Naked Science Forum
Non Life Sciences => Physics, Astronomy & Cosmology => Topic started by: Rgclark on 14/05/2012 16:23:51
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[This is in reference to an argument attached below that the Ariane 5 core stage
can be SSTO with 3 Vulcain engines.]
The most important accomplishment of SpaceX may turn out to be they showed in
such stark terms the savings possible when launchers are privately financed:
SpaceX Might Be Able To Teach NASA A Lesson.
May 23, 2011
By Frank Morring, Jr.
Washington
“I think one would want to understand in some detail . . . why would it be
between four and 10 times more expensive for NASA to do this, especially at a
time when one of the issues facing NASA is how to develop the heavy-lift
launch vehicle within the budget profile that the committee has given it,”
Chyba says.
He cites an analysis contained in NASA’s report to Congress on the market for
commercial crew and cargo services to LEO that found it would cost NASA
between $1.7 billion and $4 billion to do the same Falcon-9 development that
cost SpaceX $390 million. In its analysis, which contained no estimates for
the future cost of commercial transportation services to the International
Space Station (ISS) beyond those already under contract, NASA says it had
“verified” those SpaceX cost figures.
For comparison, agency experts used the NASA-Air Force Cost Model—“a
parametric cost-estimating tool with a historical database of over 130 NASA
and Air Force spaceflight hardware projects”—to generate estimates of what it
would cost the civil space agency to match the SpaceX accomplishment. Using
the “traditional NASA approach,” the agency analysts found the cost would be
$4 billion. That would drop to $1.7 billion with different assumptions
representative of “a more commercial development approach,” NASA says.
http://www.aviationweek.com/aw/generic/story_generic.jsp?channel=awst&id=news/awst/2011/05/23/AW_05_23_2011_p36-324881.xml
The SpaceX experience of developing a launcher in the Falcon 9 at 1/10th the
cost of a government financed one also holds for the crew capsule development
costs since the Dragon capsule cost about $300 million to develop while the
Orion costs several billion and still counting. So it can't be said this cost
saving is just due to the Falcon 9 being, so far, unmanned.
Speaking about Orion and billions of dollars, I read an article about plans
to use the Orion on the Ariane 5 to get a European manned spaceflight
capability:
French govt study backs Orion Ariane 5 launch.
By Rob Coppinger
on January 8, 2010 4:45 PM
http://www.flightglobal.com/blogs/hyperbola/2010/01/french.html
This would cost several billion dollars to man-rate the Ariane 5. I have to
believe the solid rocket boosters, which can not be shut down when started,
play a significant role in that high cost. The article mentions also the
core stage would have to be strengthened. But such strengthening is based on
it having to support a 20 mT Orion capsule and a 20 mT upper stage which
wouldn't be used with a much smaller capsule such as the Dragon, at a dry mass
of about 4 mT.
Note also that quite likely an even smaller manned capsule could be designed
at about a 2 mT dry mass to carry a 3 man crew, which given its half size
compared to the Dragon, might cost in the range of only $150 million to
develop as privately financed. It's hard to imagine that private investment
could not be found to finance such a capsule development when it could lead to
a manned European space capability.
In regards to the costs of a privately financed SSTO version of the Ariane
launcher we might make a comparison to the Falcon 9. It cost about $300
million to develop and this includes both the structure and engines, the
engines making up the largest share of the development cost of a launcher. But
for the SSTO Ariane both engine and structure are already developed and it's
only a single stage instead of the two stages of the Falcon 9. You would have
the development cost of adding 2 additional engines and of the new avionics,
but again I have to be believe the development cost would once again be less
than the SpaceX development cost of the Falcon 9 if privately financed.
I also read that the ESA is attempting to decide whether to upgrade the
Ariane 5 or move to a Next Generation Launcher(NGL):
Ariane rocket aims to pick up the pace.
25 June 2011 Last updated at 06:39 ET
http://www.bbc.co.uk/news/science-environment-13911901
Thu, 9 February, 2012
France, Germany To Establish Working Group To Resolve Ariane 5 Differences.
By Peter B. de Selding
http://www.spacenews.com/policy/120209-france-germany-resolve-ariane5-differences.html
If the NGL is chosen then a quite expensive new large engine development
would have to be made, and the launcher might not enter service until 2025. In
contrast the SSTO-Ariane, given that the engine and stage already exist, a
prototype probably could be ready within 1 to 2 years, and moreover by using a
second stage it could also be used to launch the medium sized payloads.
So the SSTO-Ariane would solve the twin problems at low cost of providing
Europe with a manned spaceflight capability and giving it a lower cost medium
lift capability.
Bob Clark
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Newsgroups: sci.space.policy, sci.astro, sci.physics, sci.space.history, rec.arts.sf.science
From: Robert Clark
Date: Thu, 8 Sep 2011 13:56:20 -0700 (PDT)
Subject: Re: A kerosene-fueled X-33 as a single stage to orbit vehicle.
I saw this discussed on a space oriented forum:
WSJ: Europe Ends Independent Pursuit of Manned Space Travel.
"LE BOURGET, France—Europe appears to have abandoned all hope of
independently pursuing human space exploration, even as the region's
politicians and aerospace industry leaders complain about shrinking
U.S. commitment to various space ventures.
"After years of sitting on the fence regarding a separate, pan-
European manned space program, comments by senior government and
industry officials at the Paris Air Show here underscore that budget
pressures and other shifting priorities have effectively killed that
longtime dream."
http://www.orbiter-forum.com/showthread.php?t=23006
In this post I discussed getting a SSTO by replacing the Vulcain
engine on the Ariane 5 core with a SSME:
Newsgroups: sci.space.policy, sci.astro, sci.physics, sci.space.history
From: Robert Clark
Date: Wed, 23 Feb 2011 10:14:42 -0800 (PST)
Subject: Re: Some proposals for low cost heavy lift launchers.
http://groups.google.com/group/sci.physics/msg/e1736e7586cc269f?hl=en
However, in point of fact Europe can produce a manned launch vehicle
from currently *existing*, European components. This will consist of
the Ariane 5 and three Vulcain engines. The calculations below use the
Ariane 5 generic "G" version. You might need to add another Vulcain
for the larger evolution "E" version of the Ariane 5 core.
In a following post I'll also show that the Hermes spaceplane also
can become a SSTO by filling the entire fuselage aft of the cockpit
with hydrocarbon propellant.
The impetus for trying the calculation for a Ariane 5 core based SSTO
using Vulcains instead of the SSME was from a report by SpaceX that
you could get the same performance from a planned heavy lift first
stage using a lower performance Merlin 2 compared to the high
performance RS-84 engine. The reason was the lower Isp of the Merlin
was made up for by its lower weight.
THIS IS A VERY IMPORTANT FACT BECAUSE WHAT IT MEANS IS THAT YOU DON'T
NEED THE HIGH PERFORMANCE ENGINES TO GET THE SSTO. YOU CAN USE ENGINES
OF LOWER CHAMBER PRESSURE AND SIMPLER COMBUSTION CYCLES, SUCH AS THE
VULCAIN WITH A CA. 100 BAR COMBUSTION PRESSURE AND A GAS GENERATOR
CYCLE. THIS MEANS THE ENGINES ARE CHEAPER, EASIER TO MAKE REUSABLE,
REQUIRE LESS ROUTINE MAINTENANCE, AND CAN LAST FOR MANY RESTARTS.
In the discussion of the Ariane/Vulcain SSTO below, I note you can
get a prototype, test vehicle quite quickly since the components are
already existing. To improve the payload though you would want to use
altitude compensation on the Vulcains. In a following post I'll
discuss some methods of altitude compensation.
In regards to achieving this at low cost, I think the most important
accomplishment of SpaceX might turn out to be that they showed in
stark terms that privately financed spacecraft, both launchers and
crew capsules, can be accomplished at 1/10th the developmental cost of
government financed ones. Imagine a manned, reusable orbital launcher,
for example, instead of costing, say, $3 billion, only costing $300
million to develop.
Here's how you can get an all European manned SSTO using the Ariane 5
core stage but with Vulcain engines this time. Note that this is one
that can be produced from currently existing components, aside from
the capsule, so at least an unmanned prototype vehicle can be
manufactured and tested in the short term and at lowered development
cost.
We'll use three Vulcain 2's instead of the 1 normally used with the
Ariane 5 core stage. There are varying specifications given on the
Vulcain 2 depending on the source. I'll use the Astronautix site:
Vulcain 2.
http://www.astronautix.com/engines/vulcain2.htm
From the sea level thrust given there, using three Vulcain 2's will
give us one engine out capability. The weight is given as 1,800 kg. So
adding on two will take the dry mass from 12 mT to 15.6 mT.
To calculate the delta-V achieved I'll use the idea again to just use
the vacuum Isp, but adding the loss due to back pressure onto the
delta-V required for orbit, as I discussed previously. However, here
for hydrogen fuel which has higher gravity loss, I'll use a higher
required delta-V of 9,400 m/s when you add on the back pressure loss.
With the vacuum Isp given for the Vulcain 2 of 434 s, we get a payload
of 3.8 mT:
434*9.8ln(1+158/(15.6+3.8)) = 9,412 m/s.
Note this is just using the standard nozzle Isp for the Vulcain, no
altitude compensation. So this could be tested, like, tomorrow.
However, for a SSTO you definitely want to use altitude compensation.
Using engine performance programs such as ProPEP we can calculate that
using long nozzles, you can get a vacuum Isp of 470 s for this engine.
As a point of comparison of how high an Isp you can get even with a
low chamber pressure engine as long as you have a long nozzle, or
equivalent, note that the RL10-B2 with a ca. 250 to 1 area ratio, and
only a ca. 40 bar chamber pressure, gets a 465 s vacuum Isp. So we'll
assume we can get a comparable Isp by using altitude compensation.
This allows us to get payload of 8 mT:
470*9.8ln(1+158/(15.6+8) = 9,400 m/s.
This allows us to add a Dragon-sized capsule and also the reentry and
landing systems to make it reusable.
Bob Clark
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Bob - The Naked Scientists Forum is a Question and Answer Forum, it is not a place for people to x-post long opinion pieces. If you have questions to ask, or ideas to be explored please post them, but please refrain from posting long texts that are already available on numerous other sites.
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