5 ms·

I'm really interested in seeing how it will perform its "belly flop" landing. Seems like a high risk maneuver https://www.youtube.com/watch?v=DdTYMry7fq0#t=1m17

I'm really interested in seeing how it will perform its "belly flop" landing. Seems like a high risk maneuver https://www.youtube.com/watch?v=DdTYMry7fq0#t=1m17s https://www.youtube.com/watch?v=DdTYMry7fq0#t=1m17s

zlsa 6y ago
They've already done it[0], and it was a complete success until a propellant pressure issue resulted in lower than needed thrust, and a hard impact on the pad. [0]: https://www.youtube.com/watch?v=_qwLHlVjRyw https://www.youtube.com/watch?v=_qwLHlVjRyw
- doomlaser 6y ago
  It oriented almost perfectly. I'm truly amazed at what SpaceX has accomplished so far. Just need to stick that landing a few dozen more times. It's quite a reorientation.
  - deleted 6y ago
    [deleted]
  - systemvoltage 6y ago
    Curious why does it need to wait so long to reorient? I thought it was going to crash and in last few hundred feet, it flipped! Can it orient straight - way up in the air like Falcon boosters?
    - SECProto 6y ago
      Reorienting requires the use of main engines. You want to relight them only once, to ensure that the header tanks and the "downcomer" remain full. Additionally you want to burn off as much speed as possible with the bellyflop, so flipping vertical as late as possible. All combined this means combining the landing burn with the flip is best, as close to landing as possible.
      - ateng 6y ago
        It has a cute nickname, “Suicide Burn”. Why is it efficient? [https://www.reddit.com/r/KerbalSpaceProgram/comments/2z534g/can_someone_explain_the_physics_of_why_suicide/?utm_source=amp&utm_medium=&utm_content=post_body https://www.reddit.com/r/KerbalSpaceProgram/comments/2z534g/...]
        CGZp9X9k 6y ago
        Guessing we won't be using constant altitude landings in real life?
    - deleted 6y ago
      [deleted]
  - tenuousemphasis 6y ago
    It actuallyoriented perfectly, but due to the flip, fuel pressure was lost leading an oxygen rich exhaust eating away the engine (becoming what's known as engine rich exhaust) before it was able to complete the landing burn. They should just have to fix the fuel pressure problem to have a complete success.
    - Koiwai 6y ago
      I'm very dumb so I'm asking: is "engine rich exhaust" a real term?
      - jholman 6y ago
        What do you mean by "real term"? Real rocket science teams really use phrases like this, including this one. Is it a joke? Yeah, kind of. Is it what they would say if they had no sense of humour? No, probably not. Is it still a thing the experts actually say to actually talk about what's going on? Yeah, it is. a few more examples: "Rapid Unscheduled Disassembly" : explosive destruction of the rocket "Lithobraking" : it's like aerobraking, but with less aero and more litho
- yalok 6y ago
  On landing video, I see only 2 engines turn on instead of 3 - why is that? Was one engine malfunctioning, or was it the result of low pressure?
  - MartinodF 6y ago
    The rocket weighs quite a bit less at the end, having used most of its fuel, so only two engines are needed to land. The engines cannot be throttled down more than ~50% (as all rocket engines), so a third one would add too much thrust. Falcon 9 does the same, relighting 3 engines (out of 9 total) for the boostback burn, 3 for the entry burn and then just 1 for landing.
    - ygra 6y ago
      For that flight the engines are even too powerful for the ascent (it wasn't fully fueled, I think) and as soon as they couldn't throttle any lower, an engine was turned off instead.
    - Koiwai 6y ago
      Thanks for the explanation! it this also the reason why Raptor is (relatively compared to like F-1) small and BFR uses so many of them?
      - morlockabove 6y ago
        That, and for redundancy. I've heard it's designed so that even if a significant number of engines malfunction, others can be used to compensate.
- fergbrain 6y ago
  > “a hard impact on the pad.” It’s called a RUD: Rapid Unscheduled Disassembly
- GordonS 6y ago
  Wow, that's surely one of the most amazing feats of human achievement I've ever witnessed - incredible!
- JohnJamesRambo 6y ago
  A complete resounding success until it burst into flames!
TylerE 6y ago
I guess the counterargument is that as long as you bring it down in a "safe" area, you don't really need a 100% success rate. If you can reuse it, great, if not, well, it's a rocket.
- rtkwe 6y ago
  The belly flop is also how passenger variants will be landing so you do actually need a reliable program....
  - rlt 6y ago
    ...eventually. They didn’t launch humans on the Falcon 9 for the first 10 years either. Lots of time to iron out the kinks (though it will likely be much less than 10 years this time)
    - iso947 6y ago
      Humans aren’t landing propulsively on f9 either - if the landing fails it just costs money. The capsule lands with parachutes.
    - throwaway316943 6y ago
      The Mars mission has a somewhat tighter timeline.
      - DennisP 6y ago
        Aspirationally, yes, but it's not like they run out of money if they don't get to Mars that fast.
  - blackrock 6y ago
    How many G’s will passenger experience when the ship transitions from the belly flop to the suicide burn? That looks like an awful lot of G’s that this maneuver is pulling there.
deleted 6y ago
[deleted]
karmicthreat 6y ago
My guess would be it will still have a launch escape system for the passenger variant. So if the belly flop doesn't look right or if it doesn't stick the landing it just ejects the crew.
- kiba 6y ago
  A launch escape system is not necessarily safer than without one.
  - numpad0 6y ago
    In theory you’re right, in reality Space Shuttle.
    - TeMPOraL 6y ago
      IIRC never fired in actual missions; did not help avoid any of the two fatal accidents.
      - numpad0 6y ago
        All of standalone LES activation ever in the history of human spaceflight had been successful in saving all occupants' lives. Space Shuttle failed twice on the other hand, each time killing all aboard, and in neither cases of it its integral abort systems/abort modes did help at all. So in theory the lack of capsule-only LES do not necessarily mean safer rocket, in the history and in the statistics it does.
        iso947 6y ago
        Statistics say you shouldn’t call your reusable ship a word beginning with ‘C’ In 1963 a LES killed someone, in 1983 it saved lives.
        numpad0 6y ago
        > In 1963 a LES killed someone Which manned abort in 1963 is that specifically? Why are you trying to skew discussion into some direction? Note: LES stands for Launch Escape System, usually a small solid rocket that activates in case of a failure during ascent to take the manned capsule away from exploding rocket under it, perhaps equivalent to airbags in a car.

zlsa 6y ago

They've already done it[0], and it was a complete success until a propellant pressure issue resulted in lower than needed thrust, and a hard impact on the pad. [0]: https://www.youtube.com/watch?v=_qwLHlVjRyw https://www.youtube.com/watch?v=_qwLHlVjRyw

doomlaser 6y ago
It oriented almost perfectly. I'm truly amazed at what SpaceX has accomplished so far. Just need to stick that landing a few dozen more times. It's quite a reorientation.
- deleted 6y ago
  [deleted]
- systemvoltage 6y ago
  Curious why does it need to wait so long to reorient? I thought it was going to crash and in last few hundred feet, it flipped! Can it orient straight - way up in the air like Falcon boosters?
  - SECProto 6y ago
    Reorienting requires the use of main engines. You want to relight them only once, to ensure that the header tanks and the "downcomer" remain full. Additionally you want to burn off as much speed as possible with the bellyflop, so flipping vertical as late as possible. All combined this means combining the landing burn with the flip is best, as close to landing as possible.
    - ateng 6y ago
      It has a cute nickname, “Suicide Burn”. Why is it efficient? [https://www.reddit.com/r/KerbalSpaceProgram/comments/2z534g/can_someone_explain_the_physics_of_why_suicide/?utm_source=amp&utm_medium=&utm_content=post_body https://www.reddit.com/r/KerbalSpaceProgram/comments/2z534g/...]
      - CGZp9X9k 6y ago
        Guessing we won't be using constant altitude landings in real life?
  - deleted 6y ago
    [deleted]
- tenuousemphasis 6y ago
  It actuallyoriented perfectly, but due to the flip, fuel pressure was lost leading an oxygen rich exhaust eating away the engine (becoming what's known as engine rich exhaust) before it was able to complete the landing burn. They should just have to fix the fuel pressure problem to have a complete success.
  - Koiwai 6y ago
    I'm very dumb so I'm asking: is "engine rich exhaust" a real term?
    - jholman 6y ago
      What do you mean by "real term"? Real rocket science teams really use phrases like this, including this one. Is it a joke? Yeah, kind of. Is it what they would say if they had no sense of humour? No, probably not. Is it still a thing the experts actually say to actually talk about what's going on? Yeah, it is. a few more examples: "Rapid Unscheduled Disassembly" : explosive destruction of the rocket "Lithobraking" : it's like aerobraking, but with less aero and more litho
yalok 6y ago
On landing video, I see only 2 engines turn on instead of 3 - why is that? Was one engine malfunctioning, or was it the result of low pressure?
- MartinodF 6y ago
  The rocket weighs quite a bit less at the end, having used most of its fuel, so only two engines are needed to land. The engines cannot be throttled down more than ~50% (as all rocket engines), so a third one would add too much thrust. Falcon 9 does the same, relighting 3 engines (out of 9 total) for the boostback burn, 3 for the entry burn and then just 1 for landing.
  - ygra 6y ago
    For that flight the engines are even too powerful for the ascent (it wasn't fully fueled, I think) and as soon as they couldn't throttle any lower, an engine was turned off instead.
  - Koiwai 6y ago
    Thanks for the explanation! it this also the reason why Raptor is (relatively compared to like F-1) small and BFR uses so many of them?
    - morlockabove 6y ago
      That, and for redundancy. I've heard it's designed so that even if a significant number of engines malfunction, others can be used to compensate.
fergbrain 6y ago
> “a hard impact on the pad.” It’s called a RUD: Rapid Unscheduled Disassembly
GordonS 6y ago
Wow, that's surely one of the most amazing feats of human achievement I've ever witnessed - incredible!
JohnJamesRambo 6y ago
A complete resounding success until it burst into flames!

TylerE 6y ago

I guess the counterargument is that as long as you bring it down in a "safe" area, you don't really need a 100% success rate. If you can reuse it, great, if not, well, it's a rocket.

rtkwe 6y ago
The belly flop is also how passenger variants will be landing so you do actually need a reliable program....
- rlt 6y ago
  ...eventually. They didn’t launch humans on the Falcon 9 for the first 10 years either. Lots of time to iron out the kinks (though it will likely be much less than 10 years this time)
  - iso947 6y ago
    Humans aren’t landing propulsively on f9 either - if the landing fails it just costs money. The capsule lands with parachutes.
  - throwaway316943 6y ago
    The Mars mission has a somewhat tighter timeline.
    - DennisP 6y ago
      Aspirationally, yes, but it's not like they run out of money if they don't get to Mars that fast.
- blackrock 6y ago
  How many G’s will passenger experience when the ship transitions from the belly flop to the suicide burn? That looks like an awful lot of G’s that this maneuver is pulling there.

deleted 6y ago

[deleted]

karmicthreat 6y ago

My guess would be it will still have a launch escape system for the passenger variant. So if the belly flop doesn't look right or if it doesn't stick the landing it just ejects the crew.

kiba 6y ago
A launch escape system is not necessarily safer than without one.
- numpad0 6y ago
  In theory you’re right, in reality Space Shuttle.
  - TeMPOraL 6y ago
    IIRC never fired in actual missions; did not help avoid any of the two fatal accidents.
    - numpad0 6y ago
      All of standalone LES activation ever in the history of human spaceflight had been successful in saving all occupants' lives. Space Shuttle failed twice on the other hand, each time killing all aboard, and in neither cases of it its integral abort systems/abort modes did help at all. So in theory the lack of capsule-only LES do not necessarily mean safer rocket, in the history and in the statistics it does.
      - iso947 6y ago
        Statistics say you shouldn’t call your reusable ship a word beginning with ‘C’ In 1963 a LES killed someone, in 1983 it saved lives.
        numpad0 6y ago
        > In 1963 a LES killed someone Which manned abort in 1963 is that specifically? Why are you trying to skew discussion into some direction? Note: LES stands for Launch Escape System, usually a small solid rocket that activates in case of a failure during ascent to take the manned capsule away from exploding rocket under it, perhaps equivalent to airbags in a car.