Quote from: eeergo on 11/15/2021 11:31 amI wasn't referring to the heat load being prohibitive (which might also be a factor), I was referring to the enormous drag force it is experiencing while it's flying under such conditions. For your 7% figure, you're assuming the assisted launch will get you at 2 km/s once in space. They're having a 2.1 km/s goal for *exit* velocity, which works out to 1.7 km/s at altitude *with no drag losses* - which I'm arguing in my post will be substantial, just by looking at things like Sprint, because that thing was accelerating from 0 to manyMach while in the lower atmosphere, and still glowed red because of friction, while still accelerating. SpinLaunch's projectiles will have their maximum speeds at release, and decelerate from then until vacuum altitudes, so their losses will start at maximum (much beyond Sprint's max losses, I postulate) and decrease exponentially. Can't see how that won't be a substantial %, which will get you into (I suspect) 1.5 km/s territory by the point the chemical stage can ignite. Regarding the possibility of making it heavier so that it has larger momentum (and potentially helping with the heat load dissipation), sure - but then your centrifuging issues also scale up."For your 7% figure, you're assuming the assisted launch will get you at 2 km/s once in space."No this was a master thesis for my personal master in Space Engineering, not a back of the enveloppe thing i just thought about this afternoon.It included atmospheric models, gravity model, rotating earth etc, etc.I optimized 11 different parameters of both the vehicle (chamber pressure, oxidizer to fuel ratio, nozzle exit pressure, nozzle exit diameter, length of the tanks, diameter of the tanks) as well as the trajectory (initial flight path angle and 4 parameters to model the pitch behavior).I did this for several combinations of initial velocity and initial altitude. (i.e. 2km/s, 0m altitude or 2km/s, 5000m altitude) for both kerolox and hydrolox single stages.So no I was not assuming the assisted launch would get me 2 km/s once in space. I assume it will get me 2 km/s at sea level.At which point optimum inclination or initial flight path angle would be 39.9 degrees for example.Also, since I did not limit mass but simply optimized for highest payload ratio in orbit, my optimization selected a 243 ton kerolox stage and a 233 ton hydrolox stage as the optimal solutions for this type of assist. Much heavier than for example the 54 and 30 ton vehicles it spat out when I optimized an assist of 2 km/s at 40 km altitude. This difference was clearly due to trying to limit drag losses by sizing up the vehicle.Now the drag loss for kerolox was calculated to be 238 m/s whereas the hydrolox vehicle had a drag loss of 341 m/s.Since spin launch will probably require an order of magnitude smaller vehicle the drag losses will become a lot more extreme than that.Drag losses follow the cube square law meaning that as your mass decreases with the cube of your dimensions, drag force only decreases with the square of your dimensions. However the drag coefficient will be a lot better due to the shape of to cocoon they launch their vehicle in.I'd guesstimate that for a 20 ton vehicle, the drag losses of a full kerolox system would be in the 350 m/s range, whilst for hydrolox in the 500 m/s range. It might be prudent to consider higher density propellants (solid) that could get it down to 250 m/s though.It is worth noting that small launch vehicles also have considerable drag losses of probably in excess of 200m/s and that the launch assist will likely help keeping gravity losses low.So I don't think it will be a dealbreaker. Just make it slender, dense, aerodynamic and as heavy as possible.
I wasn't referring to the heat load being prohibitive (which might also be a factor), I was referring to the enormous drag force it is experiencing while it's flying under such conditions. For your 7% figure, you're assuming the assisted launch will get you at 2 km/s once in space. They're having a 2.1 km/s goal for *exit* velocity, which works out to 1.7 km/s at altitude *with no drag losses* - which I'm arguing in my post will be substantial, just by looking at things like Sprint, because that thing was accelerating from 0 to manyMach while in the lower atmosphere, and still glowed red because of friction, while still accelerating. SpinLaunch's projectiles will have their maximum speeds at release, and decelerate from then until vacuum altitudes, so their losses will start at maximum (much beyond Sprint's max losses, I postulate) and decrease exponentially. Can't see how that won't be a substantial %, which will get you into (I suspect) 1.5 km/s territory by the point the chemical stage can ignite. Regarding the possibility of making it heavier so that it has larger momentum (and potentially helping with the heat load dissipation), sure - but then your centrifuging issues also scale up.
Quote from: Lars-J on 02/07/2020 11:38 pmEven if that is all resolved But they still need to provide a substantial upper stage, otherwise this is just a suborbital cannon.Perhaps I missed something but won't the upper stage need to contribute several km/s to reach orbit?Yeah, probably around 6km/s of required rocket dV. This is why while I think their system will actually work, I'm skeptical that it will be cheap enough to get large numbers of customers to switch to them. ~Jon
Even if that is all resolved But they still need to provide a substantial upper stage, otherwise this is just a suborbital cannon.Perhaps I missed something but won't the upper stage need to contribute several km/s to reach orbit?
It was already determined they'll be at 1.7 km/s *without drag losses* with SpinLaunch's system. By your own numbers, that'd translate in a 20-25%-ish difference in payload hit just due to altitude (1.7 - 0.3 (avg kero/hydrolox) = 1.4 km/s, and you stated 22.5% for 1.5 km/s), which is what I was puzzling about.
Quote from: edzieba on 11/10/2021 05:51 pmThat confirms the shock-resistance of SMT, for long duration loading that's down to creep-resistance of the solder alloy (and/or the conformal coating if you assume that will take the majority of the load). Some existing research (e.g. https://doi.org/10.1108/eb037718) at kilogee levels shows that some lead-free solder alloys are highly creep resistant (e.g. 96.5Sn/3.5Ag having around half a percent creep rate), and test electronics can be placed within an ultracentrifuge if you want to perform direct testing under design g loads for long periods.If the problem is creep due to long spin up time, then reduce the spin up time. Let’s say it takes 120 minutes to spin up to 2km/s. If the projectile is 10 tons and the whole mass including the projectile is 100 tons, then the effective energy is ~.5*(100000kg)*(2km/s)^2 ( less than that since most of the mass is relatively close to the center of rotation), so over 120 minutes it takes 28MW. Over 12 minutes it takes 280MW. One Tesla Model S puts out 1MW peak power, for scale.A cheap brushless motor, driver, and backing battery cost about 10¢/Watt, so you’re looking at about $30 million in electric power train costs vs $3 million.$30M is small for aerospace, BUT this launcher is supposed to try to get to well under $500,000 launch costs. So that’s ~60 launches in revenue.
That confirms the shock-resistance of SMT, for long duration loading that's down to creep-resistance of the solder alloy (and/or the conformal coating if you assume that will take the majority of the load). Some existing research (e.g. https://doi.org/10.1108/eb037718) at kilogee levels shows that some lead-free solder alloys are highly creep resistant (e.g. 96.5Sn/3.5Ag having around half a percent creep rate), and test electronics can be placed within an ultracentrifuge if you want to perform direct testing under design g loads for long periods.
These high power demands put extra restraints on launch site selection as nearby grid needs to be able to supply this power. A lot of local grids are struggling with peak loadings around dinner time and breakfast so launch windows will be reduced. In saying that power is lot cheaper at offpeak times so there is lot of incentives to launch in middle of night.Sent from my SM-G570Y using Tapatalk
I'd say they should go with a solid upper stage. Will be a bit inaccurate but is probably the easiest to sustain 10000 g's.
Quote from: fatjohn1408 on 11/15/2021 04:22 pmI'd say they should go with a solid upper stage. Will be a bit inaccurate but is probably the easiest to sustain 10000 g's.Is it though? 10k Gs is quite a lot, and I would think you could easily have issues with the solid propellant cracking under the strain. That is quite bad, as it increases the surface area during combustion, and usually leads to RUD.I actually think they are on the right track with pressure-fed liquid propulsion. It should handle the Gs quite well.
Quote from: Robotbeat on 11/15/2021 01:42 pmQuote from: edzieba on 11/10/2021 05:51 pmThat confirms the shock-resistance of SMT, for long duration loading that's down to creep-resistance of the solder alloy (and/or the conformal coating if you assume that will take the majority of the load). Some existing research (e.g. https://doi.org/10.1108/eb037718) at kilogee levels shows that some lead-free solder alloys are highly creep resistant (e.g. 96.5Sn/3.5Ag having around half a percent creep rate), and test electronics can be placed within an ultracentrifuge if you want to perform direct testing under design g loads for long periods.If the problem is creep due to long spin up time, then reduce the spin up time. Let’s say it takes 120 minutes to spin up to 2km/s. If the projectile is 10 tons and the whole mass including the projectile is 100 tons, then the effective energy is ~.5*(100000kg)*(2km/s)^2 ( less than that since most of the mass is relatively close to the center of rotation), so over 120 minutes it takes 28MW. Over 12 minutes it takes 280MW. One Tesla Model S puts out 1MW peak power, for scale.A cheap brushless motor, driver, and backing battery cost about 10¢/Watt, so you’re looking at about $30 million in electric power train costs vs $3 million.$30M is small for aerospace, BUT this launcher is supposed to try to get to well under $500,000 launch costs. So that’s ~60 launches in revenue.These high power demands put extra restraints on launch site selection as nearby grid needs to be able to supply this power. A lot of local grids are struggling with peak loadings around dinner time and breakfast so launch windows will be reduced. In saying that power is lot cheaper at offpeak times so there is lot of incentives to launch in middle of night.Sent from my SM-G570Y using Tapatalk
Quote from: TrevorMonty on 11/15/2021 04:54 pmQuote from: Robotbeat on 11/15/2021 01:42 pmQuote from: edzieba on 11/10/2021 05:51 pmThat confirms the shock-resistance of SMT, for long duration loading that's down to creep-resistance of the solder alloy (and/or the conformal coating if you assume that will take the majority of the load). Some existing research (e.g. https://doi.org/10.1108/eb037718) at kilogee levels shows that some lead-free solder alloys are highly creep resistant (e.g. 96.5Sn/3.5Ag having around half a percent creep rate), and test electronics can be placed within an ultracentrifuge if you want to perform direct testing under design g loads for long periods.If the problem is creep due to long spin up time, then reduce the spin up time. Let’s say it takes 120 minutes to spin up to 2km/s. If the projectile is 10 tons and the whole mass including the projectile is 100 tons, then the effective energy is ~.5*(100000kg)*(2km/s)^2 ( less than that since most of the mass is relatively close to the center of rotation), so over 120 minutes it takes 28MW. Over 12 minutes it takes 280MW. One Tesla Model S puts out 1MW peak power, for scale.A cheap brushless motor, driver, and backing battery cost about 10¢/Watt, so you’re looking at about $30 million in electric power train costs vs $3 million.$30M is small for aerospace, BUT this launcher is supposed to try to get to well under $500,000 launch costs. So that’s ~60 launches in revenue.These high power demands put extra restraints on launch site selection as nearby grid needs to be able to supply this power. A lot of local grids are struggling with peak loadings around dinner time and breakfast so launch windows will be reduced. In saying that power is lot cheaper at offpeak times so there is lot of incentives to launch in middle of night.Sent from my SM-G570Y using TapatalkI knew someone was going to say that, which is why I specified a backing battery in my original post, which naturally was completely ignored.
That is 56MWhr battery. Sent from my SM-G570Y using Tapatalk
New article with a very respectful, measured, and skeptical approach to what SpinLaunch is doing over at CleanTechnica: https://cleantechnica.com/2021/12/19/spinlaunch-successfully-throws-a-10-meter-dart-toward-space/No new information, but one of the better independent articles about I've seen.
SpinLaunch says it will announce the site for its full-scale orbital launcher within the next five months. It will likely be built on a coastline, far from populated areas and regular airplane service. Construction costs would be held down if the machine can be built up the side of a hill. If all goes well, expect to see the first satellite slung into orbit sometime around 2025.
On a coastline, far from populated areas and air travel. Kind of narrows the options down.Alaska is a good option, but far from the equator. Hawaii is out (Spinlaunch already tried, got shot down by local opposition). Most other places on the East Coast or South Coast have lots of stuff built up on the coast.
https://spectrum.ieee.org/amp/spin-me-up-scotty-up-into-orbit-2656442408QuoteSpinLaunch says it will announce the site for its full-scale orbital launcher within the next five months. It will likely be built on a coastline, far from populated areas and regular airplane service. Construction costs would be held down if the machine can be built up the side of a hill. If all goes well, expect to see the first satellite slung into orbit sometime around 2025.
Quote from: PM3 on 01/27/2022 07:26 amhttps://spectrum.ieee.org/amp/spin-me-up-scotty-up-into-orbit-2656442408QuoteSpinLaunch says it will announce the site for its full-scale orbital launcher within the next five months. It will likely be built on a coastline, far from populated areas and regular airplane service. Construction costs would be held down if the machine can be built up the side of a hill. If all goes well, expect to see the first satellite slung into orbit sometime around 2025.Hang on a sec.. Why would construction costs "be held down if the machine can be built up the side of a hill"?? Surely (a) hauling up extremely heavy construction equipment, counterweights and the like and (b) building solid foundations that can handle forces generated in spinning up would be more expensive to install on the side of a hill?And doesn't this concept require a ridiculous amount of power to spin up?? Unless they plan to steal the power feed to a regional city for a few hours, upsetting the locals in the process, remote areas don't tend to contain that kind of infrastructure.
