Author Topic: Landing the F9 V1.1 first stage  (Read 124253 times)

Offline Paper Kosmonaut

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Landing the F9 V1.1 first stage
« on: 01/10/2015 10:23 am »
Out of curiosity; Why don't SpaceX and NASA try and land the Falcon 9 first stage on land instead of on a barge? There must be enough unused space on land at the cape where even a mishap, like toppling over leading to an explosion at landing will be 'acceptable', without destroying equipment. In that case, trying to land the rocket on a barge bobbing at sea would not have been necessary. And it would have been better controllable, observable and manageable. What is the advantage of not doing this? Even the Antares explosion last year didn't cause that much damage to the pad that it wasn't repairable. So, without even a launch pad in the neighbourhood, what damage would a toppling F9 do on a more distant part of the Cape's premises?
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Offline NovaSilisko

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Re: Landing the F9 V1.1 first stage
« Reply #1 on: 01/10/2015 10:28 am »
It needs to be approved by the FAA (I think the FAA?) first. They need to be sure it won't overshoot and come to rest gently on top of a suburban home, for example.

The fact the stage hit the barge today is a big step toward being allowed to attempt a land landing though.

Offline eriblo

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Re: Landing the F9 V1.1 first stage
« Reply #2 on: 01/10/2015 11:22 am »
Remember that the landing accuracy (until today) was stated as +-10 km. There are quite a few people and expensive things within that radius from anywhere on the cape. From their intended landing site at LC-13 that includes more or less all of CCAFS, the KSC industrial complex as well as Port and Cape Canaveral.

Offline Hobbes-22

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Re: Landing the F9 V1.1 first stage
« Reply #3 on: 01/10/2015 11:57 am »
Landing on a barge downrange requires less delta-V than a return-to-launch-site trajectory. AIR, SpaceX have stated they need the barge anyway for missions where the payload is too large to afford an RTLS.

Offline Paper Kosmonaut

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Re: Landing the F9 V1.1 first stage
« Reply #4 on: 01/10/2015 01:50 pm »
Those are clear answers. I kind of knew about the Delta-V aspect of it all, that on case of the stage being far out at sea they'd need it anyway, but the landing area margins were new to me. Thanks for explaining.
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Offline Llian Rhydderch

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Re: Landing the F9 V1.1 first stage
« Reply #5 on: 01/10/2015 02:01 pm »
There are other threads that have discussed this for many months, including a lot of recent info.

I don't have the resources to find them just now, but hopefully we can get a pointer in here and then close this redundant thread.
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Offline llanitedave

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Re: Landing the F9 V1.1 first stage
« Reply #6 on: 01/10/2015 03:00 pm »
I wonder if some of those higher-inclination orbits might save fuel by boosting back to some sea island in Georgia rather than all the way back to the Cape...
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Offline nadreck

Re: Landing the F9 V1.1 first stage
« Reply #7 on: 01/10/2015 04:31 pm »
I do believe that barge landings will end up being the norm for Falcon 9 and Falcon Heavy central core recovery. The Falcon Heavy because it the core will travel much further (and have to slow from a much higher speed to be recovered at all) the Falcon 9 because the difference in performance between RTLS and the barge will be significant enough for a lot of cases to be either barge or discarding. That said, I am positive that they will at least demonstrate landing on land and return to launch site on the F9 and that the FH outer cores will routinely RTLS.
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Offline RonM

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Re: Landing the F9 V1.1 first stage
« Reply #8 on: 01/10/2015 04:49 pm »
I wonder if some of those higher-inclination orbits might save fuel by boosting back to some sea island in Georgia rather than all the way back to the Cape...

I don't know if there would be a good spot for a landing site on Georgia sea islands. They are either developed, national parks, states parks, or marshlands. Might be a good place for a platform just offshore. The water is shallow. A bridge connecting to a road onshore would be expensive, but if they refuel the stage and fly it back then they wouldn't need a bridge.

Offline sghill

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Re: Landing the F9 V1.1 first stage
« Reply #9 on: 01/10/2015 05:10 pm »
Those are clear answers. I kind of knew about the Delta-V aspect of it all, that on case of the stage being far out at sea they'd need it anyway, but the landing area margins were new to me. Thanks for explaining.

And there isn't really much unused land at the Cape that's not also right next to land that IS being used or protected.
« Last Edit: 01/10/2015 05:19 pm by sghill »
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Offline Elmar Moelzer

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Re: Landing the F9 V1.1 first stage
« Reply #10 on: 01/10/2015 05:30 pm »
I do believe that barge landings will end up being the norm for Falcon 9 and Falcon Heavy central core recovery.
F9 has enough performance for the missions it is meant for. The numbers on the website already factor in first stage reusability. I think barge landings will only be used for heavy GTO missions and the FH central core. Landing on a barge is higher risk and makes reusability slower/more expensive.

Offline guckyfan

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Re: Landing the F9 V1.1 first stage
« Reply #11 on: 01/10/2015 06:13 pm »
I do believe that barge landings will end up being the norm for Falcon 9 and Falcon Heavy central core recovery.
F9 has enough performance for the missions it is meant for. The numbers on the website already factor in first stage reusability. I think barge landings will only be used for heavy GTO missions and the FH central core. Landing on a barge is higher risk and makes reusability slower/more expensive.

Yes but there must be a range where landing the Falcon 9 first stage downrange makes the difference between using Falcon 9 R and needing Falcon Heavy or expending the Falcon 9 core. How frequent that may be we don't know but when the barge already exists it can be used for that purpose.


Offline Kabloona

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Re: Landing the F9 V1.1 first stage
« Reply #12 on: 01/10/2015 06:17 pm »
Out of curiosity; Why don't SpaceX and NASA try and land the Falcon 9 first stage on land instead of on a barge? There must be enough unused space on land at the cape where even a mishap, like toppling over leading to an explosion at landing will be 'acceptable', without destroying equipment.

There is such a place, it's the LC-13 complex and it is being developed for landings. There's a whole thread devoted to that topic here:

http://forum.nasaspaceflight.com/index.php?topic=36513.0

Offline macpacheco

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Re: Landing the F9 V1.1 first stage
« Reply #13 on: 01/14/2015 05:21 pm »
If the landing accuracy is +-10Km, how about positioning the ASDS 30Km from the cape, demonstrating a strong boostback. This would be specially interesting since the DSCOVR launch appears to go southbound. If they shoot for a similar 100+ Km position from the cape, that's over 50Km south of the cape, quite a cruise from JAX. Might take 3-4 days to go back and forth from port.
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Offline AncientU

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Re: Landing the F9 V1.1 first stage
« Reply #14 on: 01/14/2015 05:29 pm »
I suspect that the boostback for next flight will cover more of the ground back to launch site.  Two or three demonstrated pinpoint (barge sized accuracy) returns will do it for FAA, I think, so increasing the boostback and seeing no loss of accuracy is last unproven parameter (other than sticking the landing which should not matter to FAA).
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Offline mme

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Re: Landing the F9 V1.1 first stage
« Reply #15 on: 01/14/2015 05:36 pm »
Out of curiosity; Why don't SpaceX and NASA try and land the Falcon 9 first stage on land instead of on a barge? There must be enough unused space on land at the cape where even a mishap, like toppling over leading to an explosion at landing will be 'acceptable', without destroying equipment. In that case, trying to land the rocket on a barge bobbing at sea would not have been necessary. And it would have been better controllable, observable and manageable. What is the advantage of not doing this? Even the Antares explosion last year didn't cause that much damage to the pad that it wasn't repairable. So, without even a launch pad in the neighbourhood, what damage would a toppling F9 do on a more distant part of the Cape's premises?

1. KSC and Range Safety (rightfully) need evidence that the F9 is accurate enough that there is no risk to assets nor human life.
2. SpaceX likely prefers doing their experiments that can end in fireballs away from the public view.
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Offline Dudely

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Re: Landing the F9 V1.1 first stage
« Reply #16 on: 01/14/2015 05:56 pm »
I suspect that the boostback for next flight will cover more of the ground back to launch site.  Two or three demonstrated pinpoint (barge sized accuracy) returns will do it for FAA, I think, so increasing the boostback and seeing no loss of accuracy is last unproven parameter (other than sticking the landing which should not matter to FAA).

Permits show that the barge will be FURTHER from shore than on CRS-5. . . 600km+

Offline douglas100

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Re: Landing the F9 V1.1 first stage
« Reply #17 on: 01/14/2015 08:41 pm »
I suspect that the boostback for next flight will cover more of the ground back to launch site.  Two or three demonstrated pinpoint (barge sized accuracy) returns will do it for FAA, I think, so increasing the boostback and seeing no loss of accuracy is last unproven parameter (other than sticking the landing which should not matter to FAA).

Permits show that the barge will be FURTHER from shore than on CRS-5. . . 600km+

Yes, but will it be further downrange than CRS-5?
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Offline Kabloona

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Re: Landing the F9 V1.1 first stage
« Reply #18 on: 01/14/2015 08:58 pm »
I suspect that the boostback for next flight will cover more of the ground back to launch site.  Two or three demonstrated pinpoint (barge sized accuracy) returns will do it for FAA, I think, so increasing the boostback and seeing no loss of accuracy is last unproven parameter (other than sticking the landing which should not matter to FAA).

Permits show that the barge will be FURTHER from shore than on CRS-5. . . 600km+

Yes, but will it be further downrange than CRS-5?

Yes, significantly further downrange. Thanks to Darga's excellent map (click on the map menu to enable CRS-5 waypoint display), we can find the following distances for the barge:

CRS-5: 353 km downrange
DSCOVER: 646 km downrange

http://forum.nasaspaceflight.com/index.php?topic=30543.msg1316189#msg1316189
« Last Edit: 01/14/2015 09:00 pm by Kabloona »

Offline The Amazing Catstronaut

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Re: Landing the F9 V1.1 first stage
« Reply #19 on: 01/14/2015 09:19 pm »

Yes, significantly further downrange. Thanks to Darga's excellent map (click on the map menu to enable CRS-5 waypoint display), we can find the following distances for the barge:

CRS-5: 353 km downrange
DSCOVER: 646 km downrange

http://forum.nasaspaceflight.com/index.php?topic=30543.msg1316189#msg1316189

Yeah, that's quite the difference.

Does anybody know of (or rather, have an educated guess at) how varying trajectories alter the prerequisite positioning of the Barge for first stage return? Or would the varying lengths of the boostback and re-entry burns make this estimate overtly tricky/too inaccurate to be of use?  :o

What are the min/max distance variations in downrange barge positioning we could potentially see for future F9 first stage returns?

Edit: Attempted clarity.

« Last Edit: 01/14/2015 09:22 pm by The Amazing Catstronaut »
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