A Space & astronomy forum. SpaceBanter.com

If this is your first visit, be sure to check out the FAQ by clicking the link above. You may have to register before you can post: click the register link above to proceed. To start viewing messages, select the forum that you want to visit from the selection below.

Go Back   Home » SpaceBanter.com forum » Space Science » Policy
Site Map Home Authors List Search Today's Posts Mark Forums Read Web Partners

Were liquid boosters on Shuttle ever realistic?



 
 
Thread Tools Display Modes
  #11  
Old October 25th 17, 07:17 AM posted to sci.space.policy
Fred J. McCall[_3_]
external usenet poster
 
Posts: 9,793
Default Were liquid boosters on Shuttle ever realistic?

"Greg \(Strider\) Moore" wrote:

"Fred J. McCall" wrote in message
.. .

There is no such thing as assembly line production 'spewing out'
rocket engines. It made sense to use Merlin engines because the idea
was to have three identical cores for Falcon Heavy, sort of like what
Delta IV Heavy does. In the event, Musk found they couldn't do that
and that they couldn't just use three Falcon 9 cores for Falcon Heavy.
The side boosters are now different from the central 'core'.


What are the differences? Last I knew the side boosters for the primary
flight are B1023.2 and B1025.2 (i.e 2nd flight for those two boosters)


It's mostly got to do with mechanical loading. The side boosters are
close (but not an exact match) for what they fly on Falcon 9. They're
only slightly modified so as to be able to take structural loading
from the attachment points on the sides rather than straight down
through the center of the core. The center booster requires a lot
more structural work to stand loads, both the side loads from the two
attached boosters and the increased load on the front of the booster
from the second stage and payload. Musk himself has said that he
doesn't necessarily expect the first launch attempt to reach orbit and
would consider it getting far enough away to avoid pad damage a win.
Look at how many Falcon 9 launches failed before they got a success.
According to Musk, Falcon Heavy was "shockingly difficult" to develop.
It was originally supposed to use fuel cross-feed among the three
cores, but that proved too difficult and was dropped. It was
originally supposed to be three 'standard' Falcon 9 cores (with Falcon
9 eating the additional structure) but now the center booster is
different from the side boosters. Yes, it really is rocket science...


--
"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
Ads
  #12  
Old October 25th 17, 11:31 AM posted to sci.space.policy
Jeff Findley[_6_]
external usenet poster
 
Posts: 1,739
Default Were liquid boosters on Shuttle ever realistic?

In article ,
says...

Yes, but the difference isn't as preposterous as your case makes it
sound. LH2/LOX is going to be around 50% more expensive for engines
for 'similar' performance. The ability to stage higher and faster
because of Isp differences makes up for some of that (because you're
either carrying a smaller mass of fuel or because you're carrying the
same mass of fuel and it burns longer). You then have to adjust that
for tank weight and aerodynamic drag from the need for bigger volume
tanks. There are 'sweet spots' in there where LH2/LOX is competitive
and there are hypothetical cases that make LH2/LOX look even worse
than one would expect.

GENERALLY, a higher density exhaust (from a denser fuel) makes sense
for a first stage, but that's not always the case or Delta IV wouldn't
look like it does.



While you're making valid points, do note that Delta IV is the (far)
more expensive launch vehicle compared to Atlas V. LOX/LH2 may not cost
much more in the engine department, but the costs start mounting when
you consider everything else which has to go into the (larger, better
insulated) first stage and all of its associated plumbing. That
includes all of the headaches involved with buying, storing, and loading
large amounts of LH2 into the first stage at the pad (the upper stage is
tiny by comparison).

That's why ULA wants to drop Delta IV as quickly as it can. It's too
expensive and simply can't compete, even with Atlas V, made by the same
company. LOX/LH2 makes very little sense as a first stage propellant
combination due to the many disadvantages that quickly drive up costs
compared to pretty much any other (sane) liquid fuel.

LOX/methane is the fuel of choice for new development today because it
offers a good compromise on density and performance. Plus in its liquid
form it can share a common bulkhead with LOX without a lot of (any?)
insulation on the bulkhead. And yes, having common engines and common
fuel/oxidizer on both the lower stage and upper stage simplifies
manufacturing and operations, lowering costs. So that's a win for
LOX/methane as well.

In a world where SpaceX has set the bar very low on cost, everyone is
scrambling to optimize on cost rather than performance. Henry Spencer
used to call optimizing for performance the "performance uber alles"
mindset which came along with former German engineers who were used to
designing missiles rather than launch vehicles. That still holds today.

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.
  #13  
Old October 25th 17, 12:13 PM posted to sci.space.policy
Jeff Findley[_6_]
external usenet poster
 
Posts: 1,739
Default Were liquid boosters on Shuttle ever realistic?

In article ,
says...
It does not necessarily mean that it is the optimal design from an
engineering point of view. It's the design that makes the most business
sense.


It may not even be that. Certainly no one here is advocating 'optimal
engineering design' as a GOAL, although that usually makes the most
business sense.


Depends on what you mean by "optimal engineering design". For example,
missiles are optimized for long storage times and for minimum size and
mass for a fixed payload size. The requirement to store them on subs
and in smallish launch facilities drives the requirements. But, they
are not in any way shape or form designed for minimum manufacturing
costs. In terms of overall program costs, that's just not a big
consideration.

Put those same engineers on a launch vehicle program and they'll design
an "optimum" launch vehicle with different engines on every stage,
maximum ISP engines (at the bleeding edge of what the materials can
take), and stages which have to be transported by barge and by over-
sized cargo aircraft. Different stages will have different fuels
driving up handling complexity and costs at the launch pad. All those
little things add up to launch vehicles which are far more expensive
than they need to be. Why? Because "we've always done things that
way" and "performance uber alles"!

The revolution brought by SpaceX (and somewhat by Blue Origin) isn't at
all technology driven. There was no magic breakthrough technology that
drove down costs (like SABRE engines). There is absolutely nothing
technically challenging about how they've designed their engines and
launch vehicle stages (to date anyway). But what they have done is
optimize for lower cost at every step of the process. Lower development
costs, lower testing costs, lower build costs, lower transportation
costs (Falcon stages are transported by semi-truck), lower integration
costs (horizontal integration), and etc.

On top of that, both SpaceX and Blue Origin are pursuing reusability
with a tenacity never before seen in the industry (space shuttle SRBs
and orbiters were refurbished after flight over many months, so they
don't really count). That will be the next step towards even cheaper
access to space.

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.
  #14  
Old October 25th 17, 12:26 PM posted to sci.space.policy
Fred J. McCall[_3_]
external usenet poster
 
Posts: 9,793
Default Were liquid boosters on Shuttle ever realistic?

Jeff Findley wrote:

In article ,
says...

Yes, but the difference isn't as preposterous as your case makes it
sound. LH2/LOX is going to be around 50% more expensive for engines
for 'similar' performance. The ability to stage higher and faster
because of Isp differences makes up for some of that (because you're
either carrying a smaller mass of fuel or because you're carrying the
same mass of fuel and it burns longer). You then have to adjust that
for tank weight and aerodynamic drag from the need for bigger volume
tanks. There are 'sweet spots' in there where LH2/LOX is competitive
and there are hypothetical cases that make LH2/LOX look even worse
than one would expect.

GENERALLY, a higher density exhaust (from a denser fuel) makes sense
for a first stage, but that's not always the case or Delta IV wouldn't
look like it does.


While you're making valid points, do note that Delta IV is the (far)
more expensive launch vehicle compared to Atlas V.


Is it? When I look at cost numbers they're both around $13k/kg of
payload. ULA plays games with the cost of Atlas V by giving
'incremental cost' of an additional launch while charging all the pad
support, etc, to USAF contract.


LOX/LH2 may not cost
much more in the engine department, but the costs start mounting when
you consider everything else which has to go into the (larger, better
insulated) first stage and all of its associated plumbing. That
includes all of the headaches involved with buying, storing, and loading
large amounts of LH2 into the first stage at the pad (the upper stage is
tiny by comparison).

That's why ULA wants to drop Delta IV as quickly as it can. It's too
expensive and simply can't compete, even with Atlas V, made by the same
company. LOX/LH2 makes very little sense as a first stage propellant
combination due to the many disadvantages that quickly drive up costs
compared to pretty much any other (sane) liquid fuel.


Actually, they aren't built by the same company (one is Boeing and one
is LockMart, although both are sold through the joint venture ULA) and
they want to get rid of Atlas V, too. In fact, Atlas V is the one
they really want to get rid of because it uses Russian RD-180 engines.


LOX/methane is the fuel of choice for new development today because it
offers a good compromise on density and performance. Plus in its liquid
form it can share a common bulkhead with LOX without a lot of (any?)
insulation on the bulkhead. And yes, having common engines and common
fuel/oxidizer on both the lower stage and upper stage simplifies
manufacturing and operations, lowering costs. So that's a win for
LOX/methane as well.


But practically no one in the methane/LOX game is using common engines
among all their stages. ULA will be using BE-4 and SRBs on the first
stage and LH2/LOX on the second stage. New Glenn uses BE-4 on the
first two stages and LH2/LOX on the third stage (when used). There
are two versions of the BE-4, one sea level optimized and one vacuum
optimized. The same is true of the Raptor engine SpaceX will use and
once again SpaceX is the only one using the same engine everywhere.
SpaceX pays the price for not having a high energy LH2/LOX upper stage
by refueling on orbit.


In a world where SpaceX has set the bar very low on cost, everyone is
scrambling to optimize on cost rather than performance. Henry Spencer
used to call optimizing for performance the "performance uber alles"
mindset which came along with former German engineers who were used to
designing missiles rather than launch vehicles. That still holds today.


In the old days you almost had to go for performance because the
payloads and dry weight of the vehicles were always right at the edge.
Even SpaceX has done some of that, going with superchilled RP1 to
improve performance. I don't think Henry invented that phrase, as it
was pretty commonly used by a lot of people back in the day, but I
can't prove he didn't, either.


--
"Insisting on perfect safety is for people who don't have the balls to
live in the real world."
-- Mary Shafer, NASA Dryden
  #15  
Old October 26th 17, 12:29 AM posted to sci.space.policy
Fred J. McCall[_3_]
external usenet poster
 
Posts: 9,793
Default Were liquid boosters on Shuttle ever realistic?

Jeff Findley wrote:

In article ,
says...
It does not necessarily mean that it is the optimal design from an
engineering point of view. It's the design that makes the most business
sense.


It may not even be that. Certainly no one here is advocating 'optimal
engineering design' as a GOAL, although that usually makes the most
business sense.


Depends on what you mean by "optimal engineering design". For example,
missiles are optimized for long storage times and for minimum size and
mass for a fixed payload size. The requirement to store them on subs
and in smallish launch facilities drives the requirements. But, they
are not in any way shape or form designed for minimum manufacturing
costs. In terms of overall program costs, that's just not a big
consideration.


Most aerospace stuff isn't designed for "minimum manufacturing costs"
because we just don't build enough of them to do that.


Put those same engineers on a launch vehicle program and they'll design
an "optimum" launch vehicle with different engines on every stage,
maximum ISP engines (at the bleeding edge of what the materials can
take), and stages which have to be transported by barge and by over-
sized cargo aircraft. Different stages will have different fuels
driving up handling complexity and costs at the launch pad. All those
little things add up to launch vehicles which are far more expensive
than they need to be. Why? Because "we've always done things that
way" and "performance uber alles"!


Not necessarily. Depends on what the requirements are. If you're a
commercial outfit trying to compete for launch business, you're going
to want to drive overall costs per launch down. That might make you
decide on designs that don't push the envelope as hard because they're
cheaper to build because you can use cheaper materials and fuels that
are cheap and don't require expensive storage and handling facilities.
Or it might drive you to more expensive practices so that stages are
reusable, using more expensive materials and squeezing more
performance so that you have capability left to get the stages back.

On the other hand, if your primary business is government payloads
you're not going to have to compete as hard to get a share (because
the government won't want all its eggs in one basket) and you might
just push pure performance harder because you can afford to do it.

Back in the 1940's and 1950's, there wasn't a lot of choice but to
push performance because nothing less would get **** on orbit. That
doesn't mean modern missile engineers are obtuse (or even that the old
time ones were).


The revolution brought by SpaceX (and somewhat by Blue Origin) isn't at
all technology driven. There was no magic breakthrough technology that
drove down costs (like SABRE engines). There is absolutely nothing
technically challenging about how they've designed their engines and
launch vehicle stages (to date anyway). But what they have done is
optimize for lower cost at every step of the process. Lower development
costs, lower testing costs, lower build costs, lower transportation
costs (Falcon stages are transported by semi-truck), lower integration
costs (horizontal integration), and etc.


Actually they haven't. Superchilled RP1 drives up costs in order to
improve performance. Going for reusability drives up manufacturing
costs and design costs because you have to make things that can be
used dozens of times without attention (so you need better materials
and tighter designs without pushing for extra performance, figure out
some way to avoid 'coking' on an RP1/LOX engine, etc). It's the
normal engineering evolution of launch vehicles that was stalled while
most payloads were government.


On top of that, both SpaceX and Blue Origin are pursuing reusability
with a tenacity never before seen in the industry (space shuttle SRBs
and orbiters were refurbished after flight over many months, so they
don't really count). That will be the next step towards even cheaper
access to space.


BFR and the BFR Ship are sort of the end result of that. Reliability
of airliners with the ability to do hundreds of flights with only
routine servicing is the goal.


--
"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
  #16  
Old October 26th 17, 11:25 AM posted to sci.space.policy
Jeff Findley[_6_]
external usenet poster
 
Posts: 1,739
Default Were liquid boosters on Shuttle ever realistic?

In article ,
says...
Actually they haven't. Superchilled RP1 drives up costs in order to
improve performance. Going for reusability drives up manufacturing
costs and design costs because you have to make things that can be
used dozens of times without attention (so you need better materials
and tighter designs without pushing for extra performance, figure out
some way to avoid 'coking' on an RP1/LOX engine, etc). It's the
normal engineering evolution of launch vehicles that was stalled while
most payloads were government.


As far as engines go, this isn't really true. All liquid fueled engines
are designed to be fired multiple times, at least on the test stand.
That's how they're qualified. Henry Spencer used to say (paraphrasing
here), there is absolutely nothing fundamental about a liquid fueled
rocket engine that makes it expendable.

Same goes for tanks and plumbing. They pretty much have to be
"certified" for a certain number of fill and drain cycles even if
they're "expendable" in order to account for tanking tests, aborts, and
etc.

Solids on the other hand are single use, excepting for complete tear
down to component parts accompanied by extreme cleaning.

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.
  #17  
Old October 26th 17, 09:21 PM posted to sci.space.policy
Fred J. McCall[_3_]
external usenet poster
 
Posts: 9,793
Default Were liquid boosters on Shuttle ever realistic?

JF Mezei wrote:

On 2017-10-24 23:02, Greg (Strider) Moore wrote:

What are the differences? Last I knew the side boosters for the primary
flight are B1023.2 and B1025.2 (i.e 2nd flight for those two boosters)


Musk said that the reason Falcon Heavy is so late is that they had
underestimated the structural changes needed to the rocket because of
different loads (and heavier payload at top).

Whether they retrofitted existing stage 1s as boosters (and the core
stage) or built new ones, reusing only engines, I have no idea.


That's because you're either not paying attention or you have the
memory of a mayfly, Mayfly. It's been mentioned several times that
the side boosters are 'used', which means they're original Falcon 9
equipment that has been retrofitted. The center booster is apparently
new build. Perhaps the modifications required for the center booster
are too extensive to economically use old Falcon 9 stages.


--
"Some people get lost in thought because it's such unfamiliar
territory."
--G. Behn
  #18  
Old October 26th 17, 09:27 PM posted to sci.space.policy
Fred J. McCall[_3_]
external usenet poster
 
Posts: 9,793
Default Were liquid boosters on Shuttle ever realistic?

Jeff Findley wrote:

In article ,
says...
Actually they haven't. Superchilled RP1 drives up costs in order to
improve performance. Going for reusability drives up manufacturing
costs and design costs because you have to make things that can be
used dozens of times without attention (so you need better materials
and tighter designs without pushing for extra performance, figure out
some way to avoid 'coking' on an RP1/LOX engine, etc). It's the
normal engineering evolution of launch vehicles that was stalled while
most payloads were government.


As far as engines go, this isn't really true. All liquid fueled engines
are designed to be fired multiple times, at least on the test stand.
That's how they're qualified. Henry Spencer used to say (paraphrasing
here), there is absolutely nothing fundamental about a liquid fueled
rocket engine that makes it expendable.


Well, actually it is. You go into engine design knowing how many
'refires' the engine needs to stand. If it needs to stand 3 with some
safety margin, the robustness required is a lot less than if it needs
to stand up to 36 of them with the same safety margin. That is going
to drive up manufacturing costs (which you hopefully get back through
the savings by reusing hardware).


Same goes for tanks and plumbing. They pretty much have to be
"certified" for a certain number of fill and drain cycles even if
they're "expendable" in order to account for tanking tests, aborts, and
etc.


And they have to be "certified" for a magnitude (or multiple
magnitudes in the case of something like BFR) more fill and drain
cycles if they're supposed to be reusable.


Solids on the other hand are single use, excepting for complete tear
down to component parts accompanied by extreme cleaning.


Solids are expensive for what they bring to the table when compared to
liquids, even if you fully expend all hardware. I really don't
understand ULA's love affair with them.


--
"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
  #19  
Old October 27th 17, 02:24 AM posted to sci.space.policy
Fred J. McCall[_3_]
external usenet poster
 
Posts: 9,793
Default Were liquid boosters on Shuttle ever realistic?

JF Mezei wrote:

On 2017-10-25 07:13, Jeff Findley wrote:

On top of that, both SpaceX and Blue Origin are pursuing reusability
with a tenacity never before seen in the industry (space shuttle SRBs
and orbiters were refurbished after flight over many months, so they
don't really count). That will be the next step towards even cheaper
access to space.


In fairness, SpaceX is likely at the same stage now that NASA was when
it had flown a Suttle orbiter 2 or 3 times. Doing costly turn-around
examinations in order to gauge how much work will really be needed in
the future.

Until it has reflown enough stages, AND SpaceX releases some number of
the work/costs involved in turning stages around "in production", nobody
outside of SpaceX know how cost effective turning stages around is.


SpaceX doesn't need to release anything. You can look at what they
charge customers for expending a stage vs allowing it to be recovered
and what discount they offer for using a 'used' stage to get some idea
of the costs.


It may very well be a no brainer either way (eg: 50% cheaper than new
stages or 75% cheaper than new stages ) So the question becomes how MUCH
will SpaceX revolutionlize launch industry, not whether it will or not.


Look at the manufacturing cost for a new stage, which we can estimate
from what they charge for a launch. Even if you have to do a complete
tear down it's going to be cheaper to reuse than to buy new. This was
even true for the Space Shuttle (look at what a new Shuttle Orbiter
cost).


--
"Some people get lost in thought because it's such unfamiliar
territory."
--G. Behn
  #20  
Old October 27th 17, 02:29 AM posted to sci.space.policy
Fred J. McCall[_3_]
external usenet poster
 
Posts: 9,793
Default Were liquid boosters on Shuttle ever realistic?

JF Mezei wrote:

On 2017-10-26 16:21, Fred J. McCall wrote:

That's because you're either not paying attention or you have the
memory of a mayfly, Mayfly. It's been mentioned several times that
the side boosters are 'used', which means they're original Falcon 9
equipment that has been retrofitted.



In his recent Australian speech, Musk explicitely said that ALL of it
had to be re-engineered, hence the delay for Falcon Heavy. The original
expectation close to what you described.


Except what you're getting from his statement is not what he said. Are
the engines different? No. OK, that's already NOT "all of it
re-engineered". Are the tanks, piping, or electronics different? No.
There's more. Mayfly, we KNOW that the two side boosters are 'reused'
from Falcon 9. It's been announced. The boosters have been
identified. It's been talked about here before. We also know there
are structural changes required in order to handle getting loads from
the side attachment points vs straight down through the axis of the
booster. There will obviously be software changes, but that's 'just
software'.

Does your brain reset to factory fresh every time you get a new fact?


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




Thread Tools
Display Modes

Posting Rules
You may not post new threads
You may not post replies
You may not post attachments
You may not edit your posts

vB code is On
Smilies are On
[IMG] code is On
HTML code is Off
Forum Jump

Similar Threads
Thread Thread Starter Forum Replies Last Post
Are rotating stations realistic ? John Doe Space Station 2 May 19th 10 10:15 AM
"Boeing To Study Liquid Fly Back Shuttle Boosters For NASA" gaetanomarano Policy 19 November 27th 07 06:59 AM
shuttle, tank and boosters on its crawler Rich Space Shuttle 37 September 11th 06 09:09 AM
Shuttle Liquid Fly-Back Booster to save money, improve safety(flashback) Bob Wilson Space Shuttle 0 July 16th 06 02:12 AM
Space Shuttle Boosters and Launch Pad Revell Model Kit on eBay TB Space Shuttle 2 February 1st 05 08:00 AM


All times are GMT +1. The time now is 10:37 PM.


Powered by vBulletin® Version 3.6.4
Copyright ©2000 - 2018, Jelsoft Enterprises Ltd.
Copyright 2004-2018 SpaceBanter.com.
The comments are property of their posters.