BFR early next year.

In article ,
says...

The other difference is that while NASA was able to greatly reduce
weight after Enterprise prototype, this doesn't happen anymore because
the modern design software already optimizes structures and generally,
some parts need to be beefed up after prototype is built. (aka: 787
ended up significantly heavier than originally predicted by Boieing,
same with the A380 from Airbus).


Untrue. It certainly does still happen.

Agreed. You don't know your final aircraft/launcher/spaceship mass
until it's completely designed and done with test flights. The best
software in the world doesn't have a freaking clue what your
constratints, loads, and etc. are. Some of those you won't know exactly
until after your test flights.

That's why the structure of both Enterprise and Columbia was heavier
than the other orbiters. The engineers weren't certain what the flight
loads would be, so they were conservative in their estimates. In the
end, they were a bit too conservative so subsequent orbiters were
designed and built with lighter structures.


It was originally
intended to rebuild it to 'space standard' after the tests were over,
but that just proved to be much more expensive than they'd
anticipated. The same thing could wind up being true of the first
Block of BFR Spaceship.


With Modern design techniques, Enterprise would have been built
pre-optimized.


Horse****. They didn't design the thing using bearskins and stone
axes, you know.

Agreed. Some of the first finite element analysis software came out of
NASA. Its roots date back to the early 1960s. It eventually led to the
commercial FEA software known as MSC Nastran.

https://en.wikipedia.org/wiki/Nastran

Due to a finding that they were a monopoly in the US, my company
obtained a copy of the source code and we hired several NASTRAN
developers, so today you can buy Siemens NX Nastran:

https://en.wikipedia.org/wiki/Nastran#NX_Nastran

https://www.plm.automation.siemens.c...enter/nastran/

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.

In article ,
says...

JF Mezei wrote on Fri, 16 Mar 2018
17:05:50 -0400:

On 2018-03-16 03:16, Niklas Holsti wrote:

I hope that SLS is also a transitional temporary project, and that BFR
will replace it. In this ephemeral role, too, Falcon Heavy competes with
SLS.


Since SLS has no commercial goals, has limited set of test flights with
no planned use beyond one crewed flight around the moon, it is not in
any competition except for sucking up government funding away from from
more productive uses.


I'm sure we've covered this before. While of course stuff out more
than half a dozen years tends to get tentative, there are certainly
'planned uses' for SLS beyond one flight around the Moon. That flight
is EM-2 (EM-1 is the same mission but unmanned) currently scheduled
for 2022. I see 9 more missions planned after that, mostly involved
with putting together the Lunar Orbital Platform - Gateway. Is any of
this sounding at all familiar to you or have you once again lost all
memory of anything that was told to you before lunch?

I don't believe that date for EM-2. NASA recently decided to not build
a new MLP for EM-2 and instead modify the one to be used for EM-1. This
means they simply can't shorten the 33 month gap between EM-1 and EM-2.
They really can't start the MLP modifications until after EM-1 flies.
So EM-2 will keep slipping to the right by the amount that EM-1 slips to
the right.

NASA no longer seeking to develop second mobile launcher for SLS
by Jeff Foust ? February 28, 2018
http://spacenews.com/nasa-no-longer-...second-mobile-
launcher-for-sls/

If EM-1 slips into 2020, as some sites are reporting, I don't see how
EM-2 could realistically fly by 2022 with a minimum of 33 months between
them.

NASA expects first Space Launch System flight to slip into 2020
November 20, 2017 Stephen Clark
https://spaceflightnow.com/2017/11/2...-space-launch-
system-flight-to-slip-into-2020/

SLS slips are constant and always moving to the right. I have zero
faith in the 2022 date for EM-2.

Between now and EM-2 we're looking at about $15 to $18 billion to be
spent on SLS/Orion (depending on when it actually flies). That does not
include any money spent before today, only money we're going to spend.
It's absurd how much we're spending on a vehicle that will almost
certainly be obsolete before it starts flying "routinely" at a cadence
of at most 2 flights per year at a cost to the US taxpayer of well over
$1 billion a flight.

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 on Sat, 17 Mar 2018
10:04:19 -0400:

In article ,
says...

JF Mezei wrote on Fri, 16 Mar 2018
17:05:50 -0400:

On 2018-03-16 03:16, Niklas Holsti wrote:

I hope that SLS is also a transitional temporary project, and that BFR
will replace it. In this ephemeral role, too, Falcon Heavy competes with
SLS.


Since SLS has no commercial goals, has limited set of test flights with
no planned use beyond one crewed flight around the moon, it is not in
any competition except for sucking up government funding away from from
more productive uses.


I'm sure we've covered this before. While of course stuff out more
than half a dozen years tends to get tentative, there are certainly
'planned uses' for SLS beyond one flight around the Moon. That flight
is EM-2 (EM-1 is the same mission but unmanned) currently scheduled
for 2022. I see 9 more missions planned after that, mostly involved
with putting together the Lunar Orbital Platform - Gateway. Is any of
this sounding at all familiar to you or have you once again lost all
memory of anything that was told to you before lunch?

I don't believe that date for EM-2. NASA recently decided to not build
a new MLP for EM-2 and instead modify the one to be used for EM-1. This
means they simply can't shorten the 33 month gap between EM-1 and EM-2.
They really can't start the MLP modifications until after EM-1 flies.
So EM-2 will keep slipping to the right by the amount that EM-1 slips to
the right.

NASA no longer seeking to develop second mobile launcher for SLS
by Jeff Foust ? February 28, 2018
http://spacenews.com/nasa-no-longer-...second-mobile-
launcher-for-sls/

If EM-1 slips into 2020, as some sites are reporting, I don't see how
EM-2 could realistically fly by 2022 with a minimum of 33 months between
them.

NASA expects first Space Launch System flight to slip into 2020
November 20, 2017 Stephen Clark
https://spaceflightnow.com/2017/11/2...-space-launch-
system-flight-to-slip-into-2020/


NASA is managing to a launch of EM-1 just before Christmas of 2019.
Schedule risk puts the length of the slide at a maximum of 6 months
(June 2020).


SLS slips are constant and always moving to the right. I have zero
faith in the 2022 date for EM-2.


EM-2 is currently predicated on the managed date for EM-1 for launch
in June of 2022. IF EM-1 takes the maximum expected slide and they
are unable to compress the 'stick' between the two launches EM-2
launches just before Christmas of 2022.


Between now and EM-2 we're looking at about $15 to $18 billion to be
spent on SLS/Orion (depending on when it actually flies). That does not
include any money spent before today, only money we're going to spend.
It's absurd how much we're spending on a vehicle that will almost
certainly be obsolete before it starts flying "routinely" at a cadence
of at most 2 flights per year at a cost to the US taxpayer of well over
$1 billion a flight.


NASA's current long range plan puts the first Mars mission (with no
landing) out in like 2033. I think it's pretty obvious that even with
the expected schedule slides Musk will beat them there.


--
"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

In article ,
says...

On 2018-03-17 02:59, Fred J. McCall wrote:

What are you gibbering about now?

Enterprise was built in another era. No CAD/CAM and no experience in
building a flying rocket.

Irrelevant. The A-12, SR-71 Blackbird, X-15, XB-70, and a host of other
aircraft and rocket powered winged vehicles were designed before
CAD/CAM. You don't seem to have a point here. CAD isn't a panacea or
silver bullet. It's a design tool, nothing more. CAM is the same.
Very skilled machinists can do almost everything that CAM can do.
Again, it's a manufacturing tool, nothing more.

Enterprise was needed not only use to test
gliding/landing but also to develop/test mounting on the full stack, as
well as firing SRBs to measure vibration.

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

You're misrepresenting the facts here. The fact was that it was going
to be more work to dismantle Enterprise and refit it than to build upon
STA-99 which was nothing more than structure anyway (structural test
articles are like that you know).

Plus they had not yet gained the sensor data from flying Columbia to
orbit and back. That gave them the information they needed to lighten
the structure, not Enterprise's relatively mild glide landings.
Columbia's data covered launch (including being shaken by the SRBs),
max-Q, and reentry. Enterprise only provided subsonic flight data and
landing data.

BFS, on the other hand tests a fully functioning rocket capable of
taking off and landing. Engines, tanks, software, aerodynamic
controls/paddles, landing gear ad its deployment using real actuators
(Enterprise used explosive bolts) etc. (not sure if it will have side
thrusters for attitude control)


Sure, it will lack a payload, crew compartment, ECLSS etc. But from the
rocket point of view, it should be a fairly functional system.

Furthermore, it is an evolution from experience gained from Falcon 9
whereas the Shuttle was truly the "undiscovered Country" since it was
not an evolution from Apollo systems/designs.

You must be completely forgetting the myriad of research vehicles
between the USAF and NASA which were targeted at eventually making an
operational spacecraft that could reenter and land on a runway. Several
of these designs flew on top of launch vehicles and performed unmanned
reentries. There are a few sitting in the USAF Museum in Dayton Ohio.
Check their website. They'll have pictures and summaries of each
online. You might learn something.

The fact is that the space shuttle orbiter design was *not* created in a
vacuum.

You don't need the vacuum engines to lift off and land. You do need
some if you're planning on going clear to space, but even then you
probably don't need all of them until you start flying heavy cargos.


Montréal got some new Métros about 2 years ago. Previous generation was
designed in early 1970s. Alstom got the contract for the bogies/motors
and went with a fancy pneumatic suspension as well as the tires for our
métro.

All built to fit the existing tunnel dimensions, platform height and
loading gauge.

BUT... during testing, the STM (transit company)discobered that if the
tires blew AND the penumatic suspension lost pressure, a car could sway
enough to rub against tunnel walls in some areas. (previous generation
had spring suspension, so failure of suspension had not been something
they worried about when defining the specs of the vehicle).

WTF does any of this have to do with a VTVL TSTO?

They may very well make the first BDF launch without vacuum engines.
But
this would not validate things very well. If the goal is to validate the
design, and if the vacuum engines are Raptor engines with different
bells, they may want to load them up. (or peruaps load early production
Raptors with vacuum bells to occupy the space and weigfht.

Maybe. Or they could test incrementally (like they always seem to do).
Grasshopper certainly wasn't equipped with 9 Merlin engines. It wasn't
even equipped with the final design of the landing legs. It didn't need
either of them to fly and gather the data they needed.

I'm sure the SpaceX engineers understand the trades with the first
BFR/BFS stages better than we do.

Prior to launch, they can then test that interaction between engine
bells is within specs in all failure modes, and that a vacuum bell stuck
in the worng orientation won't prevent a launch engine from gaving full
gimball movement. (expecially needed for landing when rapid changes are
needed).

Not sure what you're yammering on about.

If you don't need the heat shield then you don't need the vacuum
engines.

The heat shield is just fancy outside skin. Vacuum engines are mounted
amongst launch/landing engines so ensuring the whole engine "pod" works
even when half the engines are not fired is important.

You don't have anything to back up this hand waving.

Also, assuming BFS 1,0 does not result in fireworks, the work done to
assemble a more complete vehicle would be of use for its second flight.
(and one would have to do risk management to decide wether to mount good
vacuum engines, or duds from early production but with proper vaccum bells.)

SpaceX will no doubt do many small hops with version 1 of the vehicle.
They're not going to do one small hop and declare they're ready to go to
orbit. That's not how they work. Build a little, test a little, fly a
little. Iterative. That's how they work.

Version 2 won't fly until they've gathered all the data they need from
version 1. So, version 1 may or may not be equipped with a full
compliment of Raptor engines, a combination of real and dummy engines.
That's up to the SpaceX engineers to decide.

And depending on software, I could see a case for needing the vaccum
engines in the event that sea leavel engines fail during landing.
(depending on where in teh cluster those engines are located).

No, you can't fire the vacuum engines and use them for landing. You'd
get flow separation and the bells might very well destroy themselves,
which wouldn't make for a very safe landing when your engines are
literally falling apart.

Besides, that's why there will be three Raptor engines in the center,
for redundancy during landing.

So just because the grasshoper tests doesn't require vacuum engines on
paper doesn't mean that they won't want to have them on for the test
because integrating as many compotents as possible is a better test.

We'll see, but I seriously doubt that they'd bolt a bunch of engines
that aren't needed on the test vehicle. Those engines aren't free you
know. Why risk millions of dollars in engines you don't need on a test
flight? Makes no sense unless you really do need them, which they
don't.

I don't know why you're so wrapped around the axle about the
damned tank, since we all know that's done.

Enterprise didn't have fully functioning tanks. Didn't have its real
fuel cells and O2/H2 tanks, didn't have hypergolics. BFS will have fully
functional tanks. So it is far ahead in terms of moving from "idea" to
"product" then Enterprise was.

All those systems you mention on Enterprise weren't needed for subsonic
flight of the vehicle. Not including them on Enterprise made sense. If
the first BFR/BFS test vehicle is only making "short hops" it won't need
vacuum engines. Not including real vacuum engines on the test vehicle
might make sense in the very same way.

And this is why advancing first flight is significant because first
flight really needs to have a lot of the final systems finalized.

Depends on how high the "hop" is. If it's not high enough to need
vacuum engines, why include them in the test?

No, it was designed as a test article, which is not the same thing.

Test article for something that had never been done before. And with
many changes made as it was being developped (liquid fltyback boosters
abandonned etc).

This is gobbledygook. The configuration of the STS was finalized long
before any metal was bent. That included the SRBs and drop tank (ET).
The size of the orbiter's payload bay and payload mass was set as well.

While the payload of BFS (aka: crew compartment for 100 passengers) is
likely going to change a lot from early concepts, the propulsion/tanks
portion as lower structures are likely to be fairly close to final
designs with tweaks over time. (as has happened with Falcon 9).

Untrue. Block 5 Falcon 9 has many significant differences when compared
to Falcon 9 V 1.0. Not all are visible from the outside but things like
the height of the vehicle, changing the engine configuration from a
square to the "octoweb", and the inclusion of landing legs and grid fins
are externally visible.

https://en.wikipedia.org/wiki/Falcon_(rocket_family)

Most important is the sheer size of the vehicle and engine improvements.
Improvements to Merlin allowed tank stretches and overall performance
improvements over V 1.0. Part of the reason Falcon Heavy kept getting
delayed is that Falcon 9 kept getting higher payload capacity and could
therefore launch some payloads originally intended for Falcon Heavy.

Horse****. They didn't design the thing using bearskins and stone
axes, you know.

When you look at the history of the shuttle, there was a lot that wasn't
predicted while it was being designed. Understanvbly so since this was
something that had never been done before. Re-usable design, totally
different stack at launch pad, totally different landing, HUGE crew
cabin from before, new materials, new heat shield etc etc. With each
delay, each incident and the 2 losses, failure modes that had not been
predicted during design crept up.

This is nonsense. As I said before, the overall configuration was fixed
long before metal was bent. You really need to read this book:

Space Shuttle: The History of the National Space Transportation System
The First 100 Missions Hardcover - May 11, 2001
by Dennis R. Jenkins (Author)
https://www.amazon.com/Space-Shuttle...ransportation-
Missions/dp/0963397451

In the case of BFR/BFS, Musk is scaling the experience of Falcon 9 as a
core, and adding new stuff like heat shield, and re-usable second stage
(BFS). landing and re-usability have already been tested. (and Falcon 9
learned from the experience of the difficult re-usability of Shuttle).

So first flight of BFS will incorporate systems/experience that will
make it a far more complete ship compared to eventual production than
Enterprise was compared to the production Shuttles.

That's because Enterprise was only the orbiter. The SRBs and the ET
made up 95% of the launch part of the system. The orbiter only
contained the flight computers, SSMEs, and the OMS pods. Everything
else needed for launch dropped off before the shuttle got to orbit.

BFR/BFS isn't going to dispose of any parts. It's quite different than
the space shuttle in that regard. So some of the shuttle experience
simply won't apply because it's just not the same.

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.

In article ,
says...

On 2018-03-17 09:33, Jeff Findley wrote:

If it is able to propulsively land on Earth, doesn't that more or less
imply ability to land on Mars?

Block 1 might not be able to be refueled, so it couldn't get to Mars in
the first place.

I was asking in terms of design/concept, not about early production
models.

Huh? If the vehicle built is missing key components needed for a Mars
mission, it can't really be said to be capable of such "in concept".

Earth has stronger gravity, but also denser atmosphere. So if
you have enough thrust to decererate and land on Earth, would this
imply that you have enough thrust to land on Mars? (less gravity, but
also much less atmosphere to slow you down)

Yes, you need less thrust to land on Mars.

In a "Pan Am flight 006 to Mars and back, would the mass of the vehicle
making the drop from space and land to surface be roughly the same ? Or
would landing at one planet require much more fuel?

You'd need a lot more fuel and oxidizer to land on Mars since Mars
atmosphere is so thin you won't get anywhere near as much aerodynamic
braking as you get on earth. So shedding velocity will require a much
longer burn from the engines than on earth (where the engines only need
to perform a relatively short landing burn).

So far, Falcon 9 stage 1 landed mostly enpty without payload and with
just enough fuel to land. But BFS will land with full payload of people
and 6 months worth of garbage. So onlike Falcon 9 stage 1, BFS is likely
to require a far greater percentage of its engines to land. Right ?
(hence question of whether the number of engines needed is dictated by
the eventual landing with 100 passengers on Earth or on Mars).

https://ourplnt.com/making-life-multiplanetary/bfs/

BFS will have three sea level engines for landing. But the extras are
mostly there for redundancy. Depending on the payload, I'd think one
would be sufficient in most cases, even on earth. Raptor will have
about 400,000 lbf thrust at landing. Dry mass of BFS is reported to be
about 200,000 lbs. A "typical" payload at landing is reported to be
110,000 lbs. So one Raptor is all that's needed for a "typical"
landing.

Of course, these numbers might change over time with block upgrades,
just as they did for Falcon 9.

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.

In article ,
says...

On 2018-03-17 10:48, Fred J. McCall wrote:

NASA's current long range plan puts the first Mars mission (with no
landing) out in like 2033. I think it's pretty obvious that even with
the expected schedule slides Musk will beat them there.


When must NASA start to get funding to develop whatever will travel
between Earth and Mars and back?

For a non-landing mission, you don't need much more than whatever
they're planing for "deep space gateway" plus the propulsion modules
which could be derivatives of ULA's ACES upper stage. These sorts of
missions were proposed using Apollo hardware as well. It's the landing
(and later takeoff) that are the tricky bits.

Eventually, NASA will have to stop pretending that Orion is big enough
to carry people to and from Mars on a 1 year mission, and perhaps have
to fess up that it needs to develop a Mars lander and take-off vehicle
if it intends to put humans on Mars surace and bring them back.

They know that. Orion is little more than a "taxi" to get people into
space and back. For long missions you need something like "deep space
gateway" to live and work in.

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.

Le Mar/18/2018 Ã* 9:56 AM, Jeff Findley a écritÂ*:
In article ,
says...

On 2018-03-17 09:33, Jeff Findley wrote:

If it is able to propulsively land on Earth, doesn't that more or less
imply ability to land on Mars?

Block 1 might not be able to be refueled, so it couldn't get to Mars in
the first place.

I was asking in terms of design/concept, not about early production
models.

Huh? If the vehicle built is missing key components needed for a Mars
mission, it can't really be said to be capable of such "in concept".

Earth has stronger gravity, but also denser atmosphere. So if
you have enough thrust to decererate and land on Earth, would this
imply that you have enough thrust to land on Mars? (less gravity, but
also much less atmosphere to slow you down)

Yes, you need less thrust to land on Mars.

In a "Pan Am flight 006 to Mars and back, would the mass of the vehicle
making the drop from space and land to surface be roughly the same ? Or
would landing at one planet require much more fuel?

You'd need a lot more fuel and oxidizer to land on Mars since Mars
atmosphere is so thin you won't get anywhere near as much aerodynamic
braking as you get on earth. So shedding velocity will require a much
longer burn from the engines than on earth (where the engines only need
to perform a relatively short landing burn).

So far, Falcon 9 stage 1 landed mostly enpty without payload and with
just enough fuel to land. But BFS will land with full payload of people
and 6 months worth of garbage. So onlike Falcon 9 stage 1, BFS is likely
to require a far greater percentage of its engines to land. Right ?
(hence question of whether the number of engines needed is dictated by
the eventual landing with 100 passengers on Earth or on Mars).

https://ourplnt.com/making-life-multiplanetary/bfs/

BFS will have three sea level engines for landing. But the extras are
mostly there for redundancy. Depending on the payload, I'd think one
would be sufficient in most cases, even on earth. Raptor will have
about 400,000 lbf thrust at landing. Dry mass of BFS is reported to be
about 200,000 lbs. A "typical" payload at landing is reported to be
110,000 lbs. So one Raptor is all that's needed for a "typical"
landing.

According to the numbers you give one Raptor engine isn't enough unless
you have a lot of fuel for landing. One Raptor has enough thrust for
about 1.3 g. The first g only compensates for gravitation so you have
0.3 g of deceleration. If you are coming in at say 100 m/s, you would
need a 34 second burn. That isn't a problem, but it isn't the way
the Falcon rockets land. If you have three Raptor engines, that gives
you 3.9 g - 1 g for gravitation = 2.9 g of deceleration. So now instead
of a 34 second burn you now need a 3.5 second burn. Three engines for
3.5 seconds burn less than one third what one engine burns in 34
seconds. So again, landing with one engine isn't really a problem
but you need to keep more fuel for landing if you want to do that.


Alain Fournier

JF Mezei wrote on Sun, 18 Mar 2018
07:19:06 -0400:

On 2018-03-17 02:59, Fred J. McCall wrote:

What are you gibbering about now?


Enterprise was built in another era. No CAD/CAM and no experience in
building a flying rocket.


False. And I note you 'cleverly' removed your original comments.


Enterprise was needed not only use to test
gliding/landing but also to develop/test mounting on the full stack, as
well as firing SRBs to measure vibration.


False. Enterprise was never mated to live SRBs


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


False.


BFS, on the other hand tests a fully functioning rocket capable of
taking off and landing. Engines, tanks, software, aerodynamic
controls/paddles, landing gear ad its deployment using real actuators
(Enterprise used explosive bolts) etc. (not sure if it will have side
thrusters for attitude control)


Again, you only need the three sea level engines for all of that. PAY
ATTENTION!!!!!!


Sure, it will lack a payload, crew compartment, ECLSS etc. But from the
rocket point of view, it should be a fairly functional system.


Why would it lack most of those things? 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. You can't add all that
stuff as an afterthought. It's part of dry structure. You can add
engines and heat shield later, since those things are intended to be
removable so they can be refurbished/replaced.


Furthermore, it is an evolution from experience gained from Falcon 9
whereas the Shuttle was truly the "undiscovered Country" since it was
not an evolution from Apollo systems/designs.


Well, not so much. BFR Spaceship is a totally new kind of thing using
totally different engines.



You don't need the vacuum engines to lift off and land. You do need
some if you're planning on going clear to space, but even then you
probably don't need all of them until you start flying heavy cargos.


Montréal got some new Métros about 2 years ago. Previous generation was
designed in early 1970s. Alstom got the contract for the bogies/motors
and went with a fancy pneumatic suspension as well as the tires for our
métro.

All built to fit the existing tunnel dimensions, platform height and
loading gauge.

BUT... during testing, the STM (transit company)discobered that if the
tires blew AND the penumatic suspension lost pressure, a car could sway
enough to rub against tunnel walls in some areas. (previous generation
had spring suspension, so failure of suspension had not been something
they worried about when defining the specs of the vehicle).


BFR Spaceship isn't a subway train.


They may very well make the first BDF launch without vacuum engines. But
this would not validate things very well. If the goal is to validate the
design, and if the vacuum engines are Raptor engines with different
bells, they may want to load them up. (or peruaps load early production
Raptors with vacuum bells to occupy the space and weigfht.


Why?


Prior to launch, they can then test that interaction between engine
bells is within specs in all failure modes, and that a vacuum bell stuck
in the worng orientation won't prevent a launch engine from gaving full
gimball movement. (expecially needed for landing when rapid changes are
needed).


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.



If you don't need the heat shield then you don't need the vacuum
engines.


The heat shield is just fancy outside skin. Vacuum engines are mounted
amongst launch/landing engines so ensuring the whole engine "pod" works
even when half the engines are not fired is important.


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


Also, assuming BFS 1,0 does not result in fireworks, the work done to
assemble a more complete vehicle would be of use for its second flight.
(and one would have to do risk management to decide wether to mount good
vacuum engines, or duds from early production but with proper vaccum bells.)


You think they're going to have a lot of 'dud' engines, do you?


And depending on software, I could see a case for needing the vaccum
engines in the event that sea leavel engines fail during landing.
(depending on where in teh cluster those engines are located).


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


So just because the grasshoper tests doesn't require vacuum engines on
paper doesn't mean that they won't want to have them on for the test
because integrating as many compotents as possible is a better test.


So you think you know more than Elon Musk about BFR Spaceship, do you?
The things SANE engineers would leave off the vehicle are things that
are intended to be easily removable and replaceable. That's things
like engines and heat shield. It is certainly NOT major structural
components.



I don't know why you're so wrapped around the axle about the
damned tank, since we all know that's done.


Enterprise didn't have fully functioning tanks. Didn't have its real
fuel cells and O2/H2 tanks, didn't have hypergolics. BFS will have fully
functional tanks. So it is far ahead in terms of moving from "idea" to
"product" then Enterprise was.


I repeat - I don't know why you're so wrapped around the axle about
the damned tank, since we all know that's done. You do love removing
your original remarks, don't you?


And this is why advancing first flight is significant because first
flight really needs to have a lot of the final systems finalized.


'Advancing first flight'? What the **** are you talking about now?



No, it was designed as a test article, which is not the same thing.


Test article for something that had never been done before. And with
many changes made as it was being developped (liquid fltyback boosters
abandonned etc).


Again you remove your original comment, WHERE YOU WERE ONCE AGAIN
WRONG. Then you argue with being told you were wrong.


While the payload of BFS (aka: crew compartment for 100 passengers) is
likely going to change a lot from early concepts, the propulsion/tanks
portion as lower structures are likely to be fairly close to final
designs with tweaks over time. (as has happened with Falcon 9).


Why would it 'change a lot'? Static dry structure is the EASY part of
the vehicle.

elide remaining nonsense


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

JF Mezei wrote on Sun, 18 Mar 2018
07:29:26 -0400:

On 2018-03-17 09:33, Jeff Findley wrote:

If it is able to propulsively land on Earth, doesn't that more or less
imply ability to land on Mars?

Block 1 might not be able to be refueled, so it couldn't get to Mars in
the first place.


I was asking in terms of design/concept, not about early production
models. Earth has stronger gravity, but also denser atmosphere. So if
you have enough thrust to decererate and land on Earth, would this
imply that you have enough thrust to land on Mars? (less gravity, but
also much less atmosphere to slow you down)


Asked and answered. Let me make it clear for you.

*********************** N O ***********************

Get it now?


In a "Pan Am flight 006 to Mars and back, would the mass of the vehicle
making the drop from space and land to surface be roughly the same ? Or
would landing at one planet require much more fuel?

So far, Falcon 9 stage 1 landed mostly enpty without payload and with
just enough fuel to land. But BFS will land with full payload of people
and 6 months worth of garbage. So onlike Falcon 9 stage 1, BFS is likely
to require a far greater percentage of its engines to land. Right ?
(hence question of whether the number of engines needed is dictated by
the eventual landing with 100 passengers on Earth or on Mars).


The most important difference is that you probably use vacuum engines
to land on Mars, given the lack of atmospheric pressure.


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

JF Mezei wrote on Sun, 18 Mar 2018
07:36:58 -0400:

On 2018-03-17 10:48, Fred J. McCall wrote:

NASA's current long range plan puts the first Mars mission (with no
landing) out in like 2033. I think it's pretty obvious that even with
the expected schedule slides Musk will beat them there.


When must NASA start to get funding to develop whatever will travel
between Earth and Mars and back?


They can probably just buy a B330 module.


Eventually, NASA will have to stop pretending that Orion is big enough
to carry people to and from Mars on a 1 year mission, and perhaps have
to fess up that it needs to develop a Mars lander and take-off vehicle
if it intends to put humans on Mars surace and bring them back.


No plans to land through 2033.


--
"Ignorance is preferable to error, and he is less remote from the
truth who believes nothing than he who believes what is wrong."
-- Thomas Jefferson