JF Mezei wrote:

On 2017-06-07 06:20, Jeff Findley wrote:

No, this is not correct. The Dragon "trunk" does not have any
propulsion systems. As many systems as possible are packed *inside* the
Dragon reentry capsule to be reused on subsequent flights, like this one
(CRS-11 is reusing the capsule from CRS-4).


Does this mean fuel tanks are also in the Dragon and not in the trunk?


What small fuel tanks there are, yes, although I think they've
switched over from the 90 lb thrust Draco hypergolic engines to cold
gas for OMS engines.


I guess my thoughts were tainted by Soyuz and Apollo that had mosts of
their systems in the module.


Apollo had a Service Module. Dragon does not. The trunk is not just
another name for a Service Module. It has a different name because it
is a different thing.

Note that Orion has a Service Module and not a trunk. Manned Dragon,
on the other hand, has a trunk like the cargo variant. Orion has a
longer manned duration than Dragon V2 (21.1 days vs 7 days) but Dragon
V2 carries a larger crew. It works out to 84.4 man-days for Orion vs
49 man-days for Dragon V2, although presumably support equipment could
be added in the trunk to increase flight durations. Either vehicle
will need an attached hab module for any long duration missions (both
have a docking port). Both would presumably stay attached to a high
energy upper stage for long range missions, although both have their
own propulsion systems. The Orion Service Module includes a 6,000 lb
thrust engine with enough fuel for around 1800 m/s delta-v. The eight
Super Draco engines built into the Dragon V2 are capable of delivering
more than 100,000 lbs of thrust but only around 400 m/s of delta-v due
to not carrying much fuel; there's only enough for around a 25 second
burn. Given that the fuel tanks are built into the Dragon, I don't
think it would be easy to increase that.


So when Dragon needs to accelerate forward, wouldn't engines on Dragon
throw hot gases at the solar arrays atached to the trunk ?


A child could do a design where that doesn't happen.


--
"The reasonable man adapts himself to the world; the unreasonable
man persists in trying to adapt the world to himself. Therefore,
all progress depends on the unreasonable man."
--George Bernard Shaw