PerVG
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Re: SpaceX - Tests, Launches, Developments

Wed Feb 07, 2018 9:10 am

Trololzilla wrote:
Watching the live stream of the post-launch news conference, Musk has confirmed that the core did indeed not land safely. As far as I could hear (the audio quality was a bit meh to start out with), it ran out of propellant and hit the water at 300 MPH


I understood it run out not of propellant but of TEB, the pyrophoric igniter.
 
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SeJoWa
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Re: SpaceX - Tests, Launches, Developments

Wed Feb 07, 2018 9:19 am

alberchico wrote:
SeJoWa wrote:
Elon Musk - total investment in FH probably more than half a billion. They thought of canceling it several times.


Isn't that relatively cheap for a rocket of that size ???


Absolutely. But SpaceX paid it out of company funds.
Also of note, per Elon Musk, the launch costs are not much higher than for a normal Falcon 9.
[Once all three rockets return... as the middle one is a strengthened custom build.]
 
ZaphodHarkonnen
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Re: SpaceX - Tests, Launches, Developments

Wed Feb 07, 2018 9:29 am

PerVG wrote:
Trololzilla wrote:
Watching the live stream of the post-launch news conference, Musk has confirmed that the core did indeed not land safely. As far as I could hear (the audio quality was a bit meh to start out with), it ran out of propellant and hit the water at 300 MPH


I understood it run out not of propellant but of TEB, the pyrophoric igniter.


That would explain only one firing. As running out of fuel would make more sense of all 3 firing then finishing a burn early.

Either way, a bloody impressive showing by the SpaceX team. Huge technical achievement and stupid dick waving all in one launch. :p
 
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KarelXWB
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Re: SpaceX - Tests, Launches, Developments

Wed Feb 07, 2018 9:51 am

With such a small payload, how can it run out of fuel?
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parapente
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Re: SpaceX - Tests, Launches, Developments

Wed Feb 07, 2018 10:07 am

Congratulations to Spacex.Of course it's a shame about the 3rd core but if it is what is stated ( running out of ignition fuel) then it is something easily corrected and that's the main thing (it's a test after all).
Clearly it has shown its deep space/ mars even capabilities.Add a Vulcan second stage one day and there is nowhere in our Solar system it can't go.This is important as it means there is a full back up to the SLS.Whether this capability gets political will be interesting (it probably already is).
On one hand the politicians have always loved the 'regional/political' way NASA spacecraft are built.But.The difference in cost is just Mind boggling!!How can they possibly justify such an expense?
This issue will not go away imho.For now clearly Musk has 'backed down'.By stating he does not intend to 'human rate' the FH.Yet the F9 will be.So absolutly clearly the FH could be.
Pressure from somewhere (actually lots of places/senators).We shall see.
There aren't many FH launches on the manafest.I think 4? If the next couple ( this year?) go well we will hear more I am sure.
Using the Tesla was brilliant PR I am sure the whole World knows about the FH now!
 
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KarelXWB
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Re: SpaceX - Tests, Launches, Developments

Wed Feb 07, 2018 10:13 am

parapente wrote:
Add a Vulcan second stage one day and there is nowhere in our Solar system it can't go.


Vulcan is the Ariane engine, did you mean Raptor engine instead?

This is important as it means there is a full back up to the SLS. Whether this capability gets political will be interesting (it probably already is).


Not even the same ballpark as Block 2 SLS lifts twice the payload.
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KarelXWB
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Re: SpaceX - Tests, Launches, Developments

Wed Feb 07, 2018 10:38 am

Francoflier wrote:
Is it possible that the core is just re-entering too fast to use the current recovery technique without major redesign?
There are words that it might have run out of fuel which, for such a light payload (albeit on a high orbit), would cast doubt on its chances to make it back after lofting a 50T payload...
Others say some of the engines did not ignite, which could indicate that the higher re-entry speed is damaging them too much, and thus would engender large refurbishing costs even if recovered successfully?

Just nervously speculating here, but of all the potential hurdles FH had to clear, I wasn't expecting this one to be the one to make it trip.


The center core performed an experimental 3-engine landing burn, a procedure that was done only 1 time before. Last week SpaceX attempted a 3-engine landing burn for the first time, and the booster ended up floating in the ocean.

SpaceX will have to fine tune the new procedure, until they get it right.
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KarelXWB
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Re: SpaceX - Tests, Launches, Developments

Wed Feb 07, 2018 11:06 am

Recovery of the payload fairings has also failed and requires a design change.

Musk: fairing recovery is surprisingly difficult. Hope to solve it in next six months.

Elon: fairing recovery is difficult. We were hoping in the next 6 months. now moving to fairing v2. Fairing recovery ship is like a giant catchers mitt. *chuckles *

Musk: Fairing recovery is difficult. Awkward fairing size interferes with parachute airflow. We'll be working on fairing version 2 soon

Musk: fairing recovery is difficult. Fairing version 2 is being developed.
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flyingturtle
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Re: SpaceX - Tests, Launches, Developments

Wed Feb 07, 2018 11:33 am

KarelXWB wrote:
Trajectory of the Roadster:


SpaceX surpsises me more and more. Even their failures are successes...


Now I hope to find the parts of the live stream that were recorded on the night side of the earth!


David
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ZaphodHarkonnen
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Re: SpaceX - Tests, Launches, Developments

Wed Feb 07, 2018 11:38 am

KarelXWB wrote:
With such a small payload, how can it run out of fuel?


From what I've been hearing is that it did not run out of main engine fuel. But rather the hypergolic igniter fuel. So only one engine lit instead of the three that were needed.
 
PerVG
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Re: SpaceX - Tests, Launches, Developments

Wed Feb 07, 2018 12:24 pm

KarelXWB wrote:
parapente wrote:
Add a Vulcan second stage one day and there is nowhere in our Solar system it can't go.


Vulcan is the Ariane engine, did you mean Raptor engine instead?


He might be referring to the future Vulcan rocket, by ULA.
I highly doubt that ULA would be willing to supply ACES upper stages to SpaceX, though. Or even that SpaceX would want to use them, in the first place.
 
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JetBuddy
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Re: SpaceX - Tests, Launches, Developments

Wed Feb 07, 2018 12:50 pm

Interesting that they launched Starman into this higher apogee, close to Ceres orbit. I wonder if it was on purpose or not.

What an iconic launch this was. I was so excited I was worried I'd have a heart attack. Next time I'll feel like that will probably be with the James Webb telescope launch on Ariane 5 next year.
 
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JetBuddy
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Re: SpaceX - Tests, Launches, Developments

Wed Feb 07, 2018 12:54 pm

KarelXWB wrote:
Recovery of the payload fairings has also failed and requires a design change.

Musk: fairing recovery is surprisingly difficult. Hope to solve it in next six months.

Elon: fairing recovery is difficult. We were hoping in the next 6 months. now moving to fairing v2. Fairing recovery ship is like a giant catchers mitt. *chuckles *

Musk: Fairing recovery is difficult. Awkward fairing size interferes with parachute airflow. We'll be working on fairing version 2 soon

Musk: fairing recovery is difficult. Fairing version 2 is being developed.


Yes, he repeated that on the post launch press conference as well. But he also mentioned the ship they'll use to catch it, could possibly be used to catch Dragon as well. To me it doesn't seem safe.. the bridge part of the ship is exposed, so if they're just 20m off it could be disaster.
 
parapente
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Re: SpaceX - Tests, Launches, Developments

Wed Feb 07, 2018 1:36 pm

Sorry Karel - totally meant Raptor !And yes SLS block2 is far larger - and no doubt even more eye wateringly expensive.
Having said that Boeing don't care - they're not paying for it!They have laid the challenge down for first to Mars.
Firstly it's going to be Moon first anyway and Spacex now seem to recognise this (sensible?) reality.

But secondly with SLS and block2 Boeing do - or will have next year onwards a rocket system that can get them there - Spacex simply don't right now.The question in my mind is what is Boeing planning to put on top of the SLS Block 1,2 or 3 to land and return on Moon/Mars.
One assumes they have something planned?

Thx also for the additional info.
Re centre booster.Mmmm that was ambitious (3 engine burn) but perhaps from that altitude they had no choice - but am guessing.
Getting that core back would have been useful to them I imagine as has a lot of new stuff built in.
They have 2 more FH's this year will be interesting to see what they do.

As for the fairings.I am not sure quite what they are doing.They are practically if not totally in orbit when they release.How do they slow them down,how do they guide them - really bad shape at such speeds/altitude.
And catching a parachute!! --at sea with a boat!!That's got to be near impossible.Well so far - it is.
Clearly they disagree and know better.Wont be an issue for BFR of course.

They also talk about returning the second stage.How? No legs.
But if they were ,would it not be a better idea to make the fairings a hinged clam shell design so the whole lot comes back together?
That way they have a better shape, only one piece,and an engine for reentry burn and steering.Why not then add some smaller legs / grid fins and do it the same way as the main boosters? They have clearly got the hang of this method.
Just thinking aloud.
 
ZaphodHarkonnen
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Re: SpaceX - Tests, Launches, Developments

Wed Feb 07, 2018 1:47 pm

parapente wrote:
As for the fairings.I am not sure quite what they are doing.They are practically if not totally in orbit when they release.How do they slow them down,how do they guide them - really bad shape at such speeds/altitude.
And catching a parachute!! --at sea with a boat!!That's got to be near impossible.Well so far - it is.
Clearly they disagree and know better.Wont be an issue for BFR of course.


I believe they just tumble back to earth. They're only on a suborbital trajectory at that point so heating is probably limited for such a relatively light and draggy part.

Lower down my understanding is they use parachutes. Controlled or not I don't know.

They also talk about returning the second stage.How? No legs.
But if they were ,would it not be a better idea to make the fairings a hinged clam shell design so the whole lot comes back together?
That way they have a better shape, only one piece,and an engine for reentry burn and steering.Why not then add some smaller legs / grid fins and do it the same way as the main boosters? They have clearly got the hang of this method.
Just thinking aloud.


I'm pretty sure the second stage return will involve adding a heatshield and landing legs to the second stage. As you say, how else can they recover and reuse it otherwise. This would of course eat into payload so wouldn't be used for the biggest stuff.
 
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Re: SpaceX - Tests, Launches, Developments

Wed Feb 07, 2018 3:27 pm

JetBuddy wrote:
Interesting that they launched Starman into this higher apogee, close to Ceres orbit. I wonder if it was on purpose or not.

What an iconic launch this was. I was so excited I was worried I'd have a heart attack. Next time I'll feel like that will probably be with the James Webb telescope launch on Ariane 5 next year.


I heard that the different orbit was simply a function on seeing how much propellant was left and they ran it to exhaustion. Makes sense on a test flight to see what your margin is.
 
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JetBuddy
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Re: SpaceX - Tests, Launches, Developments

Wed Feb 07, 2018 3:54 pm

bigjku wrote:
I heard that the different orbit was simply a function on seeing how much propellant was left and they ran it to exhaustion. Makes sense on a test flight to see what your margin is.


That sounds plausible and if true very interesting. Surprising that these kinds of decisions can be taken "on the fly" (pun intended) during a mission like this. I suppose they have plenty of NASA consultants giving advise and permissions. If I understand it correctly they were aiming for a Hohmann transfer around the Sun with an elliptical orbit around Mars. But now it's heading for the Astroid Belt.
 
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Tugger
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Re: SpaceX - Tests, Launches, Developments

Wed Feb 07, 2018 4:01 pm

parapente wrote:
And catching a parachute!! --at sea with a boat!!That's got to be near impossible.

Actually no, it's not. Using a square canopy like all skydivers use nowadays, you can do pinpoint landings almost anywhere (significant winds being the only real issue). You've seen the stadium skydive shows, its similar to that but with an automated system. Certainly no more difficult than land a booster like SpaceX does (but with very different issues due the vast difference in velocity).

Not saying that is what they are doing but it is what I would expect due to the control allowed.

Tugg
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bigjku
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Re: SpaceX - Tests, Launches, Developments

Wed Feb 07, 2018 4:08 pm

Tugger wrote:
parapente wrote:
And catching a parachute!! --at sea with a boat!!That's got to be near impossible.

Actually no, it's not. Using a square canopy like all skydivers use nowadays, you can do pinpoint landings almost anywhere (significant winds being the only real issue). You've seen the stadium skydive shows, its similar to that but with an automated system. Certainly no more difficult than land a booster like SpaceX does (but with very different issues due the vast difference in velocity).

Not saying that is what they are doing but it is what I would expect due to the control allowed.

Tugg


The used to catch parachute suspended film canisters from early spy satellites with helicopters.
 
zanl188
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Re: SpaceX - Tests, Launches, Developments

Wed Feb 07, 2018 4:21 pm

bigjku wrote:

The used to catch parachute suspended film canisters from early spy satellites with helicopters.


...and C-130s. I Believe C-82s also...
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parapente
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Re: SpaceX - Tests, Launches, Developments

Wed Feb 07, 2018 4:30 pm

As an ex competition level paraglide pilot I can tell you pin point landings are very difficult even in good conditions - and that's will 100% human precision!( well perhaps not 100% in my case!)
Nope I'm going to stick with my thought on this one - bring the fairings and second stage back all together.
BTW since Elon loves his old classic films. Who remembers that Sean Connery Bond classic ( you only live twice?) where the baddies had a rocket with clam shell doors that stole NASA sats in space and returned them to their volcano base.Elon would need a white cat!
 
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Francoflier
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Re: SpaceX - Tests, Launches, Developments

Wed Feb 07, 2018 4:58 pm

KarelXWB wrote:
The center core performed an experimental 3-engine landing burn, a procedure that was done only 1 time before. Last week SpaceX attempted a 3-engine landing burn for the first time, and the booster ended up floating in the ocean.

SpaceX will have to fine tune the new procedure, until they get it right.


It worked well enough last week.
Running out of fuel seems a bit amateurish and running out of igniter seems daft... SpaceX should have enough experience landing boosters to get these right. I’m just wondering if that failure has anything to do with the much higher enegy and re-entry speed. The booster did make it all the way to landing burn after all, but there’s no telling how much it suffered on the way down.
And since FH will have a much slower launch cadence than F9, it’s not like they can afford to fail too many times. There might not be more than 2 or 3 launches this year.

I’m also wondering whether the damage on OCISLY will affect any upcoming F9 booster recoveries. The damage is quite substantial after all.

In any case, Musk doesn’t seem worried.
I'll do my own airline. With Blackjack. And hookers. In fact, forget the airline.
 
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QuarkFly
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Re: SpaceX - Tests, Launches, Developments

Wed Feb 07, 2018 6:47 pm

parapente wrote:
As for the fairings.I am not sure quite what they are doing.They are practically if not totally in orbit when they release.How do they slow them down,how do they guide them - really bad shape at such speeds/altitude.

The fairings are released at far less than orbital velocity...at about 110 km (70 miles) altitude once there is no more atmosphere...at a speed approx. 8,000 km/hr (5000 mph)... less than one-third of orbital velocity (26000 km/hr)

So recovering them is possible...although I don't foresee this as being easy - because they are so awkward aerodynamically... spin and flip like a piece of paper falling to the ground.

parapente wrote:
Re centre booster.Mmmm that was ambitious (3 engine burn) but perhaps from that altitude they had no choice - but am guessing.
Getting that core back would have been useful to them I imagine as has a lot of new stuff built in.
They have 2 more FH's this year will be interesting to see what they do.

Actually, I wonder how much the center core will ever be recovered...the FH is using the identical second stage from the F9...so any payload increase is from increased velocity of the side and center cores. So the center core at least -- will be moving much faster than the F9 first stage...making sea landings much more dicey unless smaller payloads allow enough fuel for slowdown re-entry burns.

In fact, payloads close to the 65 ton (140 klb) maximum may not have any reusability -- all the cores will be lost. I think typically, the side boosters will be recovered, on land or sea...But even then, based upon F9 first stage velocity at engine-cutoff and fuel weight required in the second stage... a significant decrease of max-payload occurs...to less than 100 klb.and the loss of the center core,,. thus, more expensive launches.

So it will be interesting to see how often the center core is recovered? Elon Musk did say in the news conference that the side boosters are more valuable.
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Tugger
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Re: SpaceX - Tests, Launches, Developments

Wed Feb 07, 2018 7:10 pm

Here is the full 4 hours+ of Starman and the Roadster in space:
https://www.youtube.com/watch?v=aBr2kKAHN6M

Tugg
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bhill
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Re: SpaceX - Tests, Launches, Developments

Wed Feb 07, 2018 7:32 pm

THAT was some Buck Roger shit rhat thar...!!! Made me do a double take when the gear/foils deployed...
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estorilm
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Re: SpaceX - Tests, Launches, Developments

Wed Feb 07, 2018 7:43 pm

QuarkFly wrote:
parapente wrote:
As for the fairings.I am not sure quite what they are doing.They are practically if not totally in orbit when they release.How do they slow them down,how do they guide them - really bad shape at such speeds/altitude.

The fairings are released at far less than orbital velocity...at about 110 km (70 miles) altitude once there is no more atmosphere...at a speed approx. 8,000 km/hr (5000 mph)... less than one-third of orbital velocity (26000 km/hr)

So recovering them is possible...although I don't foresee this as being easy - because they are so awkward aerodynamically... spin and flip like a piece of paper falling to the ground.

parapente wrote:
Re centre booster.Mmmm that was ambitious (3 engine burn) but perhaps from that altitude they had no choice - but am guessing.
Getting that core back would have been useful to them I imagine as has a lot of new stuff built in.
They have 2 more FH's this year will be interesting to see what they do.

Actually, I wonder how much the center core will ever be recovered...the FH is using the identical second stage from the F9...so any payload increase is from increased velocity of the side and center cores. So the center core at least -- will be moving much faster than the F9 first stage...making sea landings much more dicey unless smaller payloads allow enough fuel for slowdown re-entry burns.

In fact, payloads close to the 65 ton (140 klb) maximum may not have any reusability -- all the cores will be lost. I think typically, the side boosters will be recovered, on land or sea...But even then, based upon F9 first stage velocity at engine-cutoff and fuel weight required in the second stage... a significant decrease of max-payload occurs...to less than 100 klb.and the loss of the center core,,. thus, more expensive launches.

So it will be interesting to see how often the center core is recovered? Elon Musk did say in the news conference that the side boosters are more valuable.

I was under the impression that (following previous listings and stats by Space-X) that published numbers do NOT include the 30%-or-so margin required to re-use the boosters.

In a typical configuration the FH isn't trying to launch payloads further, it's simply lifting heavier things - thus recovering the center core isn't entirely different than the outers, though the boost-back (and possibly re-entry?) burns will need to provide more energy.

I seem to be gathering that the center core didn't use the typical 1-3-1 engine re-entry burn program they've been using lately? Though I also believe Elon said FH staged 1000kph faster than any of the F9 missions, so there are definitely some unknown variables there.

I can't find it now, but I recall reading something about a different type of burn they attempted once recently and failed? The center core apparently used the same type of re-entry burn. That's all rather worthless since I can't for the life of me figure out where I read that. :lol:
 
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Re: SpaceX - Tests, Launches, Developments

Wed Feb 07, 2018 8:06 pm

estorilm wrote:
...In a typical configuration the FH isn't trying to launch payloads further, it's simply lifting heavier things - thus recovering the center core isn't entirely different than the outers, though the boost-back (and possibly re-entry?) burns will need to provide more energy....


Well, SpaceX has made clear that the FH second stage is exactly the same as the F9 . So the amount of fuel that can go into the second stage and the energy it provides has to be the same for both the FH and F9. Delivering something heavier to orbit requires the side-boosters/center-core to accelerate to a faster speed than the F9 first stage does...Then the second stage can deliver a heavier payload to orbit with the same energy as an F9 because it does not require as much delta-V speed gain to get to orbit...I don't see any way around it.

So the side-boosters and especially the center-core have to do engine cutoff at a faster speed...making recoveries more difficult, especially at sea for the center core -- the fastest, since it does engine cutoff after the side-boosters. Unless, of course, you trade payload weight for fuel leftover in the cores for longer re-entry burns. I believe that is what the physics requires.
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KarelXWB
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Re: SpaceX - Tests, Launches, Developments

Wed Feb 07, 2018 8:39 pm

Just in case someone needs a new wallpaper:

Image
https://www.reddit.com/r/spacex/comment ... way_its_a/
What we leave behind is not as important as how we've lived.
 
estorilm
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Re: SpaceX - Tests, Launches, Developments

Wed Feb 07, 2018 8:56 pm

QuarkFly wrote:
estorilm wrote:
...In a typical configuration the FH isn't trying to launch payloads further, it's simply lifting heavier things - thus recovering the center core isn't entirely different than the outers, though the boost-back (and possibly re-entry?) burns will need to provide more energy....


Well, SpaceX has made clear that the FH second stage is exactly the same as the F9 . So the amount of fuel that can go into the second stage and the energy it provides has to be the same for both the FH and F9. Delivering something heavier to orbit requires the side-boosters/center-core to accelerate to a faster speed than the F9 first stage does...Then the second stage can deliver a heavier payload to orbit with the same energy as an F9 because it does not require as much delta-V speed gain to get to orbit...I don't see any way around it.

So the side-boosters and especially the center-core have to do engine cutoff at a faster speed...making recoveries more difficult, especially at sea for the center core -- the fastest, since it does engine cutoff after the side-boosters. Unless, of course, you trade payload weight for fuel leftover in the cores for longer re-entry burns. I believe that is what the physics requires.

I'm agreeing with you on all of that, though wouldn't the increased mass in payload net a similar profile to the standard F9? I realize it has significantly more thrust - but also significantly more weight. I assume as the atmosphere is reduced speeds will increase however. The center is definitely faster, as I stated around 1000kph per Elon's tweet (beyond their fastest prior deployment) - I think the profiles of the outers are similar to standard higher-speed F9 launches.
---
I dug up some of what I read - basically the BulgariaSat-1 launch last June used a high-performance supersynchronous transfer orbit over 37k mi. This launch placed unusual stresses on the re-entry profile for the booster (including more fuel constraints PLUS higher speeds) - prompting a (shorter) 3-engine landing burn (which I guess would be a 1-3-3-type re-entry?)

From what I read it landed but used up almost all of its' "crush core", and was generally "extra toasty" or however Elon put it.

That's the launch that Elon was comparing the FH to yesterday - the later being 1000kph faster and obviously requiring the same "hover-slam" landing, though even more complicated. Doesn't seem like they've quite perfected the more difficult 3-engine approach yet, but both landings were arguably outside of the typical flight profiles used when they designed the F9. It's all still pretty remarkable.
 
MatthewDB
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Re: SpaceX - Tests, Launches, Developments

Wed Feb 07, 2018 9:00 pm

parapente wrote:
As an ex competition level paraglide pilot I can tell you pin point landings are very difficult even in good conditions - and that's will 100% human precision!( well perhaps not 100% in my case!)
Nope I'm going to stick with my thought on this one - bring the fairings and second stage back all together.
BTW since Elon loves his old classic films. Who remembers that Sean Connery Bond classic ( you only live twice?) where the baddies had a rocket with clam shell doors that stole NASA sats in space and returned them to their volcano base.Elon would need a white cat!


They want to dump the faring shortly after stage separation. The fairing isn't needed in the vacuum of space. Keeping it attached to the second stage means it has to be accelerated to the second stage final velocity.
 
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Re: SpaceX - Tests, Launches, Developments

Wed Feb 07, 2018 9:06 pm

QuarkFly wrote:
parapente wrote:
As for the fairings.I am not sure quite what they are doing.They are practically if not totally in orbit when they release.How do they slow them down,how do they guide them - really bad shape at such speeds/altitude.

The fairings are released at far less than orbital velocity...at about 110 km (70 miles) altitude once there is no more atmosphere...at a speed approx. 8,000 km/hr (5000 mph)... less than one-third of orbital velocity (26000 km/hr)


From what I understand, they are in controlled flight. They have control surfaces and don't tumble, but glide in a controlled manner. They can be steered to a controlled point for parachute deployment.

So recovering them is possible...although I don't foresee this as being easy - because they are so awkward aerodynamically... spin and flip like a piece of paper falling to the ground.

QuarkFly wrote:
Actually, I wonder how much the center core will ever be recovered...the FH is using the identical second stage from the F9...so any payload increase is from increased velocity of the side and center cores. So the center core at least -- will be moving much faster than the F9 first stage...making sea landings much more dicey unless smaller payloads allow enough fuel for slowdown re-entry burns.

In fact, payloads close to the 65 ton (140 klb) maximum may not have any reusability -- all the cores will be lost. I think typically, the side boosters will be recovered, on land or sea...But even then, based upon F9 first stage velocity at engine-cutoff and fuel weight required in the second stage... a significant decrease of max-payload occurs...to less than 100 klb.and the loss of the center core,,. thus, more expensive launches.

So it will be interesting to see how often the center core is recovered? Elon Musk did say in the news conference that the side boosters are more valuable.


I didn't catch the velocities at each separation, but it sure seemed like side booster cut-off and separation was rather close to the center booster cut-off and separation. Without propellant cross-feed, the difference in burn time only comes from throttling down the center booster. Also - the center booster didn't have to do a boost-back burn, and the side boosters did.
 
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Re: SpaceX - Tests, Launches, Developments

Wed Feb 07, 2018 9:29 pm

estorilm wrote:
I dug up some of what I read - basically the BulgariaSat-1 launch last June used a high-performance supersynchronous transfer orbit over 37k mi. This launch placed unusual stresses on the re-entry profile for the booster (including more fuel constraints PLUS higher speeds) - prompting a (shorter) 3-engine landing burn (which I guess would be a 1-3-3-type re-entry?)

From what I read it landed but used up almost all of its' "crush core", and was generally "extra toasty" or however Elon put it.

That's the launch that Elon was comparing the FH to yesterday - the later being 1000kph faster and obviously requiring the same "hover-slam" landing, though even more complicated. Doesn't seem like they've quite perfected the more difficult 3-engine approach yet, but both landings were arguably outside of the typical flight profiles used when they designed the F9. It's all still pretty remarkable.


I don't know exactly why the 3-engine landing burn is more useful than a longer 1-engine burn on landing...same energy, just a shorter burn with three engines. What they may be trying to do is obtain as much aerodynamic drag as possible to slow down the returning booster. Aerodynamic speed drag increases at delta-velocity squared....So perhaps by doing a three engine landing with a fast, final hover de-acceleration...they are tying to spend more time at higher speed in the low atmosphere -- thus allowing aerodynamic drag to do more work slowing down the booster ??

MatthewDB wrote:
...I didn't catch the velocities at each separation, but it sure seemed like side booster cut-off and separation was rather close to the center booster cut-off and separation. Without propellant cross-feed, the difference in burn time only comes from throttling down the center booster. Also - the center booster didn't have to do a boost-back burn, and the side boosters did.


I recorded all of this for my own back of envelope calculations...

Side booster engine cutoff at 2-min 31-sec -- at 6700 kmh...Center booster cutoff at 3-min 4-sec at approx. 9500 kmh. A bit faster than a F9, but not too much. A F9 first-stage land-recovery usually has MECO at about 6000 kmh...and about 9000 kmh for drone-ship landing.... But the FH had very little payload yesterday...so I'm sure these figures will not be typical.
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MatthewDB
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Re: SpaceX - Tests, Launches, Developments

Wed Feb 07, 2018 9:47 pm

I just re-watched it for what has got to be the 10th time by now. I'm glad there are clips now on youtube that only show the launch through landing. I come up with similar number QuarkFly.

Am I the only one that noted that there was video from one booster shown twice on the split screen? I suspected that from the start, but now I'm certain. What I noted was that the thruster shots were at the same time. Randomness wouldn't let that happen. The booster landing to the South was a bit lower and landed slightly ahead. The camera shown must have been on the booster to land on the North pad. In both views, you can see the other booster doing it's landing burn at a lower altitude. Both boosters can't be "looking down" at the other one.

All of that made me realize that one additional item SpaceX has to worry about is that the boosters don't run into each other. They're landing rather close, and it would be conceivable that slight variations in trajectory could cause them to collide.
 
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flyingturtle
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Re: SpaceX - Tests, Launches, Developments

Wed Feb 07, 2018 11:30 pm

QuarkFly wrote:
I don't know exactly why the 3-engine landing burn is more useful than a longer 1-engine burn on landing...same energy, just a shorter burn with three engines. What they may be trying to do is obtain as much aerodynamic drag as possible to slow down the returning booster. Aerodynamic speed drag increases at delta-velocity squared....So perhaps by doing a three engine landing with a fast, final hover de-acceleration...they are tying to spend more time at higher speed in the low atmosphere -- thus allowing aerodynamic drag to do more work slowing down the booster ??


This question was answered already in this thread - you have to find one of the earlier replies...

David
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thaiflyer
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Re: SpaceX - Tests, Launches, Developments

Thu Feb 08, 2018 12:10 am

Elon Musk received a speeding ticket while over flying Australia for doing 11 Km/sec.
He has apparently appealed the ticket as in his words he was not driving himself. :-)

Source:
https://w1nnersclub.com/news/elon-musk- ... ding-fine/
 
zanl188
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Re: SpaceX - Tests, Launches, Developments

Thu Feb 08, 2018 2:44 am

Ground based video of entire flight of Falcon Heavy side boosters....

https://youtu.be/59pY74ZhQ50
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Francoflier
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Re: SpaceX - Tests, Launches, Developments

Thu Feb 08, 2018 7:01 am

Of all the funny memes and material that came out of the mission, this is probably the one I enjoyed most, for some stupid reason:

Image
I'll do my own airline. With Blackjack. And hookers. In fact, forget the airline.
 
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Nomadd
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Re: SpaceX - Tests, Launches, Developments

Thu Feb 08, 2018 7:24 am

KarelXWB wrote:
With such a small payload, how can it run out of fuel?

The real story will come out, but they want the core to have exactly as much fuel as it needs to land and no more, so a small miscalculation could make it run out. It could have been from better performance, as counter intuitive as that sounds. Staging higher and faster than anticipated because of better performance from the core or boosters would increase the fuel needed to return. It could also be melted aluminum gridfins failing, which would also increase fuel use. There were a few factors they had to guess at.
If it was igniter fuel running out, that could have been from a hard start using more than anticipated. The telemetry should give them what they need to pinpoint it.
 
HAL
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Re: SpaceX - Tests, Launches, Developments

Thu Feb 08, 2018 7:27 am

Has anyone reported what the deceleration G-force is on the returning boosters during the boost-back and landing burns?

HAL
One smooth landing is skill. Two in a row is luck. Three in a row and someone is lying.
 
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Nomadd
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Re: SpaceX - Tests, Launches, Developments

Thu Feb 08, 2018 7:27 am

parapente wrote:
As an ex competition level paraglide pilot I can tell you pin point landings are very difficult even in good conditions - and that's will 100% human precision!( well perhaps not 100% in my case!)
Nope I'm going to stick with my thought on this one - bring the fairings and second stage back all together.
BTW since Elon loves his old classic films. Who remembers that Sean Connery Bond classic ( you only live twice?) where the baddies had a rocket with clam shell doors that stole NASA sats in space and returned them to their volcano base.Elon would need a white cat!

Every pound you have on that 2nd stage is a pound less payload, and those fairings aren't light.
 
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KarelXWB
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Re: SpaceX - Tests, Launches, Developments

Thu Feb 08, 2018 9:14 am

Final pic before the camera went dark:

Image
Falcon Heavy Demo Mission by SpaceX, on Flickr
What we leave behind is not as important as how we've lived.
 
parapente
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Re: SpaceX - Tests, Launches, Developments

Thu Feb 08, 2018 9:19 am

You are right Nomadd (and others).You would loose payload due to the additional mass carried that last part of the way.I guess (as they say) there is no free lunch!
The Shuttle clearly had to take everything up and everything back.But perhaps more importantly so does the BFR as envisaged.Indeed the 'total reusability' Elon touts for the BFR is what, according to him ,makes it so cheap to fly.
I am simply suggesting a similar thing for the F9 second stage.Even more important when it becomes a Raptor engined second stage ( and far more powerful in the vacuum of space).
He states he wants to get the second stage back and the fairings.His BFR solution ( and shuttle) looks the best method even though it will reduce payload.(but he has. Some in hand more than often and more to come with the Raptor).
One assumes the second stage would require grid fins (stub wings?)and legs to land so that's more mass and less payload ( no free lunch).
But it's gotta be the sensible way.
But perhaps that's exactly the (his) point.He could build a mini ( sort of) BFR second stage for the F9/FH. But ( in his view) why bother- if he is doing that already for the larger BFR .
This is where it's possible his enthusiasm for Mars is getting in the way of commercial realities.It is the F9/FH that is making the money so that 'his' BFR can be built. Make a wrong turn with the bread winners and he's toast.
His rationale for BFR is it can launch circa 4 seats in one go.But is that really what the market wants? Is the market even geared that way in timing terms - not forgetting very different orbital requirements.Personally I think it's total hogwash - just like going to Sydney in 20 mins.

If he cares to look over his shoulder he's got Boeing and Lockheed together ( my God) creating a new rocket for the ULA.And the all conquering Jeff Bezos with New Glen.(Not counting the Europeans et al none of whom are lying down).
FACTS Mr Musk.
You have a winner - now is the time to stamp on the oppositions throat,not go off doing other things.Ot they will stamp on yours.
 
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flyingturtle
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Re: SpaceX - Tests, Launches, Developments

Thu Feb 08, 2018 10:17 am

parapente wrote:
One assumes the second stage would require grid fins (stub wings?)and legs to land so that's more mass and less payload ( no free lunch).


ESA has an idea to put little wings on the engine (not the whole stage), and make it glide to a runway. It even has little propellers for propulsion. https://www.youtube.com/watch?v=tV29pEvZvZw

It's intended to be used on Ariane 6.

Well, perhaps I would tweak the trajectory in such a way that the 2nd stage engine would glide to either Africa or Europe thanks to its stubby wings, where it finally lands by parachute.


David
Keeping calm is terrorism against those who want to live in fear.
 
WIederling
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Re: SpaceX - Tests, Launches, Developments

Thu Feb 08, 2018 10:37 am

HAL wrote:
Has anyone reported what the deceleration G-force is on the returning boosters during the boost-back and landing burns?


stage empty weight 25t and fuel diminishing to zero.
Merlin 1D thrust 650kN nom.
throttle 70 .. 100 %
3 engine burn allows 78m/s² acceleration. Throttled : 55m/s²
that is 8g throttled: 5.5g

seat one of the Space Cowboys on top and he'd show a happy grin.
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estorilm
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Re: SpaceX - Tests, Launches, Developments

Thu Feb 08, 2018 3:12 pm

QuarkFly wrote:
estorilm wrote:
I dug up some of what I read - basically the BulgariaSat-1 launch last June used a high-performance supersynchronous transfer orbit over 37k mi. This launch placed unusual stresses on the re-entry profile for the booster (including more fuel constraints PLUS higher speeds) - prompting a (shorter) 3-engine landing burn (which I guess would be a 1-3-3-type re-entry?)

From what I read it landed but used up almost all of its' "crush core", and was generally "extra toasty" or however Elon put it.

That's the launch that Elon was comparing the FH to yesterday - the later being 1000kph faster and obviously requiring the same "hover-slam" landing, though even more complicated. Doesn't seem like they've quite perfected the more difficult 3-engine approach yet, but both landings were arguably outside of the typical flight profiles used when they designed the F9. It's all still pretty remarkable.


I don't know exactly why the 3-engine landing burn is more useful than a longer 1-engine burn on landing...same energy, just a shorter burn with three engines. What they may be trying to do is obtain as much aerodynamic drag as possible to slow down the returning booster. Aerodynamic speed drag increases at delta-velocity squared....So perhaps by doing a three engine landing with a fast, final hover de-acceleration...they are tying to spend more time at higher speed in the low atmosphere -- thus allowing aerodynamic drag to do more work slowing down the booster ??


That's exactly the basis I've been working on, I found some good quotes but won't attempt to paraphrase them myself - as I'm much less of a "rocket scientist" than most people on here, or the places quoted below. :lol:
Assuming that Falcon 9 has a speed of 300 m/s at the start of the landing burn and that the 1-engine TWR at that moment is 2,3. (source: u/veebay)

With one engine we would have an acceleration of about 13 m/s2 and a landing burn of 23 seconds. In that time we continually have to fight gravity, adding 230 m/s of DeltaV to the landing burn.

If we burn with 3 engines our acceleration quadruples to 58 m/s2 and we need only a good 5 seconds to complete our landing burn. In that time we only add about 50 DeltaV to the landing burn, saving a good 180 m/s.=


And..
Conclusion:
By performing a 3-Engine Landing Burn, The booster of JCSAT-14 saved about 296 m/s of Δv compared to CRS-8

If the first stage has 5% of its propellant (fuel+oxidizer) left after landing, this is 4825 kg of propellant saved. If the tanks are completely emptied, it saves 2510 kg of propellant.

EDIT: Propellant saving may be larger than calculated, due to JCSAT-14's landing burn being shorter than 15 seconds. Don't want to fiddle too much with the original post.

Basic Idea:
Right now, we have 2 examples of an ASDS landing, CRS-8 and JCSAT-14

There are two ways the 3 engine landing burn saves fuel. Because of atmospheric drag, the longer the booster waits the slower it is going (until it hits terminal velocity), meaning less fuel has to be spent to kill the remaining velocity. The rocket also spends less time fighting gravity. If, for example, a rocket is hovering, it wouldn't be accelerating but it would still be burning fuel.

https://www.reddit.com/r/spacex/comments/4isnn3/estimating_the_fuel_savings_of_a_3engine_landing/ Plus some other pieces from space forums, etc.

There's clearly a strong desire for them to achieve this and build a more efficient rocket, however as I mentioned - I would imagine doing so would require exponentially more complicated landing burn / correction equations and much quicker response time of ALL systems involved.
 
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Tugger
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Re: SpaceX - Tests, Launches, Developments

Thu Feb 08, 2018 4:49 pm

More info on the Raodsters orbit:
astronomers online noticed some discrepancies with the numbers Musk tweeted, and SpaceX ultimately sent a revised orbit to NASA’s Jet Propulsion Laboratory on Wednesday [...] The new orbit shows that the car will indeed travel farther out than the orbit of Mars, but not far enough to make it to the asteroid belt. The belt begins about 329 million miles from the Sun, and the Tesla will reach a distance about 160 million miles away from the Solar System’s star.

https://www.theverge.com/2018/2/6/16983 ... -musk-mars

Tugg
I don’t know that I am unafraid to be myself, but it is hard to be somebody else. -W. Shatner
 
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Nomadd
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Re: SpaceX - Tests, Launches, Developments

Thu Feb 08, 2018 11:48 pm

The SES-16 booster is no longer floating. SpaceX called in an airstrike, and the Air Force sent it to the bottom.
 
MatthewDB
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Re: SpaceX - Tests, Launches, Developments

Thu Feb 08, 2018 11:54 pm

Was the moon visible at any point in the starman video? Or was the brightness of the sun always so much that it couldn't ever be seen?

How about the second stage 3rd burn? Was that ever caught on video?
 
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KarelXWB
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Re: SpaceX - Tests, Launches, Developments

Fri Feb 09, 2018 8:57 am

MatthewDB wrote:
How about the second stage 3rd burn? Was that ever caught on video?


I'm pretty sure SpaceX has it on video. I guess we will have to wait for the next episode of How Not to Land an Orbital Rocket Booster.
What we leave behind is not as important as how we've lived.
 
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KarelXWB
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Re: SpaceX - Tests, Launches, Developments

Fri Feb 09, 2018 6:08 pm

Nice video of the booster landings, including sonic booms:

https://www.youtube.com/watch?v=Z_kfM-BmVzQ
What we leave behind is not as important as how we've lived.

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