Quote from: edzieba on 11/09/2021 10:25 pmToo large to attach here, but their website has a much higher quality copy of the twitter video. If you go through the drone shot frame-by-frame, it does appear that the projectile is tumbling after exit, and the high-speed shot also shows it starting to lean over.I would guess this is just a dummy rocket, and they need active aerodynamic guidance for stability after release.
Too large to attach here, but their website has a much higher quality copy of the twitter video. If you go through the drone shot frame-by-frame, it does appear that the projectile is tumbling after exit, and the high-speed shot also shows it starting to lean over.
SpinLaunch’s first suborbital flight utilized about 20% of the accelerator’s full power capacity for the launch [not clear if they're referring to this particular centrifuge, which is said to be one-third scale, or 20% of the full design], and reached a test altitude “in the tens of thousands of feet,” according to Yaney. [i.e. a few km at most]
I appreciate it's a proof of concept... but they're claiming "90% of the system's risk has now been retired"
Quote from: eeergo on 11/10/2021 03:10 pmI appreciate it's a proof of concept... but they're claiming "90% of the system's risk has now been retired"Because "doesn't vibrate itself into a pile of parts during spinup", "doesn't burst into a pretty pinwheel of fragments on projectile release" and "projectile release puncturing the port membrane doesn't cause a catastrophic gas inrush" are the unique risks they needed to retire. "Electronics and component that can handle extreme g and shock loads" are already a retired risk (guided rocket-boosted artillery shells are an existence proof), and hypervelocity flight in dense atmosphere is an at least understood regime (existing artillery and missile rounds, and re-entering projectiles) even if existing applications are not a direct match for their particular flight regime.Definitely more work to scale up rotor speed and actually manufacture a non-brick projectile, but it's a question of whether they will run out of money before succeeding rather than a question of outright possibility of success.
Some calculations on the G-levels (and times):https://twitter.com/DJSnM/status/1458467841779253253For reference, artillery shells have (instantaneous) accelerations of 10-30k Gs. Sprint ABM's acceleration was 100 G (remember the glowing when already beyond the apogee altitude of this vertical, "suborbital" test). Maximum instantaneous tested G-loading on electronics is just ten times the G level this thing will have to endure for hours.
Quote from: eeergo on 11/10/2021 04:50 pmSome calculations on the G-levels (and times):https://twitter.com/DJSnM/status/1458467841779253253For reference, artillery shells have (instantaneous) accelerations of 10-30k Gs. Sprint ABM's acceleration was 100 G (remember the glowing when already beyond the apogee altitude of this vertical, "suborbital" test). Maximum instantaneous tested G-loading on electronics is just ten times the G level this thing will have to endure for hours.10000G for an hour must be wrong. 10G for an hour must be wrong. 1 minute at 10000G would over 5000 km/s velocity. 10000 * 9.8 meter/sec for 1 -second- gives 98 km/sec velocity at the end - way faster than escape velocity of 11 km/s. Or was this a European decimal point? 10G for 1 hour = 9.8 meters/sec * 60*60 = 3600 seconds ~ 35 km/sec which is also unbelievable fast.
Any idea how they are handling the imbalance on release issue? The goto solution has been said that you just release a counterweight. However, even with the shorter arm, it's gonna be coming out with a lot of energy. Perhaps they use a fluid counterweight? Just release water?
The centripetal high-g environment is unique and few testing environments exist. Leveraging the SpinLaunch 12-meter and 33-meter accelerators, which are capable of spinning hardware to 10,000g and up to five times a day, SpinLaunch engineers rapidly iterate through many design-analyze-build-test cycles to optimize satellite components for the centripetal environment.This engineering process has been used to develop high-g reaction wheels for 20kg and 200kg-class satellites, deployable solar arrays and electric propulsion modules. Even unmodified smartphones, action cameras, and telescope lenses have survived without damage. In comparison to mechanical systems, electronics are surprisingly simple to ruggedize for kinetic launch. Because of the relatively low mass of resistors, capacitors, and electronic chips, many existing designs can be flown without any substantial modifications.
[re: DOD interest in SpinLaunch]Strictly speaking, SpinLaunch's technology is an artillery system and not a rocket system. That's only important if you're splitting hairs on treaties related to ballistic missiles.Given the $M's per launch estimated cost of the Zumwalt's (?) hypersonic projectiles, something like SpinLaunch could potentially deliver a similar speed projectile for a lot less.
I have made some comments about [the counterweight issue] in the past. I'm referencing that here because said comments predate any NDA I might have with SL...There is a counterweight that is released at the same time as the projectile. It is captured in the vacuum chamber. As you can see in the video, the current tether is symmetric so the counterweight is the same mass as the projectile but it could be heavier (and slower) on a shorter arm in the future.The interesting bit is that there are higher-order vibration modes associated with releasing that much tension on the tether. Those never balance out. So you've got to build the hub to withstand quite a bit of off-axis loading. It's enough that it's not out of the question that instead of releasing a counterweight simultaneously with the projectile, you can wait half a turn and release a second projectile out the same exit tube.
ivekadi wrote:Re: SpinLaunch:I'd like to point out that the aforementioned exit velocity of 2 235 m/s is ~140 m/s short of lunar escape velocity. As for (lunar) orbit, minimal extra dV will be required to raise the perigee. As such, this is very promising device.They are very aware of that.
Yeah, [a lunar SpinLaunch is] definitely infrastructure. There's certainly no need for it if you're only looking to lift a Starship's worth of payload off the surface. I don't know that they think they need a dust guard. Erosion can be managed, heating cannot.The solar panels and batteries needed to run the system probably weigh more than the tether. But with mag-lev bearings and superconducting magnet motors maybe the power requirement can be dropped very low and the overall mass reduced greatly. Such a system would just take a really long time to spin up.
There is another potential advantage for SpinLaunch that I think danielravennest came close enough to the other day. The tether weighs way more than the payload so the change in rotational energy isn't actually very high when you release. So you don't want to just spin down. At the least SL has talked about regeneratively braking to recover their energy cost. However, as danielravennest pointed out the other day, that energy can instead be used to spin up a second tether with a payload either through an electric or hydraulic transfer system. Given that spinning up from a dead start is between half- to two hours, you're potentially shaving 90% of that time. I don't know how fast they're going to be able to replace the mylar films on the exits, but you're potentially looking at multiple payloads that can be launched in any given launch window.For small launchers, the overhead cost of a launch plays a big role. It's not just the rocket materials cost. So if you can shoot off a dozen or so payloads every time you prep a launch you're able to underwrite your overhead more quickly. Manufacturing at-scale is always an issue for small launchers, but if your rocket is a relatively simple blow-down design that only has to add 7 km/s then you can manufacture more of them relatively easily. That assumes one can make the carbon fiber bodies relatively well. But once you've got the mandrels, that's not actually hard.
I just watched the Scott Manley video looking at SpinLaunch. His analysis is pretty spot-on for not having inside information. A few of his concerns have already been retired. But his overall take is "this doesn't seem impossible" is a far sight better than his first visitation of the topic in 2018. Then again, he seemed to be under the impression it was a "slingatron" idea at the time rather than a simple centrifuge.
[The] question is whether you're cheaper than Electron. It all depends on cadence as I've said. If you can launch hundreds of times per year, the amortization of the launcher works out to very little cost per launch - far less than the first stage of an Electron. So then is the two-stage rocket SpinLaunch is proposing less expensive than Electron's second stage? I would say it almost has to be since there's clearly not going to be any turbomachinery.So the final analysis will boil down to whether your payload modifications are more expensive than your cost savings. SpinLaunch claims that for a wide variety of applications there is almost no added cost to engineering for massive acceleration. I have no particular insight into this area. If I were a prospective customer that's a claim I would want backed up before I committed to SL as a launch provider.But the other potential market niche is to rapidly deploy a constellation of satellites. Except for SpaceX, there aren't a lot of launch providers that can put a few hundred satellites into orbit in a short period of time. Rocket Labs just can't maintain the cadence no matter their cost. SpinLaunch truly believes they're designing for "dozens" of launches per day.
Quote[re: DOD interest in SpinLaunch]Strictly speaking, SpinLaunch's technology is an artillery system and not a rocket system. That's only important if you're splitting hairs on treaties related to ballistic missiles.Given the $M's per launch estimated cost of the Zumwalt's (?) hypersonic projectiles, something like SpinLaunch could potentially deliver a similar speed projectile for a lot less.
A bit faster, and this thing makes a decent weapon. Can do fractional orbital conventional bombardment from the continental US at an advantaged cost ratio, similar to having an Aegis missile ship near your target using cruise missiles. And similar time from launch to impact.
So another "suborbital" hop which is actually an endoatmospheric throw:QuoteSpinLaunch’s first suborbital flight utilized about 20% of the accelerator’s full power capacity for the launch [not clear if they're referring to this particular centrifuge, which is said to be one-third scale, or 20% of the full design], and reached a test altitude “in the tens of thousands of feet,” according to Yaney. [i.e. a few km at most]I appreciate it's a proof of concept... but they're claiming "90% of the system's risk has now been retired" Plus for some obscure reason they're looking at sea-level launch sites, sporting 1 km more of denser atmosphere to clear than their proof-of-concept's location
Quote from: edzieba on 11/10/2021 03:22 pmQuote from: eeergo on 11/10/2021 03:10 pmI appreciate it's a proof of concept... but they're claiming "90% of the system's risk has now been retired"Because "doesn't vibrate itself into a pile of parts during spinup", "doesn't burst into a pretty pinwheel of fragments on projectile release" and "projectile release puncturing the port membrane doesn't cause a catastrophic gas inrush" are the unique risks they needed to retire. "Electronics and component that can handle extreme g and shock loads" are already a retired risk (guided rocket-boosted artillery shells are an existence proof), and hypervelocity flight in dense atmosphere is an at least understood regime (existing artillery and missile rounds, and re-entering projectiles) even if existing applications are not a direct match for their particular flight regime.Definitely more work to scale up rotor speed and actually manufacture a non-brick projectile, but it's a question of whether they will run out of money before succeeding rather than a question of outright possibility of success. Well, not really because the system is at 20% of its RPL, and 1/3rd the scale. It's certainly a test of the three things you mention but those risks are not retired at all, not even close: they just showed they understand the low-energy end of the dynamics, up to those very basic levels of "it's not RUDing itself apart at the first opportunity", but those dynamics might not (in fact, will not) scale predictably to operational levels.More illustratively, 20% of Mach 3 (i.e. Mach 0.6) with a 1/3rd scale large R/C fighter jet high-fidelity model should not give you much confidence on your operational design, other than perhaps giving you confidence the analysis tools you used are not completely unable to do the job.
And even assuming they don't really need to make compromises in the design to withstand the G-loads, how will they qualify the payload for the loads? Run it in an ultra-centrifuge? At what cost?
I just don't see this as being competitive with Virgin Orbit/Astra/Electron/ridesharing, even in the best case scenario.
BTW, here's another technical risk I thought of - immediately upon exiting the vacuum chamber, the rocket will start decelerating. That again means the propellant flows forward in the tanks. Lighting the first stage would be a bit complicated. Maybe they can use bladders to force the propellant into the engines. Or just wait until the stage is clear of most of the atmosphere.
But that means no thrust vector control for a minute or more, and with the atmospheric pressure dropping as it ascends, less and less aerosurface control. You could start tumbling and similar before engine start.
