From: alain245@videotron.ca   
      
   On Aug/22/2020 at 23:10, JF Mezei wrote :   
   > On 2020-08-22 17:07, Snidely wrote:   
   >   
   >> Keep an eye on the High Bay at Boca Chica.   
   >   
   > I assume they will wait to have perfected the welding on the new allow   
   > they will start to test on SN7 before they start building a Super Heavy.   
   >   
   > How many engines would it need to liftoff as a Super Heavy with no   
   > payload to do a hop ? to do a suborbital flight with no payload?  (can   
   > they fit a dome on it?   
   >   
   > O MUST any SuperHeavy launch with a Starship on top, which likely means   
   > 37/39 engines at the bottom right from the start?   
   >   
   > A test launch with both would require Starship have ebough fuel to land   
   > once it detaches from Super Heavy. Doubtful SuperHeavy will have   
   > software to land with a payload (Starship)  attached to it, correct?   
      
   Enough fuel to land is a very small fraction of the total fuel. The dry   
   mass of the SuperHeavy/Starship stack is about 6.5% of the total mass of   
   the system fuelled up with a payload. Add a little fuel mass to that   
   6.5% and you get about 3/37. So three engines should be enough   
   especially if you don't want to have as much acceleration at lift-off   
   compared to an orbital launch. But you might want to add in a little   
   more margin, have the same acceleration as for orbital launches and do   
   the test with five engines. SpaceX might also want to do a full test   
   with all engines.   
      
      
   Alain Fournier   
      
   --- SoupGate-Win32 v1.05   
    * Origin: you cannot sedate... all the things you hate (1:229/2)