SpaceX (general discussion)

[quellish]

Am I missing something? Soft landing a reusable first stage seems like a rather big deal, and yet this is the first time I have heard SpaceX actually accomplished this. Kinda odd that it hasn't been plastered all over the usual news rags.

It is strange to think that if they had just re-calibrated expectations on the delta clipper and made it a "first stage", we would have been here long ago....

Delta Clipper was originally funded by SDIO (through the SSRT program) to be a technology demonstrator for a reusable first stage for launching ballistic missile targets.

 

[Orionblamblam]

Kinda odd that it hasn't been plastered all over the usual news rags.

Not really. SpaceX success features a few things that work *against* it being newsworthy:
1) It's an example of American exceptionalism/ingenuity
B ) It's an example of private enterprise succeeding where government has not
iii) It's a success for the One Percent
Δ) It's not a success for the likes of Gubmint-Entrenched MegaBloatCorps
∞) No Kardashian involvement

 

[sublight_]

Am I missing something? Soft landing a reusable first stage seems like a rather big deal, and yet this is the first time I have heard SpaceX actually accomplished this. Kinda odd that it hasn't been plastered all over the usual news rags.

It is strange to think that if they had just re-calibrated expectations on the delta clipper and made it a "first stage", we would have been here long ago....

Delta Clipper was originally funded by SDIO (through the SSRT program) to be a technology demonstrator for a reusable first stage for launching ballistic missile targets.

Jerry Pournelle said his original idea for the Delta Clipper was a low cost Single-Stage-To-Orbit spacecraft.

 

[Machdiamond]

In my opinion these sea landing trials don't make the news yet because the unspecialized media fails to grasp the historical significance and engineering feat that they represent.
This will change when the first landings will occur at Cape Canaveral (or some other place).

 

[Dragon029]

Am I missing something? Soft landing a reusable first stage seems like a rather big deal, and yet this is the first time I have heard SpaceX actually accomplished this.

Minor correction here, but this is now the second time they've successfully done a soft landing; the only issue is that last time the video was so terrible (either an error with the camera / recording, or a poor feed back to base) that if SpaceX hadn't said it worked, you wouldn't have been able to tell. The new video isn't that great either due to frost (which might be part of why the media hasn't covered the story), but it was still far better than the last video and will get better later in time.

Expect the barge landing to get far more exposure.

 

[flanker]

Am I missing something? Soft landing a reusable first stage seems like a rather big deal, and yet this is the first time I have heard SpaceX actually accomplished this. Kinda odd that it hasn't been plastered all over the usual news rags.

It is historic and huge deal indeed, and it is second time, first time was with CRS-3 rocket. First stage is about 70% of the rockets costs. And that is purely economics, never mind the awesomesause of bringing back first stage from about 100 km height and mach 8 or so down to 0 m/s.

Minor correction here, but this is now the second time they've successfully done a soft landing; the only issue is that last time the video was so terrible (either an error with the camera / recording, or a poor feed back to base) that if SpaceX hadn't said it worked, you wouldn't have been able to tell. The new video isn't that great either due to frost (which might be part of why the media hasn't covered the story), but it was still far better than the last video and will get better later in time.

Ahem, i guess you havent seen the crowd-sourced fixed one.

In my opinion these sea landing trials don't make the news yet because the unspecialized media fails to grasp the historical significance and engineering feat that they represent.
This will change when the first landings will occur at Cape Canaveral (or some other place).

Agreed.

 

[Dragon029]

Minor correction here, but this is now the second time they've successfully done a soft landing; the only issue is that last time the video was so terrible (either an error with the camera / recording, or a poor feed back to base) that if SpaceX hadn't said it worked, you wouldn't have been able to tell. The new video isn't that great either due to frost (which might be part of why the media hasn't covered the story), but it was still far better than the last video and will get better later in time.

Ahem, i guess you havent seen the crowd-sourced fixed one.

I saw it; and it's attached here for others:

https://www.youtube.com/watch?v=er66BActC4E

But I don't think that many news companies would run with that kind of footage; you can tell that the rocket fires and that there's steam, but you can't tell what speed it touches down at. Coupled with the fact that much of the public won't know who SpaceX is (technologically / financially & in terms of their view on space travel), you could expect people to doubt the story, especially considering that the rocket was destroyed before they could recover it.

 

[flanker]

Eh, no, that is not the video. The one you posted was fixed by SpaceX themself as much as they could/had time to.

I will repeat, crowd sourced video. It was a huge task:

http://forum.nasaspaceflight.com/index.php?topic=34597.0

And the final video:

https://www.youtube.com/watch?v=CjZ33C9JZTM

 

[Dragon029]

Ah, I'd never seen or heard about that one.

 

[fredymac]

Picture of the landing attempt on the barge from the last Spacex Dragon launch.
According to Musk, grid fins ran out of gas and folded up, engines tried to compensate and failed and then they too ran out. Next attempt will add more fuel reserves.
This is actually a better "fail" than I had imagined. I was thinking "world record JDAM drop" but this is a pretty good first try.

 

[Dragon029]

And here's the video of it's rapid unscheduled disassembly ;D

Contrary to what you'd expect, I'm now more confident in their next attempt after watching that.

 

[Bill Walker]

The simple fact that they hit the barge, in the dark, is a major accomplishment. I look forward to the next attempt.

 

[Demon Lord Razgriz]

Looks to me the rocket thought it was an F-14 landing on the deck of a carrier! XD

 

[Michel Van]

https://www.youtube.com/watch?v=uBfhmXj0rYo


it came close yes, BUT
to fast and wrong angle and it look like the flight computer try compensate it to late

 

[fredymac]

Picture of the first stage booster re-entry from Wednesday's launch. Doesn't say how high up at this point but I am guessing it was fairly low. The booster wound up maintaining vertical orientation before finally ditching into the water. Rough seas prevented a barge landing attempt.
On the video of the launch itself, there were clear images of the first stage booster firing its' vernier rockets to separate and orient the stage showing a controlled separation and attitude control rather than just a toss off.

 

[flanker]

Picture of the first stage booster re-entry from Wednesday's launch. Doesn't say how high up at this point but I am guessing it was fairly low. The booster wound up maintaining vertical orientation before finally ditching into the water. Rough seas prevented a barge landing attempt.
On the video of the launch itself, there were clear images of the first stage booster firing its' vernier rockets to separate and orient the stage showing a controlled separation and attitude control rather than just a toss off.

Re-entry burn starts at ~70km and ends at ~40km. So not low at all. And camera work + weather was exceptional for the DSCOVR launch.

 

[fredymac]

Picture of the first stage booster re-entry from Wednesday's launch. Doesn't say how high up at this point but I am guessing it was fairly low. The booster wound up maintaining vertical orientation before finally ditching into the water. Rough seas prevented a barge landing attempt.
On the video of the launch itself, there were clear images of the first stage booster firing its' vernier rockets to separate and orient the stage showing a controlled separation and attitude control rather than just a toss off.

Re-entry burn starts at ~70km and ends at ~40km. So not low at all. And camera work + weather was exceptional for the DSCOVR launch.

You are correct about the re-entry burn altitude. In fact, you can see grid fin deployment right after separation in the video. However, there is a second landing burn and I mistook the photo for that.

Regarding weather, here is the statement from the SpacEx website:

While extreme weather prevented SpaceX from attempting to recover the first stage, data shows the first stage successfully soft landed in the Atlantic Ocean within 10 meters of its target. The vehicle was nicely vertical and the data captured during this test suggests a high probability of being able to land the stage on the drone ship in better weather

Weather at the launch site was great (as evidenced by the clarity of the separation images). Weather at the landing location out at sea was not.


Note 3:50 time mark

http://www.youtube.com/watch?v=zkvw56LqUJ4&feature=player_embedded

 

[flanker]

In fact, you can see grid fin deployment right after separation in the video. However, there is a second landing burn and I mistook the photo for that.

Hmm, no. What you see in the video are the N2 RCS. Gridfind deployment happens some minutes after MECO1 and it happens *together* with re-entry burn.

In the case of DSCOVR launch: After MECO1 S1 continues to travel upwards to peak altitude of 130-140 km. Then it starts to fall downwards and re-entry burn starts at ~70km, at which point gridfins deploy. The last burn is the landing burn which starts around 2km above surface so indeed, fairly low.

Now in previous cases they did a boostback burn ~30seconds after peak altitude. With DSCOVR there was no boostback.

Also to be picky there is no "second landing burn" . There is a boostback, re-entry burn and a landing burn. Calling re-entry burn "first landing burn" so to speak is not accurate, so imho one should stick to boostback, re-entry, landing.

 

[fredymac]

What are these? They show up at 3:50-3:51 and weren't there until then. They are not rocket plumes.

 

[TomS]

I think you're looking at exhaust from the cold gas thrusters on the first stage. They push the first stage clear of the second stage exhaust plume and then pitch it around to an engine-first attitude for the boost-back and retro burns.

 

[flanker]

Indeed, these are some sort of thrusters artifacts. For one thing we know for sure they don't deploy til re-entry and secondly they are tiny compared to S1. One would never be able to see them 100km+ up and significant downrange.

 

[fredymac]

Well you may be right. However, looking at 3:46 now I think I see the same white spots but with much reduced size/brightness which correlates to stowed/deployed fins. However, this is arguing over fuzz. Unless/until a rocket cam video is released I can't assert anything more than speculation.

 

[Machdiamond]

The fins are firmly stowed at that time.
No need for a rocket cam or speculate. If you are interested to follow this more closely, I recommend you check the forum at nasaspaceflight.com.
There are sections dedicated to SpaceX with highly knowledgeable participants, some of whom are actually working on the thing.
--Luc

 

[flanker]

Well you may be right. However, looking at 3:46 now I think I see the same white spots but with much reduced size/brightness which correlates to stowed/deployed fins. However, this is arguing over fuzz. Unless/until a rocket cam video is released I can't assert anything more than speculation.

Hydraulics are usually closed, but that adds mass vs short acting open systems. F9 fins only work for 4 mins. We were ~10% off.

- Elon Musk.

It takes longer than 4 min from MECO1 to landing. IE they deploy at a later point.

 

[TomS]

The timeline below says that the grid-fins deploy just after T+3 minutes. Stage separation was at T+2:48, so the fins should come out no earlier than 12 seconds after the staging.

http://www.spaceflight101.com/dscovr-mission-updates.html

 

[flanker]

Sigh. And that is wrong because:

a - There is zero logical reason to use them then
b - Elon Musk said nope.
c - There is no source for that claim

 

[Grey Havoc]

http://science.slashdot.org/story/15/03/02/1251205/spacex-falcon-9-launches-dual-satellite-mission

 

[fredymac]

Well another landing attempt. Spacex twitter says first stage landed on drone ship but came down too hard and didn't survive. Hopefully they will release a video. Even in failure they will learn so the next try should go better especially if they collected telemetry from the vehicle flight control system.

 

[Deino]

Well another landing attempt. Spacex twitter says first stage landed on drone ship but came down too hard and didn't survive. Hopefully they will release a video. Even in failure they will learn so the next try should go better especially if they collected telemetry from the vehicle flight control system.

Not exactly ...

Looks like Falcon landed fine, but excess lateral velocity caused it to tip over post landing

https://twitter.com/elonmusk/status/588082574183903232

 

[Michel Van]

first video about the landing attempt

https://www.youtube.com/watch?v=FVpaDT-OX6Q&spfreload=10

 

[fredymac]

Well another landing attempt. Spacex twitter says first stage landed on drone ship but came down too hard and didn't survive. Hopefully they will release a video. Even in failure they will learn so the next try should go better especially if they collected telemetry from the vehicle flight control system.

Not exactly ...

Looks like Falcon landed fine, but excess lateral velocity caused it to tip over post landing

https://twitter.com/elonmusk/status/588082574183903232

Benefit of a later posting. Here is what I saw:

"Ascent successful. Dragon enroute to Space Station. Rocket landed on droneship, but too hard for survival."

Later posts then added the video and additional commentary.

Looks like they are getting close. They need to fine tune lateral positioning higher up so they don't have to do those corrections at the last moment.

 

[TomS]

Might be easier if they weren't trying to hit a moving target.

 

[sferrin]

Looks like it was still oscillating quite a bit at touchdown.

 

[sferrin]

Might be easier if they weren't trying to hit a moving target.

Are you saying the drone is under way rather than station keeping in one spot?

 

[flanker]

Might be easier if they weren't trying to hit a moving target.

And why do you think the barge was moving? There were barely any wind and barely and waves. ~0.9m waves and ~6m/s winds. It is supposed to hold a position and it held it just fine. There was a small issue with control lag;

Looks like the issue was stiction in the biprop throttle valve, resulting in control system phase lag. Should be easy to fix.

A still pic;

 

[TomS]

"Stationkeeping" isn't stationary -- typical dynamic positioning keeps the platform within is a few meters of its target. The barge is moving around a bit to maintain station, and it's heaving and pitching a bit due to wave action. All of that movement adds complexity to the landing task. It's not insurmountable, but it's a set of factors that would not be at play in the original Grasshopper test vehicle.

 

[flanker]

...and it still has nothing to do with this. If this particular test was on land chances are it would have been the same outcome, assuming that it tipped over this time because of "overcorrection" due to sticky valve rather than stepping outside of the barge with a leg or two.

 

[Bill Walker]

The scale of the movement seen in the video is way more than anything required for platform movement. The slow oscillatory movement of the flight vehicle is classical performance with large phase lag somewhere in the control loop. A sticky control valve would indeed produce what we see here.

 

[TomS]

Fair enough. I wasn't trying to say that this failure was due to platform movement, but it does seem to add (in general) an extra layer of complexity to an already complex problem.

 

[sferrin]

Fair enough. I wasn't trying to say that this failure was due to platform movement, but it does seem to add (in general) an extra layer of complexity to an already complex problem.

Obviously SpaceX thinks the benefits outweigh the issue of complexity.