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#360 by Basto on 18 May, 2017 14:19
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There would also be targeting accuracy to take into account here. A small difference in a retro-burn at 60,000 km could make a large difference in where reentry will take place. The deep south Pacific or Indian Ocean are big places, but even so...
The stage will come down on its own eventually. At least with a deorbit burn you can give a push in the general direction you want it to go. -
#361 by Kaputnik on 18 May, 2017 14:36
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Is venting of residuals a possibility for deorbit impulse?
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#362 by ulm_atms on 18 May, 2017 15:02
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Is venting of residuals a possibility for deorbit impulse?
I was thinking the same thing. Use all the GN2, and you still have what's left of the helium...the rest of the O2 to boil off (can you use the left over electrical power to heat the LO2 and change it into GO2 faster?)...and then basically increase the pressure in the O2 tank to it's max. After that just open the O2 valve and let the pressurized gas be burped out the MVac and rinse repeat until all He/LO2 is gone? That should provide some dV for deorbit. As stated above...you don't need that much. -
#363 by Star One on 18 May, 2017 15:07
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...
Zenit-3SL can do 6.16 to a 1,477m/s deficit GTO. That's a ~95m/s difference. If they used less delta-v GTO, and they didn't had structural limits on the rocket, it would be much higher performance. Using a linear approximation I get 7.8 tonnes.
Isn't Zenit retired or on last launch?
I am not so sure on that. I certainly wouldn't recommend you go to Ukraine and say that.
Why not? It's not like people in Yuzhmash are oblivious to the fact that RD-170 is not made in Ukraine.
I thought they were doing their upmost to keep Zenit going.
How? Ukraine will not use a Russian engine. It's a political suicide to anyone to even propose that.
Do they not have the capacity to develop an alternative? -
#364 by Pete on 18 May, 2017 16:15
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Is venting of residuals a possibility for deorbit impulse?
...and then basically increase the pressure in the O2 tank to it's max. ...
This is a scenario that should rather be avoided. The possibility, even the remote chance, of a rupturing O2 tank at a high apogee altitude is nightmare material.
A more sedate approach might well work just fine, as even a few m/s at a 60000km apogee (or even 35000km) will shift the perigee drastically. -
#365 by John Alan on 18 May, 2017 20:19
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Swap has taken place:42698 INMARSAT 5-F4 2017-025A 1401.67min 24.50deg 69839km 381km
42699 FALCON 9 R/B 2017-025B 1410.43min 24.47deg 70181km 384km
I believe these are identified backwards: the payload is in the 384 x 70,181 km orbit; and the Falcon-9 upper stage rocket body is in the 381 x 69,839 km orbit. Expect 18 SPCS to swap these in the next couple of days.
42698 INMARSAT 5-F4 2017-025A 1409.24 min 24.52deg 70134km 385km
42699 FALCON 9 R/B 2017-025B 1401.51 min 24.47deg 69835km 378km
Well... there were no more burns...
That stage will be up there for years... SAD!!
(on re-edit... my opinion is used stages should self deorbit within 1 year or much less... just my opinion)...
On later edit... @AncientU's post below
LouScheffer indicated within 25 years is the agreed on practice... Source from a couple pages back...
https://forum.nasaspaceflight.com/index.php?topic=41560.msg1679379#msg1679379
My opinion... with the increased flight rate world wide... this number needs revisited...
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#366 by AncientU on 18 May, 2017 20:39
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Swap has taken place:42698 INMARSAT 5-F4 2017-025A 1401.67min 24.50deg 69839km 381km
42699 FALCON 9 R/B 2017-025B 1410.43min 24.47deg 70181km 384km
I believe these are identified backwards: the payload is in the 384 x 70,181 km orbit; and the Falcon-9 upper stage rocket body is in the 381 x 69,839 km orbit. Expect 18 SPCS to swap these in the next couple of days.
42698 INMARSAT 5-F4 2017-025A 1409.24 min 24.52deg 70134km 385km
42699 FALCON 9 R/B 2017-025B 1401.51 min 24.47deg 69835km 378km
Well... there were no more burns...
That stage will be up there for years... SAD!!
(on edit... my opinion is should require deorbit in 1 year or much less... just my opinion)...
Quite unusual/surprising for one of their second stages to not deorbit almost immediately. Is that a failure or planned with the burn to limits?
Isn't the residual atmospheric drag sufficient below 400km to strip significant orbital energy each pass through perigee? The VLEO constellation tech document had 2.9 years to reentry at 400km and 2.1 at 350km -- of course those were circular orbits with continual drag. <25 years is the requirement, right? -
#367 by macpacheco on 18 May, 2017 20:56
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Quite unusual/surprising for one of their second stages to not deorbit almost immediately. Is that a failure or planned with the burn to limits?
Completely different scenario, an object on a circular orbit with below 400Km apogee will be constantly subjected to the little atmosphere there.
Isn't the residual atmospheric drag sufficient below 400km to strip significant orbital energy each pass through perigee? The VLEO constellation tech document had 2.9 years to reentry at 400km and 2.1 at 350km -- of course those were circular orbits with continual drag. <25 years is the requirement, right?
The perigee is the point of faster speed, which means it will be below even 500Km for a tiny fraction of the whole orbit, time wise.
One question though, the higher energy orbit, wouldn't that furthermore mean that the cumulative period the GTO object must be exposed to the lower atmosphere is even longer, or the inverse ?
On the other hand, the influence of air drag has a lot to do with the objects surface vs its mass. A denser object will be subject to a smaller deceleration force than a less dense one. I think the F9 stage gets more deceleration due to this effect.
Anyhow, the shorter exposure to whatever little atmosphere there is during perigee should dominate the effects.
Ideally SpaceX should move to 200ish km perigee. That would accelerate re-entry to take place under a year.
Edit: This discussion really doesn't belong here. Move or delete my post freely mods. -
#368 by andrewsdanj on 18 May, 2017 21:03
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Regarding the decay of Stage 2: The perigee height won't stay there for long. It will be perturbed higher or lower by the Moon etc. when nearer to apogee. This should be even more marker on a super-synchronous transfer orbit. Next question being, which way will it be perturbed and by how much...?
I notice Echostar 23's upper stage has a perigee of 179 km, it'll be interesting to see how quickly it drops from GTO from there! -
#369 by saliva_sweet on 18 May, 2017 21:16
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Quite unusual/surprising for one of their second stages to not deorbit almost immediately. Is that a failure or planned with the burn to limits?
To my knowledge, none of the second stages on SpaceX GTO flights have been actively deorbited. They stay up for a few months up to a couple of years. -
#370 by rsdavis9 on 18 May, 2017 21:24
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Quite unusual/surprising for one of their second stages to not deorbit almost immediately. Is that a failure or planned with the burn to limits?
To my knowledge, none of the second stages on SpaceX GTO flights have been actively deorbited. They stay up for a few months up to a couple of years.
I you peruse the launch elements you will see some falcon rocket body's still up there from years ago. And you will see a number of more recent ones missing.
So I think mostly they deorbit.
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#371 by Lar on 18 May, 2017 21:43
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Is there a general thread for this ( do/don't S2s deorbit, how to deorbit them more cleverly, etc) that might be more well suited?
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#372 by ulm_atms on 18 May, 2017 22:40
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Is venting of residuals a possibility for deorbit impulse?
...and then basically increase the pressure in the O2 tank to it's max. ...
This is a scenario that should rather be avoided. The possibility, even the remote chance, of a rupturing O2 tank at a high apogee altitude is nightmare material.
A more sedate approach might well work just fine, as even a few m/s at a 60000km apogee (or even 35000km) will shift the perigee drastically.
I miss wrote. At max pressure, I mean max flight pressure....not max, if even 1 more pa it pops. Or in other terms...max safe pressure.
And I agree with Lar, this has zip to do with Immarsat but can also not find a better home. I will stop discussion unless a better home is found....
Carry on! -
#373 by envy887 on 19 May, 2017 02:56
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Is there a general thread for this ( do/don't S2s deorbit, how to deorbit them more cleverly, etc) that might be more well suited?
F9 general thread?
GTO upper stages decay and are not deorbited. They don't have the lifetime to burn at apogee, or the performance to burn sooner. -
#374 by Lars-J on 19 May, 2017 03:56
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Is there a general thread for this ( do/don't S2s deorbit, how to deorbit them more cleverly, etc) that might be more well suited?
F9 general thread?
GTO upper stages decay and are not deorbited. They don't have the lifetime to burn at apogee, or the performance to burn sooner.
They do have that lifetime now, or will soon. -
#375 by gospacex on 19 May, 2017 14:16
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Why not? It's not like people in Yuzhmash are oblivious to the fact that RD-170 is not made in Ukraine.
I thought they were doing their upmost to keep Zenit going.
How? Ukraine will not use a Russian engine. It's a political suicide to anyone to even propose that.
Do they not have the capacity to develop an alternative?
This deserves an extended reply. Bear with me.
Yuzhnoye is a government enterprise.
In Ukraine, government enterprises are commonly used by political forces in government to milk money from state budget. A simplest way to do that is to buy materials through shell companies, paying them above market prices, and sell produced goods through other shell companies with reduced price (but there are many more creative methods).
As a result, Ukraine currently has some 3000 government enterprises (I believe USA has about 300?) and some 2000 of them are already bankrupt and are essentially dead, exist only on paper. The remaining ones are generally limping along, generating losses and subsisting on government loans and subsidies.
It's risky to have any sort of business relations with such an enterprise for any long-term project.
However. This general situation is not new or unknown, and generally everybody agrees than this can not continue forever and they all need to be privatized. People in power just stonewall this process (while always talking that it needs to be done) so that they can drain a few more hundreds of millions $$$ here and there.
Foreign observers (embassies, intelligence agencies, foreign business) must be understanding the situation as well. Thinking otherwise would assume they are naive idiots.
If anyone would be interested in partnering or otherwise using Ukrainian aerospace capabilities, I would say the only sensible choice would be to work through your official government channels and propose to privatize (buy) Yuzhnoye. Be ready that they will talk about this being a great idea but the actual paperwork process will be slow as a snail (the "stonewalling" thing); and you can get "interesting" proposals that, say, "it's better to form a joint company". As soon as these shenanigans begin, consider going public about it. Unlike situation in Russia, they are afraid of publicity.
This will be good for Ukraine as well - the way Yuzhnoye works today is not beneficial to the country in general, it is beneficial only to individuals who currently control it and enrich themselves through those schemes.
I believe Yuzhnoye can build reasonably good tanks / stages, and they can be very inexpensive (very low salaries compared to the West).
They also can produce some engines, but the ones definitely in production are small-to-medium thrust hypergolic engines. Largest seems to be RD-861 - a seven-ton thrust engine.
They _talk_ about having large(r) kerosene engines of 120-200 tons thrust "in development", but I would very carefully verify what do they actually have, not taking any words / presentations for granted. I would actually send my own engineers to see the goods. In the worst case, it may be just empty talk.
Also Yuzhnoye has some solid-rocket facilities (both fuel and motors), used mostly for military products. -
#376 by kevin-rf on 19 May, 2017 14:18
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I ment to comment on this sooner, One can look up the NORAD ID for each spaceX GTO/Super Sync launch. What you will notice is each payload and upper stage has a separate (should be sequential) NORAD tracking ID. With that ID you can look up the decay dates for stages not currently in orbit. Stages that they immediately de-orbit do not get NORAD ID's.
space-track.org would be the site you go to dig up all those fun numbers. (That or state something that is statistically incorrect and several NSF members will dig out all the numbers to correct you ).
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#377 by Star One on 19 May, 2017 14:25
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Why not? It's not like people in Yuzhmash are oblivious to the fact that RD-170 is not made in Ukraine.
I thought they were doing their upmost to keep Zenit going.
How? Ukraine will not use a Russian engine. It's a political suicide to anyone to even propose that.
Do they not have the capacity to develop an alternative?
This deserves an extended reply. Bear with me.
Yuzhnoye is a government enterprise.
In Ukraine, government enterprises are commonly used by political forces in government to milk money from state budget. A simplest way to do that is to buy materials through shell companies, paying them above market prices, and sell produced goods through other shell companies with reduced price (but there are many more creative methods).
As a result, Ukraine currently has some 3000 government enterprises (I believe USA has about 300?) and some 2000 of them are already bankrupt and are essentially dead, exist only on paper. The remaining ones are generally limping along, generating losses and subsisting on government loans and subsidies.
It's risky to have any sort of business relations with such an enterprise for any long-term project.
However. This general situation is not new or unknown, and generally everybody agrees than this can not continue forever and they all need to be privatized. People in power just stonewall this process (while always talking that it needs to be done) so that they can drain a few more hundreds of millions $$$ here and there.
Foreign observers (embassies, intelligence agencies, foreign business) must be understanding the situation as well. Thinking otherwise would assume they are naive idiots.
If anyone would be interested in partnering or otherwise using Ukrainian aerospace capabilities, I would say the only sensible choice would be to work through your official government channels and propose to privatize (buy) Yuzhnoye. Be ready that they will talk about this being a great idea but the actual paperwork process will be slow as a snail (the "stonewalling" thing); and you can get "interesting" proposals that, say, "it's better to form a joint company". As soon as these shenanigans begin, consider going public about it. Unlike situation in Russia, they are afraid of publicity.
This will be good for Ukraine as well - the way Yuzhnoye works today is not beneficial to the country in general, it is beneficial only to individuals who currently control it and enrich themselves through those schemes.
I believe Yuzhnoye can build reasonably good tanks / stages, and they can be very inexpensive (very low salaries compared to the West).
They also can produce some engines, but the ones definitely in production are small-to-medium thrust hypergolic engines. Largest seems to be RD-861 - a seven-ton thrust engine.
They _talk_ about having large(r) kerosene engines of 120-200 tons thrust "in development", but I would very carefully verify what do they actually have, not taking any words / presentations for granted. I would actually send my own engineers to see the goods. In the worst case, it may be just empty talk.
Also Yuzhnoye has some solid-rocket facilities (both fuel and motors), used mostly for military products.
Thank you for that comprehensive response as it was very informative. -
#378 by kevin-rf on 19 May, 2017 14:51
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To help the US GTO de-orbit debate, NORAD ID's for all SpaceX GTO/Super Synch payloads and upper stages. To date all SpaceX upper stages to those orbits have stuck around long enough to be cataloged.
SES-8 39460, US 39461
Thiacom 6 39500, US 39501
AsiaSat 8 40107, US 40108
AsiaSat 6 40141, US 40142
ABS-3A 40424, Samex 7 40425, US 40426
MonacoSAT 40617, US 40618
SES-9 41380, US 41381
JCSAT-14 41471, US 41472
Thiacom 8 41552, US 41553
ABS 2 41588, EUTELSAT 117W B 41589, US 41590
JCSAT-16 41729, US 41730
Echostar 23 42070, US 42071
SES-10 42432, US 42433
Inmarsat-5 F4 42698, US 42699
It is left as an exercise for the reader to figure out which ones have decayed and any typos. -
#379 by friendly3 on 19 May, 2017 15:05
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SES-8 39460, US 39461
Thiacom 6 39500, US 39501
AsiaSat 8 40107, US 40108
AsiaSat 6 40141, US 40142
ABS-3A 40424, Samex 7 40425, US 40426
MonacoSAT 40617, US 40618
SES-9 41380, US 41381
JCSAT-14 41471, US 41472
Thiacom 8 41552, US 41553
ABS 2 41588, EUTELSAT 117W B 41589, US 41590
JCSAT-16 41729, US 41730
Echostar 23 42070, US 42071
SES-10 42432, US 42433
Inmarsat-5 F4 42698, US 42699
It is left as an exercise for the reader to figure out which ones have decayed and any typos.
Thaicom and not Thiacom, also Satmex and not Samex.
