Spinlaunch on the Moon

[Barley]

There are also limitations on how slowly a VFD can operate,

I've use VFD for hill hold, which is as close to zero speed as we can measure.  If we needed better hill hold we could up the precision of speed or position measurement input to the VFD controller and the VFD would handle zero speed even better.  If you are simply trying to startup or stop (to/from zero speed) a VFD should work seamlessly without any special handling.

Using the VFD as a sort of very sloooow soft start, taking 30 minutes to get up to speed.  I was thinking more along the lines of my personal design experience, operating a pump or a fan for very long periods at low speed using a VFD, and the control guys at my firm tell me to try not to go bellow 40% of velocity.  Some of this has to do with cooling of TEFC (totally enclosed fan cooled) motors, which will not be a problem on the Moon. I guess HVAC experience is not directly applicable.

The electronics would have to maintain constant torque, or even supply a little start up jolt, despite the varying frequency as the motor ramps up to its maximum of about 650 rpm.
A large multipolar motor ( six poles for 600 rpm?) might be the best choice, or perhaps a DC motor.  These go all the way to 5MW, so more than enough.  After all, if we have a DC solar source...

Generally, the things the motor is attached to is more finicky than the motor controller or motor.

In your case it was probably the pump.  The working fluid can act as a lubricant, but below some speed it's no longer viscus enough and you get metal to metal contact and rapid pump wear.  This is particularly common in a first generation VFD equipped system that just replace the motor, using an existing pump that was selected only for properties near the synchronous speed.  It can get better in a second generation that replaces the pump with one selected to operate across more of the range.

For spinlaunch you might not want constant torque and acceleration.  You might be able to handle resonances by accelerating more rapidly through resonant speeds and lingering at the antiresonances while things damp down.  VFDs give lots of room to tweak things like this instead of just piling on stiffness.

For a motor that's running continuously the limiting factor is often cooling, and you end up picking a motor that is so oversized for power and torque that details like the number of poles barely matter.

[lamontagne]

There are also limitations on how slowly a VFD can operate,

I've use VFD for hill hold, which is as close to zero speed as we can measure.  If we needed better hill hold we could up the precision of speed or position measurement input to the VFD controller and the VFD would handle zero speed even better.  If you are simply trying to startup or stop (to/from zero speed) a VFD should work seamlessly without any special handling.

Using the VFD as a sort of very sloooow soft start, taking 30 minutes to get up to speed.  I was thinking more along the lines of my personal design experience, operating a pump or a fan for very long periods at low speed using a VFD, and the control guys at my firm tell me to try not to go bellow 40% of velocity.  Some of this has to do with cooling of TEFC (totally enclosed fan cooled) motors, which will not be a problem on the Moon. I guess HVAC experience is not directly applicable.

The electronics would have to maintain constant torque, or even supply a little start up jolt, despite the varying frequency as the motor ramps up to its maximum of about 650 rpm.
A large multipolar motor ( six poles for 600 rpm?) might be the best choice, or perhaps a DC motor.  These go all the way to 5MW, so more than enough.  After all, if we have a DC solar source...

Generally, the things the motor is attached to is more finicky than the motor controller or motor.

In your case it was probably the pump.  The working fluid can act as a lubricant, but below some speed it's no longer viscus enough and you get metal to metal contact and rapid pump wear.  This is particularly common in a first generation VFD equipped system that just replace the motor, using an existing pump that was selected only for properties near the synchronous speed.  It can get better in a second generation that replaces the pump with one selected to operate across more of the range.

For spinlaunch you might not want constant torque and acceleration.  You might be able to handle resonances by accelerating more rapidly through resonant speeds and lingering at the antiresonances while things damp down.  VFDs give lots of room to tweak things like this instead of just piling on stiffness.

For a motor that's running continuously the limiting factor is often cooling, and you end up picking a motor that is so oversized for power and torque that details like the number of poles barely matter.

Making a lot of sense.  So for control I would have the VFD and its electronic magic, plus the possibility of rotating a split counterweight (about 30 degrees) in order to maintain the center of mass at the center of rotation with a quick angular displacement.  For the hold down method of the payload I guess I can trust whatever Spinlaunch has figured out as a solution.  Liquid cooling, a radiator.
And that's about as far as I can go on my own.  Guess all we need now is a USRU plant and some clients 

[Twark_Main]

There are also limitations on how slowly a VFD can operate,

I've use VFD for hill hold, which is as close to zero speed as we can measure.  If we needed better hill hold we could up the precision of speed or position measurement input to the VFD controller and the VFD would handle zero speed even better.  If you are simply trying to startup or stop (to/from zero speed) a VFD should work seamlessly without any special handling.

Using the VFD as a sort of very sloooow soft start, taking 30 minutes to get up to speed.  I was thinking more along the lines of my personal design experience, operating a pump or a fan for very long periods at low speed using a VFD, and the control guys at my firm tell me to try not to go bellow 40% of velocity.  Some of this has to do with cooling of TEFC (totally enclosed fan cooled) motors, which will not be a problem on the Moon. I guess HVAC experience is not directly applicable.

The electronics would have to maintain constant torque, or even supply a little start up jolt, despite the varying frequency as the motor ramps up to its maximum of about 650 rpm.
A large multipolar motor ( six poles for 600 rpm?) might be the best choice, or perhaps a DC motor.  These go all the way to 5MW, so more than enough.  After all, if we have a DC solar source...

Generally, the things the motor is attached to is more finicky than the motor controller or motor.

In your case it was probably the pump.  The working fluid can act as a lubricant, but below some speed it's no longer viscus enough and you get metal to metal contact and rapid pump wear.  This is particularly common in a first generation VFD equipped system that just replace the motor, using an existing pump that was selected only for properties near the synchronous speed.  It can get better in a second generation that replaces the pump with one selected to operate across more of the range.

For spinlaunch you might not want constant torque and acceleration.  You might be able to handle resonances by accelerating more rapidly through resonant speeds and lingering at the antiresonances while things damp down.  VFDs give lots of room to tweak things like this instead of just piling on stiffness.

For a motor that's running continuously the limiting factor is often cooling, and you end up picking a motor that is so oversized for power and torque that details like the number of poles barely matter.

Making a lot of sense.  So for control I would have the VFD and its electronic magic, plus the possibility of rotating a split counterweight (about 30 degrees) in order to maintain the center of mass at the center of rotation with a quick angular displacement.  For the hold down method of the payload I guess I can trust whatever Spinlaunch has figured out as a solution.  Liquid cooling, a radiator.
And that's about as far as I can go on my own.  Guess all we need now is a USRU plant and some clients 

I note that in your rendering, the counterweights are still wrong. The CoM of the arm and both counterweights needs to be co-planar, otherwise it shakes apart.

It may seem like a nitpick, but given Akin #30 I worry that if not corrected this mistake will get "baked in" the concept and difficult to dislodge...   

[lamontagne]

Like this?

[Twark_Main]

Like this?

Beautiful! Thank you for that.

Damn, it looks really good, too....   

[lamontagne]

Hadn't had the opportunity to do any machine design for years...
It's all notional, no real engineering here    Cutaway view through the spinlaunch hub.  Green is the electric motor, red is the bearings.  The motor is linked to the main support and bearing using a flexible coupling.  The main support takes all the stress, and supports vertically.
There are four much smaller bearings for the movable counterweights.  The whole assembly is a bit less than 4 meters high.

[lamontagne]

An orbital transfer vehicle, solar electric, moving the cargo from Low lunar orbit to L-2 or L-5.
2 MW electrical power, Vasimir or some form of ion.
It moves 100 tonnes of cargo per trip up to L-2, returns empty.

This completes the transportation system.  All for cargo, not for people, too slow.

[lamontagne]

Is there a distance that should be kept between an ion exhaust and a solar panel?

The image shows a SEP tug, with it's panels angled to follow the sun.  Is the distance problematic, in particular from ion buildup on the panels from the divergent exhaust, or some other phenomenon?

Just in case it isn't obvious, the ion engines would be on the lower end of the long boom.  That could easily be made longer, if need be.

[TrevorMonty]

Is there a distance that should be kept between an ion exhaust and a solar panel?

The image shows a SEP tug, with it's panels angled to follow the sun.  Is the distance problematic, in particular from ion buildup on the panels from the divergent exhaust, or some other phenomenon?

Just in case it isn't obvious, the ion engines would be on the lower end of the long boom.  That could easily be made longer, if need be.

A hydrolox fuelled tug would be simpler and cheaper solution. Any cislunar economy that requires spinlaunch will have fuel depots in orbit supplied by lunar water.
The tugs won't be burning lot of fuel as DV requirements are low.

[lamontagne]

Is there a distance that should be kept between an ion exhaust and a solar panel?

The image shows a SEP tug, with it's panels angled to follow the sun.  Is the distance problematic, in particular from ion buildup on the panels from the divergent exhaust, or some other phenomenon?

Just in case it isn't obvious, the ion engines would be on the lower end of the long boom.  That could easily be made longer, if need be.

A hydrolox fuelled tug would be simpler and cheaper solution. Any cislunar economy that requires spinlaunch will have fuel depots in orbit supplied by lunar water.
The tugs won't be burning lot of fuel as DV requirements are low.

I agree it would be simpler to develop, but it would add about an order of magnitude a factor of five to the operational cost compared to an ion drive. The idea being to ship high volume low value materials with Spinlauch.  If you don't have very high volumes, there really isn't any point in developing the Spinlaunch in the first place.  If you are handling high volumes, then the lunar water isn't going to last long.
If you are going to develop an ion engine for the catcher, might as well apply it to the orbital transfer vehicle as well.

One thing that might invalidate this argument is if there is a significant gain to using a short burst of chemical propulsion on low lunar orbit versus the long spiral of the ion engine.  The ion engine also needs to be pretty efficient and use something cheap, like oxygen or very low mass, like hydrogen.

The comparison is in the joined spreadsheet, on the orbital transfer tab.

[lamontagne]

Two spinlaunch units on the Moon.  Angled at 28 degrees for optimum rise vs velocity at 300 km high.
Each arm launches 100 kg every two hours, offset by one hour, so the pair runs at 100 kg per hour.
This would be a fairly early setup, no longer prototypes but not very high volumes yet.

Catchers collect the payloads in orbit, and every month or so a orbital transfer SEP vehicle moves up the accumulated payoad units to higher orbits and some kind of space manufacturing plant.

[lamontagne]

My presentation to the British Interplanetary Society, Spinlaunch on the Moon.  Based on the discussion that happened here.  can't say it made a great splash, but I enjoyed making it and the general experience.

The .pdf is the whole presentation.

And the spreadsheet.

[lamontagne]

BTW there has been no change to the Spinlaunch website for a year, and the original project initiator has been replaced by a new CEO, so I'm afraid we may see the foreclosure notices ant time now...

[TrevorMonty]

BTW there has been no change to the Spinlaunch website for a year, and the original project initiator has been replaced by a new CEO, so I'm afraid we may see the foreclosure notices ant time now...

If they do go under hope likes of Blue pickup them im some form. Most likely company to use this technology on moon.

[JulesVerneATV]

SpinLaunch Picked A Location For Its Orbital Accelerator

[Robotbeat]

My presentation to the British Interplanetary Society, Spinlaunch on the Moon.  Based on the discussion that happened here.  can't say it made a great splash, but I enjoyed making it and the general experience.

The .pdf is the whole presentation.

And the spreadsheet.

Seems to me a big limitation of this is the small payload. There’s an overhead to trying to collect a bunch of tiny payloads, just like trying to refuel in LEO using RocketLab’s Electron. Tons, or tens to tons, makes this problem much more tractable.

[lamontagne]

My presentation to the British Interplanetary Society, Spinlaunch on the Moon.  Based on the discussion that happened here.  can't say it made a great splash, but I enjoyed making it and the general experience.

The .pdf is the whole presentation.

And the spreadsheet.

Seems to me a big limitation of this is the small payload. There’s an overhead to trying to collect a bunch of tiny payloads, just like trying to refuel in LEO using RocketLab’s Electron. Tons, or tens to tons, makes this problem much more tractable.

The developed system is about 2 tonnes per shot.  The quality of collections depends a lot on the launch precision and capture mechanisms.  For the smaller initial payloads, that are intended to reduce development costs, we need a market for the materials, and I don’t know when the cost becomes less than the cost from Earth.
The system can increase capacity by adding launch units.  It’s important for this to work to develop a high strength steel from lunar materials, and that is still something of an unknown. 
There is a practical limitation to the strength of the launch arm that limits launch velocities, unless we use science fictional carbon Nanotube strengths.
Compared to a mass driver, we replace a linear motor with a smaller rotating motor, and we store the energy mechanically in the arm rather than in some kind of capacitive or inductive energy storage system.
I think heavier payloads are possible, but I haven’t explored this.

[Robotbeat]

Why would you limit it to lunar launched materials? That puts it in the realm of, not fantasy exactly but some weird where there’s already massive lunar industry.

ISRU structure for spin launch is a terrible idea. Use high performance earth launched material

[TrevorMonty]

Spinlaunch is ideal for delivering lunar water to orbit to be used to fuel landers and vehicles on return trip to earth. Water is more compact and easier deal with than hydrolox so makes sense to do the conversion in orbit where there is 24/7 sunlight. In space transporters can use water as is for fuel, Momentum and others have SEP thrusters that use it.

In the early days probably easier to reuse the launch canisters which were made on earth. These do need some electronics ie beacon radio and some reaction wheels to stablise them to enable SEP tug to find and capture them. Can be returned to surface on a cargo lander which would refuel from orbital depot.

Once this architecture is in place only fuel that needs to be launched from earth is for outbound trips and even these maybe replaced by lunar fuel if it works out cheaper. This would also create market that Asteriod sourced water can be sold into.

Initial lunar activity would be fuelled solely from earth, followed by ISRU to refuel landers for return trip to orbit. Can use tanker landers to deliver fuel to orbit but means for every kg delivered to orbit another kg of water has to be extracted and converted to hydrolox on surface to fuel tanker. This is why mass launchers are so important for grow of any lunar economy.

[lamontagne]

Why would you limit it to lunar launched materials? That puts it in the realm of, not fantasy exactly but some weird where there’s already massive lunar industry.

ISRU structure for spin launch is a terrible idea. Use high performance earth launched material

Indeed.  The ISRU steel is eventually for the canisters, or launch units, as an optimistic byproduct of oxygen production.  The first few generations of small plants are likely to produce useless mixtures of iron and silica, but I hope quality steel will follow shortly.  The steel needs to be strong because of the high forces involved at the attachment points.  I expect the launch’ arms, controls and motors to come from Earth for quite some time.  As well as the early canisters. 
Reusing the steel in space makes the whole system orders of magnitude less expensive to run, once there is a bit of volume.  Returning anything back to the Moon’s surface is something of a money sink.
 Steel is not an adequate material for the launch arm.