Successful flight by Blue Origin

If they can do this 4 or 5 times in a row even if they have 1 failure after
that, then might be adequate for an unmanned booster. More likely though
they'll have couple of successes then a failure. Suicide-burn is inherently
less reliable than a hovering approach.

Bob Clark



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"Jeff Findley" wrote in message
...

In article ,
says...

Rick Jones wrote:

In sci.space.policy Jeff Findley wrote:
They're reasonable if they work. SpaceX is trying to avoid adding
other engines to the Falcon 9 first stage. The stage could hover
and land, for example, if it added Super Draco engines to the first
stage. But, they require different fuel and oxidizer than the first
stage carries. This would mean adding completely different tanks,
plumbing, and etc. for those engines. Also, if Super Dracos were
used, it would be advantageous to deplete the kerosene and then vent
any remaining LOX in the tanks before landing. So, any "leftover"
fuel and oxidizer would be "wasted". In my book, this would not be
a good trade to make.

If one wanted to give the Falcon 9 first stage the ability to hover,
wouldn't the most straightforward way to do that be create a
deeply-throttled Merlin?


Straightforward, perhaps, but it's a very big design change so you
start with having to requalify as if it's a whole new engine.

And today's successful barge landing proves they don't *need* to hover!

http://www.theverge.com/2016/4/8/113...uccess-falcon-
9-rocket-barge-at-sea

I watched it live and it looked like a very nice landing.

Jeff
--

In article ,
says...

If they can do this 4 or 5 times in a row even if they have 1 failure after
that, then might be adequate for an unmanned booster. More likely though
they'll have couple of successes then a failure. Suicide-burn is inherently
less reliable than a hovering approach.

Agreed. But that said, space shuttle glide landings were inherently
less reliable than powered landings, yet it was "safe enough" that we
did not see a landing failure during that program.

SpaceX is gaining experience with this mode of recovery even if a thrust
to weight greater than one is not ideal. On their next reusable launch
vehicle design, they should have the opportunity to make improvements.
Exactly what improvements may very well depend on how the rest of the
Falcon 9/Falcon Heavy program pans out.

Jeff
--
All opinions posted by me on Usenet News are mine, and mine alone.
These posts do not reflect the opinions of my family, friends,
employer, or any organization that I am a member of.

"Jeff Findley" wrote in message
...

In article ,
says...

If they can do this 4 or 5 times in a row even if they have 1 failure
after
that, then might be adequate for an unmanned booster. More likely though
they'll have couple of successes then a failure. Suicide-burn is
inherently
less reliable than a hovering approach.

Agreed. But that said, space shuttle glide landings were inherently
less reliable than powered landings, yet it was "safe enough" that we
did not see a landing failure during that program.

To fair we'd had over 8 decades of experience of gliding/horizontal landings
and we had the Mark I eyeball in the cockpit to respond to unknowns.


SpaceX is gaining experience with this mode of recovery even if a thrust
to weight greater than one is not ideal. On their next reusable launch
vehicle design, they should have the opportunity to make improvements.
Exactly what improvements may very well depend on how the rest of the
Falcon 9/Falcon Heavy program pans out.


Ayup.

Jeff

--
Greg D. Moore http://greenmountainsoftware.wordpress.com/
CEO QuiCR: Quick, Crowdsourced Responses. http://www.quicr.net