Acceleron V - build thread

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air.command
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Acceleron V - build thread

Postby air.command » Mon May 04, 2009 2:22 pm

I thought I'd start a build thread for our latest rocket. - Acceleron V

This is going to be our highest capacity rocket(booster) to date at ~33 Liters. (Previous highest was 24L). One of the main problems with our bigger 2 stage rockets has been that they really weren't scalable in the sustainer department. With the staging mechanism at the top of the booster it meant that if the sustainer was much longer there was a real danger that it would bend at the staging mechanism and either send the rocket off course or simply snap the staging mechanism. There really wasn't a suitable option for adding support for the sustainer without adding considerable weight to the booster.

With this design we have pushed the booster's segments further appart and are now placing the sustainer lower down between the segments. This will enable the segments themselves to be used as guide rails for the sustainer and should enable us to support a 2m long sustainer. This should also allow for a smaller third stage later with a shorter second stage.

Here are some overall concept drawings:

Image
The sustainer will likely be longer than shown here.


Image



Image
Top view of the base plate that holds the segments together. It is made from a combination of aluminium, CF and PVC.


Image
Bottom view of the base plate. The central aluminium attachment point holds the entire rocket down as well as providing an air supply connection for the sustainer. It has to hold down about 80Kg when the rocket is pressurised to 130psi.

Image
Base plate in context.



One of the main concerns here is the stability of the whole rocket. With the water in the sustainer much lower down now the overall CG is much further aft. We can change the position of the staging mechanism up and down, so if the rocket is unstable we can push it higher up.

We will be using the launcher that we normally use with the drop-away boosters which can supply two different pressures to the booster and sustainter. This will allow us to optimize the pressures for both stages.

We will also be using fully redundant systems for both staging and recovery for this rocket. The primary system will be based on the booster pressure so that staging happens at the optimal time, and the other will be timer based as backup that will be set to fire about 1 second after predicted staging, should the first system fail. The booster will have two parachutes, each of which will be deployed by the separate systems.

We'll also be using bigger nozzles compared to the older boosters to get more thrust on takeoff. I am yet to run full simulations of this booster, I'll do that when I know the final weight. We expect though to get similar release velocity and altitude as with the older boosters, but with a sustainer about 3 times bigger.

We're already well into the construction phase, I'll post actual build photos shortly.
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Postby october sky » Mon May 04, 2009 2:42 pm

That is VERY impressive George. You really know your rockets ! :) 8)
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Postby ~RR~ » Mon May 04, 2009 3:14 pm

october sky wrote:That is VERY impressive George. You really know your rockets ! :) 8)


2 meters :shock: wow.... good stuff... 8)
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Postby whipfest » Mon May 04, 2009 5:41 pm

Can't wait to see this one go up !!

Nice (and obviously well thought out) design 8) 8)
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Postby OverTheTop » Mon May 04, 2009 6:01 pm

Nice stylish looking design. It's great how 3D CAD modeling takes a creation from someone's minds-eye and transforms it to paper (well, almost!) for us all to see!

I must have a look at water rockets in my spare time....

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Postby Kryten » Mon May 04, 2009 10:06 pm

Now that's impressive.
Are you expecting to have it ready for this month's launch?
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Postby air.command » Tue May 05, 2009 12:19 am

Thanks for the nice words guys,

OverTheTop: We find doing it to scale in a CAD package makes it so much easier to conceptualize how the different bits fit together and lets us check clearances on the different components. I often print out templates from the program and then manufacture from those.

Kryten: I'm trying to get it built by the next launch, although from experience I know that it often takes a bit longer than I'd like so most likely the launch after that. Better to get it right than rush it. There is still lots of pressure testing to do.
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Postby Bones » Wed May 06, 2009 12:27 pm

Wow George, you have outdone yourself this time! Looking very forward to seeing this one fly.

Love the graphics. What particular CAD program do you use?
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Postby Andrew Burns » Wed May 06, 2009 4:37 pm

Going to guess 3D studios max or similar?

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Postby air.command » Wed May 06, 2009 8:29 pm

Andrew Burns wrote:Going to guess 3D studios max or similar?


Spot on Andrew. Yes its 3DS Max.
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Postby air.command » Wed May 06, 2009 11:41 pm

Here are a couple of progress pics:

Image

The partly assembled base plate. Still missing is the air supply and retention component which will get made in the next week or so. The struts are not glued in yet.


Image

The three cluster segments with nozzles. All the bottles have now been spliced and the inter-bottle spacer rings have also been made. They still need to be pressure tested, and small reinforcing rings glued around the necks, where stretching starts to occur from around 110psi. (Planned launch pressure is 130psi)

We are using two glues for the splicing. The bulk of the splice is held by PL premium (the brown stuff), but because it can be a little porous, we use Selley's Sikaflex 11FC in the section where the bottles join to provide a better seal (the white stuff). PL can hold at least 2 times more pressure than the Sikaflex. Under full pressure, there is about half a ton pulling the two glued sections apart.

All up the booster is made from ~50 two liter bottles.
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Postby water rocketry man » Thu May 07, 2009 2:55 am

WOW that is awesome 8) what the max newton of thrust is that gonna have and what can you compare it to :shock: .
i hope every thing goes well

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Postby air.command » Thu May 07, 2009 8:34 am

water rocketry man wrote:WOW that is awesome 8) what the max newton of thrust is that gonna have and what can you compare it to :shock: .
i hope every thing goes well


@130psi initial simulation results suggest:

Booster:
Just after take-off the booster will generate about 630N. With total impulse around 405Ns. I guess the equivalent motor would be an I-155.

Sustainer:
If we use water only -
The sustainer will generate around 99N at release. The total impulse will be ~72Ns ( Equivalent: F-85 )

If we use foam - (more likely)
It will generate around 60N at release, with total impulse closer to 85Ns.
Equivalent is F-63.

With the above motor equivalents one must consider the very different power to weight ratio of water rockets compared to pyro rockets.
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Postby water rocketry man » Fri May 08, 2009 9:46 pm

air.command wrote:
water rocketry man wrote:WOW that is awesome 8) what the max newton of thrust is that gonna have and what can you compare it to :shock: .
i hope every thing goes well


@130psi initial simulation results suggest:

Booster:
Just after take-off the booster will generate about 630N. With total impulse around 405Ns. I guess the equivalent motor would be an I-155.

Sustainer:
If we use water only -
The sustainer will generate around 99N at release. The total impulse will be ~72Ns ( Equivalent: F-85 )

If we use foam - (more likely)
It will generate around 60N at release, with total impulse closer to 85Ns.
Equivalent is F-63.

With the above motor equivalents one must consider the very different power to weight ratio of water rockets compared to pyro rockets.


Still the amount of newtons produced by just water and air is amazing 8)
the weight power raitio is definetly a set back for altitude however is decreases very fast, but water rockets still fall short of an altitude that would be produced by any rocket powered by a 'I' motor.

BTW how long does the booster stage go for . ( burn is probably not the best word when relating to water rockets)

What altitudes would you expect from this marvellous creation , BTW your hobby has now turned into a mental illness :lol: JKS

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Postby air.command » Sat May 09, 2009 10:09 am

The booster's burn time (water phase) is about 850ms, although staging will occur probably closer to 1.5 seconds after liftoff, as the air pressure drops in the booster. We're delaying the staging slightly after peak velocity to ensure a cleaner separation. The booster should be just slowing down at the time of staging. We don't want the booster to still be accelerating during staging to prevent collision problems.

Final sustainer altitude still needs to be worked out depending on final weight. I am hoping over the 200m mark. Sims says closer to 240m (800'), but I always take that with a grain of salt.
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