JF Mezei wrote:

On 2017-10-01 17:44, Jeff Findley wrote:

Moreover, New Glenn is also, as Bezos repeated Tuesday, "the
smallest orbital rocket Blue Origin will ever build."

Considering the current state of rocket science, once you have the
engines, does designing a rocket to have 3, 5 , 9 or 27 engines make
such a huge difference in terms of how much experience you need?


Certainly to some extent, yes.


Once BlueOrigin has its first rocket tested, and re-uses same engines,
couldn't it aim for a bigger rocket as the next installment?


It certainly could and presumably will but first it needs to get that
'first rocket' (New Glenn) done and flying. Once there, the BE-4
engine is roughly equivalent to SpaceX Raptor; BE-4 has around 25%
more thrust but Raptor runs at higher pressures so has better power to
weight. Blue Origin also has a lot of structure and weight reduction
work to do. Right now the Blue Origin 'next rocket' isn't even at the
paper napkin stage. All we have is the name (New Armstrong).


Musk explained that they had expected Fancon9 Heavy to use existing
Falcon9 for core and the 2 boosters. Turns out they have to redesign
structures because of different loads (higher payload, + lateral loads
where boosters attach). (This was to explain the delay).

But had they decided at the onset on the need to design the structures
for the Falcon 9 Heavy Loads, wouldn't that design been straightforwards
without needing to push the enelope?


You can't 'decide that' until you're far enough in to know what the
loads are. Without knowing that you don't know what you're designing
to.


I can understand building the cryo tanks from carbon fibre for BFR means
developing new techniques and going beyond current state of the art. But
does Falcon 9 Heavy push any such limits or just scale existing tech
within what that tech is capable of?


How long has Falcon Heavy (there is no '9' in the name) taken? First
concept was in 2005. Real work couldn't start on it until Falcon 9
was done, since it was based on Falcon 9 cores. That actually wasn't
done until around 2011 (2 years late). First flight for Falcon Heavy
will probably be 2018, so it took 7 years. That's the sort of
timeline Blue Origin is looking at (if they hurry) to get from New
Glenn to New Armstrong once New Glenn is done (probably in 2020 or a
bit later). That says New Armstrong is ready for first test flight in
2028 or so, which is probably a more reasonable date for BFR than the
one Musk gave.


I guess what I am asking is whehther "baby steps" is still needed for
outfits like Blue Origin, or whether state of science allowed bigger
leaps once you have your engines?


No magic has been discovered. It still takes the better part of a
decade to get a new rocket.


--
"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