So, maybe I'll try a three-stager

JimJarvis50 said:

Keeping in mind that I only do this once a year (OK, twice sometimes) ....
And keeping in mind that I will probably have motors left over after this flight (sadly) ....

Click to expand...

Yep. I've seen you recover an unused rocket motor.

But hey, better that than other failure modes, eh?

-Kevin

H_Rocket said:

Jim

the two stage at LDRS XXX - did you ever locate the sustainer? In my sleep deprived fog, I though I remember that it staged successfully then disappeared.

Click to expand...

Another of my interesting flights. Let me say first that I repeated that flight (N2500 to M745) at LDRS 32 at BlackRock and got to 74K feet. My simulation for Argonia was 47K. There are some reasons that a 47K simulation at Argonia turned into a 74K flight at Balls, but obviously, there was a little uncertainty in the 47K estimate.

I had a feeling that my 47K estimate might be a bit low, so in the interest of protecting all aircraft above the 50K waiver, I decided to program my Raven to pop the apogee charge if the rocket reached 45K and was still going up. That was indeed the event that separated the rocket. Unfortunately, the rocket was travelling about Mach 1.4 (iirc) at the time. The rocket drifted up to 49,999 and came down with a big zipper. I re-rolled the upper airframe for the BlackRock flight 2 years later.

My simulations are much better now.

Jim

JimJarvis50 said:

Unfortunately, the rocket was travelling about Mach 1.4 (iirc) at the time. The rocket drifted up to 49,999...

Click to expand...

Wow, now that is kissing the waiver.

troj said:

Yep. I've seen you recover an unused rocket motor.

But hey, better that than other failure modes, eh?

-Kevin

Click to expand...

It's happened twice to me. Once, the blue thunder shavings failed to light, and on another, the tiltometer shut down the flight. Both motors got second chances.

Jim

A5tr0 An0n said:

Out of curiosity, what are those estimates?

Click to expand...

Numbers I recall were in the $50K range, plus or minus. Those assumed much larger rockets, custom machining, test flights, etc. Now we know it can be done with a fiberglass, Class II, two-stage rocket.

Jim

Glad I can make it to Balls this year. Looking forward to seeing the flight, assuming it happens.

How are you getting the RockSim and Rasaero sims so close to each other? RockSim Pro?

One thing I can share at this point is the electronics strategy for the flight. Here are the things that control the flight (excluding tracking/telemetry):

1st stage: Two Perfectflight Stratologgers
2nd stage: One Stratologger and one Raven 3
3rd stage: Two Raven 2's with the high altitude firmware.

The plan for the Raven's is laid out in the attached pic. For the second stage Raven:

- The first channel is barometric apogee deployment with a delay. The purpose of the delay is to allow the second and third stages to separate before their apogee charges go off in the event the second stage motor doesn't fire.
- Channel 3 will light the second stage motor (through the tiltometer). The motor ignition is based on a timer with an altitude check.
- Channel 4 is the separation charge between the 1st and 2nd stages. It will probably not be needed (i.e., I expect these to drag separate).

The third stage has two Ravens. For the first Raven:

- Channel 2 would fire the separation charge between the second and third stages after two burnouts and a 12-second delay. The delay will allow these stages to coast together until the velocity drops to a reasonable level.
- Channel 3 would fire the separation charge if the 2nd stage motor doesn't light. The charge would fire at barometric apogee, and the apogee charges on the two stages would fire 2 seconds later. The stages are pinned together, and I would like to separate them before the apogee charges fire.
- Channel 4 would fire the 3rd stage motor (via a second tiltometer) based on time with an altitude check.

For the second Raven:

- Channel 1 is barometric apogee if the altitude is less than 90K feet. This channel would be responsible for apogee deployment in the event that either the second or third stage motors didn't light, of if apogee is less than 90K for whatever reason.
- Channels 2 and 3 would be apogee deployment, based on time, in the event all three motors fire (i.e., apogee is above 90K). The time is based on the simulation results, and Channel 3 has a 2-second delay.

I always run these simulations by Adrian just to get the benefit of his experience. We've pretty much stacked hands on this plan.

Jim

JimJarvis50 said:

Numbers I recall were in the $50K range, plus or minus. Those assumed much larger rockets, custom machining, test flights, etc. Now we know it can be done with a fiberglass, Class II, two-stage rocket.

Jim

Click to expand...

I for one am glad to see that they were way off.

JimJarvis50 said:

After the second stage burn, however, the speed is too high to drop the second booster right away.
Jim

Click to expand...

As discussed - Pad slave #n here.

Noob question - what happens when you try to separate stages at a "too high" velocity?

Zebedee said:

As discussed - Pad slave #n here.

Noob question - what happens when you try to separate stages at a "too high" velocity?

Click to expand...

I don't usually get much data from my boosters (they only have simple deployment electronics, so no lateral acceleration for example). I have noticed that they slow down very quickly though. I also saw this Rockets Magazine video of my LDRS flight:

https://www.youtube.com/watch?v=j2Q1TeNx6SI&index=3&list=PLEISeVEqORmyQ_SWUlpwt-U4INlmn0PNj

This separation would have been at about Mach 1.3. I don't think I'd like to see this happen at Mach 2.

Jim

With respect to integrating a winch into the raising of the pad: Could you create a longer lift bar that attaches to the CG of the rail, fit it into a guide track on the ground so it can't wobble side to side, run that track to a winch that is placed directly under the pad, connect the cable for the winch to the lift bar near the ground and pull the lift bar toward the pad raising the rail? How many degrees it could get you to vertical would be dependent upon the length of the lift bar as a multiple of the height of the rail CG above ground level.

This is almost certainly more trouble than it is worth...I don't claim all my ideas are good ones.

Because pictures are better:



Even better would be if the arm attachment to both guide and launch rails could be locked or be free to slide. Then you could pull it to 45 degrees in the config shown, lock the bottom, move the cable to a point near the launch rail/arm pivot, unlock that pivot (labeled above as "fixed pivot CG"), and pull the lifting arm down. This would then push the rail nearly to vertical as the lifting arm approaches the winch.

Cl(VII) said:

With respect to integrating a winch into the raising of the pad: Could you create a longer lift bar that attaches to the CG of the rail, fit it into a guide track on the ground so it can't wobble side to side, run that track to a winch that is placed directly under the pad, connect the cable for the winch to the lift bar near the ground and pull the lift bar toward the pad raising the rail? How many degrees it could get you to vertical would be dependent upon the length of the lift bar as a multiple of the height of the rail CG above ground level.

This is almost certainly more trouble than it is worth...I don't claim all my ideas are good ones.

Because pictures are better:

View attachment 175547

Even better would be if the arm attachment to both guide and launch rails could be locked or be free to slide. Then you could pull it to 45 degrees in the config shown, lock the bottom, move the cable to a point near the launch rail/arm pivot, unlock that pivot (labeled above as "fixed pivot CG"), and pull the lifting arm down. This would then push the rail nearly to vertical as the lifting arm approaches the winch.

Click to expand...

Ah, this is the sort of thinking that I was hoping to get. Going with the Part 1 idea, the CG would be about 12 feet up at vertical. So, at least a 12-foot bar. The initial stress on things could be reduced by starting with the rail raised as much as possible (giving the PS's something to do).

The biggest issue I see is the downward force on the rail when the lifting bar is at a shallow angle. The rail itself is segmented. There is a four foot section on the bottom and then two six-foot sections. The joint is overlapped by a pipe on the bottom and two 1/4" plates on the sides. This joint can be seen in Post 17. It would take a bit of thinking to figure out what the net force was on that joint, and also the net force trying to move the pad itself horizontally. Perhaps a winch could be mounted on the pad legs?

Thanks for taking the time to draw this out.

Jim

Please forgive me if I missed it, but is your CG with the rocket loaded on the rail? Also do you happen to have an estimated weight of the 3 stages and the rail?

Also, if you have the location of the fulcrum I could try a little math and physics to see how much torque you would have to overcome to raise the rocket.

JimJarvis50 said:

Ah, this is the sort of thinking that I was hoping to get. Going with the Part 1 idea, the CG would be about 12 feet up at vertical. So, at least a 12-foot bar. The initial stress on things could be reduced by starting with the rail raised as much as possible (giving the PS's something to do).

The biggest issue I see is the downward force on the rail when the lifting bar is at a shallow angle. The rail itself is segmented. There is a four foot section on the bottom and then two six-foot sections. The joint is overlapped by a pipe on the bottom and two 1/4" plates on the sides. This joint can be seen in Post 17. It would take a bit of thinking to figure out what the net force was on that joint, and also the net force trying to move the pad itself horizontally. Perhaps a winch could be mounted on the pad legs?

Thanks for taking the time to draw this out.

Jim

Click to expand...

No problem. Your projects are just astounding, I look forward to following along on this one.

BLKKROW said:

Please forgive me if I missed it, but is your CG with the rocket loaded on the rail? Also do you happen to have an estimated weight of the 3 stages and the rail?

Also, if you have the location of the fulcrum I could try a little math and physics to see how much torque you would have to overcome to raise the rocket.

Click to expand...

Roughly, the rail assembly itself is 95 lb about 10' up the 16' rail. The rocket is 115 lb about 7.5' up from the base of the rocket (which is close to the base of the rail). The net CG is 210 lb about 8.6' up. I'm just assuming 9' to make things simple. With the clamshell pad in post 17, the fulcrum would be about 2' off the ground and the base of the rail about 3' up (the pad can be set lower than what is shown in Post 11). So, the CG point would be about 12' up (9 + 3) with the rail elevated.

Jim

If my understanding is correct and the rocket/rails CG is about 12 feet from the fulcrum. All of the numbers the below are approximate as there is no exact weight and exact CG.

Then the rocket and rail are imparting 2,424 foot/lbs of torque on the fulcrum. If you put one man on the very end of the rail pushing orthogonally to the rail and they are pushing at 70lbs of force. They will impart roughly 959.9 ft/lbs of torque.

So without any help you can overcome about half of the torque.

What I would do to make it easy is get a few people to push from below. Then support the rail with some 2X4's that way it does not fall back. Then have some people on ropes on the other side of the rail pulling it into the vertical position.

The longer the rope the easier it will be, and as the angle between the rail and the force vector increases it will also be easier.

I think this will save on time and complex designs. Now that I am typing this I believe Derek Deville lifted his tower for the Qu8k rocket with nothing but man power. The tower looks rather tall and heavy.

Just my 2 Cents. Take it as you will.

Maybe you could do something like a suspension bridge: have a pole about 2/3 the length of the tower that stands vertical when the rail is horizontal. That way, when people pull down on the other end of the rope, the pole pulls upward on the rail.

I don't know if you can understand it by description or not...

CarVac said:

Maybe you could do something like a suspension bridge: have a pole about 2/3 the length of the tower that stands vertical when the rail is horizontal. That way, when people pull down on the other end of the rope, the pole pulls upward on the rail.

I don't know if you can understand it by description or not...

Click to expand...

I was thinking about the same thing. Derek did the same thing on his tower.

The key is the angle of the force vector to the object. The optimal angle is 90*.

Jim,
First, what he said (Stealth 6, post 5, above.) I love your projects! And, thank you so much for your guidance in the past.
On your project, Kyle has the right idea on lifting the rail. It is most efficient to lift from the top of rail. If you lift at the cg, you have to lift the entire weight of the rocket and the rail. However, when the rail is horizontal and supported at the ends, roughly half the weight is supported by the base (probably significantly more than half) and the people lifting at the top have to lift half the weight. If you are worried about stress on the joints, you could have an aluminum pole attached at the top and another 6' down at the next joint. When the rail is horizontal (worst case) each person would have to apply a little more than 50 lbs, and much less as the rail approaches vertical.
It would be fairly easy to attach the poles with a couple L brackets bolted to each side of the rail. The top pole would only need to be about 10 feet long for a 6' tall person to easily push the 19' tall(6+6+4+3 ?) rail nearly vertical. I would think a couple 10' X 1.5" aluminum poles and a few L brackets would add very little to the budget, comparatively. KIS(I took the second S out for you.)
I hope this helps a little bit.
Matt

NorthwoodsRockets said:

Jim,
First, what he said (Stealth 6, post 5, above.) I love your projects! And, thank you so much for your guidance in the past.
Matt

Click to expand...

You're welcome! I'm glad you pointed out S6's post. That one came in while I was responding to the one below it, and I didn't see it.

I'm reluctant to lift the rail in a way that puts torque on the rail or on the point where the rail attaches to the pad. Some torque is OK, but there is no way that I would lift the far end of the rail only.

My version of the geometry is in the attached pic. Pad Slave #1 is pretty tall. Let's assume that with some help (2 Pad Slaves on the other side of the CG), he could hold up the rail at a point 1' beyond the CG to a height of 8'. This puts the rail at an angle of 33 degrees to the ground. For reference, the distance between the fulcrum and the CG is 10' (1' of pad support and 9' of rail) and the weight at the CG is 210#.

Now, let's assume Pad Slave #2 grabs the clamshell rod at a point 5' from the fulcrum. He hangs off this rod and is able to apply a force perpendicular to the rod of 60#. That relieves 5/10x60=30# of the 210# weight. Let's also assume that Pad Slave #3 pushes at a point midway between the CG and the fulcrum. If he pushes perpendicular to the rail at 60#, that relieves another 30# of the 210# weight. Agree?

So, when Pad Slave #1 lets go, we have to make up 150# of force to hold the rail where it is. One option is to have Pad Slaves 4 and 5 grab the T bar and lift at 75# each (or angle the T bar more perpendicular to the rail and lift at 63# each). As the rail goes up, the weight they have to lift goes down as the mechanical advantage for Pad Slaves 2 and 3 improves. The initial weight, though, just seems like a little too much to me? Yes, the T bar could be placed outside of the CG, but that applies a torque to the rail and the rail attachment point.

Alternatively, one could use a rope. The "rope" in the pic is a 50' rope held 4' off the ground. For the angle shown, I calculate that the rope would have to be pulled with a force of 260# to hold the rail static (i.e., to hold the 150# remaining weight). Can someone check this calc? It assumes 126# upward force needed perpendicular to the rail, with 260# of pull resulting in 126# perpendicular to the rail and 227# down the rail.

Let's assume that a Pad Slave could pull tug-of-war style with a force of 30# (it's sandy out there). That would take 9 Pad Slaves (plus the Slave on the clamshell rod and the Slave pushing between the fulcrum and the CG). I don't have that many Pad Slaves! That would take a winch. Or perhaps a couple of Pad Slaves pulling on the rope could reduce the weight at the T bar a bit? Or perhaps I can just tie a rope to my truck and pull it up that way?

I believe that the rope at the CG would apply a force down the rail (about 227#) but would not apply a radial torque to the rail or at the point of attachment. Agree? This is important!

As a relatively minor point, pulling at the clamshell and pushing between the CG and the fulcrum will apply a counterclockwise torque where the rail attaches to the pad. Thus, it might be better to attach the rope a little higher on the rail, which would apply a "clockwise" torque at the point of attachment. Agree?

If one used a rope and winch only (i.e., no Pad Slaves at all), the required pull on the rope would be 364# and the force down the rail would be 318#. This might be OK as long as there is no torque on the rail. The resultant horizontal force on the pad, applied at the fulcrum, would be 305# (I think this is right?). Most likely, the pad would want to slide. I think it would be possible to attach guide wires to the fulcrum area and stake these down such that the pad won't slide. Make sense?

After considering the above, I'm thinking the best way to do this would be to have 3 Pad Slaves lift the rocket to the position in the pic, support the rail in that position with a 2x4, and then raise the rail with a winch attached to a vehicle, with a rope/wire attached to the CG, with no Pad Slaves near the rocket. This really depends on the lift not torquing the rail, but if the rail failed, the rail/rocket would just fall with no one getting hurt. PLEASE give me some feedback on the calculations and this plan.

Jim

JimJarvis50 said:

After considering the above, I'm thinking the best way to do this would be to have 3 Pad Slaves lift the rocket to the position in the pic, support the rail in that position with a 2x4, and then raise the rail with a winch attached to a vehicle, with a rope/wire attached to the CG, with no Pad Slaves near the rocket. This really depends on the lift not torquing the rail, but if the rail failed, the rail/rocket would just fall with no one getting hurt. PLEASE give me some feedback on the calculations and this plan.

Jim

Click to expand...

I think this is really the best option, take some people and lift the rocket as much as possible. Then place a brace under the rocket and move everyone to the other side and lift it with a few ropes.

This is the safest and simpliest option in my opinion. Again, please take what I say with a grain of salt because I have no experience with rockets this big or rails this tall. All I know is the math and physics behind it. I would strongly urge you to avoid winches/trucks pulling on the ropes the load they can place on the rail can be tremendous.

Sorry if I derailed your thread also.

Edit: To give you an idea about pulling with the ropes. If you have one person pulling at the 29* angle you have indicated on your drawing and they are 25 feet away with a force of 70lbs they will impart 116.59 foot/lbs.

Since the Qu8k rocket was mentioned here is a photo of them lifting it. Its mass was 320lbs + the weight of the tower. Basically my idea looks like this but instead of pad slaves pulling on the rope it would be done via a low powered winch. This takes away your dependance on having an increased number of slaves. Although I agree that a winch can possibly place overloads I think that doing it with a low powered winch at a slow and cautious rate while not using a vehicle to pull, will work no problem.

The small winch I had in mind was this one linked below.

https://www.harborfreight.com/2500-lb-atvutility-electric-winch-with-wireless-remote-control-61297.html

It is wireless and possibly easy enough to control and doable without having to mount on the vehicle. With this option you would still use the T-bar to initially lift via slave power and then the winch could take over and the use of 2x4's could aid/support it on the way up.

CarVac said:

Maybe you could do something like a suspension bridge: have a pole about 2/3 the length of the tower that stands vertical when the rail is horizontal. That way, when people pull down on the other end of the rope, the pole pulls upward on the rail.

I don't know if you can understand it by description or not...

Click to expand...

Yes, I follow. Worth thinking about.

Jim

BLKKROW said:

I think this is really the best option, take some people and lift the rocket as much as possible. Then place a brace under the rocket and move everyone to the other side and lift it with a few ropes.

This is the safest and simpliest option in my opinion. Again, please take what I say with a grain of salt because I have no experience with rockets this big or rails this tall. All I know is the math and physics behind it. I would strongly urge you to avoid winches/trucks pulling on the ropes the load they can place on the rail can be tremendous.

Sorry if I derailed your thread also.

Edit: To give you an idea about pulling with the ropes. If you have one person pulling at the 29* angle you have indicated on your drawing and they are 25 feet away with a force of 70lbs they will impart 116.59 foot/lbs.

Click to expand...

No problem. Thread is intact.

I'm not sure that a winch or truck would impart any more force than if the ropes (wires more likely) were pulled at the same angle. It's still my opinion that they key question is whether pulling at the CG will impart a torque on the rail. I don't think it does, but I'd like to hear from you on that question.

Not sure I understand your math or units, but I've posted my numbers and let's see what others think.

Jim

A5tr0 An0n said:

Since the Qu8k rocket was mentioned here is a photo of them lifting it. Its mass was 320lbs + the weight of the tower. Basically my idea looks like this but instead of pad slaves pulling on the rope it would be done via a low powered winch. This takes away your dependance on having an increased number of slaves. Although I agree that a winch can possibly place overloads I think that doing it with a low powered winch at a slow and cautious rate while not using a vehicle to pull, will work no problem.

The small winch I had in mind was this one linked below.

https://www.harborfreight.com/2500-lb-atvutility-electric-winch-with-wireless-remote-control-61297.html

It is wireless and possibly easy enough to control and doable without having to mount on the vehicle. With this option you would still use the T-bar to initially lift via slave power and then the winch could take over and the use of 2x4's could aid/support it on the way up.

Click to expand...

I'm pretty sure that the three-stage will be significantly more difficult to raise. The weights don't differ much, but wait till you see what it's like to have structure 25' over your head. It would be nice to support a winch with the T-bar or whatever, but if I can figure out how to not have folks nearby, that will be my preference.

I looked at that particular winch. The reviews of it, and certain aspects of the operation, don't look very appealing. I'm thinking we need something a little better.

Jim

xenon said:

Glad I can make it to Balls this year. Looking forward to seeing the flight, assuming it happens.

How are you getting the RockSim and Rasaero sims so close to each other? RockSim Pro?

Click to expand...

Dang, I missed your post. Came in while I was posting.

I was a little surprised that the simulations were in agreement. My experience is that Rocsim tends to come in a little low. I doubt anyone will be all that interested in the details, but I did a write-up on exactly how I did the RasAero and Rocsim simulations, and the document is attached. For some reason, my Rocsim file is a little too large, and I can't attach it.

The RasAero procedure involves piecing together a number of single-stage simulations. Chuck is aware of the procudure and understands what I'm doing, but he also cautions that the model may not support everything I'm trying to use it for (such as starting a single stage simulation at a launch altitude of 50K). So, I just represent that this is what I did and not necessarily that it is correct. I'm still looking forward to the multistage model (although with my luck, it won't do three-stagers).

In the write-up, you might note that I'm separating the second and third stages at burnout (versus letting them coast together and slow down a bit). I simulated both versions, and there is not much difference between the results.

Jim

View attachment Flight simulation documentation.pdf

JimJarvis50 said:

No problem. Thread is intact.

I'm not sure that a winch or truck would impart any more force than if the ropes (wires more likely) were pulled at the same angle. It's still my opinion that they key question is whether pulling at the CG will impart a torque on the rail. I don't think it does, but I'd like to hear from you on that question.

Not sure I understand your math or units, but I've posted my numbers and let's see what others think.

Jim

Click to expand...

First, your main concern is where to apply the force to prevent from hurting the structure/rocket. I believe the best place would be at the CG. However, the best place to apply the force to raise the rail the easiest would not be at the CG. So this is where I am conflicted, if you pull from the CG it would require more force to raise the rail. But applying more force to the CG may potentially hurt the rocket/structure more than applying less force not at the CG.

There is no simple answer on where to apply the force. If I were in this situation I would strengthen the rail as much as possible and enforce the area's you want to apply the force.

Also, sorry if my numbers or units don't make sense. I was just calculating the torque the rocket/rail is imparting to the fulcrum. Essentially that is the amount of force you would need to overcome. That is why I provided examples of the amount of torque generated by someone in different locations. I calculated everything in the standard SI units, then converted to foot/lbs as I feel more people on the forum would be able to imagine foot/lbs compared to Newton/meters. More info about torque:

https://en.wikipedia.org/wiki/Torque

If anything does not make sense please feel free to ask. I do my best at describing what I am thinking but may fall short at times.

BLKKROW said:

First, your main concern is where to apply the force to prevent from hurting the structure/rocket. I believe the best place would be at the CG. However, the best place to apply the force to raise the rail the easiest would not be at the CG. So this is where I am conflicted, if you pull from the CG it would require more force to raise the rail. But applying more force to the CG may potentially hurt the rocket/structure more than applying less force not at the CG.

There is no simple answer on where to apply the force. If I were in this situation I would strengthen the rail as much as possible and enforce the area's you want to apply the force.

Click to expand...

Agreed. Actually, supporting the rail at the CG isn't the complete answer. The torque on the center of the rail from the weight at the far end of the rail is significant. That problem still needs to be solved.

Also, sorry if my numbers or units don't make sense. I was just calculating the torque the rocket/rail is imparting to the fulcrum. Essentially that is the amount of force you would need to overcome. That is why I provided examples of the amount of torque generated by someone in different locations. I calculated everything in the standard SI units, then converted to foot/lbs as I feel more people on the forum would be able to imagine foot/lbs compared to Newton/meters. More info about torque:

https://en.wikipedia.org/wiki/Torque

If anything does not make sense please feel free to ask. I do my best at describing what I am thinking but may fall short at times.

Click to expand...

Well, I think the units of torque are foot-lbs not foot/lb. Not sure if that affects your calculation, but any time I see a units issue I question the calculation. But then again, it's been 40 years since I took statics, and I don't recall having been particularly good at it. That's why I ask for review.

Jim

JimJarvis50 said:

Agreed. Actually, supporting the rail at the CG isn't the complete answer. The torque on the center of the rail from the weight at the far end of the rail is significant. That problem still needs to be solved.



Well, I think the units of torque are foot-lbs not foot/lb. Not sure if that affects your calculation, but any time I see a units issue I question the calculation. But then again, it's been 40 years since I took statics, and I don't recall having been particularly good at it. That's why I ask for review.

Jim

Click to expand...

Yes it is foot-lbs sorry I mistyped in my responses. The calculations are still accurate.

What we need to do is the beam calculations for the rail. It would very likely be awful though because of the collinear constraint of the rail guides.