ARLISS Team NH - Page 57 — Parallax Forums

ARLISS Team NH

• Posts: 59
edited 2011-05-29 08:04
Hello Everyone,
I have been working on a calculation that will tell us the exact amount of strain that we are putting on the axle. This calculation is:
J = ∆P = m∆v = m(v1 – v2)
J is the impulse, v1 and v2 are the beginning and end velocities and ∆P is the change in momentum, m is the mass.
To get the first velocity, or v1, I calculated the velocity of the rocket 2 seconds after apogee with a simple equation to get the free fall velocity.
vf = vi + (-9.8 m/s)(2 sec)
Vi equals 0 since it is the velocity at apogee. This comes out to our rocket’s speed being 19.6 m/s or 43.84 mph after 2 seconds of free fall.
To get the speed after the parachute deployed we simply assumed that the ASP would be going at around 5 m/s which is about 10 mph, if anyone has a more accurate number based on previous data please post it so that we can put it into the equation.
This leaves us with:
J = 1.684kg (19.6 m/s – 5 m/s)
J = 1.684kg (14.6 m/s)
J = 24.58 kg m/s
Kg m/s actually equals newtons seconds so our final impulse is 24.58 newton seconds so a sustained impulse of 24.58 newtons over a period of one second or a higher impulse over a. This is the impule without taking into account the elastics in the shock line, the deployment bag, or the method of folding the shock cord. If this looks right we need to test how many newtons the axle can handle and then compare it to see if this would work before even a drop test. I want to test the servo axle until failure but I clearly don’t want to just break a servo until all of you look over the information and agree if this is even a worthwhile test and that my math assumptions and reasoning is correct since this is all new to me.
Justin
• Posts: 235
edited 2011-05-29 08:47
Justin,
I'm impressed by your calculations aha, but there is one thing. At apogee, the rocket won't be halted. These rockets rarely will shoot straight up, to reach momentary stillness. What will most likely happen, Is the rocket will still be shooting off side ways as it stops it's raise in altitude to then return back to ground. I am uncertain of the speed, as that is unpredictable to me, but thAt will still effect your calculations I believe.
• Posts: 59
edited 2011-05-29 10:03
Hi Dylan,

Do you have any suggestions on how we could improve the calculation so that it is more accurate. Thank you for postig the issue.

Justin
• Posts: 235
edited 2011-05-29 10:48
Justin,

The path the rocket takes is unpredictable for us. There are too many variables such as wind, condition of the launch pad etc.. I believe that your ending calculation is a good starting point to see how many newtons the "axle" must sustain. Although, word of caution. I have never had a chance to take an in depth look at the release mechanism, and we must be sure that the forces exerted are on the axle, and not possibly the side of the wheel or a certain bolt. Its just something to double check that I believe is very important in the success of the release mechanism working properly.
• Posts: 546
edited 2011-05-29 18:52
Sylvie,
Thank you very much for you explanation.... I will have to wait until Mr. Kibler has the convenience of testing it inside of his gas chamber.

Great dialogue team!

It's actually called a vacuum chamber, not a gas chamber. A gas chamber is something that's very, very different and it has a dark past. They were used at Auschwitz and Treblinka, two places I've visited. I cried at both places. If you aren't familiar with Auschwitz and Treblinka (and Bergen-Belsen, etc.) do a bit of research.

Yes, Sylvie, we did discuss-- and use-- a parachute deployment bag two years ago. I hadn't considered use rubber bands around the shock line to dissipate the energy of the parachute opening though. Great ideas. I'm inclined to use all three of your suggestions:

1) A parachute deployment bag
2) A long(er) shock line, and
3) Rubber bands around the shroud lines.

Thanks for tweaking the "wiggle" program. We'll try it at practice tomorrow and have the Rocketeers report back. We'll also be "testing to failure" by drop testing the full sized rover prototype until the servo comes apart. Then we'll have a better idea where the weak points are and how to mitigate any failure.

Did I tell you the Rocketeers are presenting at the University of New Hampshire Space Grant Consortium conference on Thursday? They're also getting a full "VIP" tour of the facilities and they get to meet NASA astronauts, etc. Pretty cool, huh?

Attached is a video of bench tests of the parachute release mechanism. It wll give everyone a better idea how it connects to the wheel hub and where the stress forces will be focused.

Mark
(rhymes with TARC)
:cool:
• Posts: 546
edited 2011-05-29 19:37
Hello Everyone,
I have been working on a calculation that will tell us the exact amount of strain that we are putting on the axle. This calculation is:
J = ∆P = m∆v = m(v1 – v2)
J is the impulse, v1 and v2 are the beginning and end velocities and ∆P is the change in momentum, m is the mass.
To get the first velocity, or v1, I calculated the velocity of the rocket 2 seconds after apogee with a simple equation to get the free fall velocity.
vf = vi + (-9.8 m/s)(2 sec)
Vi equals 0 since it is the velocity at apogee. This comes out to our rocket’s speed being 19.6 m/s or 43.84 mph after 2 seconds of free fall.
To get the speed after the parachute deployed we simply assumed that the ASP would be going at around 5 m/s which is about 10 mph, if anyone has a more accurate number based on previous data please post it so that we can put it into the equation.
This leaves us with:
J = 1.684kg (19.6 m/s – 5 m/s)
J = 1.684kg (14.6 m/s)
J = 24.58 kg m/s
Kg m/s actually equals newtons seconds so our final impulse is 24.58 newton seconds so a sustained impulse of 24.58 newtons over a period of one second or a higher impulse over a. This is the impule without taking into account the elastics in the shock line, the deployment bag, or the method of folding the shock cord. If this looks right we need to test how many newtons the axle can handle and then compare it to see if this would work before even a drop test. I want to test the servo axle until failure but I clearly don’t want to just break a servo until all of you look over the information and agree if this is even a worthwhile test and that my math assumptions and reasoning is correct since this is all new to me.
Justin

Justin,

Fine work~! You're certainly of the right track. You can measure the stress forces with the Pasco force sensor I gave you to use. Simply attach it in-line to the cord that's connected to the servo on the rover prototype. Then "test to failure" by drop testing like we discussed. We'll do that at practice tomorrow. We have several replacement servos.

Keep in mind that the maximum force that the force sensor can measure is 50 Newtons. I'll have Chase work on this with you at practice tomorrow. If the shock force required to "fail" the servo is greater than the stress forces you calculated then we *should* be good to launch. Even better if there's a big difference between the two. If not-- if the servo fails below the calculated failure point-- then we have to reconsider. So it'smportant that your calculations are correct...

Mr. Kibler
• Posts: 546
edited 2011-05-30 05:45

This comes out to our rockets speed being 19.6 m/s or 43.84 mph after 2 seconds of free fall. [/FONT][/SIZE][/FONT]

To get the speed after the parachute deployed we simply assumed that the ASP would be going at around 5 m/s which is about 10 mph...

This may be a faulty assumption about the speed (velocity) of the parachute. Since the rocket is traveling at a calculated speed of 19.6 m/s (43.84 mph) and since the parachute is coming out of the rocket, wouldn't the parachute (and the ASP) also be traveling at the same velocity?

To calculate the ASP's descent speed we can use RockSim rocket simulation software. Simply enter the parachute diameter and the weight of the payload. But then, both are also traveling at the same relative velocity since one is attached to the other...

Maybe Dr. Allen and friends can enlighten us here?

Good morning (yawn),

Mr. Kibler
:cool:
• Posts: 85
edited 2011-05-30 17:30
Hi all- just to make sure that everyone knows, what is the exact time again the team should be there? Thanks.

Also, I think we should all be very happy with the results today. The release mechanism worked like a charm.

Mr. Kibler- were you serious about singing the UNH song, and if so where can I find it and what us it called.

See you tomorrow!
-Jake-
• Posts: 235
edited 2011-05-30 18:52
We should be at the presentation by 7:15 at the latest to get everything set up by 7:30
which is when the rotary STARTS.
• Posts: 17
edited 2011-05-30 19:26
What time will the rotary presentation be done by? I cannot miss or be late to my A block class which starts at 8:15.
• Posts: 546
edited 2011-06-01 18:41
Hi all- just to make sure that everyone knows, what is the exact time again the team should be there? Thanks.

Also, I think we should all be very happy with the results today. The release mechanism worked like a charm.

Mr. Kibler- were you serious about singing the UNH song, and if so where can I find it and what us it called.

See you tomorrow!
-Jake-

Jake,

Are you and Obie prepared to sing the UNH fight song, 'On To Victory', at UNH tomorrow? I thought you guys researched and rehearsed it on Sunday...! If not, here are the words. The tune is somewhat similar to "Old McDonald Had a Farm", but not exactly. I do know the 'UNH Alumni Song' is sung to the tune of "Lancashire" by Henry Smart.

On to Victory (the UNH fight song)

On to victory
Our team will fight and do or die
Old New Hampshire's here
We'll raise our banners high
for alma mater dear
New Hampshire fight with all your might
On to victory
forever Blue and White

See you in the morning,

Mr. Kibler
<
(with tongue in cheek... what does that mean?!)
• Posts: 85
edited 2011-06-04 06:21
Hi all- Just wondering how the procedures are coming. Is there a procedure you would like me to work on? Besides getting the procedures written and packing for the trip, we are fairly good to go.

Have we decided to go with the release mechanism?

Mr. Kibler- Did you recover the forward reverse, forward reverse program?

Thanks again,
-JAKE-
• Posts: 46
edited 2011-06-04 07:53
Hola,
I had a marvelous time at UNH, and I particularly liked the ice cores. It's really cool seeing the layers in the ice that designate the different years. Plus the cold was nice too and made the air outside feel really warm. The cosmic rays study with LRO was really interesting in how they were testing the effects of radiation on humans with blocks of plastic.

Anyways to help answer your question Jake we have most of the procedures done or being nearly done. Dylan help me out here, are there anymore procedures that need to be worked on?

And well Jake what do you think, should we use this mechanism? What does everyone think of it? I think that we should use it because it gets the job done and is very simple and easy to use. Also Mr. Kibler, Dyaln and Andrew have the forward, back, forward program working so it is nearly ready. And so far none of our tests have failed but the future isn't written. I still think we need a hubcap on the other side though to help roll it in case it lands vertical. So how is that coming? Is it being worked on now?

See everyone Friday,
Obie
• Posts: 235
edited 2011-06-04 18:37
Obie,

What procedures do we have done? The only one I can think of that is finished is the one for the Bee-Line transmitter, and thats it. There are still many more to write that I can think of. Such as the night before procedure, pre-launch, recovery as well as some for certain transmitters/receivers.

Some how at the end of the day at UNH, someone had closed the laptop and/or shut it down without saving the current programs. We had to re-write the program to as close as possible, but there is still something that is confusing both Mr. Kibler, Andrew and I.

Our program was edited to incorporate a "wiggle" once it lands.... We used a variable to say in the program-
wiggle = wiggle + 1

If "wiggle" = 1 then blah blah blah

If wiggle > 1 then gosub movement

return
(you can see more in the program attached.)

For whatever reason, "wiggle" didn't equal one nor two, even though it was never put into use anywhere in the program besides that section. It equaled 68 the first time we had the program. After re-creating it.. It now equals 112, 113, 114 and so on. It is NEVER even used anywhere else in the program. How is it jumping 111 digits to that number before it is even used? we changed the program to-

IF wiggle = 112 THEN (and so on)

Then it worked. How is the stamp somehow coming up with this almost random number?

*** We added a DEBUG statement when it is suppose to "add one to wiggle".. The number one "CR," under is the value of the VAR "wiggle" ***
• Posts: 85
edited 2011-06-05 06:14
Dylan- Because i'm still fairly new to the team, what do you suggest I do in terms of procedures. I shouldn't do the night before procedure because I don't know what to expect. What about the others?

Thanks again,
-JAKE-
• Posts: 546
edited 2011-06-05 07:12
Dylan- Because i'm still fairly new to the team, what do you suggest I do in terms of procedures. I shouldn't do the night before procedure because I don't know what to expect. What about the others?

Thanks again,
-JAKE-

Rocketeers,

Attached are the two Procedures that have been written so far. I posted these to Emily before. There should be Procedures from last year on some team members' computers. You should figure out which Procedures haven't been written and get them in order before we go to Nevada. What about an 'arming' (turning on the BOE) and a disarming procedure? What about the MAWD, and a procedure for packing the parachute. loading the rover, etc.? Will you remember to clear the data buffer on the flash drive if you don't write it down? Does the CO2 sensor have to be calibrated or 'warmed up'? Do the rover and the parachute go in the payload tube right-side up or upside-down...?

Andrew and Dylan can, and should guide you along because they know the load-launch-recover sequence from previoue years. If they don't post to the forum I suggest that you e-mail them.

Mr. Kibler
:cool:
• Posts: 46
edited 2011-06-05 11:29
Just got back from the mooseman triathlon, had a great time. I took a quick glance at the code and was wondering if this part may be the problem?

IF wiggle = 112 THEN

PULSOUT nInp, 1000
PULSOUT nInp, 500

PAUSE 2000

PULSOUT nInp, 10000
PULSOUT nInp, 10000

PAUSE 2000

PULSOUT nInp, 500
PULSOUT nInp, 1000

PAUSE 2000

PULSOUT nInp, 10000
PULSOUT nInp, 10000

PAUSE 2000

PULSOUT nInp, 1000
PULSOUT nInp, 500
ENDIF

IF wiggle > 112 THEN GOSUB movement

I'm not sure about this but it seems a little odd that the "If wiggle > 112" is in there twice with two different statements. But thats just me.
That's it for now,
Obie
• Posts: 546
edited 2011-06-06 07:52
Obie Wan wrote: »
Just got back from the mooseman triathlon, had a great time. I took a quick glance at the code and was wondering if this part may be the problem?

IF wiggle = 112 THEN

PULSOUT nInp, 1000
PULSOUT nInp, 500

PAUSE 2000

PULSOUT nInp, 10000
PULSOUT nInp, 10000

PAUSE 2000

PULSOUT nInp, 500
PULSOUT nInp, 1000

PAUSE 2000

PULSOUT nInp, 10000
PULSOUT nInp, 10000

PAUSE 2000

PULSOUT nInp, 1000
PULSOUT nInp, 500
ENDIF

IF wiggle > 112 THEN GOSUB movement

I'm not sure about this but it seems a little odd that the "If wiggle > 112" is in there twice with two different statements. But thats just me.
That's it for now,
Obie

Thanks Obie,

How was the triathlon? I didn't know you did them. Good for you~!

I'll download the program fix and try it to see what happens. Then I'll report back. Why does a "PAUSE 3000" make the motor move for three seconds...? I thought a pause is a pause is a pause.

Hard to believe we;ll be in Nevada in less that two weeks. Bring your sunglasses and sun screen.

Mr. Kibler
:cool:
• Posts: 235
edited 2011-06-06 16:01
Obie,
I'm not sure about this but it seems a little odd that the "If wiggle > 112" is in there twice with two different statements.
That statement is only in there once. The one at the bottom is different then at the top.

Mr. Kibler,
A pause does not make the servo move. When we sent the commands to the ServoPal to make the motor move, the pause just waits for the servo to have time to move. Its sort of like asking someone to move, then waiting for them to fulfill the task.
• Posts: 235
edited 2011-06-06 16:05
I did a check through my computer for check lists from last year. Since they are from last year, they will have to be updated..
These include..
-Arming Sequence
-PreFlight Checklist
-Night Before Checklist

Also the packing list for each individual person is included. Once again, these two years are different. So the list might need to be changed.
• Posts: 46
edited 2011-06-07 13:34
That statement is only in there once. The one at the bottom is different then at the top

Dylan Landry

My bad, but I still don't understand why you need to of them. The look like they do the same thing for different requirements. And don't we have the movement program elsewhere in the program besides it being after "If wiggle>112". That's it for now, got to go study for finals.
Obie
• Posts: 235
edited 2011-06-07 14:21
Obie,
We are not essentially having two of them. They are each different and do different things according to the size of the variable. I don't quite understand your question.
• Posts: 46
edited 2011-06-08 17:39
Nevermind Dylan I just figured it out. I mean answered my question.
Have a good week all,
Obie
• Posts: 546
edited 2011-06-09 06:01
Obie Wan wrote: »
Nevermind Dylan I just figured it out. I mean answered my question.
Have a good week all,
Obie

Obie,

Please explain it to us if you would. See you tomorrow for the presentation at the Planetarium.

Mr. Kibler
:cool:
• Posts: 59
edited 2011-06-11 06:26
Hi Everyone,

Just wanted to post for anyone not at McAuliffe Planetarium last night that the presentation went fairly smoothly. I talked to some of the attendees after and they said that they really enjoyed the launch. I also think we owe a thanks to the guy who climbed the tree to get our rocket back!

Justin
• Posts: 546
edited 2011-06-11 19:54
Hi Everyone,

I also think we owe a thanks to the guy who climbed the tree to get our rocket back!

Justin

Ah yes, the Unknown Man who climbed the tree to retrieve our rocket. He seemed eager to go up after it, didn't he?

Thank you, Unknown Man, wherever you are~! (see attached photo)

Vaya con huevos,

Mr. Kibler
:cool:
• Posts: 235
edited 2011-06-12 18:32
Here is the packing list for personal use...
• Posts: 46
edited 2011-07-01 11:48
I guess no one has been on the forum in a while. But just in case anyone happens to glance at it it, What should we plan on doing next year?
Great job at Nevada everyone. The rocket launches were amazing, no? And we were able to retrieve our rover and accomplished our goals...sorta.
Keep in contact and have a great summer!!

-Obie
• Banned Posts: 5,065
edited 2011-07-01 13:21
Great job at Nevada everyone. The rocket launches were amazing, no? And we were able to retrieve our rover and accomplished our goals...sorta.

Details, I've been waiting - Enquiring minds want to know.
• Posts: 1,622
edited 2011-07-02 11:14
I'm with PJ - how about a launch report?