SpaceX (general discussion)

aim9xray said:
As a thought experiment, I can not imagine any circumstance where a 35 degree Angle of Attack can be considered as being within the structural design envelope for any large liquid-fueled rocket at altitudes where atmospherically induced drag forces predominate. (I'll admit to a lack of imagination.)
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Please note that that 35 degrees is not the Angle of Attack. The AoA is close to zero.

The rocket starts vertically at a 90 degrees angle (vertical upward) but after take-off it gradually reduces the angle (by gimballing the engines) as it gains altitude and speed. The flight is a curved trajectory that starts with an angle of 90 degrees and ends which an angle of 0 degrees relative to the earth's surface when orbit is reached.
 
Now SuperHeavy doesn’t need extra reinforcements…to survive the Adama maneuver…Starship articles may need them? Or is “corrugation” enough?

I have heard it said that R-7 can launch in any weather short of a hurricane.

Dagger, did you work on R-7?
 
publiusr said:
Now SuperHeavy doesn’t need extra reinforcements…to survive the Adama maneuver…
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What the heck is an Adama maneuver? Most aerospace workers are not scifi geeks.

Starship and Superheavy are one in the same vehicle. Can have one without the other for an orbital launch.
 
Dagger said:
Please note that that 35 degrees is not the Angle of Attack. The AoA is close to zero.

The rocket starts vertically at a 90 degrees angle (vertical upward) but after take-off it gradually reduces the angle (by gimballing the engines) as it gains altitude and speed. The flight is a curved trajectory that starts with an angle of 90 degrees and ends which an angle of 0 degrees relative to the earth's surface when orbit is reached.
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Codemonkey is a simple man. Codemonkey not Rocket Surgeon like Manager Rob. However, Codemonkey feels that Manager Rob's static analysis of a 35 degree angle (wrt Earth reference, thank you ) assumes a static fuel load of that at launch, not a decreasing load as seen as the flight [hopefully] progresses (i.e., the vehicle is getting lighter and lighter).

Further, Manager Rob's static analysis fails to take into account relieving moments and stresses (dynamic loads) reacted into the vehicle (and into the interstage) by airloads as the vehicle ascends (again diminishing as delta T since launch increments, post Max Q).

Codemonkey must leave now for mandatory MIT (Management Interface Training) in cubicle on Teams. It is left for Manager Rob to write login script himself.

Jonathan Coulton was not harmed during the writing of this post.
 
Byeman said:
What the heck is an Adama maneuver? Most aerospace workers are not scifi geeks.
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Starship does something of a belly flop on the way down….so perhaps Dagger’s idea for added bracing has merit.

Hearing scuttlebutt about 42 engines
 
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At this point, given their record, I have to assume that SpaceX has a strong notion how their product will perform, and if not, how to remedy it.
 
aim9xray said:
Codemonkey is a simple man. Codemonkey not Rocket Surgeon like Manager Rob. However, Codemonkey feels that Manager Rob's static analysis of a 35 degree angle (wrt Earth reference, thank you ) assumes a static fuel load of that at launch, not a decreasing load as seen as the flight [hopefully] progresses (i.e., the vehicle is getting lighter and lighter).

Further, Manager Rob's static analysis fails to take into account relieving moments and stresses (dynamic loads) reacted into the vehicle (and into the interstage) by airloads as the vehicle ascends (again diminishing as delta T since launch increments, post Max Q).

Codemonkey must leave now for mandatory MIT (Management Interface Training) in cubicle on Teams. It is left for Manager Rob to write login script himself.

Jonathan Coulton was not harmed during the writing of this post.
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The fuel load of Starship (the 2nd stage of the whole rocket) is static until stage separation.
Until then it's only the booster that is consuming its propellants, not Starship.

The 1450 metric ton that I mentioned is the mass of only that Starship stage. The gravitational pull (vertical downward) on that mass is 1,450,000 kgf or 3,190,000 lbf or 14,225,000 N, whichever units of measurements you are used to work with.
When the rocket flies at an angle of say 35 degrees shortly before stage separation, the shear force acting on the vented interstage is cosinus(35 degrees) times that gravitational pull of Starship. Follows from decomposing the gravitational pull. Simple college highschool physics.

The stage separation of Falcon 9 occurs around 70 km altitude. I don't know at what altitude the Starship separation is supposed to take place but I would expect a similar altitude. Dynamic forces by airloads can be neglected at that altitude.
 
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TheSpaceBucket has just put out a video concerning an un-crewed cargo variant of the Dragon to fly to the Moon to deliver cargo to the Lunar Gateway space-station:


Earlier today SpaceX’s Dragon spacecraft docked with the International Space Station carrying 4 crew members. This specific spacecraft is apart of the Dragon 2 class and has been launching crew quite frequently over the past few years. Interestingly, there are a few other variants of Dragon, including one that isn’t even meant to carry a crew.
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Back in 2020, NASA selected SpaceX to deliver cargo, experiments, and other supplies to the agency’s Gateway station in lunar orbit. However, due to the distance and amount of cargo required, the company’s standard Dragon spacecraft wouldn’t have the necessary capabilities. We then learned about a new spacecraft under development named Dragon XL.
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In the time since this spacecraft’s announcement, it went years without progress as NASA focused on other aspects related to Gateway. On the other hand, recent updates suggest the design will still be used and development will start for eventual missions to the Moon. Here I will go more in-depth into this spacecraft’s design, why it was delayed, its application for future lunar missions, and more.
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Full article here - https://thespacebucket.com/spacexs-dr...
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Michel Van said:
you know what guy ?
let's clam down and wait
in several weeks is second test flight

Then we all gonna see if interstage works or not...
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This! SpaceX will find out one way or another whether their redesign works when the test-flight occurs.
 
This is a simplified explanation of what happens. A rocket intended to reach orbit is not required to perform like a bridge or even an aeroplane. Instead, it is constantly accelerating on a parabolic, ballistic trajectory until the peak of the curve meets with the desired orbit. Acceleration is parallel with the trajectory. At no point does the rocket's long axis deviate significantly from the line of its acceleration. The main forces it experiences are longitudinal compression due to acceleration and (in the initial phase) aerodynamic drag. That is, it is not travelling 'sideways' or at an 'angle of attack' because it is not generating lift. According to its own frame of reference, the second stage is always directly 'on top' of the first as it accelerates. Therefore bending forces in the interstage are not great. If its nose is pointed away from that direction of acceleration/trajectory, so too are its engines and the thrust they exert. In this case the rocket is tumbling and will shortly undergo a catastrophic but quite pretty omnidirectional disassembly.

This has already been explained more than once. For more detail:

en.wikipedia.org

Ballistics - Wikipedia

en.wikipedia.org en.wikipedia.org

en.wikipedia.org

Classical mechanics - Wikipedia

en.wikipedia.org en.wikipedia.org

en.wikipedia.org

Gravity turn - Wikipedia

en.wikipedia.org en.wikipedia.org

Some people speak very highly of this fellow. He's currently in residence at Westminster Abbey but doesn't give interviews.

en.wikipedia.org

Isaac Newton - Wikipedia

en.wikipedia.org en.wikipedia.org
 
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Most rockets don't do a belly flop, either...but Starship has...just not at any real speed.

Something I'd like to ask:

Rocket engines are designed carefully...but the propellant lines run to them more simply.

Has anyone thought to reverse the process?

Propellant lines in an organic lay-out...and engines with intakes to match the curves?


SLS only has four...and they are throaty.


I often wonder if Boeing and SpaceX needed to make each other's rockets.

Elon could build a four Raptor SLS stage-and-a-half in his sleep and stack them like cordwood...still cheap even if expendable.


Boeing---at it's height mind you---could have made the Starship SuperHeavy like Space Freighter.


Now Boeing makes what should be a simpler design expensive... and a part of me wonders if Elon is out of his depth.
 
publiusr said:
Most rockets don't do a belly flop, either...but Starship has...just not at any real speed.

Something I'd like to ask:

Rocket engines are designed carefully...but the propellant lines run to them more simply.

Has anyone thought to reverse the process?

Propellant lines in an organic lay-out...and engines with intakes to match the curves?


SLS only has four...and they are throaty.


I often wonder if Boeing and SpaceX needed to make each other's rockets.

Elon could build a four Raptor SLS stage-and-a-half in his sleep and stack them like cordwood...still cheap even if expendable.


Boeing---at it's height mind you---could have made the Starship SuperHeavy like Space Freighter.


Now Boeing makes what should be a simpler design expensive... and a part of me wonders if Elon is out of his depth.
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No. What are you trying to fix and get at?
What is
Propellant lines in an organic lay-out?
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Engines have to be same similar for performance and cost. The propellant lines are run simply. SpaceX makes each engine installation similar to save costs.

SpaceX would never want to deal with SLS and Marshall. SLS lines are not more "throaty" than Starship
Boeing could never have done Starship at any time in their timeline.

old ideas are no longer applicable because of Falcon's success and the shuttle not living up to expectations.
 
Rhinocrates said:
This is a simplified explanation of what happens. A rocket intended to reach orbit is not required to perform like a bridge or even an aeroplane. Instead, it is constantly accelerating on a parabolic, ballistic trajectory until the peak of the curve meets with the desired orbit. Acceleration is parallel with the trajectory. At no point does the rocket's long axis deviate significantly from the line of its acceleration. The main forces it experiences are longitudinal compression due to acceleration and (in the initial phase) aerodynamic drag. That is, it is not travelling 'sideways' or at an 'angle of attack' because it is not generating lift. According to its own frame of reference, the second stage is always directly 'on top' of the first as it accelerates. Therefore bending forces in the interstage are not great. If its nose is pointed away from that direction of acceleration/trajectory, so too are its engines and the thrust they exert. In this case the rocket is tumbling and will shortly undergo a catastrophic but quite pretty omnidirectional disassembly.
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I know all that, and as I explained earlier to aim9xray, the angle that I refer to is not the AoA:
Dagger said:
Please note that that 35 degrees is not the Angle of Attack. The AoA is close to zero.

The rocket starts vertically at a 90 degrees angle (vertical upward) but after take-off it gradually reduces the angle (by gimballing the engines) as it gains altitude and speed. The flight is a curved trajectory that starts with an angle of 90 degrees and ends which an angle of 0 degrees relative to the earth's surface when orbit is reached.
Click to expand...
Every time I wrote 'angled flight' I meant: the angle of the rocket centerline relative to the earth's surface, which (at zero AoA) is the same angle as the flightpath relative to the earth's surface.

Shortly before stage separation that angle is about 30 degrees in case of a Falcon 9 rocket, probably it won't be much different for Starship.
The lateral force on the vented interstage (force perpendicular to the stringers) is then the weight of Starship (1450 mtf) times cosines(30 degrees). I sincerely doubt that the vented interstage can withstand that in view of the insignificant bracing in the present design.
I trust it is now clearer what I was trying to say in previous posts.
 
Dagger said:
I know all that, and as I explained earlier to aim9xray, the angle that I refer to is not the AoA:

Every time I wrote 'angled flight' I meant: the angle of the rocket centerline relative to the earth's surface, which (at zero AoA) is the same angle as the flightpath relative to the earth's surface.

Shortly before stage separation that angle is about 30 degrees in case of a Falcon 9 rocket, probably it won't be much different for Starship.
The lateral force on the vented interstage (force perpendicular to the stringers) is then the weight of Starship (1450 mtf) times cosines(30 degrees). I sincerely doubt that the vented interstage can withstand that in view of the insignificant bracing in the present design.
I trust it is now clearer what I was trying to say in previous posts.
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It's clearer, but it's also clear that you are very confused about basic physics. Gravity does not work that way. Every part of the rocket is equally influenced by gravitational acceleration, and therefore it creates no structural loads. The force of thrust from the rocket engines can be considered in isolation, and is almost entirely axial.

You are in good company, though. Robert H. Goddard had the same misconception, and it caused him no ends of trouble until he finaly figured it out.
 
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Dagger said:
I know all that, and as I explained earlier to aim9xray, the angle that I refer to is not the AoA:

Every time I wrote 'angled flight' I meant: the angle of the rocket centerline relative to the earth's surface, which (at zero AoA) is the same angle as the flightpath relative to the earth's surface.

Shortly before stage separation that angle is about 30 degrees in case of a Falcon 9 rocket, probably it won't be much different for Starship.
The lateral force on the vented interstage (force perpendicular to the stringers) is then the weight of Starship (1450 mtf) times cosines(30 degrees). I sincerely doubt that the vented interstage can withstand that in view of the insignificant bracing in the present design.
I trust it is now clearer what I was trying to say in previous posts.
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Yes, it is clearer that you don't know what you are talking about. A rocket in flight is a free body. Gravity acts on all parts equally. The first stage is not constrained and there is no force or torque between between the stages *. If there was, there would be a rotation at the moment of separation. For Falon 9, the main engines shutdown and the vehicle is in a free fall and there are no exterior forces on the vehicle other than gravity, but then again, it is acting equally on all parts.

*The only lateral forces at the interface between the stages are those induced by aero loads and from the engines gimbaling the stack. But at separation, the engines go to zero degree gimbal and shutdown; and the event is above most of the atmosphere, so there are negligible aero loads.

Starship will still have some axial loads since still it will be using fire in the hole staging.
 
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Byeman said:
Yes, it is clearer that you don't know what you are talking about. A rocket in flight is a free body. Gravity acts on all parts equally. The first stage is not constrained and there is no force or torque between between the stages.
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Well put - and covered in the linked articles on ballistics and gravity turn. You can lead a horse an ass to water...

Another source, Einstein's famous 'elevator' thought experiment.

https://www.wondriumdaily.com/einsteins-experimental-elevator/

This applies to its contents, bullets fired out of guns, joined components, whether they are in free fall, accelerating or on a ballistic trajectory (which is free fall) are all considered as the same set. Since YouTube is apparently an authority:

View: https://www.youtube.com/watch?v=sbSxxsb30_E

Consider: astronauts in orbit are affected by earth's gravity - that's why they stay in orbit and don't head out into space. However, while they have mass and inertia they do not feel weight. A rocket is not an aeroplane fuselage cantilevered from its wing spars and the ISS itself does not have to be considered as a bridge.
 
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Dagger might be remembering all the talk about how you could walk on R-7, unlike balloon tank Atlas.

There it was used as a bridge and could "feel" the stress he talks about.

If I have a stack of shot glasses in my hand...I can tip my hand and they will fall.

BUT if I push up and to the side....I can just about get that stack horizontal.
 
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After DoJ went after SpaceX, it now term for TESLA
DoJ accuses Musk of embezzlement on TESLA, for "Project42"

Seems its building project in Austin Texas,
DoJ claim Project42 is Glas Building planned as Musk personal residence.

Law specialist say this not inevitably lead to prosecution.
Since Project 42 is in planning stage.

TESLA Manager Omead Afshar left company and work now in SpaceX.
Afshar was responsible for record build of Giga Texas factory, and was accordingly DoJ involved in Project42.
Seems he now responsible for Starbase factories (this explain the fast speed its currently build)


Souce:
Business Insider
www.spiegel.de

Verdacht der Veruntreuung: US-Behörden ermitteln offenbar gegen Tesla

Es geht um ein extravagantes Bauvorhaben namens »Projekt 42«: US-Behörden untersuchen offenbar, ob Tesla-Chef Elon Musk Firmenmittel für den Bau eines Privatanwesens aus Spezialglas eingesetzt hat.
www.spiegel.de www.spiegel.de
 
Michel Van said:
After DoJ went after SpaceX, it now term for TESLA
DoJ accuses Musk of embezzlement on TESLA, for "Project42"
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I just hope he can hold himself together long enough to get humanity to Mars and then he can get as nasty, crazy, or crooked as he likes.
 
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Dagger said:
A support with only vertical struts is unstable. That is very basic mechanics that every engineering student already learns.
To make it stable sufficient triangular or diagonal struts are necessary, but those are missing in the present design
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To summarize, you are assuming that SpaceX is making mistakes that any mechanical engineering student would be able to avoid, and is also not doing any stress simulation in CAD. Given the performance of SpaceX products in the past in this regard (0 structural failures in their launch history), do you think that assumption is warranted?
 
Hobbes said:
To summarize, you are assuming that SpaceX is making mistakes that any mechanical engineering student would be able to avoid, and is also not doing any stress simulation in CAD. Given the performance of SpaceX products in the past in this regard (0 structural failures in their launch history), do you think that assumption is warranted?
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Some posts with photo(s) in this topic about Starship in the recent past:
- implosion of a pipe running inside one of the propellant tanks, apparently wall thickness was calculated to thin,
- destruction of the concrete under the launch table with debris flying miles away,
- a photo placed by Michel Van showing that the Starship rocket was bent before attempting stage separation, which did not succeed.

In the mean time more than 1000 changes have been made to Starship rocket, including reinforcements that need not have been necessary if the original design calculations had been correct.

Pardon me if I assume that SpaceX engineers can make mistakes.

Musk is known to have said: If things are not failing, you are not innovating enough.
I don't agree with that. All failures are due to mistakes in design and engineering, not due to lack of innovation.
SpaceX seems to do things mainly by trial and error, without much thought in advance.
Of course one learns from ones mistakes, but that does not mean that one could learn as much as possible by making as many as possible mistakes.
SpaceX can work like that at a remote location in a state like Texas. The rest of the industry however can't get away with that way of working. Imagine Boeing building and testing planes like SpaceX has been doing the past 20 years. Or companies building refineries, chemical plants, nuclear power plants, skyscrapers, .......

Musk is also known for saying: The best part is no part.
I agree with that. However I estimate that the vented interstage consists of 300 or more separate pieces of metal (depending on how much pieces are used in the construction of the inner ring), held together by some 9000 spotwelds and other welds. That's without counting the heat shield.
It's a mystery how this ever got Musk's approval.
 
Whether or not the interstage design is faulty will be demonstrated in the next test-flight.
 
Here's a new video by TheSpaceBucket concerning the partial-thrust test of the rebuilt launchpad (Elon Musk's bidet):


By now there have been two separate Booster 9 Static fires within the month of August as SpaceX prepares to launch Starship a second time. Both of which used the new water-cooled steel plate to dampen and deflect the heat, power, and sound waves that 33 Raptor engines produce. While only partial thrust and for a few seconds, they still give a great insight into how these pad upgrades have performed and what it will look like on launch day.
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Before Starship’s first launch back in April, the static fire certainly didn’t destroy the pad, but it didn’t necessarily provide a lot of confidence in its integrity. Even using partial thrust small pieces of debris could still be seen flying during and after the test. This eventually led to the launch day and complete destruction of the Fondag concrete.
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This time around SpaceX is paying a lot more attention to the pad and its surrounding structures. Even launch day timelines have changed which will no doubt have an effect on the pad and what forces it’s exposed to during the launch. Here I will go more in-depth into the state of Starship’s new pad protection, how it held up against two different static fires, the difference on launch day, and more.
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Full article here - https://thespacebucket.com/how-did-sp...
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publiusr said:
Dagger might be remembering all the talk about how you could walk on R-7, unlike balloon tank Atlas.

There it was used as a bridge and could "feel" the stress he talks about.

If I have a stack of shot glasses in my hand...I can tip my hand and they will fall.

BUT if I push up and to the side....I can just about get that stack horizontal.
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You can walk on an Atlas.
This has nothing to do with the topic.
Why do you always compare something to Russian? Their methods are archaic
 
All inconsequential items
Dagger said:
- implosion of a pipe running inside one of the propellant tanks, apparently wall thickness was calculated to thin,
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That was ULA.
Dagger said:
- destruction of the concrete under the launch table with debris flying miles away,
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A known risk that Musk took. Delay the launch several weeks/months or launch and get data.
Dagger said:
- a photo placed by Michel Van showing that the Starship rocket was bent before attempting stage separation, which did not succeed.
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It was not bent before staging.
 

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