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#320
by
AncientU
on 17 May, 2017 14:11
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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?
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#321
by
Shanuson
on 17 May, 2017 14:55
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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
Roughly a 1,570m/s deficit to GEO. That's almost Zenit-3SL/Proton-M/Briz-M performance.
Just a question about your sign convention: how can the DEFICIT to GEO be this large, when this mission used a super-synchronous transfer orbit? It would seem to have a significantly smaller deficit, since the semi-major axis is much closer to GEO than a standard Hohmann GTO, or indeed, even the S/C separation orbit of a Briz-M for a payload of equal mass... isn't the energy of the orbit a function of semi-major axis?
Function of semimajor axis, but also of eccentricity
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#322
by
Kaputnik
on 17 May, 2017 16:32
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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?
It's looking that way, but the point of the discussion was to compare F9 with other all Kerolox launchers.
It's pretty remarkable that Falcon can be within sight of a three stage vehicle using staged combustion engines.
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#323
by
baldusi
on 17 May, 2017 16:36
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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
Roughly a 1,570m/s deficit to GEO. That's almost Zenit-3SL/Proton-M/Briz-M performance.
Just a question about your sign convention: how can the DEFICIT to GEO be this large, when this mission used a super-synchronous transfer orbit? It would seem to have a significantly smaller deficit, since the semi-major axis is much closer to GEO than a standard Hohmann GTO, or indeed, even the S/C separation orbit of a Briz-M for a payload of equal mass... isn't the energy of the orbit a function of semi-major axis?
The most expensive orbital maneuver is the plane change, so you should look at the 24.5deg parameter. The reason for a supersynchronous injection is because the more eccentric the orbit, the cheaper it is to do the orbital plane change at apogee (because most energy is potential energy and not actual velocity). If you were on the equatorial plane already, which is the Zenit-3SL case, there would be no reason whatsoever to do a supersynchronous injection, from an energy optimization point of view. In fact, you would then have to spend more energy to reduce it to GEO altitude.
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#324
by
baldusi
on 17 May, 2017 16:39
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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?
Sea Launch is, apparently, going to be re-purposed for another, TBD launcher. While Zenit I think still has a single launch left from Baikonour. But the comment was on the performance level, rather than the current competitors.
The EELV can easily do that, and so does Ariane 5. But on both cases they offer a range of payloads above and below. Proton and Zenit had, in their GTO configuration, a single performance level, no scaling. Now Proton might be introducing Medium variants and such. But, as with all Russian LV project, I'll believe it when it launches.
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#325
by
macpacheco
on 17 May, 2017 16:42
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May I ask how high an apogee would this launch have produced if it did zero inclination reduction ?
Perhaps this will better explain to people how significant this performance was, considering it was also the heaviest F9 GTO payload to date !
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#326
by
edkyle99
on 17 May, 2017 18:15
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Here's how I was finally able to get my mind around this launch result.
It would take an Atlas 541 to match this performance, or a Proton M Briz M Phase 3 or 4. Ariane 5 ECA could do it, of course, as could Delta 4 Heavy. CZ-5, theoretically though it has yet to demonstrate the capability. H-2B, ditto. That's it, I think, among active launchers.
Delta 4 Mediums can't do this at all. Neither can H-2A, or CZ-3B, or CZ-7, or GSLV Mk 3.
When Falcon 9 first began flying, I thought of it as slightly better than Delta 2 class. The machine has evolved, and the most recent two flights have exhibited a new level of performance - to the extent that I'm convinced we are seeing at least a Block 4 second stage.
- Ed Kyle
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#327
by
baldusi
on 17 May, 2017 19:42
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May I ask how high an apogee would this launch have produced if it did zero inclination reduction ?
Perhaps this will better explain to people how significant this performance was, considering it was also the heaviest F9 GTO payload to date !
The problem with orbital mechanics is that mixing apogee increase AND plane change is a lot cheaper than doing one and then the other one. I will yield to Lou to do such calculation, though.
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#328
by
AC in NC
on 17 May, 2017 19:44
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Here's how I was finally able to get my mind around this launch result.
It would take an Atlas 541 to match this performance, or a Proton M Briz M Phase 3 or 4. Ariane 5 ECA could do it, of course, as could Delta 4 Heavy. CZ-5, theoretically though it has yet to demonstrate the capability. H-2B, ditto. That's it, I think, among active launchers.
Delta 4 Mediums can't do this at all. Neither can H-2A, or CZ-3B, or CZ-7, or GSLV Mk 3.
When Falcon 9 first began flying, I thought of it as slightly better than Delta 2 class. The machine has evolved, and the most recent two flights have exhibited a new level of performance - to the extent that I'm convinced we are seeing at least a Block 4 second stage.
- Ed Kyle
Here's how I was finally able to get my mind around Ed's excellent explanation of this launch result.
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#329
by
LouScheffer
on 17 May, 2017 20:09
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May I ask how high an apogee would this launch have produced if it did zero inclination reduction ?
The same delta-V, no inclination reduction, would give a apogee of about 81,000 km at 28 degrees. Interestingly, this is only a few m/s further from GEO than the orbit they got. (The curve of remaining delta-V vs inclination removed is quite shallow). By my calculation, they would have been slightly better off with an orbit half way between these two (78000 km apogee and 26.13 degrees, but the difference is small (9 m/s). I suspect the difference is due to SpaceX optimizing for least delta-V remaining, assuming worst-case performance of the burn to depletion, but then having a non-worst-case burn.
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#330
by
clegg78
on 17 May, 2017 20:22
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Perhaps Chris can give away a free L2 subscription to the 1st person that can identify which of the preceeding 12 isn't like the others.
Hmm... I was going to say they all have strap on boosters (Solid or liquid) except for Proton and F9.
Is it that the Proton is a 4 stage rocket? I don't think any of the others are.
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#331
by
AC in NC
on 17 May, 2017 20:26
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Perhaps Chris can give away a free L2 subscription to the 1st person that can identify which of the preceeding 12 isn't like the others.
Hmm... I was going to say they all have strap on boosters (Solid or liquid) except for Proton and F9.
Is it that the Proton is a 4 stage rocket? I don't think any of the others are.
Oh ... I wasn't going for anything tricky ... I was considering the Proton to have protuberances as well regardless of whether they were literally a strap on booster. Gotta be some performance bonus versus a clean stick.
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#332
by
macpacheco
on 17 May, 2017 20:32
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Perhaps now I actually understand why people are so reluctant to even entertain the possibility that F9 expendable with zero margins might be able to put an 8.3 ton payload in GTO-1800 m/s. That would challenge every rocket in service, except for Ariane V and D4H.
It really must be hard to conceive that such a cheap rocket can get that much performance. But I'm a believer, eventually there will be one Block V expendable launch that will place something like a 7.5 ton payload to an orbit similar to this, and awe the world ! A payload large enough that in requires the same effort to put that 8.3 tons to GTO-1800 !
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#333
by
gospacex
on 17 May, 2017 20:48
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Perhaps Chris can give away a free L2 subscription to the 1st person that can identify which of the preceeding 12 isn't like the others.
Hmm... I was going to say they all have strap on boosters (Solid or liquid) except for Proton and F9.
Is it that the Proton is a 4 stage rocket? I don't think any of the others are.
The first stage consists of a central cylindrical oxidizer tank with the same diameter as the other 2 stages, with 6 fuel tanks attached to its circumference, each carrying an engine. These side fuel tanks do not separate at MECO, the entire stage detaches as a unit from S2.
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#334
by
macpacheco
on 17 May, 2017 20:58
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May I ask how high an apogee would this launch have produced if it did zero inclination reduction ?
Perhaps this will better explain to people how significant this performance was, considering it was also the heaviest F9 GTO payload to date !
The problem with orbital mechanics is that mixing apogee increase AND plane change is a lot cheaper than doing one and then the other one. I will yield to Lou to do such calculation, though.
I thought that the best usage of LV performance was to put the GTO payload on as high as possible apogee, and THEN once its on a super sync trajectory, it can use the lower speeds of the apogee to effect some inclination change and reduction in apogee on each orbital apogee and increase in perigee on each orbital perigee, done by the payload itself.
That led me to think that if SpaceX could create a mini ITS rocket that had perhaps 5+ days of mission endurance, it could do a bi elliptical transfer by itself, by going into a super sync orbit, doing the entire inclination change and apogee reduction in a single burn, then the perigee raising in the other half orbit and deliver a large number of GEO payloads into GEO-500m/s with zero inclination and just some circularization left, so the orbital period is a few hours away from GEO, so the payloads can pace themselves to go directly into their exact slots, although they would all be delivered to the same initial orbit.
The mini ITS would then do the required orbital transfer to re-enter and land, avoiding brute force trajectory corrections to get to the LZ.
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#335
by
saliva_sweet
on 17 May, 2017 21:19
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The machine has evolved, and the most recent two flights have exhibited a new level of performance - to the extent that I'm convinced we are seeing at least a Block 4 second stage.
Not sure about two latest flights, but the last one was totally out of family. Looks like a different rocket.
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#336
by
Dante80
on 17 May, 2017 21:22
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A factor to consider when talking about F9 v1.2 performance as a kerolox gas generator TSTO is the use of sub-cooled propellants. When originally introduced, SpaceX got a lot of flak for that decision (and they still are afaik when talking about CC).
During the OG2 M2 and SES-9 campaigns, SpaceX was struggling a lot to work out the bugs and streamline the GSE and launch procedures. Here is a reminder.
Falcon 9 Flight 20 - ORBCOMM-2 RTF Mission
core number: 1019
S) 2015-12-16, Unsuccessful static fire [59]
S) 2015-12-17, Unsuccessful static fire, deep cryo liquid oxygen presenting some challenges [59]
F) 2015-12-18, Successful static fire [59]
D) 2015-12-20, 24h delay for improved odds for landing attempt and better analysis for subcooled LOX (Possibly due to wind gusts that affect landing and LOX temps) [60]
L) 2015-12-21, Successful launch (the one with the epic landing at LZ1)[61]
BR) 2015-12-21, Successful landing at LZ1[61]
S) 2016-01-14, Static fire scrub (ground side issues) [67]
F) 2016-01-15, Successful static fire (engine 9 showed thrust fluctuations. Maybe some debris ingestion) [67]
Falcon 9 Flight 22 - SES-9
payload mass: 5,271 kilograms, orbit: geosynchronous, delivered orbit: 334 x 40648 km x 27.96° [65], [69]
core number: 1020
F) 2016-02-22, Successful static fire [64]
D) 2016-02-24, 24h delay to ensure liquid oxygen temperatures are as cold as possible in an effort to maximize performance of the vehicle (due to high winds) [66]
C) 2016-02-25, Scrub at T-1:41, LOX loading issues [65] R) 2016-02-28, Delay, wayward boat got into range [65] C) 2016-02-28, Scrub at T-0, aborted on low thrust alarm. Rising oxygen temps due to hold for boat and helium bubble triggered alarm [65]
D) 2016-03-01, Delay due to extreme high altitude wind shear [68]
L) 2016-03-05, Successful launch (the one with the difficult landing attempt) [65] BL) 2016-03-05, Hard landing at OCISLY (3 engine landing burn, run out of propellant, no boostback burn) [65][74]
A lot of people back then (a little more than a year ago, now feels like a decade ago to me), were starting to say that it would be impossible to work the issues out and reach a good launch cadence with that feature on the rocket. Even industry officials like George Sowers (then working on ULA) were saying that it really was not worth the trouble.
Ultimately, it took a year and a half, including a freak pad accident to surmount this challenge. Judging from the last two campaigns though, I think it was worth it in the end.
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#337
by
baldusi
on 17 May, 2017 22:26
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May I ask how high an apogee would this launch have produced if it did zero inclination reduction ?
Perhaps this will better explain to people how significant this performance was, considering it was also the heaviest F9 GTO payload to date !
The problem with orbital mechanics is that mixing apogee increase AND plane change is a lot cheaper than doing one and then the other one. I will yield to Lou to do such calculation, though.
I thought that the best usage of LV performance was to put the GTO payload on as high as possible apogee, and THEN once its on a super sync trajectory, it can use the lower speeds of the apogee to effect some inclination change and reduction in apogee on each orbital apogee and increase in perigee on each orbital perigee, done by the payload itself.
That led me to think that if SpaceX could create a mini ITS rocket that had perhaps 5+ days of mission endurance, it could do a bi elliptical transfer by itself, by going into a super sync orbit, doing the entire inclination change and apogee reduction in a single burn, then the perigee raising in the other half orbit and deliver a large number of GEO payloads into GEO-500m/s with zero inclination and just some circularization left, so the orbital period is a few hours away from GEO, so the payloads can pace themselves to go directly into their exact slots, although they would all be delivered to the same initial orbit.
The mini ITS would then do the required orbital transfer to re-enter and land, avoiding brute force trajectory corrections to get to the LZ.
Well, as long as you want to go to GTO, and you are not launching from the Equator, you will really have at least a two-burn profile mission. First you go to a parking orbit (say 185km circular), and then, when you are over the equatorial plane, you make your burn so that your apogee is also at the Equator.
But guess what? If you mix a an apogee burn, and a plane change burn, you actually make a vector sum of both solution vectors (assuming instantaneous impulse, which it isn't). But those vectors are orthogonal, so your resulting impulse vector will be at an angle to both. And thus you have something that is less than the sum of both. So doing both at the same time, actually saves delta-v.
Of course that once you are on the apogee transfer, the upper stage mass is dead weight. So you actually save total mass by letting the payload do the circularization at apogee (which will also involve a plane change). So, yes, the plane change is cheaper to do at apogee, but that's the payload's job. And since you are already doing an apogee increasing burn with your LV, you should also put some plane change in there and you will have less delta-v to GEO.
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#338
by
LouScheffer
on 18 May, 2017 00:26
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The machine has evolved, and the most recent two flights have exhibited a new level of performance - to the extent that I'm convinced we are seeing at least a Block 4 second stage.
Not sure about two latest flights, but the last one was totally out of family. Looks like a different rocket.
The last two flights look like they are from the same family, despite first glance appearances. Minimum residual shutdown makes a big difference. The last 1% of the fuel provides about 350 m/s of delta-V, for about a 220 m/s better deficit.
I draw these on top of the existing plot, below. First there is a parallel line through Echostar (thick blue line, for a new family). This is for targetted shutdowns, and I agree represents a new family of increased performance compared to previous launches. From this line you can move left by about 220 m/s (magenta arrow) and end up with another family line, for minimum residual shutdowns. This new line then extends up to the estimated 7.38 tonnes at GEO-1800.
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#339
by
Robotbeat
on 18 May, 2017 00:28
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Perhaps now I actually understand why people are so reluctant to even entertain the possibility that F9 expendable with zero margins might be able to put an 8.3 ton payload in GTO-1800 m/s. That would challenge every rocket in service, except for Ariane V and D4H.
It really must be hard to conceive that such a cheap rocket can get that much performance. But I'm a believer, eventually there will be one Block V expendable launch that will place something like a 7.5 ton payload to an orbit similar to this, and awe the world ! A payload large enough that in requires the same effort to put that 8.3 tons to GTO-1800 !
Actually, can anyone calculate what Ariane 5's payload would be if it were launched from 28 degrees?
