Beginner's Mistake (Staging)

Beginner's Mistake (Staging)

Post by Roger Iv » Thu, 14 Sep 1995 04:00:00




Quote:
> I built my first 2-stage rocket, an Estes Mini-Cobra.

> First flight on a A10-0T and A3-4T (I think -- whatever the recommended
> engines were, sort-of) ended in a "prang".

[[[[ snip ]]]]
> What happened? Well I didn't understand that there are real differences in
> operation between "single stage" motors and "upper stage" motors. Single stage
> motors require igniters to light them. Upper stage motors are apparently made
> to light more easily, and will light from either an igniter or from the
> booster burn-through.

Hmm. I did the same thing to my mini-Cobra. When I looked at the engine in the
upper stage, though, I saw black marks about halfway between the opening in
the nozzle and the casing. It looked to me as though the flaming chunks from
the booster simply missed the hole in the upper stage engine.

It was also my first attempt at staging. I subsequently CHAD-staged an
ultra-stable scratch design with a D booster on the bottom and an E on
the top. Worked fine, despite the E being a single-stage motor.
--
----------------+------------------------------------------------------
Roger Ivie      | "Did you know the AIDS spore can live in sweaters?"

 
 
 

Beginner's Mistake (Staging)

Post by Larr » Fri, 15 Sep 1995 04:00:00



Quote:
> I built my first 2-stage rocket, an Estes Mini-Cobra.
> First flight on a A10-0T and A3-4T (I think -- whatever the recommended
> engines were, sort-of) ended in a "prang".

[stuff deleted]

Quote:
> What happened? Well I didn't understand that there are real differences in
> operation between "single stage" motors and "upper stage" motors. Single stage
> motors require igniters to light them. Upper stage motors are apparently made
> to light more easily, and will light from either an igniter or from the
> booster burn-through.
> I verified the difference by experiments I did in the back yard with motors in
> a test stand. I proved to myself that the single stage motors were good, but
> couldn't be started from the booster.
> What are the detailed differences between upper-stage motors and single-stage
> motors? Will my Mini-Cobra still fly with it's cusomized (1" shorter) fuselage?
> Mike
> [Mike Devour, Citizen, Libertarian                 ]

> [I am speaking only for myself.                    ]
> [My employer in no way endorses what I have to say ]
> [     and I don't speak for them in any capacity...]

To my knowledge, there are no differences between single-stage motors and
upper-stage motors, other than the delay length. There is a slight difference
between booster motors and single-stage motors, in that boosters have more
propellant at the top; however that extra propellant functions only as a
bulkhead. (This may be where the inflated catalog propellant mass values
come from. I weighed a C6-0 motor's propellant, and it was exactly the
catalog value - but this has to be a random event since I have it on good
authority that propellant mass is adjusted according to the performance of
the shipment of black powder.)

I took many motors apart to measure the grains, so that I could test a thrust
curve simulation package. I examined them and made measurements. Later, I got
actual grain dimensions from a reliable source.

Honestly ZARE EEZ NO DEEFAIRAWNCE!

Regards,
-Larry Curcio

 
 
 

Beginner's Mistake (Staging)

Post by Craig Utl » Fri, 15 Sep 1995 04:00:00


: It was also my first attempt at staging. I subsequently CHAD-staged an
: ultra-stable scratch design with a D booster on the bottom and an E on
: the top. Worked fine, despite the E being a single-stage motor.

I have never built a true multi-stage rocket, but I have CHAD staged a
C6-0 with a B6-4.  No problems at all.  My next attempt will be the C6-0
with a C6-5.  We'll see.  I'd really hate to have this rocket prang.

--Craig
--
+---------------------------+
| Finger for PGP Public Key |
+---------------------------+

 
 
 

Beginner's Mistake (Staging)

Post by Roger Iv » Fri, 15 Sep 1995 04:00:00


Quote:



>> [munch]

>>It was also my first attempt at staging. I subsequently CHAD-staged an
>>ultra-stable scratch design with a D booster on the bottom and an E on
>>the top. Worked fine, despite the E being a single-stage motor.

>> [munch]

> Forgive me for being stupid and/or naive, but I thought the only
> difference between an 'upper stage' and 'single stage' motor (at least
> for Estes motors) was the delay.  Upper stage motors have a longer
> delay than single stage motors, I suppose to allow the upper stage to
> reach apogee before ejecting.  I didn't think there was any difference
> in the nozzle size...

That's what I thought also, which is why I included the story about
CHAD staging an E.

In my examination of _my_ Mini-Cobra after the sudden severe shortening
of the upper stage (BONK!) was that the A10-0Ts were a bit iffy in
igniting the upper stage. If you look in an A10-0T, the propellant is all
at the bottom and there's a big gap between it and the upper stage. In my
case, it looked like flaming chunks that should have ignited the upper
stage simply missed the hole in the nozzle.

The other fellow says he's done some experiments that say there's some
sort of difference between single-stage engines and upper-stage engines.
I thought the only difference was in the delay.

BTW, When you suddenly sorten your Mini-Cobra, you are left with extra boosters
that you have no idea what do with and the bottom stage of the Mini-Cobra,
also with no obvious use. It is not a good idea to attach the bottom stage
of the Mini-Cobra to a Mosquito. Unstable. Not that I really expected it to
be stable, mind you. I never found the Mosquito.

I have, however, succesfully used an A10-0T to CHAD stage another rocket
with larger engines. Peel a little bit off the top of the A10-0T and it will
snugly fit inside a standard A, B, or C. I've successfully flown an A8-?
from an A10-0T, but the C rocket I tried was just too heavy (went horizontal
right after it left the launch rod).
--
----------------+------------------------------------------------------
Roger Ivie      | "Did you know the AIDS spore can live in sweaters?"

 
 
 

Beginner's Mistake (Staging)

Post by Helen Rapo » Sat, 16 Sep 1995 04:00:00


Quote:




>>> [munch]

>>>It was also my first attempt at staging. I subsequently CHAD-staged an
>>>ultra-stable scratch design with a D booster on the bottom and an E on
>>>the top. Worked fine, despite the E being a single-stage motor.

>>> [munch]

>> Forgive me for being stupid and/or naive, but I thought the only
>> difference between an 'upper stage' and 'single stage' motor (at least
>> for Estes motors) was the delay.  Upper stage motors have a longer
>> delay than single stage motors, I suppose to allow the upper stage to
>> reach apogee before ejecting.  I didn't think there was any difference
>> in the nozzle size...

>That's what I thought also, which is why I included the story about
>CHAD staging an E.

*********
Beside the delay time, the Estes upper stage engines have a purple
label vs the green label on the single stage engines, plus the upper
stage engines will weigh a little bit more due to the extra delay charge.

As far as engine thrusting goes it should be the same be it a B6-0,
B6-2, B6-4 or B6-6 (in theory at least).

For the Estes E engines, they never made a kit that had an upper
stage that need an E engine.  If it did then they would have made
the E15-8 an 'upper stage' engine in terms of the label.

Quote:

>In my examination of _my_ Mini-Cobra after the sudden severe shortening
>of the upper stage (BONK!) was that the A10-0Ts were a bit iffy in
>igniting the upper stage. If you look in an A10-0T, the propellant is all
>at the bottom and there's a big gap between it and the upper stage. In my
>case, it looked like flaming chunks that should have ignited the upper
>stage simply missed the hole in the nozzle.

************
Not much experience with staging T engines so I don't know what I can
add to this.

Quote:

>The other fellow says he's done some experiments that say there's some
>sort of difference between single-stage engines and upper-stage engines.
>I thought the only difference was in the delay.

***********
Longer delay charges will have more inital weight to them.  Just check
out the weight listings for the B6 series of engines.

I also doubt that the size of the nozzle is a factor in the single
stage/upper stage engines.  I know the width of the nozzle determines
the thrust of an engine (check on the nozzle widths on the B4,B6 and
B8 engines from Estes).

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Beginner's Mistake (Staging)

Post by kaplo.. » Sat, 16 Sep 1995 04:00:00


Quote:

> I also doubt that the size of the nozzle is a factor in the single
> stage/upper stage engines.  I know the width of the nozzle determines
> the thrust of an engine (check on the nozzle widths on the B4,B6 and
> B8 engines from Estes).

Actually its the other way around. The thrust (and more than that)
determines the size the nozzle needs to be. On any given motor, if you make
the nozzle larger, you LOSE total impulse.


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Beginner's Mistake (Staging)

Post by C. D. Tavar » Sat, 16 Sep 1995 04:00:00



Quote:
> What happened? Well I didn't understand that there are real differences in
> operation between "single stage" motors and "upper stage" motors. Single stage
> motors require igniters to light them. Upper stage motors are apparently made
> to light more easily, and will light from either an igniter or from the
> booster burn-through.

Actually, this isn't so.

In the low-end black-powder motors, the nozzle and propellant formulation
for all engines in a family are identical.  Only the delay length and
forumlation differs.

Quote:
> I verified the difference by experiments I did in the back yard with motors in
> a test stand. I proved to myself that the single stage motors were good, but
> couldn't be started from the booster.

Incredible coincidence, but coincidence nonetheless.

Quote:
> What are the detailed differences between upper-stage motors and single-stage
> motors?

The "upper-stage" motors have a delay that is too long to be flown
in the average kit made by the manufacturer without plowing into the
dirt.  End of story.

It's just Estes' way of saying, "Don't put the D12-7 in your Phoenix,
dodo."  Then they color it purple to give the clueless one more clue.

However, you could put in your Ranger (if they still made the
Ranger) with no problem at all.  And you could put the C6-3 in the
topmost stage of your Comanche, too, if you didn't mind it deploying
only halfway up.
--


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Beginner's Mistake (Staging)

Post by Bill Nels » Sun, 17 Sep 1995 04:00:00


: Actually its the other way around. The thrust (and more than that)
: determines the size the nozzle needs to be. On any given motor, if you make
: the nozzle larger, you LOSE total impulse.

Hm, to some extent maybe - due to lowered chamber pressure. Usually, the
main result is that the fuel burns a bit slower - so the total impulse is
about the same, but the average impulse is lower.

Bill

 
 
 

Beginner's Mistake (Staging)

Post by M. G. Devo » Fri, 22 Sep 1995 04:00:00


Quote:
Helen Rapozo writes:
>Roger Ivie writes:
>>In my examination of _my_ Mini-Cobra after the sudden severe shortening
>>of the upper stage (BONK!) was that the A10-0Ts were a bit iffy in
>>igniting the upper stage. If you look in an A10-0T, the propellant is all
>>at the bottom and there's a big gap between it and the upper stage. In my
>>case, it looked like flaming chunks that should have ignited the upper
>>stage simply missed the hole in the nozzle.

>Not much experience with staging T engines so I don't know what I can
>add to this.

>>The other fellow says he's done some experiments that say there's some
>>sort of difference between single-stage engines and upper-stage engines.
>>I thought the only difference was in the delay.

I'm the "other fellow" Roger is referring to. My conclusion was based on the
failure of three attempts to get an A3-4T to light from a A10-0T and the
success in all three attempts to get an 1/2A3-4T (purple label) to light from
the same type of booster.

Somebody else has had exactly the *opposite* experience, so it appears to be a
reliability problem unique to these small engines, *not* a design difference
between upper stage and single stage motors.

I take it that most folks here, like Helen, have more experience staging
bigger motors than these mini-motors. Staging larger motors is pretty reliable
from what I've been hearing on the group.

I'd like to figure out how to improve the reliability of staging small motors.
These really tiny models are kind of fun. But then, I've never witnessed the
launch of one of these HPR monsters yet! <grin>

Mike

[Mike Devour, Citizen, Libertarian                 ]

[I am speaking only for myself.                    ]
[My employer in no way endorses what I have to say ]
[     and I don't speak for them in any capacity...]