BFR early next year.

JF Mezei wrote on Sun, 18 Mar 2018
20:58:23 -0400:

On 2018-03-18 13:10, Fred J. McCall wrote:

False. Enterprise was never mated to live SRBs

https://en.wikipedia.org/wiki/Space_...ion_Test_(MGVT)

##
Mated Vertical Ground Vibration Test (MGVT)
Following the conclusion of the ALT test flight program, on March 13,
1978, Enterprise was flown once again, but this time halfway across the
country to NASA's Marshall Space Flight Center (MSFC) in Alabama for the
Mated Vertical Ground Vibration Testing (MGVT). The orbiter was lifted
up on a sling very similar to the one used at Kennedy Space Center and
placed inside the Dynamic Test Stand building, and there mated to the
Vertical Mate Ground Vibration Test tank (VMGVT-ET), which in turn was
attached to a set of inert Solid Rocket Boosters (SRB) to form a
complete shuttle launch stack, and marked the first time in the
program's history that all Space Shuttle elements, an Orbiter, an
External Tank (ET), and two SRBs, were mated together.
##

Granted, the text provides for the vibration forces having been
generated by the facility and not the SRBs. But it was mated to SRBs
even if later were not fired.


Which part of 'inert' is it that you don't understand? Again, the
Enterprise was never mated to live SRBs. In fact, it wasn't even
mated to a real External Tank (and there would be no point to that,
since it had no engines).


Enterprise was also mated with an ET and SRBs and moved to 39-A 20
months before Columbia's first flight. (fit and facilities checks).


Do you have any idea what 'fit checks' are?

The knowledge gained from it resulted in a production design
sufficiently different that it wasn't worth retrofitting Enterprise.


False.


Again from that Wikipedia page:
##
However, in the period between the rollout of Enterprise and the rollout
of Columbia, a number of significant design changes had taken place,
particularly with regard to the weight of the fuselage and wings, which
meant retrofitting the prototype would have been a much more expensive
process than previously realized,
##


Again, which part of "knowledge gained from it" don't you understand?
Wonkypaedia says nothing like what you originally claimed. The design
changed. Nothing says it changed because of things flowing out of
Enterprise tests.

This is why you're such an annoying ****, Mayfly. You ask questions,
some of which are stupid. That's fine. People give you answers to
your questions. That's fine. Then you argue with the answers that
people gave you to your questions. That's not fine.



Why would it lack most of those things?


SpaceX hasn't even flown its manned Dragon capsule. You think it would
have a fully built out crew compartment this early into the BFS development?


You don't know the difference between paperwork required for manned
spaceflight (tons and a long time) and paperwork to operate an
atmospheric vehicle on a test range (small and fast), I see.



If you're going to test
handling and flight, you need the moment arms and CGs to be as close
as possible to the intended final article.


Yep.

I was told in this thread that SpaceX wuld flty a BFS, not some other
vehicle retrofitted to support Raptor engines.


And yet you argue that what they're going to fly is NOT a BFR
Spaceship, but rather some empty hull.


If the goal is to test BFS as a ship, then, depending on how far
advanced in its design, you want to simulate as much of the end product
as possible.


Which is why it will have all that structure that you claim won't be
there. That stuff can't really be built in after the hull is
complete, so your argument is that they're not building a BFR
Spaceship at all, but rather a test jib.


Crew compartment can be sumulated with any mass inside the fairing.


And the easiest way to have that mass in the right place is to
actually build the static structure in the first place. You can't
really add that structure later, so when your testing program gets to
where you need it, you can't put it in.


But the engine area is harder to mimulate if you have empty spaces where
the vacuum engines would be.


No, it's easier. It's simple to just plug in weights for those if you
need to, since they're intended to be removable in the first place.
Same with nozzles, if you actually need them. But by the time you get
to the point in your testing where you need that stuff, you just add
it.


You also need to consider they may want to simulate the plumbimg for
fuel and oxydizer since it will serve both types of engines.


Why? The plumbing associated with the tank will already be there. The
plumbing associated with the engines comes when you install the real
engines. Again, you can add the engines any time because they're
designed to be removed, refurbished, and replaced. You can't do that
with dry structure inside the pressure hull, so if that stuff isn't
there when you build the thing you're building a 'throw away' test
article and not a BFR Spaceship.


The vehicle that will do first flight is also going to be used to do a
whole lot of integration tests before flight (and if it survives, after
flight).


Of course it will. That's why the dry structure will be there.



BFR Spaceship isn't a subway train.


It's called integration tests because unforeseen problems come up when
you have everything, which, when tested indepemdandly, ends up causing
problem s when assembled together.


Well, duh! What do you do for a living, Mayfly? I spent 30+ years as
an engineer working for a missile company. I suspect I know a bit
more about integration testing than you do.


Possible interference between vacuum and sea leavel engines is best
detected as early as possible.


Which is why you've run flow field analyses and fired them in test
jigs long before you start bending metal on an actual vehicle.


If it is the same engine come with just
different Bell (and software), then might as well populated the spots
with Raptors fitted with vacuum bells. (those Raptors could be early
builds with defects, not intended to be fired).


Elon Musk disagrees with you. So do I. There's no need for those
engines or the heat shield until you get to test points in your master
test plan that require them. And once you put them on, there is no
reason not to use real working engines, since you're getting to parts
of the master test plan that require them.



Mayfly, engineers don't just build **** and hope it works. Yes, some
things only come out with full up testing but this is not one of those
things.


When they started in the 40s and 50s, it was a lot of trial and error,
with lots of rocket failures.


I don't know if you've notices, but it hasn't been "the 40s and 50s"
for over half a century now.


SpaceX ramped up to success launches much much faster, and rampted up
landings fairly quickly. The pace is faster now because
software/simulations allow to weed out many more problems before an ship
is built.


No, the pace is faster now because we have over half a century more
experience.


And materials like carbon fibre require cokputers to design the layup
and obtain the desired strength/durability at least amount of weight
posssible. (and despite the facy software, during flight tests, there
are many adjustments that have to be made, generally to strenghten what
the computer optimmized a bit too much.


How many times do I have to tell you YOU'RE ****ING WRONG ABOUT THAT?
Are you getting it yet?



Do you have any conception at all of how engineering works?


The issue here is that if they are to be ready to lauch BFS next year,
how much of BFS will have been built, and how much will be an empty shell.


They have two years. You're aware that Musk wants to fly a cargo
mission with BFR Spaceship to Mars in 2022 and follow that with a
combined cargo/manned mission in 2024, right? If you believe those
dates (I don't and expect at least a two year slide) that means he
needs to start testing BFR, BFR Spaceship, and BFR Tanker just real
soon now (like next year).


IOf they are ready to test propulsion and tanks, then they should test
these. And since vacuum engines are common with sea level ones, then
they should populate the rocket fully for the test to provide more
complete data on co-existence of the engines.


Let me try this one more time, given that both Musk and I disagree
with you.

* * * * * Y O U A R E F U C K I N G W R O N G ! * * * * *

Go back and read that again. And again. And again until if finally
penetrates. Look at the dates Musk says he is trying to hit with
regard to actual Mars missions and tell me just how incomplete BFR
Spaceship can be by the end of 2019 and still make those dates.


Question: have there ever been cases where a rocket took off with not
all engines producing thrust? Asking about airflow being affected by
regions of the bottom of rocket not producing thrust.


Lots of operational rockets do this, much less stuff under test.


Or are vacuum engines going to be all on the outermost ring of engines?


BFR Spaceship has four vacuum engines in a square on the outside rim
and three sea level engines in a triangle at the center. How can you
sit there and argue with me (and Elon Musk) and not know even the most
trivial details about the thing?



There are 3 sea level engines. You need ONE in order to land.


Even when you are returning from Mars with 100 passengers and their luggage?


Passengers aren't coming back, Mayfly. What planet have you been
living on to not know this? They're not doing 'Mars tours' where you
pack up your luggage and embark on a cruise.



So you think you know more than Elon Musk about BFR Spaceship, do you?


No.


THEN WHY THE **** ARE YOU ARGUING AGAINST WHAT HE SAID HE'S GOING TO
DO?


My thoughts reflect the PR spin around these test flights that lack
enough details to explain to layman what is REALLY being tested.


Well, perhaps you should try listening to people who know what the
**** they're talking about instead of arguing with them, then.


Just like NASA claiming in its PR and to politicians that SLS and Orion
are going to Mars.


You're wrong about that, too. SLS isn't going to Mars. Orion is, but
it's not going by itself. It will be starting from Lunar orbit, going
on some high energy upper stage, and will be taking a hab module like
the B330 along with it. SLS will be what gets all those pieces to the
Gateway platform.


From this discussion, I have learned it was BFS and not BFR being
tested. And as you pointed out, 1 engine needed to land (but not clear
if only for this empty flight or even when landing with full payload of
100 passengers).


Where did you ever get the idea that they're landing on Earth with 100
passengers? Have you considered that you have disposed of around
1,000 tonnes of propellant that you had on board when you launched?
The empty mass of the vehicle is only around 85 tonnes. Cargo and
other consumables is around 250 tonnes. A single sea level Raptor
engine (Block 1) can produce around 175 tonnes of thrust (this goes up
significantly when they increase the chamber pressure in later block
engines by 20%). Do the math.

ON ANY REASONABLE MISSION, ONE ENGINE WILL BE SUFFICIENT TO LAND. This
is because most of the mass of the vehicle (propellant, cargo,
consumables) just isn't there to be landed.


So the question revolves around how much of a BFS will be built by the
time of first flight. If insufficiently buit, the the test is either PR
stunt, or just an engine test that could have been done on an "open"
rocket without a skin or being called "BFS".


Again, look at the dates for actual Mars missions that Musk says he
wants to hit. I don't think he can hit those dates and that
everything will slide 2-4 years, but if he intends to hit the dates
he's said he'd better have something just pretty damned close to a
full up BFR and BFR Spaceship ready to start testing by the end of
next year.


--
"Some people get lost in thought because it's such unfamiliar
territory."
--G. Behn