5 ms·

How so?

gridspy 6y ago
No orbital upper stage has been rapidly reusable. No existing rocket has tried to perform either the "belly flop" or the "Landing flip manouver" that SpaceX is trying to do. The failures are due to complex issues (fuel tanks, valves, engine reliability under complex forces) not simple control system issues (choosing wrong thrust, not able to orient using thrusters, etc)
- GizmoSwan 6y ago
  I don't understand the term belly flop or rapidly reusable. Do You mean that it is becoming horizontal to reduce the falling speed rate to land on its belly? shuttle was reused and landed on wheels parallel to its belly.
  - gridspy 6y ago
    Belly flop - https://youtu.be/vRPrLvVaQq8?t=145 https://youtu.be/vRPrLvVaQq8?t=145 (Yes, to reduce the falling speed. No, it lands vertically). Rapidly reusable - You can land it directly on (or next to) a launch platform, refuel it and launch it again the same day. Same as a regular aircraft. The Space shuttle had a disposable tank (which was lost on launch), recovered but basically destroyed solid rocket boosters (ditched into ocean) and finally on landing it had (potentially) damaged heat tiles which all needed inspection and which were all fragile and different.
    - GizmoSwan 6y ago
      Does it use Nasa's pica heat shield. Nasa could have upgraded shuttle too to use their own tech so the shield tech is not material argument. The boosters were recovered. https://www.nasa.gov/centers/marshall/about/star/shuttle_110803.html https://www.nasa.gov/centers/marshall/about/star/shuttle_110...
      - gridspy 6y ago
        SpaceX Starship boosters are refueled after they land themselves using a pump. Shuttle solid rocket boosters have their shells fished out of the ocean by a boat. Then they return to the factory to be broken into sections and filled with a solid propellent. Different tech.
        GizmoSwan 6y ago
        Yes but in real life they are not necessarily landing in the same spot the same day to be reused again. They could have multiple replacement boosters. Regardless, I have no problem with the booster return design unless it induces reckless danger to human life. The explosion is not a positive data.
        gridspy 6y ago
        Given two options 1. People doing analysis and hoping to check everything through engineering rigor and (hopefully) good assumptions 2. Test early and often, learning along the way until many positive tests have proven the system I'd prefer 2. Look at systems like SLS to see the schedule results of (1). No people were put on Falcon launches until almost 100 successful launches. I imagine a similar situation for StarShip. For example NASA is funding in orbit refuelling experiments (unmanned) and also a StarShip moon landing (unmanned) which will help prove the system prior to human flight. Don't worry, plenty of people will carefully do analysis (1) later on. But the data they will review will include telemetry from real flights rather than just hopeful simulation / analysis results.
        GizmoSwan 6y ago
        Don't get your hopes up. Since it is rotating on an axis while moving and twice, it has a huge degree of freedom for failure. Even if successfully returns 100 times, any untested change to its payload can change the parameters which are apparently unknown because they have not used any fancy simulation. Good luck. I will be watching and ready to say I told you so. The staff could be absolute geniuses by they will not be able to foresee all the unexpected results.
  - Me1000 6y ago
    Rapidly reusable means the goal is to have Starship (or at the very least the Super Heavy booster) fly multiple times a day. The Space Shuttle needed a new external fuel tank each flight, and the SRBs required significant refurbishment, to say nothing of the orbiter's own refurbishment. Also important to note that Starship is going to be an interplanetary vehicle. And that means it needs to be able to land in places with little to no atmosphere on a surface with no runway. The Space Shuttle was an impressive engineering marvel, especially for the time, but even if it could leave low earth orbit, there was no way it could land anywhere other than Earth.
ctdonath 6y ago
Pedantic trolling noted; I’ll engage just to hone my thoughts. Every production rocket is fully expendable. Launch, expect discard of 100%* of launch system. Starship is designed for 100% reusable, with same-day fly/land/refuel/repeat. That’s obviously a huge difference. * - exceptions: Space Shuttle discarded most of the launch system, acting as glider to return crew/cargo and some engines. Reuse turnaround was months, with extensive repairs expected. Boosters required prolonged recovery and refurbishing, with high likelihood of loss. Falcon 9 is only one remotely viable for same day return to pad and reuse of first stage. Second stage is discarded. SN# is a fast-reuse second stage. Landing involves leveraging the terminal velocity physics of a brick (not gentle glide of Shuttle), followed by effectively flipping a 16-story building ~90° in free fall with powered deceleration to 0m/s in less than 2km vertical. Nothing in the industry resembles the fast launch/fall/relight/reorientate/decelerate/land/refuel/repeat sequence, of SN#. There is no established industry specifications addressing such operation. And as the history of rocketry shows, establishing such specifications practically involves lots of crashes. [cue How Not To Land A Booster]
- gridspy 6y ago
  All true. Also, the only company doing propulsive landings of 10 storey tall rockets is SpaceX. I'm looking forward to seeing the landing structure that is going to catch the booster using the grid fins at the launch site.

How so?

No orbital upper stage has been rapidly reusable. No existing rocket has tried to perform either the "belly flop" or the "Landing flip manouver" that SpaceX is trying to do. The failures are due to complex issues (fuel tanks, valves, engine reliability under complex forces) not simple control system issues (choosing wrong thrust, not able to orient using thrusters, etc)

GizmoSwan 6y ago
I don't understand the term belly flop or rapidly reusable. Do You mean that it is becoming horizontal to reduce the falling speed rate to land on its belly? shuttle was reused and landed on wheels parallel to its belly.
- gridspy 6y ago
  Belly flop - https://youtu.be/vRPrLvVaQq8?t=145 https://youtu.be/vRPrLvVaQq8?t=145 (Yes, to reduce the falling speed. No, it lands vertically). Rapidly reusable - You can land it directly on (or next to) a launch platform, refuel it and launch it again the same day. Same as a regular aircraft. The Space shuttle had a disposable tank (which was lost on launch), recovered but basically destroyed solid rocket boosters (ditched into ocean) and finally on landing it had (potentially) damaged heat tiles which all needed inspection and which were all fragile and different.
  - GizmoSwan 6y ago
    Does it use Nasa's pica heat shield. Nasa could have upgraded shuttle too to use their own tech so the shield tech is not material argument. The boosters were recovered. https://www.nasa.gov/centers/marshall/about/star/shuttle_110803.html https://www.nasa.gov/centers/marshall/about/star/shuttle_110...
    - gridspy 6y ago
      SpaceX Starship boosters are refueled after they land themselves using a pump. Shuttle solid rocket boosters have their shells fished out of the ocean by a boat. Then they return to the factory to be broken into sections and filled with a solid propellent. Different tech.
      - GizmoSwan 6y ago
        Yes but in real life they are not necessarily landing in the same spot the same day to be reused again. They could have multiple replacement boosters. Regardless, I have no problem with the booster return design unless it induces reckless danger to human life. The explosion is not a positive data.
        gridspy 6y ago
        Given two options 1. People doing analysis and hoping to check everything through engineering rigor and (hopefully) good assumptions 2. Test early and often, learning along the way until many positive tests have proven the system I'd prefer 2. Look at systems like SLS to see the schedule results of (1). No people were put on Falcon launches until almost 100 successful launches. I imagine a similar situation for StarShip. For example NASA is funding in orbit refuelling experiments (unmanned) and also a StarShip moon landing (unmanned) which will help prove the system prior to human flight. Don't worry, plenty of people will carefully do analysis (1) later on. But the data they will review will include telemetry from real flights rather than just hopeful simulation / analysis results.
        GizmoSwan 6y ago
        Don't get your hopes up. Since it is rotating on an axis while moving and twice, it has a huge degree of freedom for failure. Even if successfully returns 100 times, any untested change to its payload can change the parameters which are apparently unknown because they have not used any fancy simulation. Good luck. I will be watching and ready to say I told you so. The staff could be absolute geniuses by they will not be able to foresee all the unexpected results.
- Me1000 6y ago
  Rapidly reusable means the goal is to have Starship (or at the very least the Super Heavy booster) fly multiple times a day. The Space Shuttle needed a new external fuel tank each flight, and the SRBs required significant refurbishment, to say nothing of the orbiter's own refurbishment. Also important to note that Starship is going to be an interplanetary vehicle. And that means it needs to be able to land in places with little to no atmosphere on a surface with no runway. The Space Shuttle was an impressive engineering marvel, especially for the time, but even if it could leave low earth orbit, there was no way it could land anywhere other than Earth.

ctdonath 6y ago

Pedantic trolling noted; I’ll engage just to hone my thoughts. Every production rocket is fully expendable. Launch, expect discard of 100%* of launch system. Starship is designed for 100% reusable, with same-day fly/land/refuel/repeat. That’s obviously a huge difference. * - exceptions: Space Shuttle discarded most of the launch system, acting as glider to return crew/cargo and some engines. Reuse turnaround was months, with extensive repairs expected. Boosters required prolonged recovery and refurbishing, with high likelihood of loss. Falcon 9 is only one remotely viable for same day return to pad and reuse of first stage. Second stage is discarded. SN# is a fast-reuse second stage. Landing involves leveraging the terminal velocity physics of a brick (not gentle glide of Shuttle), followed by effectively flipping a 16-story building ~90° in free fall with powered deceleration to 0m/s in less than 2km vertical. Nothing in the industry resembles the fast launch/fall/relight/reorientate/decelerate/land/refuel/repeat sequence, of SN#. There is no established industry specifications addressing such operation. And as the history of rocketry shows, establishing such specifications practically involves lots of crashes. [cue How Not To Land A Booster]

gridspy 6y ago
All true. Also, the only company doing propulsive landings of 10 storey tall rockets is SpaceX. I'm looking forward to seeing the landing structure that is going to catch the booster using the grid fins at the launch site.