Dragot de-Orbit

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JF Mezei

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Sep 18, 2021, 6:22:43 PM9/18/21
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Looking at Inspiration4 landing.
They were the highest a human has been since last Hubble repaid mission
(and may have been higher).

They jettisomed the "trunk" before de-orbit burn. Is this SOP for
Dragon or special for this mission? By detaching before de-orbit,
doesn't that create space debris with trucnk staying high up for a long
time (since that orbit was bery high) ?

I was under the impression the standard was to fire de-orbit engines and
then separate which ensures both portions de-orbit with the capsule
distancing itself from the trunk/service module as soon as aerodynamics
kick in.

JF Mezei

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Sep 18, 2021, 6:47:15 PM9/18/21
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The californian commentators are now talking about Nitrox being dumped
into the capsile for re-entry to keep it cool.

While the technical definition of nitrox includes normall mixture of N2
and O2 in normal atmpsphere, it is generally used only when you have
O2-rich mixture to reduce body absorbtion of N2 while diving (reduced
decompression requirements when going back up to surface - and extending
dive time).

Dragon is normally at 14.7 and normal N2/O2 mixture, right? If they use
Nitrox during landing does this mean they are increasing cabin pressure
significantly enough to worry aboutr the bends when the bring it back to
1 atm?

Or are the commentators just using "nitrox" to look cool and the cabin
maintains normal N2/O2 mixtures?

Snidely

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Sep 20, 2021, 1:48:32 PM9/20/21
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Thus spake JF Mezei:

> Looking at Inspiration4 landing.
> They were the highest a human has been since last Hubble repaid mission
> (and may have been higher).
>
> They jettisomed the "trunk" before de-orbit burn. Is this SOP for
> Dragon or special for this mission? By detaching before de-orbit,
> doesn't that create space debris with trucnk staying high up for a long
> time (since that orbit was bery high) ?

SOP.

Orbit was lowered in 2 steps before jettison and the rest of the
landing sequence; this was described by the SpaceX commentators.

And the trunk is very light, so sensitive the slight atmospheric drag.

> I was under the impression the standard was to fire de-orbit engines and
> then separate which ensures both portions de-orbit with the capsule
> distancing itself from the trunk/service module as soon as aerodynamics
> kick in.

Standard? You mean like ISO?

/dps

--
"First thing in the morning, before I have coffee, I read the obits, If
I'm not in it, I'll have breakfast." -- Carl Reiner, to CBS News in
2015.

Snidely

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Sep 22, 2021, 3:00:05 AM9/22/21
to
Snidely presented the following explanation :
> Thus spake JF Mezei:
>
>> Looking at Inspiration4 landing.
>> They were the highest a human has been since last Hubble repaid mission
>> (and may have been higher).
>>
>> They jettisomed the "trunk" before de-orbit burn. Is this SOP for
>> Dragon or special for this mission? By detaching before de-orbit,
>> doesn't that create space debris with trucnk staying high up for a long
>> time (since that orbit was bery high) ?
>
> SOP.

<URL:https://youtu.be/fZrSnM2xZzc?t=20632>

> Orbit was lowered in 2 steps before jettison and the rest of the landing
> sequence; this was described by the SpaceX commentators.
>
> And the trunk is very light, so sensitive the slight atmospheric drag.
>
>> I was under the impression the standard was to fire de-orbit engines and
>> then separate which ensures both portions de-orbit with the capsule
>> distancing itself from the trunk/service module as soon as aerodynamics
>> kick in.
>
> Standard? You mean like ISO?
>
> /dps

--
The presence of this syntax results from the fact that SQLite is really
a Tcl extension that has escaped into the wild.
<http://www.sqlite.org/lang_expr.html>

Snidely

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Oct 3, 2021, 6:11:33 PM10/3/21
to
On Wednesday or thereabouts, Snidely asked ...
> Snidely presented the following explanation :
>> Thus spake JF Mezei:
>>
>>> Looking at Inspiration4 landing.
>>> They were the highest a human has been since last Hubble repaid mission
>>> (and may have been higher).
>>>
>>> They jettisomed the "trunk" before de-orbit burn. Is this SOP for
>>> Dragon or special for this mission? By detaching before de-orbit,
>>> doesn't that create space debris with trucnk staying high up for a long
>>> time (since that orbit was bery high) ?
>>
>> SOP.
>
> <URL:https://youtu.be/fZrSnM2xZzc?t=20632>
>

I'd give a similar pointer to Cargo Dragon flights, but neither NASA
nor SpaceX leave longterm copies of recent cargo landings on Youtube.
The NASA livestream only goes back 12 hours, and at 8pm yesterday I
wasn't at my computer to grab anything.

/dps


--
Trust, but verify.

Snidely

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Nov 8, 2021, 1:55:14 PM11/8/21
to
JF Mezei suggested that ...
This evening, we're expecting /Endeavour/ to proceed through trunk
separation, nosecone closure, and the deorbit burn.

[Crew2 just got "Dragon is go for undocking"]

/dps

--
"That’s where I end with this kind of conversation: Language is
crucial, and yet not the answer."
Jonathan Rosa, sociocultural and linguistic anthropologist,
Stanford.,2020

Snidely

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Nov 8, 2021, 5:43:04 PM11/8/21
to
Monday, Snidely murmurred ...
> JF Mezei suggested that ...
>> Looking at Inspiration4 landing.
>> They were the highest a human has been since last Hubble repaid mission
>> (and may have been higher).
>>
>> They jettisomed the "trunk" before de-orbit burn. Is this SOP for
>> Dragon or special for this mission? By detaching before de-orbit,
>> doesn't that create space debris with trucnk staying high up for a long
>> time (since that orbit was bery high) ?
>>
>> I was under the impression the standard was to fire de-orbit engines and
>> then separate which ensures both portions de-orbit with the capsule
>> distancing itself from the trunk/service module as soon as aerodynamics
>> kick in.
>
> This evening, we're expecting /Endeavour/ to proceed through trunk
> separation, nosecone closure, and the deorbit burn.
>
> [Crew2 just got "Dragon is go for undocking"]

Fly around complete, now in free flight, with the departure phasing
burn next.

-d

--
"Inviting people to laugh with you while you are laughing at yourself
is a good thing to do, You may be a fool but you're the fool in
charge." -- Carl Reiner

Snidely

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Nov 8, 2021, 9:42:12 PM11/8/21
to
On Monday or thereabouts, Snidely asked ...
> Monday, Snidely murmurred ...
>> JF Mezei suggested that ...
>>> Looking at Inspiration4 landing.
>>> They were the highest a human has been since last Hubble repaid mission
>>> (and may have been higher).
>>>
>>> They jettisomed the "trunk" before de-orbit burn. Is this SOP for
>>> Dragon or special for this mission? By detaching before de-orbit,
>>> doesn't that create space debris with trucnk staying high up for a long
>>> time (since that orbit was bery high) ?
>>>
>>> I was under the impression the standard was to fire de-orbit engines and
>>> then separate which ensures both portions de-orbit with the capsule
>>> distancing itself from the trunk/service module as soon as aerodynamics
>>> kick in.
>>
>> This evening, we're expecting /Endeavour/ to proceed through trunk
>> separation, nosecone closure, and the deorbit burn.
>>
>> [Crew2 just got "Dragon is go for undocking"]
>
> Fly around complete, now in free flight, with the departure phasing burn
> next.

That was done, now claw separation confirmed, and then "Nominal trunk
jettison"

-d

--
Killing a mouse was hardly a Nobel Prize-worthy exercise, and Lawrence
went apopleptic when he learned a lousy rodent had peed away all his
precious heavy water.
_The Disappearing Spoon_, Sam Kean

Snidely

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Nov 8, 2021, 10:05:10 PM11/8/21
to
Snidely used thar keyboard to writen:
> On Monday or thereabouts, Snidely asked ...
>> Monday, Snidely murmurred ...
>>> JF Mezei suggested that ...
>>>> Looking at Inspiration4 landing.
>>>> They were the highest a human has been since last Hubble repaid mission
>>>> (and may have been higher).
>>>>
>>>> They jettisomed the "trunk" before de-orbit burn. Is this SOP for
>>>> Dragon or special for this mission? By detaching before de-orbit,
>>>> doesn't that create space debris with trucnk staying high up for a long
>>>> time (since that orbit was bery high) ?
>>>>
>>>> I was under the impression the standard was to fire de-orbit engines and
>>>> then separate which ensures both portions de-orbit with the capsule
>>>> distancing itself from the trunk/service module as soon as aerodynamics
>>>> kick in.
>>>
>>> This evening, we're expecting /Endeavour/ to proceed through trunk
>>> separation, nosecone closure, and the deorbit burn.
>>>
>>> [Crew2 just got "Dragon is go for undocking"]
>>
>> Fly around complete, now in free flight, with the departure phasing burn
>> next.
>
> That was done, now claw separation confirmed, and then "Nominal trunk
> jettison"
>

[This reduces the mass the Dracos have to apply delta-vee to, as well
as reducing the parachute load]

"de-orbit burn complete, performance nominal, [nose cone] closure
intiated"

[de-orbit burn was about 15 minutes]

-d

--
"I am not given to exaggeration, and when I say a thing I mean it"
_Roughing It_, Mark Twain

Snidely

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Nov 8, 2021, 10:48:06 PM11/8/21
to
Lo, on the 11/8/2021, Snidely did proclaim ...
Splash down 7:33 PST, 10:33 EST off Pensacola FL.

Great views from the WB-57.

/dps

JF Mezei

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Nov 8, 2021, 11:18:39 PM11/8/21
to
On 2021-11-08 22:05, Snidely wrote:

> [This reduces the mass the Dracos have to apply delta-vee to, as well
> as reducing the parachute load]

Are what altitude is the trunk jettisoned? It is allowed totally
uncontroled re-entry anywhere at any time because they are confident it
fully burns up?

On other ships the excess weight is ditched after de-orbit burn to force
it down in same orbit. But those happen to have de-orbit engines and
tanks on the "trunk" portion, so keeping the trunk attached for de-orbit
burn is sort of mandatory.

Yet once detached both parts follow their own trajectory and the
parachutes never worry about the trunk/service module because it only
needs to support the small capsule.


Snidely

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Nov 9, 2021, 12:03:39 AM11/9/21
to
Remember Monday, when JF Mezei asked plaintively:
> On 2021-11-08 22:05, Snidely wrote:
>
>> [This reduces the mass the Dracos have to apply delta-vee to, as well
>> as reducing the parachute load]
>
> Are what altitude is the trunk jettisoned? It is allowed totally
> uncontroled re-entry anywhere at any time because they are confident it
> fully burns up?

It's between the departure phase burn (aka landing phase burn) and the
deorbit burn. This flight also included an out-of-plane burn that was
a fuel dump, and this was also before trunk separation.

However, we don't get the "speedometer" data for height and velocity at
any point (except when we get a few views of the consoles).

> On other ships the excess weight is ditched after de-orbit burn to force
> it down in same orbit. But those happen to have de-orbit engines and
> tanks on the "trunk" portion, so keeping the trunk attached for de-orbit
> burn is sort of mandatory.

Most Apollo reentries were basically set up from the moon, so SM
separation happened well after the "de-orbit" burn. Skylab and ATSP
provide the return-from-orbit scenario, and it appears for ATSP that
the SM separated after the de-orbit burn (no scare quotes). Skylab was
probably the same, but I don't see confirmation of that in a quick
search.

Remember, though, the SM had a pretty big engine ... that rocket motor
was capable of doing the lunar return burn.

<URL:https://history.nasa.gov/apollo/apsoyhist.html>

Soyuz separated the orbital and descent modules after the de-orbit
burn, too.

[I'd expect a similar description of the Chinese capsules, based on the
"they copied the Soyuz" trope]

Gemini had the reentry rockets ("retrograde rockets") on the Adapter
Module, so that had to be jettisoned after the deorbit burn.
Astronautix says, "The sections of the adapter module remained in
decaying orbits and were burned up during reentry." That hints that
the AM might not have entered as quickly as the Reentry Module.

<URL:http://www.astronautix.com/g/geminitechnaldescription.html>

> Yet once detached both parts follow their own trajectory and the
> parachutes never worry about the trunk/service module because it only
> needs to support the small capsule.

Sure, so the NASA/SpaceX commentary is kinda being redundant about the
jettison making it easier on the parachutes, but still.

/dps

--
There's nothing inherently wrong with Big Data. What matters, as it
does for Arnold Lund in California or Richard Rothman in Baltimore, are
the questions -- old and new, good and bad -- this newest tool lets us
ask. (R. Lerhman, CSMonitor.com)

Anthony Frost

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Nov 9, 2021, 5:51:14 AM11/9/21
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In message <mn.44ef7e5bf35f870a.127094@snitoo>
Snidely <snide...@gmail.com> wrote:

> Gemini had the reentry rockets ("retrograde rockets") on the Adapter
> Module, so that had to be jettisoned after the deorbit burn.
> Astronautix says, "The sections of the adapter module remained in
> decaying orbits and were burned up during reentry." That hints that
> the AM might not have entered as quickly as the Reentry Module.

Gemini had the adapter module in two sections. The first section was
dropped off in orbit which exposed the re-entry motors, the section
holding the motors was then dropped after the burn.

Anthony

Snidely

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Nov 11, 2021, 1:20:02 AM11/11/21
to
On Tuesday, Anthony Frost queried:
Thank you. You sent me back to Astronautix and the search engine. I
see I misread the article, not catching that the "retrograde module"
was a separate section.

I've also found a NASA illustration:
<URL:https://history.nasa.gov/SP-4002/images/fig23.jpg>
from
<URL:https://history.nasa.gov/SP-4002/figures.htm>

There seem to be more pictures/illustrations of the Air Force version
of Gemini, Gemini-B, the commuter van for the Manned Orbiting
Laboratory.

Here's an article (and pictures) of the MOL/Gemini-B retrograde module:
<URL:https://www.thespacereview.com/article/3158/1>
(one of the photographers has several more pictures, too)

This has a comparison of the retrograde modules between NASA and
Gemini-B:
<URL:http://www.astrocryptotriviology.com/blog/2016/6/18/a-jones-for-mol-11-the-retroactivity-of-mol-part-1>
[there's also a bit of de-orbit analysis therein]

That last reference suggests that the MOL would have de-orbited
separately, perhaps a few hours later than the GeeBee.

/dps

--
But happiness cannot be pursued; it must ensue. One must have a reason
to 'be happy.'"
Viktor Frankl

Snidely

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Dec 31, 2021, 7:43:18 AM12/31/21
to
Snidely submitted this idea :
> Thus spake JF Mezei:
>
>> Looking at Inspiration4 landing.
>> They were the highest a human has been since last Hubble repaid mission
>> (and may have been higher).
>>
>> They jettisomed the "trunk" before de-orbit burn. Is this SOP for
>> Dragon or special for this mission? By detaching before de-orbit,
>> doesn't that create space debris with trucnk staying high up for a long
>> time (since that orbit was bery high) ?
>
> SOP.
>
> Orbit was lowered in 2 steps before jettison and the rest of the landing
> sequence; this was described by the SpaceX commentators.
>
> And the trunk is very light, so sensitive the slight atmospheric drag.
>
>> I was under the impression the standard was to fire de-orbit engines and
>> then separate which ensures both portions de-orbit with the capsule
>> distancing itself from the trunk/service module as soon as aerodynamics
>> kick in.
>
> Standard? You mean like ISO?
>
> /dps

BTW, Soyuz does re-entry burn, discards *2* sections, and then feels
for the atmosphere.

<URL:https://twitter.com/NASASpaceflight/status/1472754748805812225>

/dps

--
"That's a good sort of hectic, innit?"

" Very much so, and I'd recommend the haggis wontons."
-njm
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