SpaceX Starship Test Program

jotun? · Dec 9, 2020

m_shortpants said:
What's the purpose of the belly flop like that, as opposed to a standard Falcon 9 style entry? More maneuverability ?

It will have to come through re-entry like that in order to not destroy the engines. Falcon 9 first stage only comes in from suborbital, but this will have to come back at orbital or interplanetary velocity so it wouldn't survive going engines-first.

Daniel Jackson · Dec 9, 2020

Man that was cool. The manoeuvres work, that belly flop was amazing. It might need a softer landing next time though.

papertowel · Dec 9, 2020

m_shortpants said:
What's the purpose of the belly flop like that, as opposed to a standard Falcon 9 style entry? More maneuverability ?

This is the second stage of the rocket. This thing will be coming back from orbit so it needs to slow the f down and the best way to do that is maximize surface area to the windstream.

piratepwnsninja · Dec 9, 2020

Yeah apparently one engine didn't fire on landing, and the legs didn't deploy.

Mochi · Dec 9, 2020

Talking to a coworker, it probably would have survived intact if this were Mars right?
Really an incredible achievement, I am very excited for their future projects.

DopeyFish · Dec 9, 2020

m_shortpants said:
What's the purpose of the belly flop like that, as opposed to a standard Falcon 9 style entry? More maneuverability ?

to not execute an entry burn

entry burns screw up reusability

Kinthey · Dec 9, 2020

piratepwnsninja said:
Yeah apparently one engine didn't fire on landing, and the legs didn't deploy.

The one engine was also firing green flames which seems a bit weird, but not that I know about this stuff

Ether_Snake · Dec 9, 2020

Gustaf said:
only 2 engines ignited for the landing, maybe that was the problem?

I feel like one of the three engines busted out at some point as it went up no?

Zelas · Dec 9, 2020

I couldnt tell if they lost the one engine during the ascent or if the first engine shutting down was supposed to lead to the body catching on fire.

Deleted member 8257 · Dec 9, 2020

m_shortpants said:
What's the purpose of the belly flop like that, as opposed to a standard Falcon 9 style entry? More maneuverability ?

I think its to save fuel during descent and only using it before landing.

Crispy75 · Dec 9, 2020

That green flame on landing is a clear symptom of an engine eating itself. The combustion chamber is copper, which burns that bright green. I think if that engine had behaved itself, we'd be looking at an intact rocket standing upright.

SnakeXs · Dec 9, 2020

Green flame hints at relight not nominal. Can't wait to get some confirmations about the flight plan and overall results.

Gashprex · Dec 9, 2020

piratepwnsninja said:
I think this is actually a better result than they expected, no? I mean, best result is it all worked, but I think they expected a crash?

that was amazingly successful test - totally proved out the design.

the fact that they hit the pad directly and proved out the flop was huge

XMonkey · Dec 9, 2020

That was incredible. These tests where you really have no idea what to expect are so exciting.

Crispy75 · Dec 9, 2020

RustyNails said:
I think its to save fuel during descent and only using it before landing.

It's to keep altitude and velocity low for this first flight.
Expect later tests to run all three engines full duration

SealedSeven · Dec 9, 2020

Damaniel said:
As for why the engines cut off? I assume that was to keep the rocket under the ceiling they were cleared to fly to.

It was to control flight height. They were shutdown on purpose. Last one remained to have it hover / get in position, and then turned off to start the belly flop.

kami_sama · Dec 9, 2020

piratepwnsninja said:
Yeah apparently one engine didn't fire on landing, and the legs didn't deploy.

All due to the first engine dying after one of the propelant lines broke. Something started burning down and maybe lost control of the legs, add that you only have 2/3rds of the power, and you get a RUD lol

m_shortpants · Dec 9, 2020

NunezL said:
This a second stage, not a first stage like the falcon boster that lands. That means it's going to be in orbit around earth at around 28000 km/h and it needs to shed that velocity during reentry. The belly flop is to maximize the surface area of the vehicle and brake with the air friction.

jotun? said:
It will have to come through re-entry like that in order to not destroy the engines. Falcon 9 first stage only comes in from suborbital, but this will have to come back at orbital or interplanetary velocity so it wouldn't survive going engines-first.

papertowel said:
This is the second stage of the rocket. This thing will be coming back from orbit so it needs to slow the f down and the best way to do that is maximize surface area to the windstream.

DopeyFish said:
to not execute an entry burn

entry burns screw up reusability

RustyNails said:
I think its to save fuel during descent and only using it before landing.

Got it, makes complete sense! All of my ships in KSP usually return via a capsule so I didn't even think of that.

Staab · Dec 9, 2020

Amazing to see that live, it does work (almost completely) as planned.
SN9 test when?

Tacitus · Dec 9, 2020

Ether_Snake said:
Yeah when I saw it turn and saw the ground below I knew there was no way it would land, but it didn't come crashing straight down.

Looking forward to the next one, that was amazing!

I'm sure it could've handled it if all engines fired properly. They've landed rockets with a "suicide burn" before.

Crispy75 · Dec 9, 2020

Plugging SpaceX OT : https://www.resetera.com/threads/spacex-ot-reusable-rockets-to-mars.2508/

GrizzleBoy · Dec 9, 2020

WOOOOOOÒOOOOOOOOOOOOO

That was focking amazing man.

I thought they lhad ost an engine on the way up and spent a bit longer then they would have at the end of the ascent.

Only two engines fired on landing which seemed to confirmed what I thought as the rocket just couldn't slow down despite the flip manoeuvre executing so perfectly.

Either way I'm stoked the proof of concept has proven itself so well on the first try!

Thorrgal · Dec 9, 2020

That was fucking amazing tbh

Gashprex · Dec 9, 2020

Spacex landing engineer

JonnyDBrit · Dec 9, 2020

Crispy75 said:
That green flame on landing is a clear symptom of an engine eating itself. The combustion chamber is copper, which burns that bright green. I think if that engine had behaved itself, we'd be looking at an intact rocket standing upright.

Possibly damaged in the fire earlier?

But yeah, grabbed screenshots of that little sequence:

imgur.com

Imgur: The magic of the Internet

imgur.com

At the 1:40 mark the engine judders to the right for a bit, and in swinging back, flares up. Flames spread wide enough to reach the surrounding surfaces before the engine conks out, including some material which then ignites rapidly at the 1:48 mark, burning itself out in seconds

Hootie · Dec 9, 2020

on to SN9!

Thorrgal · Dec 9, 2020

I think one raptor died and then it didn't have enough thrust to land

Kinthey · Dec 9, 2020

It even looks like it stood still there for a moment before it exploded. This was soooo close to a successful landing

Crispy75 · Dec 9, 2020

Looks like it was low fuel pressure in the header tank

Camoxide · Dec 9, 2020

One of the engines went out a couple of seconds before landing.

Overall that was waaaaayy closer to landing than I expected though!

m_shortpants · Dec 9, 2020

Crispy75 said:
Looks like it was low fuel pressure in the header tank

Pretty incredible that the telemetry and data can give them these kinds of insights...basically immediately.

prophetvx · Dec 9, 2020

Staab said:
Amazing to see that live, it does work (almost completely) as planned.
SN9 test when?

SN9 started construction only a month after SN8. I don't believe they've announced timeframes but historically they've kept pretty close to development timelines in order of launch. SN10 is another month behind that. It's likely there'll be another launch in the next couple of months dependent on the outcomes of this test obviously.

SnakeXs · Dec 9, 2020

prophetvx said:
SN9 started construction only a month after SN8. I don't believe they've announced timeframes but historically they've kept pretty close to development timelines in order of launch. SN10 is another month behind that. It's likely there'll be another launch in the next couple of months dependent on the outcomes of this test obviously.

I believe SN9 and its engines are effectively ready to go, just gotta clean up and prep the launch/landing pads, which may take a bit. :P Next test's timeline is almost definitely not hardware related, more about the pads and the team crunching through today's data.
Biggest hurdle is if they've already designed around current problems or today's data shows them something that they need to adjust, which would make testing SN9 redundant and unnecessary. Possibly.

kami_sama · Dec 9, 2020

Crispy75 said:
Looks like it was low fuel pressure in the header tank

I am still going with my broke propellant line theory. You can see gas escape since the first raptor broke.
Tbh I don't know if it can lower the pressure enough but it's my theory :P

mere_immortal · Dec 9, 2020

So cool watching it flop through the air, like the whale in Hitchhiker's Guide.

RoKKeR · Dec 9, 2020

Not knowing what was supposed to happen, I couldn't believe my eyes when that thing just flipped on a dime. Is that the long term plan for this thing?? Wouldn't that make all the passengers unconscious from the Gs?? Haha, long way off I know.

That was impressive as hell.

jett · Dec 9, 2020

Damn it got evaporated

Hootie · Dec 9, 2020

RoKKeR said:
Not knowing what was supposed to happen, I couldn't believe my eyes when that thing just flipped on a dime. Is that the long term plan for this thing?? Wouldn't that make all the passengers unconscious from the Gs?? Haha, long way off I know.

That was impressive as hell.

Yeah I was also wondering what kind of g forces astronauts would experience during such a drastic maneuver like that

Crispy75 · Dec 9, 2020

kami_sama said:
I am still going with my broke propellant line theory. You can see gas escape since the first raptor broke.
Tbh I don't know if it can lower the pressure enough but it's my theory :P

The engines use fuel to cool the combustion chamber. With low fuel tank pressure, the fuel pumps can't run well enough to keep the engine cool so it burns itself up.

Ryno23 · Dec 9, 2020

RoKKeR said:
Not knowing what was supposed to happen, I couldn't believe my eyes when that thing just flipped on a dime. Is that the long term plan for this thing?? Wouldn't that make all the passengers unconscious from the Gs?? Haha, long way off I know.

That was impressive as hell.

Yup from the OP:

SteveMeister · Dec 9, 2020

The biggest win here was proving the belly flop works. They've already proven they can land rockets, so that'll come in time.
Awesome flight.

kami_sama · Dec 9, 2020

Crispy75 said:
The engines use fuel to cool the combustion chamber. With low fuel tank pressure, the fuel pumps can't run well enough to keep the engine cool so it burns itself up.

Mmmm, you're right. So I had it backwards. It's not the raptor dying was caused the low pressure but the other way around.

Hootie · Dec 9, 2020

Man, seeing the full-up rocket with the super heavy booster and the starship on top will truly be a sight to behold. It even dwarfs the mighty Saturn V

SteveMeister · Dec 9, 2020

Watching the NASASpaceFlight playback, they shut down two raptors on ascent and then slewed out over the water at roughly the same altitude for some distance, which gave them more room for the glide back.

Tacitus · Dec 9, 2020

RoKKeR said:
Not knowing what was supposed to happen, I couldn't believe my eyes when that thing just flipped on a dime. Is that the long term plan for this thing?? Wouldn't that make all the passengers unconscious from the Gs?? Haha, long way off I know.

That was impressive as hell.

You mean the flip before the final landing burn? Probably not for manned flights. They'll want a bigger margin for any escape manoeuvres.

Thorrgal · Dec 9, 2020

Crispy75 said:
Looks like it was low fuel pressure in the header tank

Amazing. I'm speechless

Thorrgal · Dec 9, 2020

Tacitus said:
You mean the flip before the final landing burn? Probably not for manned flights. They'll want a bigger margin for any escape manoeuvres.

I think definitely for manned flights to Mars, no escape manoeuvres possible over there...just one chance :P

But more knowledgeable people will know for sure

RoKKeR · Dec 9, 2020

Tacitus said:
You mean the flip before the final landing burn? Probably not for manned flights. They'll want a bigger margin for any escape manoeuvres.

That makes sense, yeah. I was just surprised at how sudden and fast it was.

GrizzleBoy · Dec 9, 2020

RoKKeR said:
Not knowing what was supposed to happen, I couldn't believe my eyes when that thing just flipped on a dime. Is that the long term plan for this thing?? Wouldn't that make all the passengers unconscious from the Gs?? Haha, long way off I know.

That was impressive as hell.

Remember that the habitable area of the rocket is basically just inside the triangle shaped area of the nose cone.

During the landing flip, the vehicle rotates around that uppermost point of the craft, meaning it actually doesn't really do much swinging.

Just watch a video of a gymnast doing backflips on a floor routine.

Usually their feet will be travelling faster than their head in order to get the rotation of their body, but the persons head stays central to the point of rotation and therefore does not encounter as much rotational force.

RoKKeR · Dec 9, 2020

GrizzleBoy said:
Remember that the habitable area of the rocket is basically just inside the triangle shaped area of the nose cone.

During the landing flip, the vehicle rotates around that uppermost point of the craft, meaning it actually doesn't really do much swinging.

Just watch a video of a gymnast doing backflips on a floor routine.

Usually their feet will be travelling faster than their head in order to get the rotation of their body, but the persons head stays central to the point of rotation and therefore does not encounter as much rotational force.

A very interesting point! Hadn't even considered.

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