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#680
by
llanitedave
on 21 Oct, 2013 02:55
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What's important is that the design be extendible, so that adding optimizations doesn't require a major rework. If it's tweakable, the F9 could become the next DC-3.
I would expect them to continue to upgrade F9 of course. It's what all other launch providers do, after all. But the main priority is to prove the reliability of the new design and fly the manifest. I wouldn't expect them to make large design changes while establishing v1.1.
I remember the Shuttle being compared with the DC-3 in the early days. I think F9R has a good chance of being commercially successful, but comparing it to the DC-3 is not useful. Spaceflight and aviation are too different.
Sure it's useful. It's not a comparison of propellers and rocket engines, it's a matter of simplicity, economy, reliability, robustness, and longevity. These are valid comparison points, within their respective domains.
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#681
by
Jakusb
on 21 Oct, 2013 07:44
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I would expect them to continue to upgrade F9 of course. It's what all other launch providers do, after all.
Careful. That needs to be conditional. Experience needs to be developed. Repeatability and consistency is important to customers. That the flight hardware has worked and done so together many times before is important. Several major changes bundled together doesn't make customers happy. It tends to reset the counter on the number of successful launches of a type.
I am pretty much convinced that the only true customer of SpaceX is SpaceX self.
All other customers are indeed very important but merely the means to get to their goal.
As long as they can get away with rapid innovation and new upgrades, all is fine. And I am also convinced they know just fine hoe to get away with it. Something other LPs would not dare, but also could not manage to get accepted by customers.
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#682
by
douglas100
on 21 Oct, 2013 08:44
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...I remember the Shuttle being compared with the DC-3 in the early days. I think F9R has a good chance of being commercially successful, but comparing it to the DC-3 is not useful. Spaceflight and aviation are too different.
Sure it's useful. It's not a comparison of propellers and rocket engines, it's a matter of simplicity, economy, reliability, robustness, and longevity. These are valid comparison points, within their respective domains.
Then you might just as well have compared it to the Volkswagen Beetle.
As far as simplicity is concerned, I wouldn't call a rocket with ten engines "simple." As for the other attributes you mention, time will tell.
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#683
by
douglas100
on 21 Oct, 2013 08:52
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...I am pretty much convinced that the only true customer of SpaceX is SpaceX self.
All other customers are indeed very important but merely the means to get to their goal...
Customers are not "merely" anything. They have to be the first consideration for the
company. Without them there is no SpaceX and Musk would be left without the means to realise his ambitions.
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#684
by
Ben the Space Brit
on 21 Oct, 2013 12:06
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I would expect them to continue to upgrade F9 of course. It's what all other launch providers do, after all.
True but not major changes (Falcon-9 v.1.1 is virtually an all-new launcher, after all; I regard the name as somewhat deceptive). Patches to software, IU hardware changes and progressive tightening of manufacturing margins as the company gets a better handle on what is actually needed for reliability should all be expected. Maybe even a methane-burning Merlin-1e/-2 in the fullness of time.
However, the company should seek to avoid regular complete model upgrades similar to the recent v.1.0/v.1.1 transition. Such things will only increase backlogs and reduce confidence in the reliability of the current product.
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#685
by
douglas100
on 21 Oct, 2013 13:25
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...However, the company should seek to avoid regular complete model upgrades similar to the recent v.1.0/v.1.1 transition. Such things will only increase backlogs and reduce confidence in the reliability of the current product.
Agree. I meant (and should have said)
small upgrades. Antares made a similar point.
We're talking about v1.1 generally here. Maybe this discussion belongs on another thread.
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#686
by
rcoppola
on 23 Oct, 2013 19:15
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...However, the company should seek to avoid regular complete model upgrades similar to the recent v.1.0/v.1.1 transition. Such things will only increase backlogs and reduce confidence in the reliability of the current product.
Agree. I meant (and should have said) small upgrades. Antares made a similar point.
We're talking about v1.1 generally here. Maybe this discussion belongs on another thread.
Just keep in mind that they are not done with the full roll-out / upgrade path of F9V1.1. (F9R) They still need to incorporate those legs and that's not a small thing. And after that they'll start 2nd stage re-design for boost back. Point being that, although it seems they are over the proverbial hump with 1.1, I do not get the sense they'll be slowing down upgrades. However, they have probably bought themselves enough time and stability to do so in a less disruptive way even if they do decide to radically alter F9 again within the next few years. Which I think they will. But by that time, they'll be able to cycle in a new design without disrupting their current manifest. IMO.
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#687
by
Jason1701
on 23 Oct, 2013 21:19
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...However, the company should seek to avoid regular complete model upgrades similar to the recent v.1.0/v.1.1 transition. Such things will only increase backlogs and reduce confidence in the reliability of the current product.
Agree. I meant (and should have said) small upgrades. Antares made a similar point.
We're talking about v1.1 generally here. Maybe this discussion belongs on another thread.
Just keep in mind that they are not done with the full roll-out / upgrade path of F9V1.1. (F9R) They still need to incorporate those legs and that's not a small thing. And after that they'll start 2nd stage re-design for boost back. Point being that, although it seems they are over the proverbial hump with 1.1, I do not get the sense they'll be slowing down upgrades. However, they have probably bought themselves enough time and stability to do so in a less disruptive way even if they do decide to radically alter F9 again within the next few years. Which I think they will. But by that time, they'll be able to cycle in a new design without disrupting their current manifest. IMO.
They might choose not to attempt recovery of the second stage.
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#688
by
Lars_J
on 23 Oct, 2013 21:28
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And after that they'll start 2nd stage re-design for boost back.
The 2nd stage will not be doing any boost back to the launch site. Since it will be doing at least one orbit it would be boost
forward to the launch site.
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#689
by
rcoppola
on 23 Oct, 2013 21:36
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And after that they'll start 2nd stage re-design for boost back.
The 2nd stage will not be doing any boost back to the launch site. Since it will be doing at least one orbit it would be boost forward to the launch site.
Ha, ha, very good.
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#690
by
rcoppola
on 23 Oct, 2013 21:52
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They might choose not to attempt recovery of the second stage.
Perhaps. I think they will certainly focus on fully implementing 1st stage return and Cargo Dragon V2 first. But I fully suspect they will transition into 2nd stage return after. Perhaps sometime in late 2014 after they have completed some pad abort tests using the Super Dracos on Crewed Dragon. As I believe they will use the same configuration on a redesigned 2nd stage. It fits with their philosophy of using common systems. Ok, off topic...
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#691
by
RonM
on 23 Oct, 2013 22:00
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They might choose not to attempt recovery of the second stage.
Perhaps. I think they will certainly focus on fully implementing 1st stage return and Cargo Dragon V2 first. But I fully suspect they will transition into 2nd stage return after. Perhaps sometime in late 2014 after they have completed some pad abort tests using the Super Dracos on Crewed Dragon. As I believe they will use the same configuration on a redesigned 2nd stage. It fits with their philosophy of using common systems. Ok, off topic...
With all the modifications required for the 2nd stage to be reusable, it might not be economically viable. It could be cheaper to launch a new one each time.
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#692
by
Silmfeanor
on 23 Oct, 2013 22:22
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Can you please stop discussing those subjects here? this is the CASSIOPE general discussion, not future spacex plans for reuse.
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#693
by
ugordan
on 01 Nov, 2013 12:07
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I wonder if this is showing MVac throttling down near the end of the burn? It doesn't seem to me to be related to camera exposure variation as seen earlier in the burn. Once the bright Earth exited the frame, nozzle glow was roughly constant between T+8:00 and T+8:30 and then it starts slowly dropping off.
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#694
by
Pete
on 07 Nov, 2013 10:49
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I wonder if this is showing MVac throttling down near the end of the burn? It doesn't seem to me to be related to camera exposure variation as seen earlier in the burn. Once the bright Earth exited the frame, nozzle glow was roughly constant between T+8:00 and T+8:30 and then it starts slowly dropping off.
Its actually dimming a lot more than the eyeball sees, towards the end.
Note how the apparent illumination level of the structure is rapidly brightening, while the nozzle seems to dim just a bit. That nozzle is actually dimming a lot faster, but the camera is adjusting its exposure to mostly compensate.
Cause.. Throttling? Mixture change? Both?
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#695
by
hrissan
on 07 Nov, 2013 13:30
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I wonder if this is showing MVac throttling down near the end of the burn? It doesn't seem to me to be related to camera exposure variation as seen earlier in the burn. Once the bright Earth exited the frame, nozzle glow was roughly constant between T+8:00 and T+8:30 and then it starts slowly dropping off.
Its actually dimming a lot more than the eyeball sees, towards the end.
Note how the apparent illumination level of the structure is rapidly brightening, while the nozzle seems to dim just a bit. That nozzle is actually dimming a lot faster, but the camera is adjusting its exposure to mostly compensate.
Cause.. Throttling? Mixture change? Both?
I'd look not on the brightness, but on the nozzle color.
There should not be mixture change, so most likely throttling.
http://en.wikipedia.org/wiki/File:Blackbody-colours-vertical.svgThe moment the nozzle color changes is the moment where the total vehicle mass multiplied by maximum allowed acceleration equals Merlin 1DVac thrust.
People with sims would be glad for the data point for model calibration.
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#696
by
aero
on 16 Dec, 2013 22:48
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Does anyone know what the actual payload mass was for the Cassiope launch? what was it?
If not, I've searched and found the satellite masses but not the mass of any ancillary parts.
Cassiope - 481 kg
CU Sat - 40.82 kg
DANDE - 50 kg
DOPACS - 4.5 kg
Does anyone know what the mass of the payload adapter? What was it?
I know the trajectory of the first stage up to MECO pretty well from repeatedly viewing the launch (available on livestream), pausing and recording the data as it is given. Using this stage 1 trajectory I conclude that the F9.1 could not reach LEO with 13,150 kg though it can with other trajectories. I'm trying to simulate the boost-back so knowing the payload would help determine the fuel available for that function.
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#697
by
Lars_J
on 16 Dec, 2013 23:06
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Using this stage 1 trajectory I conclude that the F9.1 could not reach LEO with 13,150 kg though it can with other trajectories.
How did you reach that conclusion, given the lack of specifics about the upper stage performance?
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#698
by
aero
on 17 Dec, 2013 03:48
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Using this stage 1 trajectory I conclude that the F9.1 could not reach LEO with 13,150 kg though it can with other trajectories.
How did you reach that conclusion, given the lack of specifics about the upper stage performance?
You're right, my data is weak. I integrated the stage 2 flight from staging to, or toward orbit at 200 km altitude and 7.7803 km/s. But as you point out, the key is the stage 2 data, propellant and Isp. I used 88,500 kg of propellant which is based on 375 seconds of burn time for the Merlin D Vac with an Isp of 340 seconds and thrust of 801 kN. I did try higher Isp values and at Isp = 346 it could (probably) make orbit but then I'd need to look more closely at the prop load.
S 2 dry = 4.7 or 6 tonnes (same source, different dates) and 2 tonnes for the fairing.
Reasonable perturbations of the inputs don't make orbit as I think (IMO) Isp of 346 is high for a kerlox engine even with the huge nozzle in vacuum. Of course I could be wrong. If you have some supportable conjecture as to the input values, I'd run them time permitting, to see where it goes.
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#699
by
edkyle99
on 17 Dec, 2013 04:07
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Does anyone know what the actual payload mass was for the Cassiope launch? what was it?
If not, I've searched and found the satellite masses but not the mass of any ancillary parts.
Cassiope - 481 kg
CU Sat - 40.82 kg
DANDE - 50 kg
DOPACS - 4.5 kg
Does anyone know what the mass of the payload adapter? What was it?
I know the trajectory of the first stage up to MECO pretty well from repeatedly viewing the launch (available on livestream), pausing and recording the data as it is given. Using this stage 1 trajectory I conclude that the F9.1 could not reach LEO with 13,150 kg though it can with other trajectories. I'm trying to simulate the boost-back so knowing the payload would help determine the fuel available for that function.
Cassiope went to a 300 x 1,500 km x 80 deg orbit from Vandenberg AFB. The 13.15 tonne figure is given for a 185 km x 28.5 deg orbit from Cape Canaveral, where extra delta-v is provided by the Earth's rotation. Payload from Vandenberg toward a near-polar orbit will be much less - and the higher altitude will take away even more lifting capability. Falcon 9 v1.1 is probably only able to lift 9 tonnes or less to the Cassiope orbit, assuming that the advertised capabilities are accurate.
- Ed Kyle
