Author Topic: BFR ASDS  (Read 11040 times)

Online Lars-J

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Re: BFR ASDS
« Reply #60 on: 11/03/2017 08:51 PM »
We've known about the requirement to splash a stage by moving out of the way ever since the first landing attempt - so it's not only a current feature, it's a primary one - and we've all seen what can happen after a bad  (non-emergency) landing.

The IIP is off the Landing Target until they are committed to the attempt.  The booster decides to try to hit the ASDS if things look good.  The ASDS doesn't decide to try to dodge the booster if things look bad.

Are you implying by that that they start off with the ASDS off-target and move it in if all is good??  ???

Better go read https://forum.nasaspaceflight.com/index.php?topic=39766.0 and especially http://forum.nasaspaceflight.com/index.php?topic=36326.0 again..
No, the barge doesn't move at all. The booster changes its landing target to the preset asds coords once it is happy that a safe landing can be attempted.

Right... This is determined when the landing burn starts. If the landing engine(s) starts, it will aim for the landing point. Otherwise the consensus is that it will continue in its trajectory and crash near it. The landing burn starts pretty high so it is able to do that.

Offline AC in NC

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Re: BFR ASDS
« Reply #61 on: 11/04/2017 02:33 AM »
The booster decides to try to hit the ASDS if things look good.

Are you implying by that that they start off with the ASDS off-target and move it in if all is good??  ???  Better go read ... [snip] ... again...

How could you POSSIBLY conceive that implication from what I wrote?

In pictures.  Please don't insist that this Land Based diagram doesn't mean anything with respect to ASDS landing profile.  The ASDS doesn't try to dodge the booster in a worst-case scenario anymore than LC-1 does.

« Last Edit: 11/04/2017 02:37 AM by AC in NC »

Offline yokem55

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Re: BFR ASDS
« Reply #62 on: 11/06/2017 04:20 AM »
We've known about the requirement to splash a stage by moving out of the way ever since the first landing attempt - so it's not only a current feature, it's a primary one - and we've all seen what can happen after a bad  (non-emergency) landing.

The IIP is off the Landing Target until they are committed to the attempt.  The booster decides to try to hit the ASDS if things look good.  The ASDS doesn't decide to try to dodge the booster if things look bad.

Are you implying by that that they start off with the ASDS off-target and move it in if all is good??  ???

Better go read https://forum.nasaspaceflight.com/index.php?topic=39766.0 and especially http://forum.nasaspaceflight.com/index.php?topic=36326.0 again..
No, the barge doesn't move at all. The booster changes its landing target to the preset asds coords once it is happy that a safe landing can be attempted.

Right... This is determined when the landing burn starts. If the landing engine(s) starts, it will aim for the landing point. Otherwise the consensus is that it will continue in its trajectory and crash near it. The landing burn starts pretty high so it is able to do that.
Except this didn't work with SES-9. My bet is that the 3-engine burn attempt didn't allow for enough time to retarget after knowing they had 3 good engines, so it was a committed attempt from the get go. When the engine(s?) failed the impact point was already on the ASDS and so poor OCISLY got Falcon-Punched at high speed.

Offline guckyfan

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Re: BFR ASDS
« Reply #63 on: 11/06/2017 07:36 AM »
Except this didn't work with SES-9. My bet is that the 3-engine burn attempt didn't allow for enough time to retarget after knowing they had 3 good engines, so it was a committed attempt from the get go. When the engine(s?) failed the impact point was already on the ASDS and so poor OCISLY got Falcon-Punched at high speed.

I see this event as SpaceX willing to risk damage to the ASDS to prove they can hit the target even under extreme conditions. Which would help getting approval for land landing.

Offline JamesH65

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Re: BFR ASDS
« Reply #64 on: 11/06/2017 11:22 AM »
We've known about the requirement to splash a stage by moving out of the way ever since the first landing attempt - so it's not only a current feature, it's a primary one - and we've all seen what can happen after a bad  (non-emergency) landing.

The IIP is off the Landing Target until they are committed to the attempt.  The booster decides to try to hit the ASDS if things look good.  The ASDS doesn't decide to try to dodge the booster if things look bad.

Are you implying by that that they start off with the ASDS off-target and move it in if all is good??  ???

Better go read https://forum.nasaspaceflight.com/index.php?topic=39766.0 and especially http://forum.nasaspaceflight.com/index.php?topic=36326.0 again..
No, the barge doesn't move at all. The booster changes its landing target to the preset asds coords once it is happy that a safe landing can be attempted.

Right... This is determined when the landing burn starts. If the landing engine(s) starts, it will aim for the landing point. Otherwise the consensus is that it will continue in its trajectory and crash near it. The landing burn starts pretty high so it is able to do that.
Except this didn't work with SES-9. My bet is that the 3-engine burn attempt didn't allow for enough time to retarget after knowing they had 3 good engines, so it was a committed attempt from the get go. When the engine(s?) failed the impact point was already on the ASDS and so poor OCISLY got Falcon-Punched at high speed.

Experimental landing. Has it happened since? Not that I am aware of. So the experiment lead to changes to stop is happening again. R&D.

The ASDS doesn't move.

Online envy887

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Re: BFR ASDS
« Reply #65 on: 11/06/2017 01:28 PM »
Right... This is determined when the landing burn starts. If the landing engine(s) starts, it will aim for the landing point. Otherwise the consensus is that it will continue in its trajectory and crash near it. The landing burn starts pretty high so it is able to do that.
Except this didn't work with SES-9. My bet is that the 3-engine burn attempt didn't allow for enough time to retarget after knowing they had 3 good engines, so it was a committed attempt from the get go. When the engine(s?) failed the impact point was already on the ASDS and so poor OCISLY got Falcon-Punched at high speed.

I thought the booster ran out of propellant on that attempt - which would happen after moving the impact point on target.

Offline AC in NC

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Re: BFR ASDS
« Reply #66 on: 11/06/2017 07:44 PM »
Except this didn't work with SES-9. My bet is that the 3-engine burn attempt didn't allow for enough time to retarget after knowing they had 3 good engines, so it was a committed attempt from the get go. When the engine(s?) failed the impact point was already on the ASDS and so poor OCISLY got Falcon-Punched at high speed.

Not sure what would lead one to believe that a 3-engine burn wouldn't allow enough time to retarget.  I don't think the details are public knowledge so I guess we're speculating either way, but I just don't know what suggests that the vertical distance involved in a 3-engine burn isn't plenty of room to retarget horizontally the necessary distance.


I see this event as SpaceX willing to risk damage to the ASDS to prove they can hit the target even under extreme conditions. Which would help getting approval for land landing.

SES-9 was after the first successful LZ-1 landing.


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