Jules Verne Cannon Payload To Orbit.... Feasible?

[Lisias]

1 hour ago, Spica said:

Unfortunately this trick doesn't actually let you gain significant speed beyond what you'd get from a normal gun.

Once the projectile reaches speeds close to the practical limit of a single chambered gun, any additional chambers provide little if any further velocity increase.

What means that the terminal velocity of the project will never exceed the practical expansion speed of the gas used on the expansion chambers. Good catch.

However, and we are going literally nuclear on the matter, there's not practical limit for accelerating a particle other than the speed of light, right? So we need to find something that could expand strongly and fast enough to kick the projectile fast enough to reach the desired speed.

Googling about, I found this (see page 159):

On a nuclear explosion (yeah, I know, way overkill but I'm talking about theoretical limits now), we have a pressure such that the expansion runs at more than 150 KM/sec at 10 meters of the epicentre. Dude, this is a lot.

Of course we could not use nuclear explosions on the chamber, as we don't want o obliterate the projectile - we need their atoms to reach the end of barrel on their original configuration, not scattered in vapour…  So I think that once the technical issues are overcome (assuming theiy can be overcome at all), the idea still stands.

But you hinted about another issue that I was letting pass trough: each subsequent chamber will need to inject way more energy than the previous one in order to "catch up the projectile" and then add yet more Kinect energy to it.

[magnemoe]

On 11/6/2021 at 10:49 PM, TheSaint said:

Can't believe we're ten posts in and nobody has mentioned Gerald Bull, Project HARP, or Project Babylon.

I know HARP used discarding sabot. You take an smaller projectile and put it inside an usually aluminium  sabot who hold it in place inside the barrel. 
This has multiple benefit, as the smaller bullet and the sabot framework is much lighter than an standard shell it will accelerate faster. You can also make the bullet much more aerodynamic than an standard shell who need an flat rear for the pressure to work against. 
I assume project Babylon would also use discarding sabot, but yes as the diameter was one meter you could fire something like an battleship shell as an discarding sabot

Tanks who typically file an tungsten or depleted uranium arrow from an 120 mm gun can reach over 100 km if you are firing while climbing an steep hill so you get an around 45 degree launch angle, that is Paris gun ranges, this create some range safety issues like firing into other countries  

However discarding sabots has limits, as the projectile get lighter and lighter I assume your muzzle velocity get limited by the pressure wave. 
Still it looks like Bull bypassed the V3 gun without using extra propellant chambers. He might use better powder to give constant pressure during firing. 
Still HARP was just an battleship gun they made longer, but they might used specialized powder as they they was not limited by the powder handling system on an battleship turret. 

[Spica]

16 minutes ago, Lisias said:

But you hinted about another issue that I was letting pass trough: each subsequent chamber will need to inject way more energy than the previous one in order to "catch up the projectile" and then add yet more Kinect energy to it.

Yes, each successive chamber needs to contain significantly hotter gases than the preceding one, but at that point why not make the first chamber larger and hotter. The trouble here is bridging the gap between chemical (thousands of kelvin) and nuclear (hundreds of millions of kelvin) explosions. You could use an electrical discharge instead, but then you ought to check whether an electric light gas gun is more or less efficient on an energy basis than a laser rocket like this:

Such a vehicle would also be FAR gentler to any payload it carries than a gun-launched vehicle would.

[kerbiloid]

Spoiler

 

Let the cannon look through the Earth and be several thousand kilometers long.

 

[sevenperforce]

On 11/7/2021 at 3:59 AM, Lisias said:

It depends of the mass. It's not the Acceleration that kills you exactly, but the forces transfer between your cells - your soft tissues against your harder tissues, to be more specific.

About the clock, Net Force = Mass times Acceleration (Newton's second - thanks, Wikipedia!). The wristwatch would not handle that 5K gees if it would have the mass of my grandma's swinging pendulum clock.

I will stay away from heavy Maths for while (coffee still kicking in), but a wristwatch weights about 160g. If a given wristwatch sustain 5K gees, it can withhold about 5.000 * 9.8m/s² * 0.160kg = 7840N. So the magic number is 7840.

I think a long case clock may weight about 25kg (~15kg only for the weight on the pendulum!). So… 7840N = Xm/s² * 25kg => X = 7840/25 => X = ~314M/s/s, or "merely" 32G.

It's not really that simple, unfortunately. There's nothing magic about 7480 N at all. Assuming that you're in a building of some kind right now, the building's foundations are holding far, far more than 7480 N simply because they have the requisite compressive strength.

The shock-resistance of a pendulum clock is going to depend (to a first approximation) on the cross-sectional area of the weakest material in the clock, normal to the acceleration vector.

4 hours ago, Spica said:

A more technical description is found here: https://www.researchgate.net/publication/268456817_A_comparison_of_distributed_injection_hypervelocity_accelerators

There are other tricks that can work though, which are described in more detail in the paper I linked here. One of which involved injecting gas perpendicular to the barrel and expanding it along a tapered projectile.

I do like the idea of filling the barrel with one reactant gas and injecting the other reactant gas perpendicular, using shaped grooves in the projectile to compress the reactant gas and allow it to flow into the continuously-detonating wave behind it.

[sevenperforce]

This would be an in-barrel version of the shcramjet, or oblique detonation wave engine.

A ramjet uses ram pressure to compress air through a stagnation shock where the inlet airflow drops below the speed of sound. It is then mixed with fuel and combusted like an ordinary turbojet engine. A scramjet, on the other hand, has no stagnation shock, so the combustion happens at supersonic speeds (hence Supersonic Combusting Ramjet). Because combustion is inefficient in a supersonic flow, a scramjet requires a very long and very heavy combustor in order to have a meaningful pressure increase and produce net thrust.

A shcramjet is a shock-combustion ramjet, where there is no combustor at all, and both the inlet and outlet are shaped such that there is a continuous standing wave of shock-induced detonation at the nozzle exit. Putting this inside a supergun barrel would be easier than trying to build a free-flying one. 

[Lisias]

6 hours ago, sevenperforce said:

It's not really that simple, unfortunately. There's nothing magic about 7480 N at all. Assuming that you're in a building of some kind right now, the building's foundations are holding far, far more than 7480 N simply because they have the requisite compressive strength.

Magic numbers: https://en.wikipedia.org/wiki/Magic_number_(programming)

it was stated that some shockproof wristwatch could withstand 5.000 gees. Converting that 5.000 gees into Newtons, I got into 7480N of Net-Force the wristwatch can withhold.

About the building I'm live, it doesn't weights 160 grams, neither is going to be shoved on a huge cannon barrel to be launched into space.  

[sevenperforce]

2 minutes ago, Lisias said:

it was stated that some shockproof wristwatch could withstand 5.000 gees. Converting that 5.000 gees into Newtons, I got into 7480N of Net-Force the wristwatch can withhold.

The shock resistance of any given shock-resistant electronics is not a function of the mass of those electronics. It's a function of the geometry and elastic modulus of the compressible material seating the electronics.

Shock resistance is the ability of a structure to damp high levels of acceleration to prevent stresses from being applied directly to the electronics. You're trying to calculate the weight which something can handle, which is an external measure and depends on component compressive strength.

[Lisias]

1 hour ago, sevenperforce said:

The shock resistance of any given shock-resistant electronics is not a function of the mass of those electronics. It's a function of the geometry and elastic modulus of the compressible material seating the electronics.

Yes, it is. F = m * a, so mass is a key component on this equation.

The shock resistance of a device is the the shock resistance of it's weakest component.

How you mitigate the shock propagation into this weakest component is what's related to the geometry and elasticity of the casing of the device.

What's completely off-topic, how about discussing this Thread subject instead?

Edited November 9, 2021 by Lisias
Hit "save" too soon.

[Meecrob]

I think he  is saying the delicate bits are shock mounted and thus experience a different acceleration. Mass is relatively irrelevant given an adequate shock mount.

[Lisias]

On 11/9/2021 at 12:11 AM, Meecrob said:

I think he  is saying the delicate bits are shock mounted and thus experience a different acceleration. Mass is relatively irrelevant given an adequate shock mount.

But the adequacy of the shock mount is directly affected by the mass. Also, from the context of the original discussion, we were talking exactly about this: how increasing mass would affect the shock resistance of the wristwatch.

If by some reason you scale up a wristwatch from 160g to 25KG, you can bet your SAS this will affect the shock resistance if the wristwatch components - on a pretty lame physics exercise (assuming that the resistance of the materials scales linearly, what doesn't happen!), I interpolate the gee resistance  from such scaled up wristwatch from 5000 gees to a mere 32 gees.

Please note that this mental exercise was not meant to be a accurate treaty about scaling up wristwatches (the series of oversimplifications used on the exercise was stated on the post). It was meant to demonstrate that the mass of the projectile has direct and crucial influence on the gee forces it can withhold - more the mass, less the Net Force it can withhold (at least, without some mitigation measures - but these adds more mass to the equation, leading us to a vicious cycle of a self-feeding problem).

The whole point of the argument is that, at least in principle, the less G force you manage to inject into the projectile in each "stage", the better - less material you will use to mitigate the Net Forces applies to it, and so you can increase the payload of the thing - more earnings + less cost = better cost/benefit ratio, that it's what's matter after all.

So, and going back to my original proposition that tries to satisfy the OP's question: may a pretty long barrel on a cannon filled with many expansion chambers could be effective on launching a payload from the ground into some kind of orbital trajectory?

It was already stablished that it's not possible to do such to achieve orbit from the launching celestial body. It's a physics impossibility, so we had to wave off such use case. There's also the atmosphere, the losses imposed by the mass of air on front of the projectile is far from being insignificant, so I reduced my proposal to launch thingies from Moon to Earth using such a staged cannon.

You would not launch fine manufacturings from the Moon, I think - there's no point on building factories for such things there. But I think you may want to bring down Ore (as long its value worths the costs) and, perhaps, Kerbals Humans that ended up their shift and need to go home in a cost effective way. That leaded to the problem of the Net Force injected on each stage - it should be, ideally, near 6Gs as this is relatively easy to get the passenger trained for.

So, we are nailing it into the Requirements of the stunt:

• How much G you can kick on the project on each stage
  • Dual mode? One for Humans, other for Ore?
• How many stages you will need
  • What would be the distance between each stage? And so, how long the barrel need to be?
• How such energy you will need to extract from each stage
• How much energy it's possible to generate on each stage without blowing up the barrel.
• And how in hell the projectile will land on Earth with its cargo in a useable state (alive and health, on the case of Humans), assuming we manage to kick it from the Moon at first place.

Arguing about Resistance of Materials is, indeed, a necessary step of the process (otherwise we would incur on an error similar as creating a Launching Vehicle to be used on rainy places that can't withhold moisture, or using valves on the fuel injection system that are eroded by the fuel/oxidiser - resemblances with real life events are not a coincidence). But arguing about the accuracy of some mental exercises meant to grossly demonstrate problems in a easy and fast way (prototypes - we use prototypes in order to prevent wasting resources on ideas that have no chance of working) ends up disrupting the process.

Models and abstractions are not meant to be an accurate representation of Reality - they are meant to simplify the most possible the Reality as long the resulting model/abstraction is still useful to the problem at hands. No considerations are taken for any other use case, as it would be only a waste of time and resources.

On the light of this last consideration, any discussion about how shock resistance on wristwatches really behaves is, frankly, moot. It's enough to demonstrate, empirically if possible (in order to save some time), that the shock resistance of anything (including wristwatches) are directly related to the mass : more mass, less resistance (unless further cost is added to the equation attempting to mitigate the problem - but even that, only to a certain extent).

— — POST EDIT  — — 

The guy was right, I was wrong. My model was not exactly wrong, but the reasons I was claiming the model works were wrong - and being right by the wrong reasons is not enough, as you will not be able to apply your model correctly and this may lead to wrong results - and you will not be able to fix it.

The root cause of my confusion is that I ended up unadrevtidly  using "Shock" and "Impact" as synonymous - and they are not.

Shock is an acceleration applied to a mass.

Impact may be related to a Shock, but also be related to a Force. You can't use these two terms as they would be same, as I was using on my mental model.

Edited November 10, 2021 by Lisias
post edit

[sevenperforce]

9 hours ago, Lisias said:

It's enough to demonstrate, empirically if possible (in order to save some time), that the shock resistance of anything (including wristwatches) are directly related to the mass : more mass, less resistance (unless further cost is added to the equation attempting to mitigate the problem - but even that, only to a certain extent).

This has been flogged to death, but adding mass to a shock-resistant structure does not linearly (or even monotonically) decrease its gee-resistance. If a 1 kg shock-resistant computer can handle 1,000 gees, you can bolt them together and now you have a 2 kg shock-resistant computer that can still handle 1,000 gees. And you can stack five of those on top of each other and duct tape them together and now you have a 10 kg shock-resistant computer that can still handle 1,000 gees.

"But if you're stacking them on top of each other then the one on the bottom will have more weight on it!"

Yes, but that doesn't matter. Shock resistance is not a factor of the compressive strength of the casing materials.

[Lisias]

2 hours ago, sevenperforce said:

This has been flogged to death, but adding mass to a shock-resistant structure does not linearly (or even monotonically) decrease its gee-resistance. If a 1 kg shock-resistant computer can handle 1,000 gees, you can bolt them together and now you have a 2 kg shock-resistant computer that can still handle 1,000 gees.

Not if the whole structure is the mass in movement. There's a difference between (going back to the wristwatch) letting a 160g device hit a 5.000Kg something at 5000 gees, and letting something with 5000KG hiting it at 5000 gees. 

Also, please note that if you stack these two computers one over the over, and then shove 1000 gees on the butt of the bottom one, this one will suffer stress from the source of the impact and also from the computer over it due tis inertia. So if 1.000 gees if the exact amount of shock it can withhold without leaking it into the internal components (and assuming the compression and the tension resistance is the same!!!), this one will fail for sure due the extra stress caused by the compression of the computer on top due its inertia, that by the 3rd Law of Newton will also be 1.000 gees.

The top one will survive, tough.

2 hours ago, sevenperforce said:

"But if you're stacking them on top of each other then the one on the bottom will have more weight on it!"

Yes, but that doesn't matter. Shock resistance is not a factor of the compressive strength of the casing materials.

Yes, it does. The casing is withholding twice the shock, from both sides.

— — POST EDIT — — 

However… Assuming that such casing can withhold the Forces from both sides (up and bottom), i.e., 1KG * 1.000G = 9800N, times 2 = 19600N, indeed the impact from the bottom will be nullified by the impact from the top as the acceleration from the top will be the inverse of the one from the bottom (it's still the 3rd Law). So the net acceleration is zero for whatever is inside the casing.

So, yeah. I'm seeing your point now.

Edited November 10, 2021 by Lisias
post edit.

[Spacescifi]

22 minutes ago, Lisias said:

Not if the whole structure is the mass in movement. There's a difference between (going back to the wristwatch) letting a 160g device hit a 5.000Kg something at 5000 gees, and letting something with 5000KG hiting it at 5000 gees. 

Also, please note that if you stack these two computers one over the over, and then shove 1000 gees on the butt of the bottom one, this one will suffer stress from the source of the impact and also from the computer over it due tis inertia. So if 1.000 gees if the exact amount of shock it can withhold without leaking it into the internal components (and assuming the compression and the tension resistance is the same!!!), this one will fail for sure due the extra stress caused by the compression of the computer on top due its inertia, that by the 3rd Law of Newton will also be 1.000 gees.

The top one will survive, tough.

Yes, it does. The casing is withholding twice the shock, from both sides.

  Reveal hidden contents

 

 

Yeah I agree with Lisias because:

 

1. If we can all agree that as a scifi spaceship capable of 1g will have the same effect as 1g from an earth world, then we can slso agree that a 1000 or more gees has the same effect as a 1000g planet... as much hyperbole as that is.

Basically acceleration tends to compress and crunch.... well.... everything it effects.

 

Astronauts in spacd orbit get taller due to no significant gravity strong enough to compress them.

 

You take 1000g or more and we are talking more crushing force multiplied.

 

To survive it less compressible objects would have to be used.

 

I dunno, shoot a bunch of massive shards of ice into orbit and intercept it with orbital vessels to use as fuel before the ice completes it's fatslistic orbit to hit the earth from where it launched?

Seems like other than shooting ice for orbital capture, about the best these earth to orbit cannons are for is killing satelites and weak maneuvering orbital spacecraft.

[Lisias]

10 hours ago, Spacescifi said:

Yeah I agree with Lisias because:

Me too!!

But @sevenperforcewas right too - my argument was valid in spirit, but wrong on the form, and he spotted the mistake - but I think he didn't understood exactly why my argument were flawed, and I think this ended up leading me to more confusion, as I was not linking the points and both of us ended up arguing in circles.

In a nutshell, I was using "Shock" and "Impact as they were synonymous, and they are not. "Shock" is the appliance of an acceleration over a mass. "Impact" is what happens by a Shock OR by a Force being applied to the mass. 

Use Impact on my arguing instead of Shock, and things will make more sense.  

[magnemoe]

On 11/9/2021 at 4:11 AM, Meecrob said:

I think he  is saying the delicate bits are shock mounted and thus experience a different acceleration. Mass is relatively irrelevant given an adequate shock mount.

At these levels as in more than artillery shell g forces at longer times you can not use shock absorbent. If I understand the term correctly, that only help you against an instant declarations like an impact like how cars with crumble zones and airbags spread out the time to stop you. 

In something like an smart or payload artillery shell you need to brace or reinforce sensitive parts. an circuit board simply cast it in an strong resin resting inside an void in the steel shell should work. Moving parts is the main problem, you can migrate this because only the initial position has to be able to handle insane g and stuff only have to last less than an minute after firing.
On the other hand  smart artillery shells tend to be ordered in pretty large orders so you can spread the development cost over them. 
Does not works for satellites as even starlink numbers is pretty low in this setting and obviously artillery shells are easier to test using common artillery.  

[StrandedonEarth]

Okay, time for my nickel....

I also get hung up on hitting ludicrous speed deep in the soup, The logistics of a mountaintop launch/shot for marginal gains seems dubious. One workaround would be lofting the cannon first then firing it, but that's also impractical, and the recoil....

Hey, wait, the recoil...! 

Let's see, the typical second stage engine is sleeved, aside from some Russian hot-staged ones. But what if the F9 hot-staged before separation (rework required, obviously; maybe sleeve some of the second stage as a longer "barrel"). The second stage pops free like a cork, while the booster gets some impulse to help slow it down for re-entry and recovery. Of course, any gains are not worth protecting stuff from that blast, so it's a pointless idea aside from being a thought exercise.

Edited November 11, 2021 by StrandedonEarth

[magnemoe]

This is pretty related I say. 

Scott Manley believe its possible, Benefit of this over an gun is that you can accelerate slowly, downside is that you has to handle the spin g forces and they are not in your direction of travel. Dropping the 10 ton rocket moving at mach 6 will also unbalance the spin arm. 

[wumpus]

11 hours ago, magnemoe said:

This is pretty related I say. 

Scott Manley believe its possible, Benefit of this over an gun is that you can accelerate slowly, downside is that you has to handle the spin g forces and they are not in your direction of travel. Dropping the 10 ton rocket moving at mach 6 will also unbalance the spin arm. 

Actually, he points out that the "acceleration" (although it is a change of the direction of the velocity, not the magnitude) is almost the same.  Not only that, but the g-forces are in "the wrong direction" (although presumably trivial to design around).

[Lisias]

15 hours ago, magnemoe said:

Scott Manley believe its possible, Benefit of this over an gun is that you can accelerate slowly, downside is that you has to handle the spin g forces and they are not in your direction of travel. Dropping the 10 ton rocket moving at mach 6 will also unbalance the spin arm. 

Yep, when I saw this one i became in doubt if I should post it here or in the 'Real Life Kerbalims' thread!

and yep, as always on engineering, we don't really solve problems,  we shift them to a place where they stop to be a problem for us at this moment.

This stunt solved the problem of the energy releasing- but it created another one that may hinder the applicability of the thing.

 

3 hours ago, wumpus said:

Actually, he points out that the "acceleration" (although it is a change of the direction of the velocity, not the magnitude) is almost the same.  Not only that, but the g-forces are in "the wrong direction" (although presumably trivial to design around).

You have two problems: impact absorbing on the payload, and shock absorbing on the arm (as stated by @magnemoe).

On the payload, the shock from the acceleration will be minimal, the thing will accelerate slowly and gradually. The problem will be on launch, when suddenly a lot of G force will suddenly vanish and any, absolutely any compressebility of any material will cause a slighshot effect on the opposite direction of where the G forces were happening. Both the capsule as the payload should be able to withhold that - au contraíre of the staged gun,  this will happen instantaneously. 

Another problem is the arm itself. The rebalancing mechanism needs to be triggered in such way that the arm should be rebalanced after the launch BEFORE the resulting impact from spinning with that energy in an unbalanced state hits the ball-bearings - otherwise you will witness a hell of a R.U.D. (Rapid Unplanned Dissembly).

Problem: the balancing weight needs to travel from the 'with payload' position to the 'without payload' position, and the thing will need to travel uphill against the centrifugal force.

So your payload will be severely limited by the balancing mechanism- it needs to be fast, it needs to overcome inertia, it needs to withhold the Impact the balancing mass will produce (and dumper it to preventing screwing up the ball-bearings itself!). THIS is the most challenging (and limiting) factor of this solution. 

And the reason I think it may not be cost/effective as a launching vehicle from Moon to Earth - you would need a lot of small launches instead of a probably more cost effective big one for the payloads I expect it will needed for.

Edited November 11, 2021 by Lisias
Krakens take these unholly auto-completes

[magnemoe]

16 minutes ago, Lisias said:

Yep, when I saw this one i became in doubt if I should post it here or in the 'Real Life Kerbalims' thread!

and yep, as always on engineering, we don't really solve problems,  we shift them to a place where they stop to be a problem for us at this moment.

This stunt solved the problem of the energy releasing- but it created another one that may hinder the applicability of the thing.

 

You have two problems: impact absorbing on the payload, and shock absorbing on the arm (as stated by @magnemoe).

On the payload, the shock from the acceleration will be minimal, the thing will accelerate slowly and gradually. The problem will be on launch, when suddenly a lot of G force will suddenly vanish and any, absolutely any compressebility of any material will cause a slighshot effect on the opposite direction of where the G forces were happening. Both the capsule as the payload should be able to withhold that - au contraíre of the spin acceleration,  this will happen instantaneously. 

Another problem is the arm itself. The rebalancing mechanism needs to be triggered in such way that the arm should be rebalanced after the launch BEFORE the resulting impact from spinning with that energy in an unbalanced state hits the ball-bearings - otherwise you will witness a hell of a R.U.D. (Rapid Unplanned Dissembly).

Problem: the balancing weight needs to travel from the 'with payload' position to the 'without payload' position, and the thing will need to travel uphill against the centrifugal force.

So your payload will be severely limited by the balancing mechanism- it needs to be fast, it needs to overcome inertia, it needs to withhold the Impact the balancing mass will produce (and dumper it to preventing screwing up the ball-bearings itself!). THIS is the most challenging (and limiting) factor of this solution. 

And the reason I think it may not be cost/effective as a launching vehicle from Moon to Earth - you would need a lot of small launches instead of a probably more cost effective big one for the payloads I expect it will needed for.

Realized this now, with something gun launched you only face rearward g forces, here it will be sideways, then the snap followed by serious drag  leaving the vacuum chamber, granted gun launched stuff will also have this issue. 

On the moon, you can evade many of this issues. use an wire not an arm, make it 2 km long, now put an railroad track following the curve. Elevate the center so the payload will be lifted of the ground at the time the powered cart drop it, cart brakes and is reused, real in wire while winding down. More fun you can rotate your payload. so back is rear on the cart then it changes to out after liftoff, G forces will be much lower with an 2 km radius, this can be increase if needed  
You could probably man rate this then moon become an major tourist destination. 

 

[Lisias]

3 minutes ago, magnemoe said:

On the moon, you can evade many of this issues. use an wire not an arm, make it 2 km long, 

Wire is not a good choice. The slingshot effect of a 2KM cable will be pretty devastating for the machinery.

Remember the 3rd of Newton: for each action, there's a reaction with the same intensity and opposite direction. With the sudden relief of the 'action' (the payload), the 'reaction' is free to go wild. On a wire, this is pretty nasty.

 

 

[kerbiloid]

Wire is not the best.

Spoiler

Rubber rules.

 

[Lisias]

3 hours ago, Lisias said:

 

 

Problem: the balancing weight needs to travel from the 'with payload' position to the 'without payload' position, and the thing will need to travel uphill against the centrifugal force.

There's another solution: the arm being perfectly balanced without the payload, and the balancing weight being ejected at the same time the payload.

This will solve the timings and the shock (it will be zero).

Of course,  now you need something to colect and absorb the impact of the huge Kinect power of the weight (that would go to space itself if not collected), but this is way easier than the alternative.

But it will demand more time between launches, as one will need to rebuilt the weight collector before the next launch - it will probably be destroyed and, so, you will need to remove the debris, clean all the system from any pulverized debris from the Impact, and put a new collector (and a refurbished weight) on the machine.

[sevenperforce]

1 hour ago, Lisias said:

There's another solution: the arm being perfectly balanced without the payload, and the balancing weight being ejected at the same time the payload.

This will solve the timings and the shock (it will be zero).

Of course,  now you need something to colect and absorb the impact of the huge Kinect power of the weight (that would go to space itself if not collected), but this is way easier than the alternative.

But it will demand more time between launches, as one will need to rebuilt the weight collector before the next launch - it will probably be destroyed and, so, you will need to remove the debris, clean all the system from any pulverized debris from the Impact, and put a new collector (and a refurbished weight) on the machine.

If you use a counterweight that is heavier than the payload, but closer to the center, then you can reduce the energy you have to absorb from the weight, although I believe the momentum remains the same.