stuff that’s hard to do (Starship pathfinder 150m hop test)

We Starship fans have been waiting on this test almost daily for a month or so.
The smaller Starhopper pathfinder did it’s hop about a year ago (you can see it in the left-hand vid after the cloud clears).
This test article (SN5) is mainly the tank section*, one engine, cold-gas roll-control thrusters**, landing legs, and a mass simulator on top*** without any payload/nose section or fins.
Since there’s only one engine (which is offset**** from the centerline) the vehicle has to tilt a bit so the thrust vector is directly below the center of gravity.

SpaceX drone view with inside-the-engine-bay view!

Well, sunuva… it flies!

The next major milestone is a multi-engine version with payload/nose section and control fins for a 20km flight.


You make us knuckle-dragging members of the species proud
* Integrated fuel & oxidizer tanks
** Near the bottom, you can see one fire a few times (the continuous white plume is a vent)
*** Looks like a spray-can nozzle
**** Manifold is for three engines, so there’s no center mount


  1. Stick
    Posted August 5, 2020 at 5:03 am |

    What’s that reddish flame up in the engine Doug?

  2. dick, not quite dead white guy
    Posted August 5, 2020 at 8:18 am |

    I’m fascinated with that big engine gimbaling around keeping the thing vertical. I always thought it amazing that big rocket engine(s) can adjust fast enough to keep the craft vertical; kinda like balancing a pencil with the eraser on your fingertip.
    What do they use to gimbal the engine? Hydraulics, and where does that system get power?

  3. DougM ☞ crotchety and judgmental ☜
    Posted August 5, 2020 at 1:15 pm |

    Stick ^^
    Didn’t look like a high-pressure leak.
    Mebbe a dribble fuel leak upstream of the turbine?
    At liftoff, something big flew from the launch mount area,
    so mebbe it was debris? (flame gone in final scene)
    Mechanic hid a girlie sci-fi magazine there when the supervisor walked over?

  4. DougM ☞ crotchety and judgmental ☜
    Posted August 5, 2020 at 1:15 pm |

    dick ^^
    Yep, an engine can gimbal a lot faster than you’d think.
    Watch closely, and you’ll see they use a small rotational baseline pattern. It’s often easier to do small-error control corrections that way than with jerky, linear movements trying for zero error. (I’m not sure about that; maybe it’s a modeling issue or propellant sloshing or something, but probably not demons — it’s seldom demons)
    Here’s a schematic
    Hydraulic actuator upper-right, 2ea
    TVC (thrust vector control) is engine steering
    Gimbal upper dotted line
    Hydraulic pumps are usually electrically driven from batteries.
    Actuator valves are controlled by flight computer.

  5. Paul
    Posted August 5, 2020 at 2:21 pm |

    Take that China!!!

    Screw you. Will will OWN THE MOON and MARS. USA will mine it. Tough nuts CCP and USSR-used-to-be.

  6. DougM ☞ crotchety and judgmental ☜
    Posted August 5, 2020 at 11:45 pm |

    ZARKOV !
    That‘s who Elon Musk reminds me of.
    You know, non-gov inventor of a rocket ship to Marrrrs

  7. Posted August 7, 2020 at 3:22 pm |

    I was associated with telemetry and range safety on the Pershing II missiles. Important to know where anything was that would explode and there were plenty. The hydraulic pump was powered by a thing that burned if I remember right. That thing was started with squibs. The entire hydraulics were smaller than a loaf of bread including power source. There were 3 separate systems, 1st and 2nd stage, plus reentry section.