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#960
by
TheRadicalModerate
on 15 Apr, 2023 23:22
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Great find. But have the FAA or SpaceX ever called the flight suborbita?
FWIW... The FAA launch license is neutral. The FAA WR (published concurrently), refers to "Starship Orbital Test Flight...", and also specifically refers to booster as suborbital.
Think most of us know what a significant effort this is and what it portends--whether or not this first attempt succeeds. Trolls, ankle biters and barnyard lawyers trying to minize that based on questionable self-serving interpretations just makes them look small and is a distraction.
The booster is clearly suborbital, both legally and physically.
There are rules for orbital flights, and slightly different rules for suborbital ones. I haven't waded through the permit yet, so I don't know if there's any verbiage in there that sheds light on the issue.
Another issue: I'd guess that SpaceX would like to be as gentle on the tiles as possible, in the interest of getting as much hypersonic data before a failure as possible. That implies hitting entry interface with as modest an amount of energy as possible. If that requires giving the aforementioned ankle-biters something to chew on, so be it. But I have to admit that I would smile if I saw their tears.
FWIW: I vote for calling any spacecraft with a specific orbital energy greater than -30MJ/kg "orbital". By that definition, 235km x 0km isn't orbital.
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#961
by
joek
on 16 Apr, 2023 00:19
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There are rules for orbital flights, and slightly different rules for suborbital ones. I haven't waded through the permit yet, so I don't know if there's any verbiage in there that sheds light on the issue.
...
Good luck. Was hoping there would be more specifics in the launch license, but it is pretty generic. FAA appears to have moved to an inclusive "VOL" (vehicle operator license) recently. All the specifics we use to see in previous licenses (e.g., LLS or permits) is not exposed, but buried in per-flight paperwork that is not public. More specific information is in the latest WR published concurrently with the license, but doubt that is going to convince doubters whether Starship trajectory is "orbital". (In any case, past caring about that debate.)
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#962
by
meekGee
on 16 Apr, 2023 00:37
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Another issue: I'd guess that SpaceX would like to be as gentle on the tiles as possible, in the interest of getting as much hypersonic data before a failure as possible. That implies hitting entry interface with as modest an amount of energy as possible. If that requires giving the aforementioned ankle-biters something to chew on, so be it. But I have to admit that I would smile if I saw their tears.
I think they plan to use the tiles as a backup tracking mechanism, in case they lose telemetry and radar contact.
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#963
by
Fireworking
on 16 Apr, 2023 01:43
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About whatever fell from the tower, it does seem like this could cause a delay in the launch. Here are my thoughts
If it was the elevator falling, Ok, big deal, the elevator doesn't work. The elevator is used for when workers need to make it to the top of the tower. however, starship is currently ready for launch, meaning they dont have a need to travel up and down the tower, and if they do they won't be carrying much equipment. The elevator won't be needed for a launch.
If, however, a pipe that carries methane/lox was ruptured due to the object falling, then either way the best way to check for leaks is to use the pipes, and in this case they could just proceed with the launch as planned, and if something leaks then they can scrub.
I don't think this is such a big deal that they will scrub the launch to do a thorough investigation. Maybe this will happen after the launch, but given that Starship is already fully prepared for launch, including being stacked on the booster, there really isn't another need for the tower except for the fueling of the upperstage, but like i said, if something leaks they can scrub from there.
Personally it doesn't seem like a big enough deal to scrub the launch so far in advance.
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#964
by
FutureSpaceTourist
on 16 Apr, 2023 02:07
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#965
by
FutureSpaceTourist
on 16 Apr, 2023 07:03
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#966
by
FutureSpaceTourist
on 16 Apr, 2023 07:31
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#967
by
faramund
on 16 Apr, 2023 07:39
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#968
by
PM3
on 16 Apr, 2023 07:41
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Think most of us know what a significant effort this is and what it portends--whether or not this first attempt succeeds. Trolls, ankle biters and barnyard lawyers trying to minize that based on questionable self-serving interpretations just makes them look small and is a distraction.
I think ANYONE here knows and respects what an enournous effort this is. Everything is awesome about this rocket and the first launch and the prospect of enabling humanity to live among the stars.
Seeking for correct information and terms regarding the upcoming launch, writing the right things into the history books - e. g. if it is an orbital or suborbital flight - does not impede the respect for SpaceX's achievements. It actually honours Elon's habit to alway be as honest as possible.
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#969
by
Slothman
on 16 Apr, 2023 08:21
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It actually honours Elon's habit to alway be as honest as possible.
XD
I mean.. appreciate Elon as much as you want for the development of starship,it's great.. but that statement is just objectively ridiculous.
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#970
by
CMac
on 16 Apr, 2023 12:04
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Have the Karmens stopped fighting about orbital/suborbital?
Joking aside, there was some informative bits in the midst of it.
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#971
by
Alberto-Girardi
on 16 Apr, 2023 12:10
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We are T-24 h before the opening of the launch window.
This now is feeling very real.
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#972
by
sebk
on 16 Apr, 2023 12:53
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Nope. You are totally wrong.
To have perigee below sea level and be able to do 3/4 of the circle around the Earth after standard rocket launch (Space-guns, X-30 NASP-like spaceplanes or other Sci-Fi solutions notwithstanding) you must have apogee at ~320km or higher. Otherwise your trajectory would be too shallow.
Wrong. Impossible for a pure impulsive launch (e.g. space gun) but not for any real launch vehicle, which has tens of minutes of burn time, and outside the atmosphere can vector thrust arbitrarily. Whilst eccentricity and plane changes performed within the burn to orbit are expensive in terms of delta V, physics will not stop you. You can - for example - insert directly into an orbit with an apogee above your current altitude and descending, and thus never reach apogee.
Wrong. As I wrote, this applies to everything behaving like a rocket. In fact, it'd be more doable with a space gun (realistically it must be either some type of EM gun or nuclear) than with a rocket: guns always have perigee below ground level, you must raise it later. And no rocket burns for tens of minutes. The longest ascent burns approaches 20m and it takes less than 1/10 of the full circle to ascent. Way too little to cut the exoatmospheric part of the flight below half circle which would be required to play games with lowering perigee without raising apogee.
And yes, you can insert into an apogee of an orbit, that's not a problem at all (and rockets without upper stage restart capability did this in the past). The thing is, you can't then have the perigee not only under ground but even in the significant atmosphere (i.e. below 90km)
and do a 270° around the Earth. If you wanted to go for less than half circle, then you're free to do so. But with 270° flight you're limited by the reality that perigee is necessarily 180° from the apogee. If you insert to an overhead apogee, your perigee will be at the antipode of your launch site, 180° away. Obviously, you're not doing 270° if your perigee is only 180° away and underground. It must be above the ground, and significantly at that.
The way to have the lowest perigee (if this is your particular goal; it's not even Starship goal to begin with) while keeping apogee below the set level (235km here) is to have it roughly half-way between your splashdown/landing site and your launch site (give or take 5°). Apogee then must be about half way of your flight.
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#973
by
clongton
on 16 Apr, 2023 13:48
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The confusion is because we don't have a good word to describe trajectories that have orbital speed and energy but also have a velocity vector direction that will result in entering the atmosphere before a complete revolution.
Such trajectories are much better described as "orbital" than "suborbital", but neither is completely accurate.
Why not just say "orbital velocity on a suborbital trajectory".
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#974
by
clongton
on 16 Apr, 2023 13:56
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ICBMs dont fly more than half around the globe.
They do if you don't want the target to see them coming. For example a Eurasian nation that wants to hit something in North America could launch due south, over the South Pole, and the ICBM would approach the target from the south, a direction that is not being monitored for ICBMs.
Just correcting the misstatement. Back to the topic now.
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#975
by
Legios
on 16 Apr, 2023 13:57
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Nope. You are totally wrong.
To have perigee below sea level and be able to do 3/4 of the circle around the Earth after standard rocket launch (Space-guns, X-30 NASP-like spaceplanes or other Sci-Fi solutions notwithstanding) you must have apogee at ~320km or higher. Otherwise your trajectory would be too shallow.
Wrong. Impossible for a pure impulsive launch (e.g. space gun) but not for any real launch vehicle, which has tens of minutes of burn time, and outside the atmosphere can vector thrust arbitrarily. Whilst eccentricity and plane changes performed within the burn to orbit are expensive in terms of delta V, physics will not stop you. You can - for example - insert directly into an orbit with an apogee above your current altitude and descending, and thus never reach apogee.
Wrong. As I wrote, this applies to everything behaving like a rocket. In fact, it'd be more doable with a space gun (realistically it must be either some type of EM gun or nuclear) than with a rocket: guns always have perigee below ground level, you must raise it later. And no rocket burns for tens of minutes. The longest ascent burns approaches 20m and it takes less than 1/10 of the full circle to ascent. Way too little to cut the exoatmospheric part of the flight below half circle which would be required to play games with lowering perigee without raising apogee.
And yes, you can insert into an apogee of an orbit, that's not a problem at all (and rockets without upper stage restart capability did this in the past). The thing is, you can't then have the perigee not only under ground but even in the significant atmosphere (i.e. below 90km) and do a 270° around the Earth. If you wanted to go for less than half circle, then you're free to do so. But with 270° flight you're limited by the reality that perigee is necessarily 180° from the apogee. If you insert to an overhead apogee, your perigee will be at the antipode of your launch site, 180° away. Obviously, you're not doing 270° if your perigee is only 180° away and underground. It must be above the ground, and significantly at that.
The way to have the lowest perigee (if this is your particular goal; it's not even Starship goal to begin with) while keeping apogee below the set level (235km here) is to have it roughly half-way between your splashdown/landing site and your launch site (give or take 5°). Apogee then must be about half way of your flight.
Too many mental gymnastics going on in this thread. It is a suborbital ballistic trajectory, period.
But, it's not a bad thing. It's by design. SpaceX does not want to risk a huge piece of space junk orbiting and then reentering out of control. It is a responsible course of action for an initial test flight of all-new hardware.
Plus, the fact that Starship is not going to try a controlled landing indicates that S24 is either not prepped to relight its engines or that SpaceX is still not confident that S24 will relight reliably. Either way, without relight, it is impossible to raise the perigee enough to maintain an orbit.
Too me, orbital is simple. Orbits are when the path is stable due simply to physics. No additional forces are required. (Yes, station keeping in LEO is required to overcome drag...but it's negligible for the sake of this argument.) If the perigee is low enough that atmospheric drag will cause re-entry, then by definition it is not orbital.
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#976
by
mikelepage
on 16 Apr, 2023 13:59
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I wonder if SpaceX Will attempt to catch Starship upper stage in the future? The reason I say this is because of the way they word it on the website. Only mentioning catching Super heavy and not Starship.
I think part of the issue has always been leg design with a wide enough stance (especially on the heat shield side). There’s a whole thread about this elsewhere on the forum which maybe is worth updating.
They may want to get data on how a simply-shaped heat shield performs during reentry before they even go to the effort of designing the more complex shapes that you would need to shield extendable (F9-style) legs.
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#977
by
Zed_Noir
on 16 Apr, 2023 14:20
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<snip>
The confusion is because we don't have a good word to describe trajectories that have orbital speed and energy but also have a velocity vector direction that will result in entering the atmosphere before a complete revolution.
Such trajectories are much better described as "orbital" than "suborbital", but neither is completely accurate.
<snip>
Will take a shot at a description. Called it a
retarded orbital flight. Think the Starship have enough delta-V left to make orbit, otherwise they wouldn't be venting the propellants out after engine cutoff. So it appears that SpaceX applied a vector change just before engine cutoff to attained a revised trajectory that result in atmosphere reentry later.
It is somewhat similar to deploying a tail retardation device on a piece of ordnance that is drop by a fast strike aircraft at low altitude. So said ordnance slow down enough to gave a safe horizontal separation from the departing aircraft before going boom.
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#978
by
GORDAP
on 16 Apr, 2023 14:36
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The confusion is because we don't have a good word to describe trajectories that have orbital speed and energy but also have a velocity vector direction that will result in entering the atmosphere before a complete revolution.
Such trajectories are much better described as "orbital" than "suborbital", but neither is completely accurate.
Why not just say "orbital velocity on a suborbital trajectory".
The European Space Agency had a (failed) launch some years back that in fact had orbital energy, but alas not quite the right trajectory, hence a crash. In what I think was a brilliant (and accurate) attempt at face saving, they said the craft had entered an
Earth Intersecting Orbit (EIO) :-) I nominate 'Earth Intersecting Orbit' as our descriptor for the upcoming flight.
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#979
by
joek
on 16 Apr, 2023 14:41
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Too me, orbital is simple. Orbits are when the path is stable due simply to physics. No additional forces are required. (Yes, station keeping in LEO is required to overcome drag...but it's negligible for the sake of this argument.) If the perigee is low enough that atmospheric drag will cause re-entry, then by definition it is not orbital.
This debate has little-nothing to do with physics, but legal or quasi-legal definitions of "orbital". You can speculate either way depending on your interpretation of various references. And even given those references, you can't really call it unless you know details about the trajectory and what happens when--which we do not have.
For example...
Suborbital trajectory means the intentional flight path of a launch vehicle, reentry vehicle, or any portion thereof, whose vacuum instantaneous impact point does not leave the surface of the Earth.
Deorbit means the flight of a vehicle that begins with the final command to commit to a perigee below 70 nautical miles (approximately 130 kilometers), and ends when all vehicle components come to rest on the Earth.
That is only a small selection of various sources-references. E.g., We could have a "suborbital" trajectory by definition #1, yet have a "deorbit"--which implies orbit--by definition #2 (e.g., if it were commanded later in flight).
Tempest in a teapot. People will cherry pick and speculate based on their preferences; not worth wasting more time on this. We'll know when the dust has settled.
