if the design, weight and construction techniques are less than ideal.
9. Rocket Mass, Gravity and Drag always get you and keep you down!

Bob

 

[CarVac]

Gravity drag is reduced for the N5800 versus basically all other N motors (except the N10000, which suffers in overall impulse) because of the faster burntime. That's one of the reasons it's superior to experimental motors: from what I've seen they impulse-optimized motors always tend to have lower thrust and longer burntime. Imagine if Qu8k had a 3.5 second burntime instead of around 10 seconds: it wouldn't have to lift all that propellant very far compared to what it did.

 

[butalane]

These numbers are nice but relatively meaningly in the ground launch scenerio.

1. The delta velocities only apply in space where the only force is inertia.
2. Real rockets have an airframe and payload mass that significantly reduce the Mfinal/Minitial ratio. It looks like the calculated delta velocity values presented only consider the rocket motor casing and the propellant which is not realistic.
3. Real rockets launched from the ground also have a gravity loss = mg
4. Real rockets operating in the atmosphere also have drag losses = 1/2 Cd A rho V^2 where rho is the atmospheric density.
5. Real rockets launched from the ground and through the atmosphere will not come near those velocities, and furthermore
6. The maximum velocity that any rocket can reach in the atmosphere is = sqrt(2(T-mg))/(Cd A rho)), not the delta V value obtained from a rocket operating in a force free environment.
7. Mach 4 is the absolute best that a perfectly constructed minimum weight 4" MD N5800 rocket could obtain which is ~1325 m/s and Mach 3.4 is probably wnat most 4" MD N5800 rockets might reach which is ~1150 m/s.
8. You will loose a minimum 770 m/s to rocket mass, gravity and drag in the best case, and more typically 940 m/s if the design, weight and construction techniques are less than ideal.
9. Rocket Mass, Gravity and Drag always get you and keep you down!

Bob

Bob,

Gravity and drag? Jeez I always wondered how those durned find things worked and why the rockets always came back to da earfh! Imagine that they work on both the up and down part.

I may have failed 8th grade physics....but I can still draw a free body diagram.:eyeroll:


-butalane

 

[Ring Leader]

To the above question. The leading edge will heat up to at least 1000F, but the heat transfer rate of aluminum is fairly good, though not as good as copper. I've been doing a fair amount of research for my school's liquid engine. The combustion chamber in that is 0.1" aluminum and will be cooled so it doesn't melt within a second of ignition.

Almost 80% of the thermal heating on the fins will take place on the leading edge, but the rest of the fin is a fairly large heat sink, so as long as we don't stay beyond mach 3 for more than a couple seconds, we shouldn't have any issue with physical deformation of the aluminum due to heat stress.

We know there are alternate methods, including using phenolic ablative leading edges seated against a composite fin core, which is our second option if the aluminum proves to be too troublesome. Stainless weighs ~3 times as much as aluminum, so to make a fin of comparable weight, it would need to be 1/12" thick, which is not feasable. It is, however, to use stainless as the leading edge, and a composite core.

Interesting problem there. I would think the high temps for a short duration would be fine for aluminum but it would be an interesting experiment to find out. If you made a mock fin and applied a 1000 degree heat source for a period of time you could get a close approximation of how the material would behave. Of course you wouldn't be able to simulate the erosion forces that would be present during flight.

Someone mentioned earlier the loss of strength in aluminum when heated beyond a certian point. It is true for heat treated aluminum but if you design for the annealed state that may not be a problem. Also if the heat is localized to the leading edge you may not care anyway since the leading edge may not be as highly stressed as other parts of the fin and therefore not care that the material strength is less.

I'm a big fan of doing close approximation testing on sticky design points whenever possible. You just have to use your judgement as to wether your approximation is close enough to the real thing. But then again thats one of the main functions of an engineer!

 

[edwinshap1]

Good idea on the heating. I do have a heat gun that will put out 1000 F nicely, and I could test that without issue.

In addition, the heat treatment would be removed after the fin reached a certain temperature, but even if the aluminum were to loose its tempering, it would still have 18000 PSI tensile, and 8000 PSI yield, so it would be fine for short duration at that speed. I'm still looking at a steel insert, though it would be a huge pain to affix to the fin stock.

If anyone has designs to affix steel to a fin please let me know.

 

[Tominator 2]

I'm still looking at a steel insert, though it would be a huge pain to affix to the fin stock.

Not to mention heavy! We should check out 7075 aluminum. i did some research and I found that Proteus 6 used 7075. Those guys went Mach 3+

 

[edwinshap1]

If we use aluminum, it would have to be full fin. Aluminum would get too hot as a leading edge insert to be safe for me. A steel leading edge on a CF core plate would not be too heavy, and most of the volume of the fin would still be fairly light.

It could go either way at this point, but I have to design some files and do some stress tests.

 

[blackbrandt]

Thank goodness I didn't subscribe to this thread...

 

[ClayD]

superior to experimental motors

the only difference in expermimental and the N5800, is that CTI had it certified.

the arguement has gone from kids begging to Certified motors being Superior to EX... boy... talk about an arguement of idiocy on both counts.

 

[GaryT]

I'm about to UN-subscribe....

 

[Ring Leader]

If we use aluminum, it would have to be full fin. Aluminum would get too hot as a leading edge insert to be safe for me. A steel leading edge on a CF core plate would not be too heavy, and most of the volume of the fin would still be fairly light.

It could go either way at this point, but I have to design some files and do some stress tests.

...or you could go straight to titanium. I didn't look at your design file, how many fins and what size raw material would you need?

 

[New Ocean]

the only difference in expermimental and the N5800, is that CTI had it certified.

the arguement has gone from kids begging to Certified motors being Superior to EX... boy... talk about an arguement of idiocy on both counts.

I dare say the N 5800 is better than any ex N motor made when you factor in the following: total cost of development to a flight-ready motor, overall performance, and reliability. If I am wrong, give me an example of a better motor.

 

[ClayD]

I dare say the N 5800 is better than any ex N motor made when you factor in the following: total cost of development to a flight-ready motor, overall performance, and reliability. If I am wrong, give me an example of a better motor.

well yes, your accounting is all wonkey... Thats like the nutjobs that say it costs 10k to make a q motor... well yea, if you want to spend 10k i am sure you could find a place to spend it.


It costs about 12.00 a pound to develop a formula. More if you use exotic stuff.. but still should never really exceed 16.00 per pound.... this isnt in the N development cost. My small motors that lead up to big motors, arent included in the big motors because i fly them... you dont put the cost of all those J350's you learned to fly in the cost of your L3 do you... experience to do something big, doesnt cost all the small things you did to get there.... thats just not correct.

The line your drawing is dumb because a rocket motor is a rocket motor is a rocket motor... made at CTI vs made in a grage doesnt change ISP... if your saying that CTI has people involved that know how to formulate and build an N5800, i will say that the Rocket community as a whole has people capable of the same thing... Its just ignorance to argue otherwise...

 

[Tominator 2]

Thank goodness I didn't subscribe to this thread...

Why?

 

[Reinhard]

Thanks, Reinhard. My calculations show close to the same results as yours, with the exception of the N4800 and the M1590, which I calculated to have 1557 and 1874 m/sec respectively. I'm using the Isp provided on thrustcurve.org, and taking the final mass as the initial mass - the propellant mass, because those are available on thrustcurve. (Jeroen makes a good point that the real final mass will be a little different) Would you mind checking those? I'm curious if I'm missing something.

Your numbers for the M1590 look good, compared to the CAR certification document. For the N4800T i still get 2108m/s based on thrustcurve.org data and a manually calculated ISP (I get 206s in contradiction to the value from thrustcurve.org and the certification document). I didn't find any authoritative source for its loaded weight (neither TMT nor AT), but a news release on RP seems to confirm it.
The values from my list are based on an .eng file with apparently wrong mass numbers for the M1590 (3.159kg propellant, 5.223kg loaded). Also the impulse, calculated from the thrustcurve.org, varies somewhat from the official value.

https://www.tripoli.org/LinkClick.aspx?fileticket=UMBwNg2N+fc=&tabid=177
https://www.rocketryplanet.com/content/view/992/99/


Edit: This is getting off topic here, feel free to PM me if you want more details.

Reinhard

 

[THarrison]

So what happens if you come up short and don't get to the $4400 that you need? The money gets returned?

Sooo... what's the answer on this one???

 

[k-rad du0d]

Sooo... what's the answer on this one???

"It's an All & More funding mechanism: if we don't reach our financial goal we get to keep what we raise. But if we do reach our goal, we get access to exciting opportunities."

https://www.rockethub.com/projects/7923-60-000-ft-in-60-seconds


I had never heard of Rocket Hub until this thread. I find it sketchy that it has such a mechanism. Kickstarter is a better method because it ensures that you won't be charged unless the goal has been met - thus, the project will likely succeed. On this Rocket Hub thing, it looks like if they only raise $1000 and can't get the project off the ground, they still get to keep the cash. Pretty shady.

 

[blackbrandt]

Why?

Because my inbox would be 136 messages fuller.

 

[THarrison]

"It's an All & More funding mechanism: if we don't reach our financial goal we get to keep what we raise. But if we do reach our goal, we get access to exciting opportunities."

https://www.rockethub.com/projects/7923-60-000-ft-in-60-seconds


I had never heard of Rocket Hub until this thread. I find it sketchy that it has such a mechanism. Kickstarter is a better method because it ensures that you won't be charged unless the goal has been met - thus, the project will likely succeed. On this Rocket Hub thing, it looks like if they only raise $1000 and can't get the project off the ground, they still get to keep the cash. Pretty shady.

I saw that on the page and that is standard wording on all the rockethub pages. I was really hoping these begging kids wouldn't possibly be THAT shady and slimy....

 

[CarVac]

I noticed that too. Very sketchy. What happens to the rewards for the donors if the rocket never happens?

Also, @ClayD: You cut off the relevant part of my argument: I have never heard of a similar 4-inch full N motor with as much thrust and as short a burn time by anyone that is available to hobbyists. Feel free to correct me on that fact, but until some other evidence shows up, I will maintain that this particular motor, the N5800, is superior to every other N motor available when it comes to raw performance, commercial or experimental (I make no claims regarding military motors).

 

[ClayD]

I noticed that too. Very sketchy. What happens to the rewards for the donors if the rocket never happens?

Also, @ClayD: You cut off the relevant part of my argument: I have never heard of a similar 4-inch full N motor with as much thrust and as short a burn time by anyone that is available to hobbyists. Feel free to correct me on that fact, but until some other evidence shows up, I will maintain that this particular motor, the N5800, is superior to every other N motor available when it comes to raw performance, commercial or experimental (I make no claims regarding military motors).

The conclusion you draw is incorrect. CTI has not done anything new... or that others cannot. I will grant you that CTI has changed its buisness model and gone after hobby marketshare and putting fourth high caliber motors.

You and new ocean act like everyone that builds motors have a list on the web of motors theyve made how they make them, and thier performance. They dont, because the research they do is geared to thier own ambition without regard to what a peer thinks of what they do. most would just say"no your doing it wrong." so why bother...
So ex motors are not "available"// Certified motors being available is an entirely diffrent story.


Now if you talking about max Q, most Ex'ers in the 98mm size move to O motors..... you can pack much more energy into a 4" motor than a meazly N....
https://rpl.usc.edu/projects/

Regardless, this still is the fastest, quickest accelerating, and highest flying rocket the lab has ever built, and something from which we have learned volumes.

an o that only hit 62000 feet... i think thier rocket might hold together.... But getting it back..... thats the hardest part of busting 50k... going up only takes the push of a button.....

Feel free to correct me on that fact

Your wrong... there are "researchers" out there with "faster burning motors".

 

[rfjustin]

I saw that on the page and that is standard wording on all the rockethub pages. I was really hoping these begging kids wouldn't possibly be THAT shady and slimy....

So basically rockethub is a means to try to persuade rocket enthusiasts to enthusiastically open their wallets and donate their hard earned money to a high school/collegiate project with no return on investment. Wow, just wow, you kids have some stones, I'll give you that...

Wanna go high and go fast? GET A JOB.



Justin

 

[New Ocean]

well yes, your accounting is all wonkey... Thats like the nutjobs that say it costs 10k to make a q motor... well yea, if you want to spend 10k i am sure you could find a place to spend it.

I am saying that an EX motor comparable to the N5800 in performance and reliability could not be made from scratch for less money than the case and motor for the N5800. You simply can't make a one-off N motor and expect it to be reliable and perform this well without building many other, perhaps smaller motors, to get it right. But I may be wrong; show me an example of it happening? I am not saying physically impossible, just saying it isn't done.

My small motors that lead up to big motors, arent included in the big motors because i fly them... you dont put the cost of all those J350's you learned to fly in the cost of your L3 do you... experience to do something big, doesnt cost all the small things you did to get there.... thats just not correct.

Oh it is if you are thinking about this specific scenario. From position zero, this team can either purchase an N5800 (it is an N5800 competition anyway) or learn to build comparable N motors. Do you think they can do so for $16 per pound, or say $300? All expenses between here and meeting the goal of 60K in 60S count. Or can they just stage this N rocket to a D motor and call it a $4 project?

The line your drawing is dumb because a rocket motor is a rocket motor is a rocket motor... made at CTI vs made in a grage doesnt change ISP... if your saying that CTI has people involved that know how to formulate and build an N5800, i will say that the Rocket community as a whole has people capable of the same thing... Its just ignorance to argue otherwise...

I was not being clear enough: I am not saying that a CTI motor is automatically better performing. Just that there is no EX motor out there that compares to the N5800. There is no ex motor that has the same ISP, same mass fraction, same reliability, etc. Unless you know of an example and then I would instantly see my mistake.

 

[MClark]

Aluminum fincans work fine, aluminum fins glued on may have issues.
https://www.ahpra.org/UPPERTB2%20r.JPG
This is a picture of an upper stage from an O10000 to a M3700. The aluminum conducts the heat fast enough that the paint was not burned. Mach 4, 75000' on sim. No altimeters at that time to get data.

Mark

 

[ClayD]

Just that there is no EX motor out there that compares to the N5800.

okay nepolean, like theres any way anyone could possibly know that....

There is no ex motor that has the same ISP, same mass fraction, same reliability, etc.

Well, if a commercial manufacturer can, then a research hobbiest can... infact... research motor makers can do things that 1125 manufacturers cant.... which gives them ability to push more energy out the a$$. for instance a J with a .25 second burn...

take it easey! i'm off to have a fun threeday!

 

[daveyfire]

Just that there is no EX motor out there that compares to the N5800. There is no ex motor that has the same ISP, same mass fraction, same reliability, etc. Unless you know of an example and then I would instantly see my mistake.

I liked this one that we made. (It's flown twice. The fins only stayed on once.) But y'all already know most of the details about it, and I'm guessing that the reason it hasn't been brought up is along the lines of "something something carbon fiber university something." I assure you, nothing went into this motor (or vehicle) that the average EXer couldn't replicate. The development process wasn't arduous, and it worked on the second try. As Bob, Adrian, et al. have pointed out, it's a game of mass ratios to get to >Mach 4 with burn times available in 4" motors.

When I get some time, I kind of want to run a formal sensitivity analysis on performance with Isp, Isp/(Inert Mass), and a few other performance metrics in it to see what happens, unless someone has already done that. If you have, I'd love to see it, because I'm curious and don't really want to spend my weekend coding...

 

[jadebox]

So basically rockethub is a means to try to persuade rocket enthusiasts to enthusiastically open their wallets and donate their hard earned money to a high school/collegiate project with no return on investment.

The benefit is that you get the satisfaction of helping a group of kids who are interested in science and technology. It's not uncommon for people involved in our hobby to "Pay it forward."

-- Roger

 

[daveyfire]

Aluminum fincans work fine, aluminum fins glued on may have issues.

This is a picture of an upper stage from an O10000 to a M3700. The aluminum conducts the heat fast enough that the paint was not burned. Mach 4, 75000' on sim. No altimeters at that time to get data.

The internet always seems to forget about this rocket. It shouldn't. (cite; sometimes I feel like I'm turning into JI.)