Multi Stage Rocket

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MB_SEDS_Rocketry

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I am from SEDS (Students for the Exploration and Development of Space) and every year a rocket competition is held. This year's competition is to have a multi stage rocket go to at least 3500' with the combined impulse no higher then 640 Ns. As our club or myself has never built a multi stage rocket before, we first ordered a kit to get the hang of things. I still have many more questions about building the rocket, along with questions regarding the electronics, av bay, air starting, and motor retention. Is there a good place to go for information regarding multi stage rockets, or good documentation regarding them? I did a google search but not too much came up. Thank you for your help.
 
What questions do you have? Post specific questions and you can get tons of answers pretty quickly.

To ignite composite motors you will need electronics since you can't direct ignite them like with black powder motors.

You should use rocksim or openrocket to get designs of the stages pretty good, and make sure total impulse is within range. You'll want to keep everything light, but you also have to fit recovery and staging electronics in every stage that has to be air started or recovered. You can probably use motor ejection for the booster motors, but you'll have to be careful with staging to make sure you don't ignite inside the coupler and burn up your booster.
 
I probably should have posted specific questions. I have read through the article on apogee but that is only for a 2 motor multi stage. The competition awards additional points for having 3 or 4 stages in the rocket, and I want to know if this is possible and how so? I understand you need electronics for each of the stages, but for separating the airframe does the motor thrust provide enough force to break the shear bolts or do you need additional force like as in a ejection charge?
 
Quite an ambitious (and worthwhile) project. For others like me, who hadn't heard about SEDS before: https://seds.org/wp-content/uploads/2014/01/USRC-2015-Rules1.pdf

Some of the particulars:

2. The objective of the competition is to design, build, and launch a multi-stage rocket to an altitude of at least 3000 feet above ground level (AGL) and recover the rocket intact. To compensate for the effects of launches at high-altitude launch sites, 0.002 times the elevation of the launch site above sea level, in feet, will be subtracted from the recorded altitude (in feet) and is defined as the adjusted altitude. This offsets the reduced engine/vehicle mass necessary to achieve the target height at these higher altitudes. Scoring will be based on the team's adjusted altitude.
3. All rockets must contain two or more stages. A stage is defined as a distinct portion of the rocket which provides thrust independently from other stages. Stages must burn sequentially, e.g., the second stage must burn after the first stage burn has completed. Engine clusters burning simultaneously are permissible but will all be considered part of the same stage. There is no upper limit to the amount of stages that the rocket may contain, however, total combined impulse of all engines must not exceed 640.0 Newton-seconds of impulse.
4. All rockets must carry a standardized payload provided by SEDS-USA. The payload will be cylindrical in shape, weigh 0.50lb, and will measure no larger than 2.14 inches in diameter and 5.00 inches in length. The payload must not detach from the rocket at any point during the flight and must be recovered intact and returned to SEDS-USA. The interface to this payload will be standard and further information will be provided at a later date. Tampering with the payload outside of normal operating procedures (as defined by SEDS-USA) is prohibited and will result in disqualification from the competition.
5. The provided payload will contain a standardized altimeter and data logger which will be used by all teams. Official data used in the competition scoring will be obtained only for this payload. Teams may use additional altimeters, sensors, and data loggers but only the data collected by the provided payload will be considered official.

...

b. Flight score
i. Altitude - One point will be awarded for every 200 feet of adjusted altitude reached by the rocket during flight, as measured by the provided payload.
ii. 3500 foot altitude bonus - 5 points will be awarded to teams who achieve an adjusted altitude of 3500 feet or higher. No points will be awarded to teams who do not reach this altitude.
iii. Staging bonus - Rockets that contain a third stage will receive a bonus of 4 points for a successful stage ignition. Rockets that contain four or more stages will receive a bonus of 6 points for ignition of each successive stage.
iv. Payload recovery bonus - 5 points will be awarded to teams whose rocket, less any discarded stages, is recovered without damage. "Without damage" is defined as a rocket that could be flown again if the propulsion system is reloaded and the recovery devices re-packed, without any further repairs to the rocket.
v. Stage recovery bonus - 3 points will be awarded for each discarded stage that is recovered without damage.
c. Multimedia documentation - A maximum of 10 points will be awarded for video documentation of the rocket flight. 6 points will be awarded for high-definition video taken from a camera onboard the rocket. 2 points will be awarded for high-definition video or high-resolution images taken of the launch from the ground, and an additional point will be awarded if photos and videos submitted by teams are well processed and presented.
 
I am from SEDS (Students for the Exploration and Development of Space) and every year a rocket competition is held. This year's competition is to have a multi stage rocket go to at least 3500' with the combined impulse no higher then 640 Ns. As our club or myself has never built a multi stage rocket before, we first ordered a kit to get the hang of things. I still have many more questions about building the rocket, along with questions regarding the electronics, av bay, air starting, and motor retention. Is there a good place to go for information regarding multi stage rockets, or good documentation regarding them? I did a google search but not too much came up. Thank you for your help.

Posting here is certainly a good idea. May I suggest getting in touch with these guys: https://urrg.org/ (the Buffalo area NAR/Tripoli club) In addition to possible local mentorship, they may be able to help with test flight logistics.

<edit> What kit did you order ?
 
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Avoid this. Make sure you use electronics that you can set ignition lockouts based on time and altitude.

[video=youtube_share;1VAkWgbCtA4]https://youtu.be/1VAkWgbCtA4[/video]
 
I probably should have posted specific questions. I have read through the article on apogee but that is only for a 2 motor multi stage. The competition awards additional points for having 3 or 4 stages in the rocket, and I want to know if this is possible and how so? I understand you need electronics for each of the stages, but for separating the airframe does the motor thrust provide enough force to break the shear bolts or do you need additional force like as in a ejection charge?
Start out with 2-stages until you understand what you are doing and have several successful flights under your belt.

You can easily get over 5 kft with a 2-stage rocket if you build it right. The is a chart of PML 2-stage kit and how high they will go with a given set of motors.
https://publicmissiles.com/images/PMLMotorRecommendationsTWOSTAGE.pdf Wildman has a number of 2-stage kits as well, but they may be heavier than straight fiberboard airframes. For example a PML 2.1" Mini BBX with a Terrier Booster should hit 5000' With an I booster and a H sustainer. The Rocksim file can be downloaded from the website. Wildman's 2-stage Blackhawk 29 will also do more than mile, as will any 29 mm dual deploy minis with a booster, and the 2.1" dual deploy Wildman Jr. with a booster should make 3500'+ with the right motor combinations. Wildman also as the Rocksim files on his website.

You do not use shear bolts to hold the stages together. Gravity and inertia do a fine job, and once the booster burns out, you want it to drag separate before you ignite the sustainer or you risk toasting the booster. Look at some of the URRF 2-stage flight videos to see how it's done, and talk to the URRG guys, they'll be happy to give you some help.

Bob
 
I believe Fred from MDRA, put up about four multi stage at URRF2, at least one was a triple. Very cool flights. That guy has it down.
 
Hello,

I wanted to add my 2 cent sales pitch here and ask that you try some of your simulations with Loki Research 38mm reloads. I know you are probably on a budget, so you should know that all Loki Research "G" through "I" can be shipped by the USPS without the $28.50 Haz-Mat charge. I don't have a huge selection of different motors right now, however I will make a few important points.

All of these Loki Research motors that are USPS shippable have a regressive thrust profile, meaning they produce the majority of their thrust right at ignition. It is important for any rocket to leave the launch rail at a speed fast enough for the fins to do their job and direct the rocket in a strait upward path without being affected by cross winds. It is even more important for a heavier 2 stage rocket with multiple sets of fins. If a rocket weather cocks into the wind, it will decrease your maximum altitude as it will no longer be going strait up, but up and out. When it stages, it will only continue to go even further out if there is any staging delay.

Since the payload is 2.14" in diameter, a 38mm motor mount would be ideal given the impulse restrictions. You would also be able to make the rocket shorter since a larger 38mm diameter motor will be shorter than a 29mm motor of the same total impulse. Keeping the rocket as short as possible has several advantages when it comes to staging. Long and skinny is not the best way to go in my opinion. A short rocket will have less force on your staging coupler as well. Shorter rockets also have less drag, and they weigh less, allowing you to add weight only if it is necessary to achieve the optimal mass for maximum altitude.

If you paired an I-405 Loki White (493.2Ns) and G-80 Loki White (122.5Ns) together you'd have a total impulse of 615.8Ns. That's only 24.2 Ns off the total allowed. Not bad eh? If you ask anyone about the I-405, they will agree, it's hard to find a motor that hits any harder for an I motor. Here is an example in a 4" diameter Madcow Torrent. I believe it went over 5,000'. [video=youtube;VY6xKmrAQkY]https://www.youtube.com/watch?v=VY6xKmrAQkY&list=UUW1iTWiT_ByZ0HUBoCHTiqA[/video]

The Loki White propellant it also easy to light. I know others will say that CTI's black powder ignition pellets are the way to go, and yes they are good, but a well placed, reliable igniter with a roughed up propellant surface will light Loki White nearly as fast. Also, Loki Research motors have an extremely low failure rate, two since 1/1/13. If your motor fails, then so do you. Lastly, keep it as simple as possible. Staged rockets are complex enough with only 2 stages. Simulations will show amazing results with multiple stages, but those of us who have flown know that in the real world, getting the actual flight performance to be perfect is much harder than what simulations will make it seem. Simulations assume that everything is at a set, given condition, but on the field, that is never the case.

If you have any questions with regard to using my propulsion systems, please let me know if I can help. Above all else, be safe and have fun doing it.
 
Avoid this. Make sure you use electronics that you can set ignition lockouts based on time and altitude.

[video=youtube_share;1VAkWgbCtA4]https://youtu.be/1VAkWgbCtA4[/video]

Holy sh!!!!!!!!!!!!! Yes, avoid that.
 
Posting here is certainly a good idea. May I suggest getting in touch with these guys: https://urrg.org/ (the Buffalo area NAR/Tripoli club) In addition to possible local mentorship, they may be able to help with test flight logistics.

<edit> What kit did you order ?

I actually launch with URRG monthly and know the people who run it very well but I wanted to see what information I could find on the form before going to them. I ordred a kit from Ken Allen; a US rocket kit just to get our feet wet with the idea of multi stage rockets.
 
The Loki White propellant it also easy to light. I know others will say that CTI's black powder ignition pellets are the way to go, and yes they are good, but a well placed, reliable igniter with a roughed up propellant surface will light Loki White nearly as fast.

+1 on that. Loki G80's and I405's light quick and hit like a truck.

This is a G80 in a 53" long rocket
14946300542_babbac3ab4.jpg


The hardware is also of amazing quality...
14117524945_4595453a8a.jpg
 
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