View Single Post
  #8  
Old January 19th 20, 01:18 AM posted to sci.space.policy
Alain Fournier[_3_]
external usenet poster
 
Posts: 548
Default SpaceX Dragon 2 In Flight Abort Test

On Jan/18/2020 at 17:53, Niklas Holsti wrote :
On 2020-01-19 0:11, JF Mezei wrote:
On 2020-01-18 10:17, Jeff Findley wrote:

NASA knows the details of this for sure.Â* But I believe that the Super
Draco engines are sized to pull Dragon 2 away from Falcon 9 at the same
time the engines are shutting down.


Media articles tend to "Readers Digest" what is given to them by
authorities which are already a Reders Digest version of reality.

Say an abort happens for causes other then engines. If engines are
already giving astronauts a 3G acceleration, and you fire the Super
Dracos that give 4G, the crew would go from 3G to 7G


No. If the Dragon is still attached to the launcher when the Dracos
fire, the acceleration would only increase a little, as the Draco thrust
is added to the Merlin thrust to accelerate the launcher+Dragon assembly.

If the Dragon is not attached to the launcher when the Dracos fire, the
Dragon will simply pull ahead of the launcher, at 4G, losing contact
with the launcher which will fall behind, the distance increasing at 1G.
In theory, the launcher's acceleration might increase a little when the
Dragon pulls away, because the launcher no longer has to accelerate the
Dragon's mass, but I believe that the control SW keeps the launcher's
acceleration at its programmed value, and the Dragon's mass is anyway
only a fraction of the mass of the launcher and its fuel.


Yes. Note also that even if the Dragon capsule did experience 7g for a
few seconds, that wouldn't be a problem. Such an acceleration is a
problem if it is sustained but for a few seconds 7g is uncomfortable but
not really dangerous.


Alain Fournier