Blue Origin Thread (merged)

[sevenperforce]

21 minutes ago, PB666 said:

That's a ball-sy landing. The only reason they would care about gravity losses at that point is if they were fuel strapped.

Which they were.

The one-engine landing burn was 90 seconds; this landing burn was 30 seconds. Assuming the same terminal velocity (which is close to accurate), that's just under 600 m/s of gravity drag saved.

[PB666]

3 hours ago, CptRichardson said:

 

Lighter payload, I believe. Plus less going easy on the rocket and punching the throttle through to 'Plaid' on the dial.

It shows to be about 0.2g (1.5%) more powerful, if we took of all the payload the difference between the CRS-8 payload and the S1-S2 is 0.6%. Not possibly explained by lighter payload, must be at least one percent more thrust if you go by the 4696 presented above for the payload then they increased thrust by 2%. I measured this at the 800kmh powerdown, which is apparent for both rockets.

[codepoet]

56 minutes ago, sevenperforce said:

Which they were.

The one-engine landing burn was 90 seconds; this landing burn was 30 seconds. Assuming the same terminal velocity (which is close to accurate), that's just under 600 m/s of gravity drag saved.

I picked up from here that is was a 6 second landing burn - which would be extraordinary. Is that a typo?

[sevenperforce]

24 minutes ago, codepoet said:

I picked up from here that is was a 6 second landing burn - which would be extraordinary. Is that a typo?

I imagine it has to be. The rocket is supersonic when the landing burn begins. The maximum acceleration for a nearly-empty stage on a three-engine suicide burn is about 5 gees; subtract the 1 gee of gravity and you get just 4 gees or 39 m/s². Six seconds of that will only earn you 235 m/s of dV, which is around 70% of the speed of sound.

[KerbonautInTraining]

56 minutes ago, sevenperforce said:

I imagine it has to be. The rocket is supersonic when the landing burn begins. The maximum acceleration for a nearly-empty stage on a three-engine suicide burn is about 5 gees; subtract the 1 gee of gravity and you get just 4 gees or 39 m/s². Six seconds of that will only earn you 235 m/s of dV, which is around 70% of the speed of sound.

Drag is well above 1 G just before the landing burn, so I imagine that helps quite a bit.

[Rakaydos]

1 hour ago, sevenperforce said:

I imagine it has to be. The rocket is supersonic when the landing burn begins. The maximum acceleration for a nearly-empty stage on a three-engine suicide burn is about 5 gees; subtract the 1 gee of gravity and you get just 4 gees or 39 m/s². Six seconds of that will only earn you 235 m/s of dV, which is around 70% of the speed of sound.

Can you source those numbers? if 3 engines at full is 5g, then 1 engine at 60% throttle would be 1g, capable of hovering, something the Facon 9 explicitly cannot do.

[PB666]

8 minutes ago, Rakaydos said:

Can you source those numbers? if 3 engines at full is 5g, then 1 engine at 60% throttle would be 1g, capable of hovering, something the Facon 9 explicitly cannot do.

If it had 1g of thrust it would slow down rather quickly because the plume would act to increase drag, it basically a curved structure with lots of folds, anything above mach 0.5 close to sea level you are going a huge pick up in drag as the engines fire. The least it can do is around 1.2g. You can go from 70-100% then 2 @70 (140) to full power. When you are on the deck the engines have to go full powerdown immediately. So technically the craft cannot hoover. However, those number may not be valid because ????? is full thrust is on the falcon-9.

His number on the 0.7 mach sound pretty correct. Terminal velocity for a human is 50 m/s and the Mach drag particularly on the engine facing return is going to kick in around 0.8Mach, so its got major drag and not much weight.

I suspect that they have the retro tuned to about 85% thrust which means they can throttle up or down to control descent. They are not doing a kerbalesce suicide burn.

[codepoet]

From the chatter on the technical broadcast we can approximate:

Stage 1 is trans-sonic 7:41 (does this mean dropping below Mach 1 due to drag?
Land burn starts: 8:26
Legs deploy: 8:34
Engine cutoff: 8:40 (based on the images, not sound, but image and sound  is out of sync as can be seen by the fairing deploy being called before it happens)

So that gives a maximum landing burn time of approx 14 seconds, perhaps a bit less (10 seconds?) due to a delay in the pictures compared with the chatter. If it can't hover on one engine, then a single engine is giving it more than 9.8m/s2 so three engines must be giving it more than 29.4m/s2. However, it is subject to acceleration due to gravity, so it is certainly getting more than 19.6m/s2. For ten seconds the landing burn is taking at least 196m/s off the velocity, probably much more, I guess those figures are all in the right ball park.

Is there any other more accurate source of data for the first stage during landing?

Looking at the CRS8 technical yields:

Trans-sonic - 8:00
Landing burn - 8;07
legs - 8:34
MECO - 8:40

So for CRS8 that is a landing burn for 33s (29s accounting for a four second picture delay) which is three times the duration of the JCSAT14 3 engine landing burn which is exactly what we would have expected.

I can't explain why the later&harder landing burn results in a longer time from trans-sonic to MECO - you would expect it to be less. Could it be because the JCSAT14 mission has it coming in with more horizontal velocity? I am not sure that makes any sense. 

[Kryten]

9 hours ago, StrandedonEarth said:

Probably not much to see in the dark, and then the glare from the rocket engine. 

Which begs the question, if it's a GTO flight, then why did they need to launch in the middle of the night?

GTO sats aren't designed for long periods of eclipse, so they're launched at times when they'll have sunlight between separation and apogee burn; given how far downrange separation is, that usually means night time at the launch site.

[wumpus]

2 hours ago, PB666 said:

I suspect that they have the retro tuned to about 85% thrust which means they can throttle up or down to control descent. They are not doing a kerbalesce suicide burn.

A single engine can't be reduced such that TWR<1.0 and they were using at least three times that (three engine burn).  It most certainly was a kerbalesque suicide burn, much more than usual (unless you are comparing to only Jeb at the controls.  Jeb would have all nine lit at 100%).

I have to wonder how accurate the  timing is in cutting the engines.  It has to be good enough to cut out just before landing, so presumably you could cut out the side engines just before landing and land on the center engine (without imparting too much torque).  I suspect they already checked that and the torque is too high: even a few degrees off would make it easy to miss the barge.  Still, cutting two of the engines with a second or two left on the center should make the timing a lot easier.

Another question about the re-entry I had (and probably can only be answered directly from spacex) is the vector of the entry burn.  They had a (short) entry burn, it turned on then off.  From the numbers given by the announcers, it was roughly ~300 m/s (2.3km/s on screen when MECO was called, announcers claimed 2km/s re-entry speed).  I'd be curious if the re-entry burn wasn't quite vertical and the goal was to add *more* horizontal speed.  In KSP, low level re-entry is all about having enough atmosphere to slow you down, but KSP has its 1/10th scale planet and other silliness.  But maybe letting the vertical speed get cut by making it deal with a higher square velocity in the hypotenuse might carry over into real life.

[PB666]

2 hours ago, codepoet said:

From the chatter on the technical broadcast we can approximate:

Stage 1 is trans-sonic 7:41 (does this mean dropping below Mach 1 due to drag?
Land burn starts: 8:26
Legs deploy: 8:34
Engine cutoff: 8:40 (based on the images, not sound, but image and sound  is out of sync as can be seen by the fairing deploy being called before it happens)

So that gives a maximum landing burn time of approx 14 seconds, perhaps a bit less (10 seconds?) due to a delay in the pictures compared with the chatter. If it can't hover on one engine, then a single engine is giving it more than 9.8m/s2 so three engines must be giving it more than 29.4m/s2. However, it is subject to acceleration due to gravity, so it is certainly getting more than 19.6m/s2. For ten seconds the landing burn is taking at least 196m/s off the velocity, probably much more, I guess those figures are all in the right ball park.

Is there any other more accurate source of data for the first stage during landing?

Looking at the CRS8 technical yields:

Trans-sonic - 8:00
Landing burn - 8;07
legs - 8:34
MECO - 8:40

So for CRS8 that is a landing burn for 33s (29s accounting for a four second picture delay) which is three times the duration of the JCSAT14 3 engine landing burn which is exactly what we would have expected.

I can't explain why the later&harder landing burn results in a longer time from trans-sonic to MECO - you would expect it to be less. Could it be because the JCSAT14 mission has it coming in with more horizontal velocity? I am not sure that makes any sense. 

Not just horizontal it also carries greater verticle. Why don't we ask SpaceX to feed all thier telemetry here, lol. 

[YNM]

22 hours ago, Burning For New Frontiers said:

^^ ignore that, mobile reply problems.

 

 

Yet another great job, SpaceX ! So when is the scrap rocket going to fly again ?

[codepoet]

7 hours ago, wumpus said:

A single engine can't be reduced such that TWR<1.0 and they were using at least three times that (three engine burn).  It most certainly was a kerbalesque suicide burn, much more than usual (unless you are comparing to only Jeb at the controls.  Jeb would have all nine lit at 100%).

I have to wonder how accurate the  timing is in cutting the engines.  It has to be good enough to cut out just before landing, so presumably you could cut out the side engines just before landing and land on the center engine (without imparting too much torque).  I suspect they already checked that and the torque is too high: even a few degrees off would make it easy to miss the barge.  Still, cutting two of the engines with a second or two left on the center should make the timing a lot easier.

Another question about the re-entry I had (and probably can only be answered directly from spacex) is the vector of the entry burn.  They had a (short) entry burn, it turned on then off.  From the numbers given by the announcers, it was roughly ~300 m/s (2.3km/s on screen when MECO was called, announcers claimed 2km/s re-entry speed).  I'd be curious if the re-entry burn wasn't quite vertical and the goal was to add *more* horizontal speed.  In KSP, low level re-entry is all about having enough atmosphere to slow you down, but KSP has its 1/10th scale planet and other silliness.  But maybe letting the vertical speed get cut by making it deal with a higher square velocity in the hypotenuse might carry over into real life.

Here: 

Musk confirms that they did indeed cut two of the engines at then end of the landing burn and land on one. Also that the engines can now throttle down to 40%.

So if 40% of one engine is imparting >9.8m/s2 then three at full belt would be capable of giving at least 73.5m/s2. That could really take the edge off your velocity in a hurry.

[sojourner]

The hires images of the landed stage look pretty crispy.  I don't think this one will be flying again without some heavy refurbishment. I think that post landing fire did more damage to the engine bay than they would have liked.

Edited May 7, 2016 by sojourner

[CptRichardson]

Huh. They moved the next launch up by a month for the F9. Looks like we'll see how well an F9 can re-launch in 20 days. A Thaicom launch on may 26th a 1740 EST. Then we've got a Sat constellation launch in june from Canaveral (likely early june) followed shortly by a launch from vandenburg of cubesats by the OMGWTFBBQ scale, and a June 27th launch of CRS 9 to the ISS.

 

The next two months seem to have a 100% chance.. *puts on Adam Savage hat.* OF ENGINEERING.  I bet they'll probably design a proper protective shield to go between the engines of the first stage from now on after a bit more testing.

[Karriz]

Thaicom was already late May I think. No indication that it would be the first re-launch of a stage, they already have a stage for that mission anyways.

Edited May 7, 2016 by Karriz

[CptRichardson]

3 minutes ago, Karriz said:

Thaicom was already late May I think. No indication that it would be the first re-launch of a stage, they already have a stage for that mission anyways.

 

No, it got bumped forward from late june according to the launch schedule. Also, the site doesn't mention stuff about re-use period. They just give launch dates they know about.

Edited May 7, 2016 by CptRichardson

[CatastrophicFailure]

3 hours ago, sojourner said:

The hires images of the landed stage look pretty crispy.  I don't think this one will be flying again without some heavy refurbishment. I think that post landing fire did more damage to the engine bay than they would have liked.

What images? Linky plz??

[magnemoe]

9 minutes ago, CatastrophicFailure said:

What images? Linky plz??

The bells should handle the heat if decently designed but the bay could easy take damage, however sheet metal should be enough to protect here, the hot air as it fall trough the excaust of the brake then the back blast from the flame. 

[PB666]

3 hours ago, sojourner said:

The hires images of the landed stage look pretty crispy.  I don't think this one will be flying again without some heavy refurbishment. I think that post landing fire did more damage to the engine bay than they would have liked.

aestethics, nothing is cooler than an old beat up pickup truck. Get someone out there with a squeegee and clean out a swath thats says "Clean me!".

Better yet, get a tagger to spray paint a cartoon of the Tazmanian devil on the side, thats how you spiff up old frieght cars.

[sojourner]

1 hour ago, CatastrophicFailure said:

What images? Linky plz??

Here:

https://www.flickr.com/photos/spacex/

Yeah, I'm not talking about a little soot on the tankage, that engine bay looks toasted this time.

[CatastrophicFailure]

13 minutes ago, sojourner said:

Here:

https://www.flickr.com/photos/spacex/

Yeah, I'm not talking about a little soot on the tankage, that engine bay looks toasted this time.

Wow, yeah that does look pretty well done. Maybe even some heat discoloration on the landing legs. 

[KSK]

2 hours ago, PB666 said:

aestethics, nothing is cooler than an old beat up pickup truck. Get someone out there with a squeegee and clean out a swath thats says "Clean me!".

Better yet, get a tagger to spray paint a cartoon of the Tazmanian devil on the side, thats how you spiff up old frieght cars.

Nah - get the tagger to add a row of little barges - one for each recovery of that booster.

It did look pretty cooked but that's not terribly surprising given the landing profile. Hopefully it's only cosmetic and not a sign of anything more serious. If they do manage to start multiple re-flies of the same booster though, I expect that engine bay is going to look a bit toasted after the second or third re-entry.

[CptRichardson]

2 hours ago, KSK said:

Nah - get the tagger to add a row of little barges - one for each recovery of that booster.

It did look pretty cooked but that's not terribly surprising given the landing profile. Hopefully it's only cosmetic and not a sign of anything more serious. If they do manage to start multiple re-flies of the same booster though, I expect that engine bay is going to look a bit toasted after the second or third re-entry.

They're likely to actually begin armoring the engine bay to minimize the chance of fires or damage. Probably titanium or niobium sheets with an ablative ceramic layer atop for shielding. Not much, but enough to keep things from getting toasty.

[PB666]

4 hours ago, CptRichardson said:

They're likely to actually begin armoring the engine bay to minimize the chance of fires or damage. Probably titanium or niobium sheets with an ablative ceramic layer atop for shielding. Not much, but enough to keep things from getting toasty.

I think the heat is low density enough its not too much of a problem, the real stress is in flight, particularly around Mach 1.5, when the boundary layer basically passes the plume. I would think the bay is already pretty fire resistent given its a rocket engine.