Re: [Starlink] some post Starship launch thoughts

Re: [Starlink] some post Starship launch thoughts

[David P. Reed]

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IANARS. (and most people here probably aren't, either, so I don't feel bad potentially saying something naive)
 
The discussion here about Starship's launch disaster got me thinking. The result is below:
1. Clarifying the hypotheses of problem and solution. (and a few jabs at Musk along the way, though I'm impressed by the SpaceX folks while feeling sorry for them having Musk as a boss).
2. A proposed better idea (at least my riffing on it) to launch that would be more environmentally sound, simpler, and appropriate for civilian (rather than military) rocketry.
 
I have had a lot of experience with various sorts of fluid dynamics (the study of Navier Stokes Differential Equation solutions under pragmatic boundary conditions pretty much characterizes Fluid Dynamics), especially hydrodynamics and aerodynamics near surfaces.
 
I'm finding this discussion here unsatisfying, because one thing that seems obvious to me is that people are extrapolating their "gut instincts" about fluid flow at low reynolds number in laminar flow to the situation at a rocket launch where the output is within a few meters of the ground.
 
Now I also briefly designed and tested small solid fuel amateur rocket engines (not Estes rockets - more the kind you see in the movie October Sky - zinc and sulfur cast fuel in 150 cm steel tubes, with machined steel nozzles. That was 55 years ago. This doesn't tell much about modern rocketry design, but anyone who has done that kind of rocket design (which is relatively simple) encounters very high reynolds number flows around the nozzle, especially if launched with the nozzle near a "pad" - which we avoided because of the instability of the thrust with tilt of the rocket relative to the ground causing non-vertical takeoff.
 
Now the issue here is that it is very, very hard to model or predict the transient flows during initial acceleration off the pad. I'm not at all convinced that the naive reasoning on this list (including mine here) is particularly helpful.
 
I am convinced that Elon Musk knows NOTHING about rocketry fluid dynamics - he's not a rocket engineer, though he pretends to be one, encouraging all his fans and buddies to think naively, too. He's a narcissitic investor, and by all reports a *terrible* technical manager. So anything he says is probably a completely distorted version of reality, and he tends to no let the knowledgable people who work at his companies speak openly or honestly about engineering. (Certainly we see that at Tesla regarding "self-driving" and Neuralink. A pretense of Musk being the scientific genius is required to work at those companies). I mention this because much of the technological comment here is speculation driven by Musk's PR around SpaceX and Starlink. [I'd love to hear Musk give a talk about turbulence and vorticity and stability during the first few seconds of launch and have a rocketry expert comment. I don't think he could give such a talk even with a teleprompter and ghostwritten script.]
 
OK, so a question pops up for me that has always bugged me. Other than old SF story covers always showing a rocket sitting on its nozzle on a concrete pad, with all the complex fluid dynamics involved as the fluid flow changes rapidly, why do we still try to do it this way?  
 
Ideally, the initial acceleration of a rocket would be better imparted by an external launcher (at least on the Earth - not initially on Mars). For example, an electromagnetic linear accelerator that contains the rocket while it accelerates. (We're not talking a sub-launched missile or a carrier-launched airplane here, and even on carriers, electromagnetic catapults have been developed that work better than steam ones - despite Trump's Musk-like idiotic statement that "steam is the best way" for carriers).
 
The reusability of an electromagnetic launcher is clearly far better than for the "reusable" launch stage that holds the equivalent energy in fuel form. (snark: and Musk is a genius who "invented" a whole system for using tubes and magnets called Hyperloop).
 
It doesn't need to be a tube, it could be a "rail" (railguns work, and are cool in SF, too).
Powering it just needs a way to store and release electrical energy fast - a battery, basically, which can be wired up as a collection of storage cells in parallel.
 
And this wouldn't pollute the atmosphere anywhere near as much, I'd guess.
 
The obvious drawback is that the weaponry application of this approach is a problem. ICBM's and IRBM's and sub-launched missiles really benefit from avoiding the need for external launch systems attached to the ground. So, maube that's why NASA (which is 85% military in its mission) didn't develop it. You don't want to have to put your ICBM's where they can draw power from the grid to charge up their launcher.
 
Another drawback is that rocket scientists aren't electrical power engineers (they haven't been), so you need a more interdisciplinary team than usual. They don't design linear accelerators, which are also not as simple as they look, despite the fact that I can make a working railgun using the tools and materials I have in my basement in maybe a hour that accelerates a copper ring to supersonic speeds. But they are pretty simple systems, it seems to me, compared to managing N separate rocket exhaust streams with rapidly varying and turbulent pressure fields of the sort that occur on the launch pad of a sufficiently large multistage rocket.
 
Of course, the structure of a rocket intended to launch from an EM accelerator would have very different stress loading initially, spread out more along the body of the rocket.
 
If I had Musk's capital assets, I'd even invest in such a design. I don't, of course.
 
 
 

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Re: [Starlink] some post Starship launch thoughts

[Sauli Kiviranta]

First of all I fully agree with you on launchers, we need new ideas
there... too!

On the engineering talent metrics I would give Musk a bit more credit,
surely experts who spend their lives on a very narrow topic are better
in that specific topic. What advantage Elon has is close to those of
system effects at large. The broad engineering topics he has had to
cover over the years start to compound and pattern recognition kicks
in. This is very very rare for any individual to ever be exposed to
such diversity of engineering problems that Tesla, SpaceX and all the
other adventures have exposed him to. He may not be in the most
classical sense best engineer in a given topic, but I am pretty sure
he has certain engineering qualities that many of us lack, just due to
the vast exposure. Yes, he says a lot of outrageous things on things
that does not really matter, but quite often (in my opinion) on the
matters that... matter he is spot on.

With the slingshot launchers (even just assiting ones), as you rightly
point, the structural properties have to be vastly different I would
assume. What I am worried the most with that type of approach is the
smooth transition between the power sources when sling transitions to
self propulsion. With liquid fuels this seems just too violent of an
event temporarily to design for. I may be completely wrong too! Maybe
the launch tower could assist (like an electric bicycle mostly is
there to make the world flat for us elevation challenged humans), once
there is lift, it tries to assist the lift to its best ability with
some kind of sling mechanism or maglev system whatever. Maybe way too
complicated structurally to implement at Starship-scale! :D

It was interesting to see that such a "basic" thing as the launch pad
structure was overlooked as a rather large problem vector. Even if it
was recognized as an issue, that it turned out to be a majestic
borderline catastrophic issue was surprise to me. Easy to overlook
everything when scaling up. There is a great book on the topic of
systems and their scaling parts when sizes change "Scale: The
Universal Laws of Growth" by Geoffrey West, highly recommended.

Best regards,
Sauli

On 4/25/23, David P. Reed via Starlink <starlink@lists.bufferbloat.net> wrote:
>
> IANARS. (and most people here probably aren't, either, so I don't feel bad
> potentially saying something naive)
>
> The discussion here about Starship's launch disaster got me thinking. The
> result is below:
> 1. Clarifying the hypotheses of problem and solution. (and a few jabs at
> Musk along the way, though I'm impressed by the SpaceX folks while feeling
> sorry for them having Musk as a boss).
> 2. A proposed better idea (at least my riffing on it) to launch that would
> be more environmentally sound, simpler, and appropriate for civilian (rather
> than military) rocketry.
>
> I have had a lot of experience with various sorts of fluid dynamics (the
> study of Navier Stokes Differential Equation solutions under pragmatic
> boundary conditions pretty much characterizes Fluid Dynamics), especially
> hydrodynamics and aerodynamics near surfaces.
>
> I'm finding this discussion here unsatisfying, because one thing that seems
> obvious to me is that people are extrapolating their "gut instincts" about
> fluid flow at low reynolds number in laminar flow to the situation at a
> rocket launch where the output is within a few meters of the ground.
>
> Now I also briefly designed and tested small solid fuel amateur rocket
> engines (not Estes rockets - more the kind you see in the movie October Sky
> - zinc and sulfur cast fuel in 150 cm steel tubes, with machined steel
> nozzles. That was 55 years ago. This doesn't tell much about modern rocketry
> design, but anyone who has done that kind of rocket design (which is
> relatively simple) encounters very high reynolds number flows around the
> nozzle, especially if launched with the nozzle near a "pad" - which we
> avoided because of the instability of the thrust with tilt of the rocket
> relative to the ground causing non-vertical takeoff.
>
> Now the issue here is that it is very, very hard to model or predict the
> transient flows during initial acceleration off the pad. I'm not at all
> convinced that the naive reasoning on this list (including mine here) is
> particularly helpful.
>
> I am convinced that Elon Musk knows NOTHING about rocketry fluid dynamics -
> he's not a rocket engineer, though he pretends to be one, encouraging all
> his fans and buddies to think naively, too. He's a narcissitic investor, and
> by all reports a *terrible* technical manager. So anything he says is
> probably a completely distorted version of reality, and he tends to no let
> the knowledgable people who work at his companies speak openly or honestly
> about engineering. (Certainly we see that at Tesla regarding "self-driving"
> and Neuralink. A pretense of Musk being the scientific genius is required to
> work at those companies). I mention this because much of the technological
> comment here is speculation driven by Musk's PR around SpaceX and Starlink.
> [I'd love to hear Musk give a talk about turbulence and vorticity and
> stability during the first few seconds of launch and have a rocketry expert
> comment. I don't think he could give such a talk even with a teleprompter
> and ghostwritten script.]
>
> OK, so a question pops up for me that has always bugged me. Other than old
> SF story covers always showing a rocket sitting on its nozzle on a concrete
> pad, with all the complex fluid dynamics involved as the fluid flow changes
> rapidly, why do we still try to do it this way?
>
> Ideally, the initial acceleration of a rocket would be better imparted by an
> external launcher (at least on the Earth - not initially on Mars). For
> example, an electromagnetic linear accelerator that contains the rocket
> while it accelerates. (We're not talking a sub-launched missile or a
> carrier-launched airplane here, and even on carriers, electromagnetic
> catapults have been developed that work better than steam ones - despite
> Trump's Musk-like idiotic statement that "steam is the best way" for
> carriers).
>
> The reusability of an electromagnetic launcher is clearly far better than
> for the "reusable" launch stage that holds the equivalent energy in fuel
> form. (snark: and Musk is a genius who "invented" a whole system for using
> tubes and magnets called Hyperloop).
>
> It doesn't need to be a tube, it could be a "rail" (railguns work, and are
> cool in SF, too).
> Powering it just needs a way to store and release electrical energy fast - a
> battery, basically, which can be wired up as a collection of storage cells
> in parallel.
>
> And this wouldn't pollute the atmosphere anywhere near as much, I'd guess.
>
> The obvious drawback is that the weaponry application of this approach is a
> problem. ICBM's and IRBM's and sub-launched missiles really benefit from
> avoiding the need for external launch systems attached to the ground. So,
> maube that's why NASA (which is 85% military in its mission) didn't develop
> it. You don't want to have to put your ICBM's where they can draw power from
> the grid to charge up their launcher.
>
> Another drawback is that rocket scientists aren't electrical power engineers
> (they haven't been), so you need a more interdisciplinary team than usual.
> They don't design linear accelerators, which are also not as simple as they
> look, despite the fact that I can make a working railgun using the tools and
> materials I have in my basement in maybe a hour that accelerates a copper
> ring to supersonic speeds. But they are pretty simple systems, it seems to
> me, compared to managing N separate rocket exhaust streams with rapidly
> varying and turbulent pressure fields of the sort that occur on the launch
> pad of a sufficiently large multistage rocket.
>
> Of course, the structure of a rocket intended to launch from an EM
> accelerator would have very different stress loading initially, spread out
> more along the body of the rocket.
>
> If I had Musk's capital assets, I'd even invest in such a design. I don't,
> of course.
>
>
>

Re: [Starlink] some post Starship launch thoughts

[David Lang]

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On Tue, 25 Apr 2023, David P. Reed via Starlink wrote:

> Ideally, the initial acceleration of a rocket would be better imparted by an external launcher (at least on the Earth - not initially on Mars). For example, an electromagnetic linear accelerator that contains the rocket while it accelerates. (We're not talking a sub-launched missile or a carrier-launched airplane here, and even on carriers, electromagnetic catapults have been developed that work better than steam ones - despite Trump's Musk-like idiotic statement that "steam is the best way" for carriers).
> 
> The reusability of an electromagnetic launcher is clearly far better than for the "reusable" launch stage that holds the equivalent energy in fuel form. (snark: and Musk is a genius who "invented" a whole system for using tubes and magnets called Hyperloop).
> 
> It doesn't need to be a tube, it could be a "rail" (railguns work, and are cool in SF, too).
> Powering it just needs a way to store and release electrical energy fast - a battery, basically, which can be wired up as a collection of storage cells in parallel.
> 
> And this wouldn't pollute the atmosphere anywhere near as much, I'd guess.

also not a rocket engineer, but I've been paying attention for a while

are you aware of spinlaunch? they are trying to get their initial velocity with 
electricity, via spinning the rocket at the end of an arm rather than a linear 
accelerator.

re: linear accelerator

1. you want to gain alititude quickly to get out of the thickest air, that takes 
a launch up the side of a mountain, not something horizontal.

2. having your velocity really high as you leave the launch facility (as opposed 
to as you gain speed at higher altitudes) will significantly increase your 
aerodynamic forces

3. good mountains don't tend to have ocean to the east for problems to fall 
into, even on islands you tend to have population pretty close

4. this is a LOT of mass to move, yes, the more you can power with the linear 
accelerator, the less you need in the rocket, but you still need to move a LOT 
of mass.

5. rockets aren't stressed to be on their side (at least not when fully 
assembled and fueled), adding structure to support this will reduce your gains

6. you will need to mount the rocket to a sled, there's not a lot of ferris 
metal in a rocket for magnets to grab

7. there are a lot of delicate electronics on a rocket, how will they handle the 
very strong magnetic fields (even if you have them focused on a sled, they will 
need to be strong enough that they could be a risk even further away


all these things said, I would love to see someone try it. I think that an 
accelerator up the side of a mountain could do wonders for unmanned cargo. 
Possibly not electronics, but a lot of structure, and more importantly fuel, 
could be launched this way.

But until we have a much more substantial presense in space, I don't see it 
worth anyone investing the money to make it work. The F9 reusability was 
criticised as being unneded, the Starship is being criticised as being unneeded. 
(both with the argument that there wasn't enough demand to need them). I expect 
demand to grow with capacity, and as the cost comes down, outstripping the 
capacity, but we have a ways to go.

David Lang

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Re: [Starlink] some post Starship launch thoughts

[David Lang]

On Wed, 26 Apr 2023, Sauli Kiviranta via Starlink wrote:

> It was interesting to see that such a "basic" thing as the launch pad
> structure was overlooked as a rather large problem vector. Even if it
> was recognized as an issue, that it turned out to be a majestic
> borderline catastrophic issue was surprise to me. Easy to overlook
> everything when scaling up. There is a great book on the topic of
> systems and their scaling parts when sizes change "Scale: The
> Universal Laws of Growth" by Geoffrey West, highly recommended.

It wasn't overlooked, they did a 7 engine static fire, it damaged the pad, so 
they improved it, they did a 14 engine static fire and it damaged it again, so 
they improved it again, they did a 31 engine 50% power static fire with minimal 
pad damage and had other blocks of material mounted in the engine exhaust at 
McGreggor. They just failed to catch some inflection point between the 50% power 
test and the full power test. They expected some damage to the pad, but not 
nearly as much as what happened.

David Lang

Re: [Starlink] some post Starship launch thoughts

[Sauli Kiviranta]

Somehow this ended up in spam by gmail.

What you explained makes it even more remarkable, I would not indeed
call it being overlooked. That is just plain failure of scaling
whatever they learned from those iterations. It is definitely not
obvious, just remarkable.

Thanks for sharing these details!

Best regards,
Sauli

On 4/26/23, David Lang <david@lang.hm> wrote:
> On Wed, 26 Apr 2023, Sauli Kiviranta via Starlink wrote:
>
>> It was interesting to see that such a "basic" thing as the launch pad
>> structure was overlooked as a rather large problem vector. Even if it
>> was recognized as an issue, that it turned out to be a majestic
>> borderline catastrophic issue was surprise to me. Easy to overlook
>> everything when scaling up. There is a great book on the topic of
>> systems and their scaling parts when sizes change "Scale: The
>> Universal Laws of Growth" by Geoffrey West, highly recommended.
>
> It wasn't overlooked, they did a 7 engine static fire, it damaged the pad,
> so
> they improved it, they did a 14 engine static fire and it damaged it again,
> so
> they improved it again, they did a 31 engine 50% power static fire with
> minimal
> pad damage and had other blocks of material mounted in the engine exhaust at
>
> McGreggor. They just failed to catch some inflection point between the 50%
> power
> test and the full power test. They expected some damage to the pad, but not
>
> nearly as much as what happened.
>
> David Lang
>

Re: [Starlink] some post Starship launch thoughts

[Rodney W. Grimes]

> On Wed, 26 Apr 2023, Rodney W. Grimes via Starlink wrote:
> 
> > Now that water cooled steel plate, if you treat it like a sacrificial
> > anode in a water heater, ie you expect it to be erroded over time it
> > could get interesting.
> 
> They are designing towards hourly launches, so I don't expect it to be planned 
> as a wear item. The way it was introduced (prior to the launch) was that even 
> steel plate would wear if it wasn't water cooled.

They had best consider that as a wear item.  Those steal plates are going
to rust, no mater what they do, and at those temperatures I expect the
surface rust rate to be rather high.  Even if you water cool the back
side the exposed surface is going to get very hot, anyone have the
exhaust gas temperatures of starship?  

While findin that temperature I found:
Kennedy 39A and 40 did have flame trenches lined with fire bricks, until successive
Shuttle launches blew them out and for some distance. Both flame trenches are now
lined with a thin layer of replaceable fireproof concrete. 

So seems NASA has done this science.... I hope SpaceX is paying attention!

That temperature is suppose to be 2810C, steel melts at ~1500C, and
vaporizes at 2860C, I would say they better plan on regular replacement
of those plates, even water cooled.

Its probably time to let this thread die... and wait to see what they
come up with.
--
Rod Grimes                                                 rgrimes@freebsd.org

Re: [Starlink] some post Starship launch thoughts

[David Lang]

On Wed, 26 Apr 2023, Rodney W. Grimes via Starlink wrote:

> Now that water cooled steel plate, if you treat it like a sacrificial
> anode in a water heater, ie you expect it to be erroded over time it
> could get interesting.

They are designing towards hourly launches, so I don't expect it to be planned 
as a wear item. The way it was introduced (prior to the launch) was that even 
steel plate would wear if it wasn't water cooled.

David Lang

Re: [Starlink] some post Starship launch thoughts

[Eugene Chang]

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Thinking of evalorating steel is very cool. That certainly will “absorb” a lot of energy.
Now what would happen to the vaporized steel when it cools?
Will it percipitate out into fine nanoparticles of rust? (just making that up).
The atoms have to end up somewhere.

I am not sure what we know about boilers and superheated steam applies. The boilers keeps control (keeps balance?) of the temperature and pressure contained. Would the model of a boiler apply to the lanchpad cooling system?

Gene
-----------------------------------
Eugene Chang
eugene.chang@alum.mit.edu
+1-781-799-0233 (in Honolulu)





> On Apr 26, 2023, at 12:31 PM, Rodney W. Grimes via Starlink <starlink@lists.bufferbloat.net> wrote:
> 
>> On Wed, Apr 26, 2023 at 1:41?PM Rodney W. Grimes
>> <starlink@gndrsh.dnsmgr.net> wrote:
>>> 
>>>> As always I enjoy the flood of information we get on this list!
>>>> 
>>>> still, so far, my research on a nitrogen deluge system (instead of
>>>> water) has come up empty for me, except as a fire suppressant. So it?s
>>>> either crazy or brilliant. Or both! I really liked the idea of
>>>> something cooler that was a natural byproduct of the LOX process...
>>> 
>>> I dont think cooler does much, isnt it the "energy of vaporization"
>>> that is actually doing all the "work" in this type of system?
>>> 
>>> H2O is 40.7 kJ/mol and LN2 is 5.6 kJ/mol so you would
>>> need ~7 times as much LN2 to do the same work.
>> 
>> Now that! was the kind of numbers I was looking for!
> 
> :-)
> 
>> 
>> Still, water has to come from somewhere, and be stored. I will keep
>> thinking about it. I like that they seem to think that a water cooled
>> steel plate will suffice.
> 
> Water is a pretty ubundant resource...
> 
> Now that water cooled steel plate, if you treat it like a sacrificial
> anode in a water heater, ie you expect it to be erroded over time it
> could get interesting.  Energy of vaporization of steel well... lets
> call it iron (Fe) is 340kJ/mol.  Large thick plates are rather easy
> to manufacture, and I am sure they could design the ficturing such
> that the blast held them in place against a concrete foundation.
> 
> Also there is probably lots of good research on keeping water
> in contact with steel at high temperatures and volumes, think
> Boiling Water Reactor!  Containing the flying molten slag would
> be a concern I suspect though.
> 
>> 
>>> And the reason N2 is used as a fire suppressant is again not
>>> because of temperature, but because it displaces the O2 and
>>> suffocates the fire.  N2 is also easier on our ozone layer
>>> than the prior used Halon.  Finally, this is usually
>>> compressed N2 gas, not LN2.
>>> 
>>> --
>>> Rod Grimes                                                 rgrimes@freebsd.org
>> 
>> 
>> --
>> AMA March 31: https://www.broadband.io/c/broadband-grant-events/dave-taht
>> Dave T?ht CEO, TekLibre, LLC
>> 
>> 
> _______________________________________________
> Starlink mailing list
> Starlink@lists.bufferbloat.net <mailto:Starlink@lists.bufferbloat.net>
> https://lists.bufferbloat.net/listinfo/starlink <https://lists.bufferbloat.net/listinfo/starlink>

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Re: [Starlink] some post Starship launch thoughts

[Bruce Perens]

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Note that if SpaceX wants a sacrificial coating, they have PICA-X and the
sintered silicon tiles.

On Wed, Apr 26, 2023 at 3:31 PM Rodney W. Grimes via Starlink <
starlink@lists.bufferbloat.net> wrote:

> > On Wed, Apr 26, 2023 at 1:41?PM Rodney W. Grimes
> > <starlink@gndrsh.dnsmgr.net> wrote:
> > >
> > > > As always I enjoy the flood of information we get on this list!
> > > >
> > > > still, so far, my research on a nitrogen deluge system (instead of
> > > > water) has come up empty for me, except as a fire suppressant. So
> it?s
> > > > either crazy or brilliant. Or both! I really liked the idea of
> > > > something cooler that was a natural byproduct of the LOX process...
> > >
> > > I dont think cooler does much, isnt it the "energy of vaporization"
> > > that is actually doing all the "work" in this type of system?
> > >
> > > H2O is 40.7 kJ/mol and LN2 is 5.6 kJ/mol so you would
> > > need ~7 times as much LN2 to do the same work.
> >
> > Now that! was the kind of numbers I was looking for!
>
> :-)
>
> >
> > Still, water has to come from somewhere, and be stored. I will keep
> > thinking about it. I like that they seem to think that a water cooled
> > steel plate will suffice.
>
> Water is a pretty ubundant resource...
>
> Now that water cooled steel plate, if you treat it like a sacrificial
> anode in a water heater, ie you expect it to be erroded over time it
> could get interesting.  Energy of vaporization of steel well... lets
> call it iron (Fe) is 340kJ/mol.  Large thick plates are rather easy
> to manufacture, and I am sure they could design the ficturing such
> that the blast held them in place against a concrete foundation.
>
> Also there is probably lots of good research on keeping water
> in contact with steel at high temperatures and volumes, think
> Boiling Water Reactor!  Containing the flying molten slag would
> be a concern I suspect though.
>
> >
> > > And the reason N2 is used as a fire suppressant is again not
> > > because of temperature, but because it displaces the O2 and
> > > suffocates the fire.  N2 is also easier on our ozone layer
> > > than the prior used Halon.  Finally, this is usually
> > > compressed N2 gas, not LN2.
> > >
> > > --
> > > Rod Grimes
> rgrimes@freebsd.org
> >
> >
> > --
> > AMA March 31:
> https://www.broadband.io/c/broadband-grant-events/dave-taht
> > Dave T?ht CEO, TekLibre, LLC
> >
> >
> _______________________________________________
> Starlink mailing list
> Starlink@lists.bufferbloat.net
> https://lists.bufferbloat.net/listinfo/starlink
>


-- 
Bruce Perens K6BP

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Re: [Starlink] some post Starship launch thoughts

[Rodney W. Grimes]

> On Wed, Apr 26, 2023 at 1:41?PM Rodney W. Grimes
> <starlink@gndrsh.dnsmgr.net> wrote:
> >
> > > As always I enjoy the flood of information we get on this list!
> > >
> > > still, so far, my research on a nitrogen deluge system (instead of
> > > water) has come up empty for me, except as a fire suppressant. So it?s
> > > either crazy or brilliant. Or both! I really liked the idea of
> > > something cooler that was a natural byproduct of the LOX process...
> >
> > I dont think cooler does much, isnt it the "energy of vaporization"
> > that is actually doing all the "work" in this type of system?
> >
> > H2O is 40.7 kJ/mol and LN2 is 5.6 kJ/mol so you would
> > need ~7 times as much LN2 to do the same work.
> 
> Now that! was the kind of numbers I was looking for!

:-)

> 
> Still, water has to come from somewhere, and be stored. I will keep
> thinking about it. I like that they seem to think that a water cooled
> steel plate will suffice.

Water is a pretty ubundant resource...

Now that water cooled steel plate, if you treat it like a sacrificial
anode in a water heater, ie you expect it to be erroded over time it
could get interesting.  Energy of vaporization of steel well... lets
call it iron (Fe) is 340kJ/mol.  Large thick plates are rather easy
to manufacture, and I am sure they could design the ficturing such
that the blast held them in place against a concrete foundation.

Also there is probably lots of good research on keeping water
in contact with steel at high temperatures and volumes, think
Boiling Water Reactor!  Containing the flying molten slag would
be a concern I suspect though.

> 
> > And the reason N2 is used as a fire suppressant is again not
> > because of temperature, but because it displaces the O2 and
> > suffocates the fire.  N2 is also easier on our ozone layer
> > than the prior used Halon.  Finally, this is usually
> > compressed N2 gas, not LN2.
> >
> > --
> > Rod Grimes                                                 rgrimes@freebsd.org
> 
> 
> --
> AMA March 31: https://www.broadband.io/c/broadband-grant-events/dave-taht
> Dave T?ht CEO, TekLibre, LLC
> 
> 

Re: [Starlink] some post Starship launch thoughts

[Mark Handley]

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My understanding was that a pad water deluge system isn't primarily to remove energy from the exhaust plume itself, but rather to reduce the extreme sound level all the pad equipment and the booster are exposed to outside of the exhaust plume.  At really high sound levels you're achieving a near vacuum in the rarefactions of the sound waveform, and this low pressure will cause water to boil, removing energy from the sound waves.  Or at least that's how I assumed it works :-)

Mark

On Wed, 26 Apr 2023, at 10:05 PM, Eugene Y Chang via Starlink wrote:
> Rodney, 
> I agree with your point of view.
> 
> To neutralize the exhaust of the rocket engine, it is all about taking the energy out of the exhaust. Taking out the energy will slow the speed of the exhaust gas and take down the temperature. 
> 
> To get into more nitty gritty, the amount of heat absorbed by H2O or LN2, depends on the dT (the temperature change) and also any heat of phase transition (e.g. liquid to gas).
> Gene
> ----------------------------------------------
> Eugene Chang
> eugene.chang@ieee.org
> o 781-799-0233
> 
> 
> 
>> On Apr 26, 2023, at 10:41 AM, Rodney W. Grimes via Starlink <starlink@lists.bufferbloat.net> wrote:
>> 
>>> As always I enjoy the flood of information we get on this list!
>>> 
>>> still, so far, my research on a nitrogen deluge system (instead of
>>> water) has come up empty for me, except as a fire suppressant. So it?s
>>> either crazy or brilliant. Or both! I really liked the idea of
>>> something cooler that was a natural byproduct of the LOX process...
>> 
>> I dont think cooler does much, isnt it the "energy of vaporization"
>> that is actually doing all the "work" in this type of system?
>> 
>> H2O is 40.7 kJ/mol and LN2 is 5.6 kJ/mol so you would
>> need ~7 times as much LN2 to do the same work.
>> 
>> And the reason N2 is used as a fire suppressant is again not
>> because of temperature, but because it displaces the O2 and
>> suffocates the fire.  N2 is also easier on our ozone layer
>> than the prior used Halon.  Finally, this is usually
>> compressed N2 gas, not LN2.
>> 
>> --
>> Rod Grimes                                                 rgrimes@freebsd.org
>> _______________________________________________
>> Starlink mailing list
>> Starlink@lists.bufferbloat.net
>> https://lists.bufferbloat.net/listinfo/starlink
> _______________________________________________
> Starlink mailing list
> Starlink@lists.bufferbloat.net
> https://lists.bufferbloat.net/listinfo/starlink
> 
> 
> *Attachments:*
>  • signature.asc

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Re: [Starlink] some post Starship launch thoughts

[Eugene Chang]

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I like the simplicity of just H2O or LN2.

Ok for steel plate, we need to think about
the plate exposed to the exhaust gas and how that will wear
The thickness of the plate and the thermoresistance of the plate
The water behind the plate
heat of phase transistion of water from liquid to gas
heat of absorbtion of the H2O as gas
moving the water through the cavity (behind the metal plate)
how fast can we move the water
how much heat absorbing mass needs to be moved
how to manage the escaping steam and the pressure of the steam
the machiney to force the water into the cavity and keep replacing the steam

And whether H2O or LN2,
where does it come from
what is the cost of preparing the liquid
what is the cost of the tanks holding the liquid
I assume either liquid is completely vaporized.

This solution is approaching visualizing the rocket’s engine blasting into the cooling system jet “exhaust” with neutralized gas coming out of the two opposing jets. In many sense, two equal and opposite forces. That is the implication of neutralization.


Gene
-----------------------------------
Eugene Chang
eugene.chang@alum.mit.edu
+1-781-799-0233 (in Honolulu)





> On Apr 26, 2023, at 11:10 AM, Dave Taht via Starlink <starlink@lists.bufferbloat.net> wrote:
> 
> On Wed, Apr 26, 2023 at 1:41 PM Rodney W. Grimes
> <starlink@gndrsh.dnsmgr.net <mailto:starlink@gndrsh.dnsmgr.net>> wrote:
>> 
>>> As always I enjoy the flood of information we get on this list!
>>> 
>>> still, so far, my research on a nitrogen deluge system (instead of
>>> water) has come up empty for me, except as a fire suppressant. So it?s
>>> either crazy or brilliant. Or both! I really liked the idea of
>>> something cooler that was a natural byproduct of the LOX process...
>> 
>> I dont think cooler does much, isnt it the "energy of vaporization"
>> that is actually doing all the "work" in this type of system?
>> 
>> H2O is 40.7 kJ/mol and LN2 is 5.6 kJ/mol so you would
>> need ~7 times as much LN2 to do the same work.
> 
> Now that! was the kind of numbers I was looking for!
> 
> Still, water has to come from somewhere, and be stored. I will keep
> thinking about it. I like that they seem to think that a water cooled
> steel plate will suffice.
> 
>> And the reason N2 is used as a fire suppressant is again not
>> because of temperature, but because it displaces the O2 and
>> suffocates the fire.  N2 is also easier on our ozone layer
>> than the prior used Halon.  Finally, this is usually
>> compressed N2 gas, not LN2.
>> 
>> --
>> Rod Grimes                                                 rgrimes@freebsd.org
> 
> 
> --
> AMA March 31: https://www.broadband.io/c/broadband-grant-events/dave-taht <https://www.broadband.io/c/broadband-grant-events/dave-taht>
> Dave Täht CEO, TekLibre, LLC
> _______________________________________________
> Starlink mailing list
> Starlink@lists.bufferbloat.net <mailto:Starlink@lists.bufferbloat.net>
> https://lists.bufferbloat.net/listinfo/starlink <https://lists.bufferbloat.net/listinfo/starlink>

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Re: [Starlink] some post Starship launch thoughts

[Dave Taht]

On Wed, Apr 26, 2023 at 1:41 PM Rodney W. Grimes
<starlink@gndrsh.dnsmgr.net> wrote:
>
> > As always I enjoy the flood of information we get on this list!
> >
> > still, so far, my research on a nitrogen deluge system (instead of
> > water) has come up empty for me, except as a fire suppressant. So it?s
> > either crazy or brilliant. Or both! I really liked the idea of
> > something cooler that was a natural byproduct of the LOX process...
>
> I dont think cooler does much, isnt it the "energy of vaporization"
> that is actually doing all the "work" in this type of system?
>
> H2O is 40.7 kJ/mol and LN2 is 5.6 kJ/mol so you would
> need ~7 times as much LN2 to do the same work.

Now that! was the kind of numbers I was looking for!

Still, water has to come from somewhere, and be stored. I will keep
thinking about it. I like that they seem to think that a water cooled
steel plate will suffice.

> And the reason N2 is used as a fire suppressant is again not
> because of temperature, but because it displaces the O2 and
> suffocates the fire.  N2 is also easier on our ozone layer
> than the prior used Halon.  Finally, this is usually
> compressed N2 gas, not LN2.
>
> --
> Rod Grimes                                                 rgrimes@freebsd.org


--
AMA March 31: https://www.broadband.io/c/broadband-grant-events/dave-taht
Dave Täht CEO, TekLibre, LLC

Re: [Starlink] some post Starship launch thoughts

[Eugene Y Chang]

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Rodney,
I agree with your point of view.

To neutralize the exhaust of the rocket engine, it is all about taking the energy out of the exhaust. Taking out the energy will slow the speed of the exhaust gas and take down the temperature.

To get into more nitty gritty, the amount of heat absorbed by H2O or LN2, depends on the dT (the temperature change) and also any heat of phase transition (e.g. liquid to gas).
Gene
----------------------------------------------
Eugene Chang
eugene.chang@ieee.org
o 781-799-0233




> On Apr 26, 2023, at 10:41 AM, Rodney W. Grimes via Starlink <starlink@lists.bufferbloat.net> wrote:
> 
>> As always I enjoy the flood of information we get on this list!
>> 
>> still, so far, my research on a nitrogen deluge system (instead of
>> water) has come up empty for me, except as a fire suppressant. So it?s
>> either crazy or brilliant. Or both! I really liked the idea of
>> something cooler that was a natural byproduct of the LOX process...
> 
> I dont think cooler does much, isnt it the "energy of vaporization"
> that is actually doing all the "work" in this type of system?
> 
> H2O is 40.7 kJ/mol and LN2 is 5.6 kJ/mol so you would
> need ~7 times as much LN2 to do the same work.
> 
> And the reason N2 is used as a fire suppressant is again not
> because of temperature, but because it displaces the O2 and
> suffocates the fire.  N2 is also easier on our ozone layer
> than the prior used Halon.  Finally, this is usually
> compressed N2 gas, not LN2.
> 
> --
> Rod Grimes                                                 rgrimes@freebsd.org
> _______________________________________________
> Starlink mailing list
> Starlink@lists.bufferbloat.net
> https://lists.bufferbloat.net/listinfo/starlink


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Re: [Starlink] some post Starship launch thoughts

[Rodney W. Grimes]

> As always I enjoy the flood of information we get on this list!
> 
> still, so far, my research on a nitrogen deluge system (instead of
> water) has come up empty for me, except as a fire suppressant. So it?s
> either crazy or brilliant. Or both! I really liked the idea of
> something cooler that was a natural byproduct of the LOX process...

I dont think cooler does much, isnt it the "energy of vaporization"
that is actually doing all the "work" in this type of system?

H2O is 40.7 kJ/mol and LN2 is 5.6 kJ/mol so you would
need ~7 times as much LN2 to do the same work.

And the reason N2 is used as a fire suppressant is again not
because of temperature, but because it displaces the O2 and
suffocates the fire.  N2 is also easier on our ozone layer
than the prior used Halon.  Finally, this is usually
compressed N2 gas, not LN2.

--
Rod Grimes                                                 rgrimes@freebsd.org

Re: [Starlink] some post Starship launch thoughts

[Sebastian Moeller]

Hi Dave,


> On Apr 26, 2023, at 21:29, Dave Taht via Starlink <starlink@lists.bufferbloat.net> wrote:
> 
> As always I enjoy the flood of information we get on this list!
> 
> still, so far, my research on a nitrogen deluge system (instead of
> water) has come up empty for me, except as a fire suppressant. So it´s
> either crazy or brilliant. Or both! I really liked the idea of
> something cooler that was a natural byproduct of the LOX process...

	This is testable... I would guess that cooling Texas outside temperature concrete down to to -195 C will cause some issues as well... given how fast this is going to happen, no?

Regards
	Sebastian


> _______________________________________________
> Starlink mailing list
> Starlink@lists.bufferbloat.net
> https://lists.bufferbloat.net/listinfo/starlink

Re: [Starlink] some post Starship launch thoughts

[Dave Taht]

As always I enjoy the flood of information we get on this list!

still, so far, my research on a nitrogen deluge system (instead of
water) has come up empty for me, except as a fire suppressant. So it´s
either crazy or brilliant. Or both! I really liked the idea of
something cooler that was a natural byproduct of the LOX process...

Re: [Starlink] some post Starship launch thoughts

[Michael Richardson]

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Bruce Perens via Starlink <starlink@lists.bufferbloat.net> wrote:
    > Once upon a time, there was a thing called Orion, which was supposed to be
    > a big heavy shield that would be propelled into space by setting off atomic
    > bombs on one side of it. Lots and lots of bombs. At some point people
    > thought they could make a shield good enough. What SpaceX puts in now is
    > going to be the closest we have come to Orion, just upside down.

For fun, read Charles Stross' Merchange Princes series.

Book "9", _Invisible Sun_, while a bit uneven, includes their Orion spacecraft.
They have the advantage that the can Jaunt to alternative universes before
doing all the atomic bombing, and then, once in orbit, Jaunt back.

ISS Astronaut in time line 2 (US) should have been given the line: "That's
not the moon"...


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Re: [Starlink] some post Starship launch thoughts

[Eugene Y Chang]

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Engine thrust is a combination of the mass of the gas and the temperature (a measure of velocity).

So coolling the gas (aka absorbing the heat) is part of absorbing the momentum from the engine thrust.

The more speed in the rocket exhaust, the more wear and tear of the equipment in the exhaust’s path.

I suggest it could be calculated
how much speed of the rocket engine exhaust needs to be reduced for a good life of the launch infrastructure
and how much energy needs to be taken out of the rocket exhaust to reduce the exhaust gas to the desired speed.
how much water is needed to absorb the energy needed to reduce the exhaust speed.

Mass and energy are both conserved. They know how much energy is at the rocket engine nozzle (point of max temperature and speed of the gas). The mass and energy have to go somewhere.

To say “only testing will tell us for sure” is to suggest cut-and-try engineering.
Of course, testing is used to confirm the calculations.


Gene
----------------------------------------------
Eugene Chang
IEEE Communications Society & Signal Processing Society,
    Hawaii Chapter Chair
IEEE Hawaii Section, Industry Engagement Coordinator
IEEE Senior Life Member
eugene.chang@ieee.org
m 781-799-0233 (in Honolulu)



> On Apr 25, 2023, at 1:22 PM, David Lang <david@lang.hm> wrote:
> 
> On Tue, 25 Apr 2023, Eugene Chang wrote:
> 
>> I found this YouTube of a deluge system test.
>> It doesn’t look like it uses enough water to succeed.
>> My intuition is the mass of water needed is approximately equal to the rocket’s mass.
> 
> nowhere close. The pad 39a where the Saturn 5 launched has a 300,000 gal take, which is ~2.4M pounds, but the Saturn 5 launch weight was around 6.5M pounds
> 
>> Maybe the system doesn’t have to fully absorb the momentum of the engine exhaust. Still, 70% would be a much greater mass than what the video shows.
> 
> it doesn't, it's not absorbing the momentum of the engine exhaust, it's vaporizing to cool the area and disrupt the airflow so the exhaust is less of a blowtorch when it hits a solid surface, and absorb enough sound to prevent it from damaging the rocket.
> 
> distance helps with both of these, as do the materials that the exhaust finally hits. Regular concrete has too much moisture in it and the water flashes to steam and breaks the concrete (concrete is strong in compression, weak in tension).
> 
> Elon mentioned a few weeks ago that even steel plates would wear down quickly under the exhaust, and that water cooled plates were needed in the long run (and they started building water cooled plates to put under the launch mount)
> 
> will that be enough? only testing will tell us for sure.
> 
> not all rockets use a flame trench, and some have very little deluge
> 
> David Lang


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Re: [Starlink] some post Starship launch thoughts

[David Lang]

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On Tue, 25 Apr 2023, Eugene Chang wrote:

> I found this YouTube of a deluge system test.
> It doesn’t look like it uses enough water to succeed.
> My intuition is the mass of water needed is approximately equal to the rocket’s mass.

nowhere close. The pad 39a where the Saturn 5 launched has a 300,000 gal take, 
which is ~2.4M pounds, but the Saturn 5 launch weight was around 6.5M pounds

> Maybe the system doesn’t have to fully absorb the momentum of the engine exhaust. Still, 70% would be a much greater mass than what the video shows.

it doesn't, it's not absorbing the momentum of the engine exhaust, it's 
vaporizing to cool the area and disrupt the airflow so the exhaust is less of a 
blowtorch when it hits a solid surface, and absorb enough sound to prevent it 
from damaging the rocket.

distance helps with both of these, as do the materials that the exhaust finally 
hits. Regular concrete has too much moisture in it and the water flashes to 
steam and breaks the concrete (concrete is strong in compression, weak in 
tension).

Elon mentioned a few weeks ago that even steel plates would wear down quickly 
under the exhaust, and that water cooled plates were needed in the long run (and 
they started building water cooled plates to put under the launch mount)

will that be enough? only testing will tell us for sure.

not all rockets use a flame trench, and some have very little deluge

David Lang

Re: [Starlink] some post Starship launch thoughts

[Eugene Chang]

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I found this YouTube of a deluge system test.
It doesn’t look like it uses enough water to succeed.
My intuition is the mass of water needed is approximately equal to the rocket’s mass.
Maybe the system doesn’t have to fully absorb the momentum of the engine exhaust. Still, 70% would be a much greater mass than what the video shows.

Has anyone seen a rough calculation of what is needed from the deluge system?
Some elements
mass of water to absorb/dissipate the thermal energy
mass of water to absorb/dissipate the momentum of the rocket exhaust.
the rocket engine exhaust momentum is greater than the weight of the rocket.

Are there tricks that I don’t know about?

Gene
-----------------------------------
Eugene Chang
eugene.chang@alum.mit.edu
+1-781-799-0233 (in Honolulu)





> On Apr 25, 2023, at 12:31 PM, Bruce Perens <bruce@perens.com> wrote:
> 
> 
> 
> On Mon, Apr 24, 2023 at 7:20 PM David Lang via Starlink <starlink@lists.bufferbloat.net <mailto:starlink@lists.bufferbloat.net>> wrote:
> If they dig a pool under the Starship Launch Mount, it will fill with water
> (they are already having to pump water out of the hole the rocket dug), if they
> line it with concrete, water will seep through, and the concrete will try to
> float on the water.
> 
> The deluge system produces a mixture of water and air. That is necessary for the acoustic deadening effect.
> 
> Once upon a time, there was a thing called Orion, which was supposed to be a big heavy shield that would be propelled into space by setting off atomic bombs on one side of it. Lots and lots of bombs. At some point people thought they could make a shield good enough. What SpaceX puts in now is going to be the closest we have come to Orion, just upside down.


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Re: [Starlink] some post Starship launch thoughts

[Bruce Perens]

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On Mon, Apr 24, 2023 at 7:20 PM David Lang via Starlink <
starlink@lists.bufferbloat.net> wrote:

> If they dig a pool under the Starship Launch Mount, it will fill with
> water
> (they are already having to pump water out of the hole the rocket dug), if
> they
> line it with concrete, water will seep through, and the concrete will try
> to
> float on the water.


The deluge system produces a mixture of water and air. That is necessary
for the acoustic deadening effect.

Once upon a time, there was a thing called Orion, which was supposed to be
a big heavy shield that would be propelled into space by setting off atomic
bombs on one side of it. Lots and lots of bombs. At some point people
thought they could make a shield good enough. What SpaceX puts in now is
going to be the closest we have come to Orion, just upside down.

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Re: [Starlink] some post Starship launch thoughts

[David Lang]

On Tue, 25 Apr 2023, Eugene Chang wrote:

> Anything (mass, object) in the path of the engine exhaust will experience thermo-shock and mechanical stress. Both will cause the exhaust diverter or exhaust defuser to have significant wear and short life.
>
> A flame trench suggests a solution. Keep any mass farther away from the engine 
> exhaust. The logical extension of this would be to put the rocket elevated 
> (high) over the ground to have minimal force from the exhaust. I suspect this 
> would be too much distance to be practical.

in Texas and Florida you can't go down, even a couple feet puts you below sea 
level (in Texas, high tide puts water right up to the fence less than 100 ft 
from the launch mount)

The launch mount is higher than the man-made mounds on either side of the Saturn 
5 flame trench

> An alternative could be to launch the rocket over a big pool of water. Please, 
> not over a natural body of water with any living organisms in it. The 
> environmental impact of the thermo-shock would be substantial.

long term, they do expect to have over-ocean launches.

If they dig a pool under the Starship Launch Mount, it will fill with water 
(they are already having to pump water out of the hole the rocket dug), if they 
line it with concrete, water will seep through, and the concrete will try to 
float on the water. Plus the water sitting in it will very quickly be considered 
'hazardous waste' and letting the rocket exhaust blast it around will be frowned 
on, and it will become a home for mosquitoes.

This is also sea turtle territory, any pool under the rocket would be a problem 
for them.

David Lang


>
> Gene
> -----------------------------------
> Eugene Chang
> eugene.chang@alum.mit.edu
> +1-781-799-0233 (in Honolulu)
>
>
>
>
>
>> On Apr 24, 2023, at 9:16 AM, David Lang via Starlink <starlink@lists.bufferbloat.net> wrote:
>>
>> On Mon, 24 Apr 2023, Dave Taht via Starlink wrote:
>>
>>> Everyone wants a water deluge system and flame diverter
>>
>> and a flame trench...
>>
>> about 3 months ago they started building water-cooled steel plates to go under the launch pad, but it wasn't ready yet and the testing they didn (static fire at 50% thrust and firing raptors into blocks of concrete at McGregor) made them think that the concrete would be badly eroded by a full power launch, but did not predict nearly the level of damage they saw
>>
>> this is the probem you run into extrapolating from known data, you can't predict inflection points where the behavior changes significantly
>>
>> a common answer I've been giving re: flame trench
>>
>> Both Florida and Texas launch pads started with the ground just a few feet above sea level, so neither one can dig down (unless they want to create a permanent pool under the rocket, which would have all sorts of problems)
>>
>> In Florida, NASA trucked in a huge amount of dirt and built up a hill, leaving a flame trench that they then lined with concrete and bricks, later adding a ramp to divert the exhaust (and had a lot of problem finding a material that would not wear away too fast). They also had problems with some shuttle launches tearing up the walls of the flame trench.
>>
>> In Texas, SpaceX instead built stilts and put the rocket on top of that.
>>
>> As I understand it, the distance from the nozzles to the ground is higher in Texas than in Florida
>>
>> and the exhaust can get out in 6 direction, not just two.
>>
>> So if they had put the Starship stack on NASAs mobile launch platform and launched it in Florida, it would have done significantly more damage there, probagly tearing up large chunks of ground around the pad as well (imaging the ground where the crawler goes disappearing)
>>
>> The raptor engines have a significantly higher ISP than the F-1 that the Saturn 5 had, so it's exhaust is moving about 25% faster, and with double the thrust it's also moving about 60% more mass. These are conditions that have not existed anywhere on earth before this launch (I will note that the shuttle had even higher exhaust velocity from it's main engines, but less overall thrust)
>>
>> David Lang
>> _______________________________________________
>> Starlink mailing list
>> Starlink@lists.bufferbloat.net
>> https://lists.bufferbloat.net/listinfo/starlink
>
>

Re: [Starlink] some post Starship launch thoughts

[Bruce Perens]

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On Mon, Apr 24, 2023 at 7:12 AM Dave Taht via Starlink <
starlink@lists.bufferbloat.net> wrote:

> Also, I met a young lady that paints watercolors of rockets, her work
> is here: https://www.jadeboudreaux.com/


Very cute young lady. When I was young and nerdy, where were these women? I
got the right girl anyway.

One of the engines did blow off the side of the rocket. You missed that
one, but there's good video of it.

Sealaunch had some method of flinging the rocket into the air before the
engines started. Super Heavy takes 6 seconds to get them all going, this is
perhaps part of the issue.

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Re: [Starlink] some post Starship launch thoughts

[Eugene Chang]

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Anything (mass, object) in the path of the engine exhaust will experience thermo-shock and mechanical stress. Both will cause the exhaust diverter or exhaust defuser to have significant wear and short life.

A flame trench suggests a solution. Keep any mass farther away from the engine exhaust. The logical extension of this would be to put the rocket elevated (high) over the ground to have minimal force from the exhaust. I suspect this would be too much distance to be practical.

An alternative could be to launch the rocket over a big pool of water. Please, not over a natural body of water with any living organisms in it. The environmental impact of the thermo-shock would be substantial.


Gene
-----------------------------------
Eugene Chang
eugene.chang@alum.mit.edu
+1-781-799-0233 (in Honolulu)





> On Apr 24, 2023, at 9:16 AM, David Lang via Starlink <starlink@lists.bufferbloat.net> wrote:
> 
> On Mon, 24 Apr 2023, Dave Taht via Starlink wrote:
> 
>> Everyone wants a water deluge system and flame diverter
> 
> and a flame trench...
> 
> about 3 months ago they started building water-cooled steel plates to go under the launch pad, but it wasn't ready yet and the testing they didn (static fire at 50% thrust and firing raptors into blocks of concrete at McGregor) made them think that the concrete would be badly eroded by a full power launch, but did not predict nearly the level of damage they saw
> 
> this is the probem you run into extrapolating from known data, you can't predict inflection points where the behavior changes significantly
> 
> a common answer I've been giving re: flame trench
> 
> Both Florida and Texas launch pads started with the ground just a few feet above sea level, so neither one can dig down (unless they want to create a permanent pool under the rocket, which would have all sorts of problems)
> 
> In Florida, NASA trucked in a huge amount of dirt and built up a hill, leaving a flame trench that they then lined with concrete and bricks, later adding a ramp to divert the exhaust (and had a lot of problem finding a material that would not wear away too fast). They also had problems with some shuttle launches tearing up the walls of the flame trench.
> 
> In Texas, SpaceX instead built stilts and put the rocket on top of that.
> 
> As I understand it, the distance from the nozzles to the ground is higher in Texas than in Florida
> 
> and the exhaust can get out in 6 direction, not just two.
> 
> So if they had put the Starship stack on NASAs mobile launch platform and launched it in Florida, it would have done significantly more damage there, probagly tearing up large chunks of ground around the pad as well (imaging the ground where the crawler goes disappearing)
> 
> The raptor engines have a significantly higher ISP than the F-1 that the Saturn 5 had, so it's exhaust is moving about 25% faster, and with double the thrust it's also moving about 60% more mass. These are conditions that have not existed anywhere on earth before this launch (I will note that the shuttle had even higher exhaust velocity from it's main engines, but less overall thrust)
> 
> David Lang
> _______________________________________________
> Starlink mailing list
> Starlink@lists.bufferbloat.net
> https://lists.bufferbloat.net/listinfo/starlink


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Re: [Starlink] some post Starship launch thoughts

[David Lang]

On Mon, 24 Apr 2023, Dave Taht via Starlink wrote:

> Everyone wants a water deluge system and flame diverter

and a flame trench...

about 3 months ago they started building water-cooled steel plates to go under 
the launch pad, but it wasn't ready yet and the testing they didn (static fire 
at 50% thrust and firing raptors into blocks of concrete at McGregor) made them 
think that the concrete would be badly eroded by a full power launch, but did 
not predict nearly the level of damage they saw

this is the probem you run into extrapolating from known data, you can't predict 
inflection points where the behavior changes significantly

a common answer I've been giving re: flame trench

Both Florida and Texas launch pads started with the ground just a few feet above 
sea level, so neither one can dig down (unless they want to create a permanent 
pool under the rocket, which would have all sorts of problems)

In Florida, NASA trucked in a huge amount of dirt and built up a hill, leaving a 
flame trench that they then lined with concrete and bricks, later adding a ramp 
to divert the exhaust (and had a lot of problem finding a material that would 
not wear away too fast). They also had problems with some shuttle launches 
tearing up the walls of the flame trench.

In Texas, SpaceX instead built stilts and put the rocket on top of that.

As I understand it, the distance from the nozzles to the ground is higher in 
Texas than in Florida

and the exhaust can get out in 6 direction, not just two.

So if they had put the Starship stack on NASAs mobile launch platform and 
launched it in Florida, it would have done significantly more damage there, 
probagly tearing up large chunks of ground around the pad as well (imaging the 
ground where the crawler goes disappearing)

The raptor engines have a significantly higher ISP than the F-1 that the Saturn 
5 had, so it's exhaust is moving about 25% faster, and with double the thrust 
it's also moving about 60% more mass. These are conditions that have not existed 
anywhere on earth before this launch (I will note that the shuttle had even 
higher exhaust velocity from it's main engines, but less overall thrust)

David Lang

Re: [Starlink] some post Starship launch thoughts

[David Lang]

On Mon, 24 Apr 2023, Michael Richardson via Starlink wrote:

> Dave Taht via Starlink <starlink@lists.bufferbloat.net> wrote:
>    > Everyone wants a water deluge system and flame diverter, but I was
>    > thinking perhaps liquid nitrogen, as a natural byproduct of LOX
>
> Yeah, but how do you put one on the moon or mars?
> Lower gravity helps, sure, ...

lower gravity helps so much that you don't need 33 engines, the 6 engines on the 
starship will make it from mars to earth, let alone from the moon.

>    > Landing and then taking off from the moon or mars look rather
>    > problematic at the moment!
>
> Do the rockets do the swoop and flip on mars and the moon?

on mars, yes, it will do aero-braking and then flip and land. On the mood it 
will just use engines (and possibly lower powered engines mounted higher in the 
craft for the final touchdown and initial liftoff to avoid this sort of problem.

David Lang

Re: [Starlink] some post Starship launch thoughts

[David Fernández]

> Probably the best summary of the problems encountered is here:
> https://www.youtube.com/watch?v=w8q24QLXixo courtesy Scott Manley.

In Spanish, probably here:
https://www.youtube.com/watch?v=rfB0moaiax4

Regards,

David

> Date: Mon, 24 Apr 2023 07:12:24 -0700
> From: Dave Taht <dave.taht@gmail.com>
> To: Dave Taht via Starlink <starlink@lists.bufferbloat.net>
> Subject: [Starlink] some post Starship launch thoughts
> Message-ID:
> 	<CAA93jw564W-XbRP3sTzM_m93XCJKBLLXm99+d5Rwtow1HSkW2Q@mail.gmail.com>
> Content-Type: text/plain; charset="UTF-8"
>
> I was down in starbase, tx for the week of the launch. It was a great
> time, 10s of thousands of people there, my hotel had some of the musk
> family staying, and had a party on the roof... I was there packing
> guitar photobombing "this machine kills vogons" everywhere I could.
>
> Probably the best summary of the problems encountered is here:
> https://www.youtube.com/watch?v=w8q24QLXixo courtesy Scott Manley.
> The best video describing the reactions of everybody, is here:
> https://twitter.com/Erdayastronaut/status/1649141793508716583
>
> Also, I met a young lady that paints watercolors of rockets, her work
> is here: https://www.jadeboudreaux.com/
> (she gifted me a holographic raptor for my guitar, I gifted her a
> scarf from in return https://www.natashasilkart.com/# )
> (support your local artists! Hilariously none of my pictures from dusk
> came out on my camera, while jade painted away like mad)
>
> I was most impressed by losing 6 engines over the course of the
> flight... and none exploding. Modern sensor technology is amazing.
>
> Anyway, like most of the monday morning quarterbacks, thinking about
> the destruction of the pad, I had had two ideas that I would like to
> run by folk here:
>
> Everyone wants a water deluge system and flame diverter, but I was
> thinking perhaps liquid nitrogen, as a natural byproduct of LOX
> liquification, might be used rather than water? It starts off quite a
> bit cooler... but as for its ability to cushion shock waves vs a vs
> its vapor point, no idea. ? Anyone?
>
> Secondly tuning the shockwaves against the pad (somehow), might limit
> the vibrative (is that a word) force? A slower start of the motors
> might damage the pad less, also.
>
> Landing and then taking off from the moon or mars look rather
> problematic at the moment!
>
> It looks to me as though everything can be repaired in a matter of
> months, and there is a watercooled plate designed for the pad that
> will go in next time. The nextgen rocket has replaced some hydraulics
> with electric motors. That said, it seems like the day where the
> starlink v2 sats can launch on starship is at least a year, maybe 2-3
> off, and that means we will see more of the v2 minis being flown on
> falcon. Does anyone have a good summary of the capabilities of the v2
> minis vs a vs 1.5? Any updated numbers on userbase?
>
> --
> AMA March 31: https://www.broadband.io/c/broadband-grant-events/dave-taht
> Dave Täht CEO, TekLibre, LLC
>
>

Re: [Starlink] some post Starship launch thoughts

[Nathan Owens]

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*V1.5*
~ 305kg
2.8 x 1.3m bus
22.68sq m solar panel
2x Ka parabolics
4x Phased arrays (likely 3x TX, 1x RX)
3x ISLs
~20Gbps (http://www.satmagazine.com/story.php?number=1026762698, Elon
comments)

*V2.0 Mini*
< 800kg
4.1 x 2.7m bus
104.96sq m solar panel
?? Parabolics, E-Band support
?? Phased Arrays
3x ISLs? (based on photos)
~4x capacity increase over v1.5
~80Gbps

*V2.0 *
< 2000kg (~1250kg per Elon)
6.4 x 2.7m bus
256.94sq m solar panel
?? Parabolics, E-Band support
?? Phased Arrays
>= 3 ISLs?
~7-9x capacity increase over V1.5 ("almost an order of magnitude" per Elon)
Direct-to-Cell?
~140-180Gbps

On Mon, Apr 24, 2023 at 8:37 AM Michael Richardson via Starlink <
starlink@lists.bufferbloat.net> wrote:

>
> Dave Taht <dave.taht@gmail.com> wrote:
>     > On Mon, Apr 24, 2023 at 8:16 AM Michael Richardson via Starlink
>     > <starlink@lists.bufferbloat.net> wrote:
>     >>
>     >> Dave Taht via Starlink <starlink@lists.bufferbloat.net> wrote:
>     >> > Everyone wants a water deluge system and flame diverter, but I was
>     >> > thinking perhaps liquid nitrogen, as a natural byproduct of LOX
>     >>
>     >> Yeah, but how do you put one on the moon or mars?
>     >> Lower gravity helps, sure, ...
>
>     > Well, the concrete did not shatter at 1/2 thrust...
>
> Can the rocket get off the pad at 1/2 thrust?  If it could get 4-5m away,
> it
> probably could work.
>
>     >> > Landing and then taking off from the moon or mars look rather
>     >> > problematic at the moment!
>     >>
>     >> Do the rockets do the swoop and flip on mars and the moon?
>
>     > SSTO in those cases. Presently.
>
> SS... To Orbit.
> I mean... landing.  Does one flip when landing on the moon?
>
>     >> This part I just don't understand.
>     >> (But then, the entire mars mission is fraught with dozens of
> missing things,
>     >> starting with radiation shielding)
>
>     > I was a very lonely asteroid exploration advocate at the launch,
>     > futilely engaging with the "Mars Firsters" once again, as I have been
>     > since the 80s.
>
> I am with you on this.
>
> Given some mcguffin drive that could get us to another star in some
> reasonable time, when we arrive, we'll still need to live in a space colony
> for a few dozen years before said planet can be made habitable.
> (Even if it was perfect, we still need to clear some land and grow some
> crops, and find/build local source of power...)
>
>
>
> _______________________________________________
> Starlink mailing list
> Starlink@lists.bufferbloat.net
> https://lists.bufferbloat.net/listinfo/starlink
>

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Re: [Starlink] some post Starship launch thoughts

[Michael Richardson]

Dave Taht <dave.taht@gmail.com> wrote:
    > On Mon, Apr 24, 2023 at 8:16 AM Michael Richardson via Starlink
    > <starlink@lists.bufferbloat.net> wrote:
    >>
    >> Dave Taht via Starlink <starlink@lists.bufferbloat.net> wrote:
    >> > Everyone wants a water deluge system and flame diverter, but I was
    >> > thinking perhaps liquid nitrogen, as a natural byproduct of LOX
    >>
    >> Yeah, but how do you put one on the moon or mars?
    >> Lower gravity helps, sure, ...

    > Well, the concrete did not shatter at 1/2 thrust...

Can the rocket get off the pad at 1/2 thrust?  If it could get 4-5m away, it
probably could work.

    >> > Landing and then taking off from the moon or mars look rather
    >> > problematic at the moment!
    >>
    >> Do the rockets do the swoop and flip on mars and the moon?

    > SSTO in those cases. Presently.

SS... To Orbit.
I mean... landing.  Does one flip when landing on the moon?

    >> This part I just don't understand.
    >> (But then, the entire mars mission is fraught with dozens of missing things,
    >> starting with radiation shielding)

    > I was a very lonely asteroid exploration advocate at the launch,
    > futilely engaging with the "Mars Firsters" once again, as I have been
    > since the 80s.

I am with you on this.

Given some mcguffin drive that could get us to another star in some
reasonable time, when we arrive, we'll still need to live in a space colony
for a few dozen years before said planet can be made habitable.
(Even if it was perfect, we still need to clear some land and grow some
crops, and find/build local source of power...)

Re: [Starlink] some post Starship launch thoughts

[Dave Taht]

On Mon, Apr 24, 2023 at 8:16 AM Michael Richardson via Starlink
<starlink@lists.bufferbloat.net> wrote:
>
> Dave Taht via Starlink <starlink@lists.bufferbloat.net> wrote:
>     > Everyone wants a water deluge system and flame diverter, but I was
>     > thinking perhaps liquid nitrogen, as a natural byproduct of LOX
>
> Yeah, but how do you put one on the moon or mars?
> Lower gravity helps, sure, ...

Well, the concrete did not shatter at 1/2 thrust...

>     > Landing and then taking off from the moon or mars look rather
>     > problematic at the moment!
>
> Do the rockets do the swoop and flip on mars and the moon?

SSTO in those cases. Presently.

> This part I just don't understand.
> (But then, the entire mars mission is fraught with dozens of missing things,
> starting with radiation shielding)

I was a very lonely asteroid exploration advocate at the launch,
futilely engaging with the "Mars Firsters" once again, as I have been
since the 80s.

* Gravity sucks.
* NEO exploration requires less delta-v to get there and much less to
go elsewhere or return.
* You can use launch tethers to get off the class of  "fast rotators",
especially.

>
> --
> ]               Never tell me the odds!                 | ipv6 mesh networks [
> ]   Michael Richardson, Sandelman Software Works        |    IoT architect   [
> ]     mcr@sandelman.ca  http://www.sandelman.ca/        |   ruby on rails    [
>
> _______________________________________________
> Starlink mailing list
> Starlink@lists.bufferbloat.net
> https://lists.bufferbloat.net/listinfo/starlink



-- 
AMA March 31: https://www.broadband.io/c/broadband-grant-events/dave-taht
Dave Täht CEO, TekLibre, LLC

Re: [Starlink] some post Starship launch thoughts

[Michael Richardson]

Dave Taht via Starlink <starlink@lists.bufferbloat.net> wrote:
    > Everyone wants a water deluge system and flame diverter, but I was
    > thinking perhaps liquid nitrogen, as a natural byproduct of LOX

Yeah, but how do you put one on the moon or mars?
Lower gravity helps, sure, ...

    > Landing and then taking off from the moon or mars look rather
    > problematic at the moment!

Do the rockets do the swoop and flip on mars and the moon?
This part I just don't understand.
(But then, the entire mars mission is fraught with dozens of missing things,
starting with radiation shielding)

--
]               Never tell me the odds!                 | ipv6 mesh networks [
]   Michael Richardson, Sandelman Software Works        |    IoT architect   [
]     mcr@sandelman.ca  http://www.sandelman.ca/        |   ruby on rails    [

[Starlink] some post Starship launch thoughts

[Dave Taht]

I was down in starbase, tx for the week of the launch. It was a great
time, 10s of thousands of people there, my hotel had some of the musk
family staying, and had a party on the roof... I was there packing
guitar photobombing "this machine kills vogons" everywhere I could.

Probably the best summary of the problems encountered is here:
https://www.youtube.com/watch?v=w8q24QLXixo courtesy Scott Manley.
The best video describing the reactions of everybody, is here:
https://twitter.com/Erdayastronaut/status/1649141793508716583

Also, I met a young lady that paints watercolors of rockets, her work
is here: https://www.jadeboudreaux.com/
(she gifted me a holographic raptor for my guitar, I gifted her a
scarf from in return https://www.natashasilkart.com/# )
(support your local artists! Hilariously none of my pictures from dusk
came out on my camera, while jade painted away like mad)

I was most impressed by losing 6 engines over the course of the
flight... and none exploding. Modern sensor technology is amazing.

Anyway, like most of the monday morning quarterbacks, thinking about
the destruction of the pad, I had had two ideas that I would like to
run by folk here:

Everyone wants a water deluge system and flame diverter, but I was
thinking perhaps liquid nitrogen, as a natural byproduct of LOX
liquification, might be used rather than water? It starts off quite a
bit cooler... but as for its ability to cushion shock waves vs a vs
its vapor point, no idea. ? Anyone?

Secondly tuning the shockwaves against the pad (somehow), might limit
the vibrative (is that a word) force? A slower start of the motors
might damage the pad less, also.

Landing and then taking off from the moon or mars look rather
problematic at the moment!

It looks to me as though everything can be repaired in a matter of
months, and there is a watercooled plate designed for the pad that
will go in next time. The nextgen rocket has replaced some hydraulics
with electric motors. That said, it seems like the day where the
starlink v2 sats can launch on starship is at least a year, maybe 2-3
off, and that means we will see more of the v2 minis being flown on
falcon. Does anyone have a good summary of the capabilities of the v2
minis vs a vs 1.5? Any updated numbers on userbase?

-- 
AMA March 31: https://www.broadband.io/c/broadband-grant-events/dave-taht
Dave Täht CEO, TekLibre, LLC