More on SpinLaunch

[THX1138]

Now NASA and others are looking into it.

Watch NASA send a payload hurting into space with a giant slingshot

 

[Wayne Mack]

I'm not sure that this scales up.

SpinLaunch currently achieves 1,000 MPH. Escape velocity for Earth's gravity is 25,300 MPH. The scale up is more than an order of magnitude. For the current configuration, 1,000 MPH with a diameter 108 feet gives a centrifugal force of 1,238 g. Increasing the diameter by 25.3 to 2,732.4 feet gives a force at escape velocity of 31,324 g.

 

[Christine Wheelwright]

Regarding MSN.com journalism, the headline "Watch NASA send a payload hurtling into space with a giant slingshot" is obviously misleading.

Regarding SpinLaunch, there are all sorts of technological issues with scaling this to something actually useful. My prediction is they will fail.

 

[Christine Wheelwright]

I'm not sure that this scales up.

SpinLaunch currently achieves 1,000 MPH. Escape velocity for Earth's gravity is 25,300 MPH. The scale up is more than an order of magnitude. For the current configuration, 1,000 MPH with a diameter 108 feet gives a centrifugal force of 1,238 g. Increasing the diameter by 25.3 to 2,732.4 feet gives a force at escape velocity of 31,324 g.

Technological problems (just off the top of my head):

• Survivability of payload at g forces required
• Partition of vacuum inside launcher from outside air
• Means of removing partition at moment of launch
• Effect on projectile of meeting "wall of air" at such high speeds
• Fact that projectile will be spinning on release (nose and tail at different points on circle and travelling at tangent to circle...hence vector velocity of nose and tail are never the same). This could perhaps be solved by releasing nose slightly before tail....but by what mechanism?)
• Force imbalance between projectile and counterweight has been described as equivalent weight of a battleship (appearing suddenly at point of release - as an offset on the hub I suppose). Maybe could be compensated by releasing a counter projectile downwards at same moment (down into a pit?).

Personally, I think the 'supergun' (Supergun affair - Wikipedia) seemed way more feasible.

 

[THX1138]

One thing to remember is that this is not a 100% sling launch system. It's intended purpose is to replace the main launch vehicle, thus saving cost.
At a certain altitude in the upper stratosphere the mini/micro sat is deployed, and then an attached booster rocket pushes the sat into its orbital altitude.
And yes, the sats need to be built more robust.

I have been following this company for a few years and, they said we could never land a man on the moon...

 

[hitmouse]

One thing to remember is that this is not a 100% sling launch system. It's intended purpose is to replace the main launch vehicle, thus saving cost.
At a certain altitude in the upper stratosphere the mini/micro sat is deployed, and then an attached booster rocket pushes the sat into its orbital altitude.
And yes, the sats need to be built more robust.

I have been following this company for a few years and, they said we could never land a man on the moon...

Try to send someone to the moon with this and they would end up a thin red paste on the back wall of the satellite.

 

[THX1138]

Try to send someone to the moon with this and they would end up a thin red paste on the back wall of the satellite.

Thats what crash test dummies are for! Just think of the data you'll get on re-entry.

 

[LordOfWizards]

I'm not sure that this scales up.

SpinLaunch currently achieves 1,000 MPH. Escape velocity for Earth's gravity is 25,300 MPH. The scale up is more than an order of magnitude. For the current configuration, 1,000 MPH with a diameter 108 feet gives a centrifugal force of 1,238 g. Increasing the diameter by 25.3 to 2,732.4 feet gives a force at escape velocity of 31,324 g.

Agreed. Right now, this one can send a test load to 7.6 km. It said they will build a bigger one that does 60 km. That's still only half way to escape orbit. If you'd like to get seriously into the maths, check out Real Engineering's video:

 

[THX1138]

More from the NASA test. Still a ways to go but, looking good so far.
The Payload NASA Shot Into Sky With Giant Gun Came Down So Hard They Needed to Dig It Out With an Excavator

 

[Robert Zwilling]

Their solutions are interesting, simple and cost effective, and much of it off the shelf, either as raw materials or preassembled parts. That way they can keep going on for awhile. It's like a new type of cannon or it could be called a sonic matter laser. The original lasers were ruby rods with mirrored ends. Optical energy was pumped into the rod, the energy traveled back and forth through the rod until it lased, and then popped out one end of the rod. This device, pumps energy out, the air goes out instead of pressurizing behind the projectile. It runs the projectile through the barrel many many times. The two exit doors are clever, have to see if a bigger one works for the inside one, and the outside one simply breaks away, and you just pop on a new one.

The construction of the dart works well double purposed, the heat deflecting properties of the dart also act to shield the device against impact when it lands. I wouldn't be surprised if they had the top cap pop off somehow to reduce the mass of the tip, and a parachute pops out, like the Este rockets did that kids can build. It would be easier if the parachute pops out the back. All that technology already exists.

For scaling up, the force imbalance at lift off still seems to a problem. Their ultimate solution is to somehow launch 2 satellites at the same time. I don't see how you don't need to do anything extra after the second pops off, but I only watched the video once.

For getting non fragile materials into space, it would be a good relatively nonpolluting operation. As the scale goes up, the cost of operation might increase. Those high tech carbon tethers may not be reusable.

If they could build it on top of a very tall mountain, they could double the height right away. There would be a bit less air pressure for creating the vacuum, the initial shock of hitting the atmospheric pressure would be less. It would be hitting a much colder temperature right off the bat. For the electronics and machinery it would be easier to get cooler operating temps. It would require a very long extension cord. You might be able to do it with free power with very large wind turbines and a monstrous battery setup to store the power.

I am guessing that the way it is now, it would work on the Moon or Mars to put satellites or other items into orbit.

Too bad the video isn't in print as well. For me, they're good for getting a big splash, but not getting the whole picture across in one shot. You can scan print so much easier than video, back and forth, up and down, until you get everything and any tangential thoughts you might think up. You have to watch long videos a couple of times to get everything, or just settle for partial recall and think you got it all. Which sometimes is probably the goal.

 

[Wayne Mack]

Agreed. Right now, this one can send a test load to 7.6 km. It said they will build a bigger one that does 60 km. That's still only half way to escape orbit. If you'd like to get seriously into the maths, check out Real Engineering's video:

I'm not sure what mathematics can be derived from the video; I felt it was a lot of redirection on issues. The only hint of formula was a pitch by the video producer to purchase its series.

I am a little dubious of the projections to perform multiple launches on several fronts. I question the demand to support 5-10 launches per day. I question the ability to preserve the needed vacuum even if the launch tube doors close really, really fast. The current system does not involve the double door approach and requires the launch tube to be re-evacuated after launch.

I question the proposed balancing mechanism of launching two projectiles. Part of this is due to the issue of maintain a near vacuum after opening the launch tube. The second is due to the stress applied at the axle for the half revolution to bring the second object into launch orientation. The stress levels are going to be high enough to require special construction materials. The current system uses a counterbalance weight that is released simultaneously with the projectile and is destroyed, requiring clean up following launch. If there is enough clearance, however, this method could be continued to be used for multiple launches.

I got a little lost in the calculations of the cost involved with launching a satellite and what was included in the per kilogram measure (satellite only or satellite plus launch device). Unless there is a plan to launch multiple satellites at once, a simple per launch cost would be more usable. Given that it is unlikely that the system would use multiple projectile sizes, a flat rate per launch would be a more realistic value.

Concerning the survivability of the payload, the major factor for solid state electronics would be vibration rather that g force. I believe, however, satellites would also contain more fragile components such as motors and solar panels. I do not feel the digital device shown represents the actual components of a satellite.

SpinLaunch is certainly an interesting engineering pursuit, but I feel there are major challenges to make it truly viable. I am not reassured by the potential solutions that were presented.

 

[Elckerlyc]

It's an experimental approach and alternative method of launching small cube-sats into space, equipped with a booster rocket to push them into a higher orbit. It it works, great. If not, they at least tried to create a cheap and clean launch system. Many technological challenges have been overwon simply by keep trying to do the impossible. If you shoot something up 7,6km into the air, it can be doubled. And again. And...
.

 

[LordOfWizards]

Well, It's mostly science until around 27 minutes when they go into ballistic drag coefficients and then some orbital considerations. And before that the video does go into how they keep the extreme vacuum ( They have synchronized a two door system with the speed at release - like an airlock)

 

[Wayne Mack]

They have synchronized a two door system with the speed at release - like an airlock

Actually, the synchronized doors are a proposed solution that would aid in performing consecutive launches. The current system has a door at the bottom of the launch tube, but the top is sealed by some sort of sheeting that the projectile tears through. This is seems to be a viable approach for single launch approaches. The length of the launch tube, the length of the projectile, the reaction time of the doors, and the tightness of synchronization between the two door motors would all be variables. Additionally, the length of the projectile would drive the diameter of the spin body.

The mention of two back-to-back launches would require the first projectile to clear the launch tube within a half rotation and allow the two doors to reset. This would require the launch tube to be somewhat shorter than the diameter of the spin body and the length of the projectile would need to be less than the length of the launch tube in order to be able to preserve the vacuum. And this ignores the degree to which the launch tube would need to be depressurized between launches.

Given the projections that only 30% of current fuel would be needed in this approach, then the dimensions of the projectile fuel tanks would be reduced to two-thirds of current (0,67 x 0.67 x 0.67 = 0.30). This drives the size of the projectile, which in turn drives the size of the launch tube and the diameter of the spin chamber. To be viable, the system would need to launch satellites on the scale of current communications and weather satellites, which affects the amount of needed fuel and the size of the projectile.

To be fair, this is largely a marketing video. I am still unsure of the level of scaling up needed to launch actual size satellites into orbit. Given that satellites typically deploy components when in orbit, I still wonder about the viability of high G-force launch and whether bending a capacitor on a circuit board represents the whole of a satellite. I am not convinced of the viability of multiple back to back launches, even if spaced hours apart. Even raising this capability makes me wonder about the economics of the model and why the 5-10 launches per day would be needed.

 

[Astro Pen]

Yes, I started a thread on this a few weeks ago. Under 'Technology' (but it didn't gain traction.)
I had reservations about the ability of solar panels etc' to stand the G.
On the other hand I expect satellite design will become smaller and more 'solid state' as tech advances. lending itself to this system as well as reducing collision risk 'up there'.