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| Sam Wormley... |
 Posted: Sun Nov 01, 2009 9:13 pm |
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Fred J. McCall wrote:
[quote]Sam Wormley <swormley1 at (no spam) mchsi.com> wrote:
:Sylvia Else wrote:
:
:> Depends which market you're in. Space tourism, for example, needs low
:> cost per kg, but not particularly large payloads.
:
:
: I would think that space tourism, would require some margin--some extra
: safety.
:
Why? You need what you need. Why would tourists require 'extra'?
[/quote]
You lose a human in a rocket, people will want their money back. |
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| Sylvia Else... |
| Posted: Sun Nov 01, 2009 9:14 pm |
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Guest
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Sam Wormley quoted:
[quote]"Although a SSTO rocket might theoretically be built, margins would be
likely to be very thin- even comparatively minor problems may tend to
mean that a project to achieve this could fail to achieve the necessary
mass-fraction to reach orbit with useful payload".
[/quote]
I wonder how far aviation would have got if the first aircraft had been
required to be economically viable.
Sylvia. |
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| Sylvia Else... |
| Posted: Sun Nov 01, 2009 9:19 pm |
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Guest
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Sam Wormley wrote:
[quote]Fred J. McCall wrote:
Sam Wormley <swormley1 at (no spam) mchsi.com> wrote:
:Sylvia Else wrote:
:> :> Depends which market you're in. Space tourism, for example,
needs low :> cost per kg, but not particularly large payloads.
:> :
: I would think that space tourism, would require some margin--some
extra
: safety.
:
Why? You need what you need. Why would tourists require 'extra'?
You lose a human in a rocket, people will want their money back.
[/quote]
Only if they haven't read the smallprint.
Sylvia. |
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| Fred J. McCall... |
| Posted: Sun Nov 01, 2009 9:25 pm |
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Guest
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Sam Wormley <swormley1 at (no spam) mchsi.com> wrote:
:Fred J. McCall wrote:
:> Sam Wormley <swormley1 at (no spam) mchsi.com> wrote:
:>
:> :Sylvia Else wrote:
:> :>
:> :> Depends which market you're in. Space tourism, for example, needs low
:> :> cost per kg, but not particularly large payloads.
:> :>
:> :
:> : I would think that space tourism, would require some margin--some extra
:> : safety.
:> :
:>
:> Why? You need what you need. Why would tourists require 'extra'?
:>
:
: You lose a human in a rocket, people will want their money back.
:
You lose a billion dollar satellite in a rocket and they're going to
want their money back, too. That's what insurance and liability
waivers are for.
--
"Some people get lost in thought because it's such unfamiliar
territory."
--G. Behn |
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| Sam Wormley... |
| Posted: Sun Nov 01, 2009 9:28 pm |
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Guest
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Fred J. McCall wrote:
[quote]Sam Wormley <swormley1 at (no spam) mchsi.com> wrote:
:Fred J. McCall wrote:
:> Sam Wormley <swormley1 at (no spam) mchsi.com> wrote:
:
:> :Sylvia Else wrote:
:> :
:> :> Depends which market you're in. Space tourism, for example, needs low
:> :> cost per kg, but not particularly large payloads.
:> :
:> :
:> : I would think that space tourism, would require some margin--some extra
:> : safety.
:> :
:
:> Why? You need what you need. Why would tourists require 'extra'?
:
:
: You lose a human in a rocket, people will want their money back.
:
You lose a billion dollar satellite in a rocket and they're going to
want their money back, too. That's what insurance and liability
waivers are for.
[/quote]
Agreed--And they will probably use more reliable rockets too. |
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| Fred J. McCall... |
| Posted: Sun Nov 01, 2009 10:10 pm |
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Guest
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Sam Wormley <swormley1 at (no spam) mchsi.com> wrote:
:Fred J. McCall wrote:
:> Sam Wormley <swormley1 at (no spam) mchsi.com> wrote:
:>
:> :Fred J. McCall wrote:
:> :> Sam Wormley <swormley1 at (no spam) mchsi.com> wrote:
:> :>
:> :> :Sylvia Else wrote:
:> :> :>
:> :> :> Depends which market you're in. Space tourism, for example, needs low
:> :> :> cost per kg, but not particularly large payloads.
:> :> :>
:> :> :
:> :> : I would think that space tourism, would require some margin--some extra
:> :> : safety.
:> :> :
:> :>
:> :> Why? You need what you need. Why would tourists require 'extra'?
:> :>
:> :
:> : You lose a human in a rocket, people will want their money back.
:> :
:>
:> You lose a billion dollar satellite in a rocket and they're going to
:> want their money back, too. That's what insurance and liability
:> waivers are for.
:>
:
: Agreed--And they will probably use more reliable rockets too.
:
So we're to "all rockets will be reliable". So why do you think
"space tourism, would require some margin--some extra safety", again?
--
"Some people get lost in thought because it's such unfamiliar
territory."
--G. Behn |
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| Sam Wormley... |
| Posted: Sun Nov 01, 2009 10:20 pm |
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Guest
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Fred J. McCall wrote:
[quote]Sam Wormley <swormley1 at (no spam) mchsi.com> wrote:
:Fred J. McCall wrote:
:> Sam Wormley <swormley1 at (no spam) mchsi.com> wrote:
:
:> :Fred J. McCall wrote:
:> :> Sam Wormley <swormley1 at (no spam) mchsi.com> wrote:
:> :
:> :> :Sylvia Else wrote:
:> :> :
:> :> :> Depends which market you're in. Space tourism, for example, needs low
:> :> :> cost per kg, but not particularly large payloads.
:> :> :
:> :> :
:> :> : I would think that space tourism, would require some margin--some extra
:> :> : safety.
:> :> :
:> :
:> :> Why? You need what you need. Why would tourists require 'extra'?
:> :
:> :
:> : You lose a human in a rocket, people will want their money back.
:> :
:
:> You lose a billion dollar satellite in a rocket and they're going to
:> want their money back, too. That's what insurance and liability
:> waivers are for.
:
:
: Agreed--And they will probably use more reliable rockets too.
:
So we're to "all rockets will be reliable". So why do you think
"space tourism, would require some margin--some extra safety", again?
[/quote]
Let me clarify.
1. SSTO launch vehicles have never been used to put things in orbit.
2. SSTOs are hard to design.
3. I'm guessing the are not the best candidate for space tourism. |
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| kT... |
| Posted: Sun Nov 01, 2009 10:27 pm |
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Sam Wormley wrote:
[quote]Fred J. McCall wrote:
Sam Wormley <swormley1 at (no spam) mchsi.com> wrote:
:Fred J. McCall wrote:
:> Sam Wormley <swormley1 at (no spam) mchsi.com> wrote:
:> :> :Fred J. McCall wrote:
:> :> Sam Wormley <swormley1 at (no spam) mchsi.com> wrote:
:> :> :> :> :Sylvia Else wrote:
:> :> :> :> :> :> Depends which market you're in. Space tourism, for
example, needs low :> :> :> cost per kg, but not particularly large
payloads.
:> :> :> :> :> :
:> :> : I would think that space tourism, would require some
margin--some extra
:> :> : safety.
:> :> :
:> :> :> :> Why? You need what you need. Why would tourists require
'extra'?
:> :> :> :
:> : You lose a human in a rocket, people will want their money back.
:> :
:> :> You lose a billion dollar satellite in a rocket and they're
going to
:> want their money back, too. That's what insurance and liability
:> waivers are for.
:> :
: Agreed--And they will probably use more reliable rockets too.
:
So we're to "all rockets will be reliable". So why do you think
"space tourism, would require some margin--some extra safety", again?
Let me clarify.
1. SSTO launch vehicles have never been used to put things in orbit.
2. SSTOs are hard to design.
3. I'm guessing the are not the best candidate for space tourism.
[/quote]
Sam, you misunderstand the modern definition of SSTO. What most people
mean is a single core whose engine is started on the ground and flies
entirely to orbit in a single burn (either direct or with an OMS burn).
In other words there is no vertical staging event on that core, the
boosters are ... heaven forbid ... side mounted. Ideally those boosters
would be flyback hydrocarbon powered boosters, flying paying tourists. |
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| Fred J. McCall... |
| Posted: Sun Nov 01, 2009 11:35 pm |
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Guest
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Sam Wormley <swormley1 at (no spam) mchsi.com> wrote:
:Fred J. McCall wrote:
:> Sam Wormley <swormley1 at (no spam) mchsi.com> wrote:
:>
:> :Fred J. McCall wrote:
:> :> Sam Wormley <swormley1 at (no spam) mchsi.com> wrote:
:> :>
:> :> :Fred J. McCall wrote:
:> :> :> Sam Wormley <swormley1 at (no spam) mchsi.com> wrote:
:> :> :>
:> :> :> :Sylvia Else wrote:
:> :> :> :>
:> :> :> :> Depends which market you're in. Space tourism, for example, needs low
:> :> :> :> cost per kg, but not particularly large payloads.
:> :> :> :>
:> :> :> :
:> :> :> : I would think that space tourism, would require some margin--some extra
:> :> :> : safety.
:> :> :> :
:> :> :>
:> :> :> Why? You need what you need. Why would tourists require 'extra'?
:> :> :>
:> :> :
:> :> : You lose a human in a rocket, people will want their money back.
:> :> :
:> :>
:> :> You lose a billion dollar satellite in a rocket and they're going to
:> :> want their money back, too. That's what insurance and liability
:> :> waivers are for.
:> :>
:> :
:> : Agreed--And they will probably use more reliable rockets too.
:> :
:>
:> So we're to "all rockets will be reliable". So why do you think
:> "space tourism, would require some margin--some extra safety", again?
:>
:
: Let me clarify.
:
: 1. SSTO launch vehicles have never been used to put things in orbit.
: 2. SSTOs are hard to design.
: 3. I'm guessing the are not the best candidate for space tourism.
:
You mean "let me move the goal posts", don't you? So it has nothing
to with "extra safety" at all.
Now that that's out of the way, let's look at the mission requirements
for a vehicle intended for 'space tourism':
1) No more likely to blow up than any other vehicle.
2) Fast cycle times (space tourism needs to fly frequently to get
costs down to the point where it's practical).
3) Low support costs (we're looking at an airliner model of costs
here, not what is currently happening with present launch vehicles).
4) Cargo fraction can be low, since the bulk of your 'cargo' is meat
and seats. You're not staying up long enough to need to worry too
much about consumable supplies other than air and a minimum of fluids.
So what does that lead us to?
1) Liquid fuel. Failure rates are similar to solids, but
instantaneous catastrophic failures are much rarer. Plus the
vibration environment is much better.
2) Reusable. If you have to buy new hardware for every shot, there's
a very real limit to how low you can drive costs and you'll never get
anywhere near airline cost models.
3) SSTO or air launched. 'Winged flyback booster' falls in this
category, although the technology there is more difficult than
launching from a manned aircraft. If we want fast cycle times, we
can't just be dropping pieces randomly. Plus having to retrieve them
rather than having them come home on their own increases cycle costs.
4) Don't push the technology too hard. Doing that gets you better
performance, but it also leads to higher refurbishment costs between
flights as pushing limits harder means closer tolerances and running
things closer to failure points.
Conclusion: What we're looking for for space tourism (or a personnel
transport vehicle) is a reusable liquid fueled SSTO (or air-launched
vehicle) that can fly back to the launch facility and land, then take
off for another flight with minimal processing.
Seems obvious to me. Also to pretty much everyone else talking about
doing space tourism. If you think you know better, perhaps you should
get some backers and start a company?
--
"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 |
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| Sam Wormley... |
| Posted: Sun Nov 01, 2009 11:59 pm |
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Guest
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Fred J. McCall wrote:
[quote]Sam Wormley <swormley1 at (no spam) mchsi.com> wrote:
:Fred J. McCall wrote:
:> Sam Wormley <swormley1 at (no spam) mchsi.com> wrote:
:
:> :Fred J. McCall wrote:
:> :> Sam Wormley <swormley1 at (no spam) mchsi.com> wrote:
:> :
:> :> :Fred J. McCall wrote:
:> :> :> Sam Wormley <swormley1 at (no spam) mchsi.com> wrote:
:> :> :
:> :> :> :Sylvia Else wrote:
:> :> :> :
:> :> :> :> Depends which market you're in. Space tourism, for example, needs low
:> :> :> :> cost per kg, but not particularly large payloads.
:> :> :> :
:> :> :> :
:> :> :> : I would think that space tourism, would require some margin--some extra
:> :> :> : safety.
:> :> :> :
:> :> :
:> :> :> Why? You need what you need. Why would tourists require 'extra'?
:> :> :
:> :> :
:> :> : You lose a human in a rocket, people will want their money back.
:> :> :
:> :
:> :> You lose a billion dollar satellite in a rocket and they're going to
:> :> want their money back, too. That's what insurance and liability
:> :> waivers are for.
:> :
:> :
:> : Agreed--And they will probably use more reliable rockets too.
:> :
:
:> So we're to "all rockets will be reliable". So why do you think
:> "space tourism, would require some margin--some extra safety", again?
:
:
: Let me clarify.
:
: 1. SSTO launch vehicles have never been used to put things in orbit.
: 2. SSTOs are hard to design.
: 3. I'm guessing the are not the best candidate for space tourism.
:
You mean "let me move the goal posts", don't you? So it has nothing
to with "extra safety" at all.
Now that that's out of the way, let's look at the mission requirements
for a vehicle intended for 'space tourism':
1) No more likely to blow up than any other vehicle.
2) Fast cycle times (space tourism needs to fly frequently to get
costs down to the point where it's practical).
3) Low support costs (we're looking at an airliner model of costs
here, not what is currently happening with present launch vehicles).
4) Cargo fraction can be low, since the bulk of your 'cargo' is meat
and seats. You're not staying up long enough to need to worry too
much about consumable supplies other than air and a minimum of fluids.
So what does that lead us to?
1) Liquid fuel. Failure rates are similar to solids, but
instantaneous catastrophic failures are much rarer. Plus the
vibration environment is much better.
2) Reusable. If you have to buy new hardware for every shot, there's
a very real limit to how low you can drive costs and you'll never get
anywhere near airline cost models.
3) SSTO or air launched. 'Winged flyback booster' falls in this
category, although the technology there is more difficult than
launching from a manned aircraft. If we want fast cycle times, we
can't just be dropping pieces randomly. Plus having to retrieve them
rather than having them come home on their own increases cycle costs.
4) Don't push the technology too hard. Doing that gets you better
performance, but it also leads to higher refurbishment costs between
flights as pushing limits harder means closer tolerances and running
things closer to failure points.
Conclusion: What we're looking for for space tourism (or a personnel
transport vehicle) is a reusable liquid fueled SSTO (or air-launched
vehicle) that can fly back to the launch facility and land, then take
off for another flight with minimal processing.
Seems obvious to me. Also to pretty much everyone else talking about
doing space tourism. If you think you know better, perhaps you should
get some backers and start a company?
[/quote]
Go for it! |
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| Uncle Al... |
| Posted: Mon Nov 02, 2009 12:01 am |
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Robert Clark wrote:
[quote]
Table of Contents.
I.)Introduction.
II.)Lightweight propellant tanks.
III.)Kerosene fuel and engines for the X-33/Venture star.
IVa.)Aerodynamic lift applied to ascent to orbit.
b.)Estimation of fuel saving using lift.
V.)Kerosene fueled VentureStar payload to orbit.
I.) A debate among those questing for the Holy Grail of a reusable,
single-stage-to-orbit vehicle is whether it should be powered by
hydrogen or a dense hydrocarbon such as kerosene.
[/quote]
No, you hopeless ignorant ineducable idiot,
exo-tetrahydrodicyclopentadiene [exo-tricyclo[5.2.1.0^(2,6)]decane)
for its liquid high density and awesome enthalpy of combustion.
[quote]Most concepts for
such a vehicle centered on hydrogen, since a hydrogen/LOX combination
provides a higher Isp. However, some have argued that dense fuels
should be used since they take up less volume (equivalently more fuel
mass can be carried in the same sized tank) so they incur less air
drag and also since the largest hydrocarbon engines produce greater
thrust they can get to the desired altitude more quickly so they also
incur lower gravity drag loss.
Another key fact is that for dense fuels the ratio of propellant mass
to tank mass is higher, i.e., you need less tank mass for the same
mass of propellant.
[snip 500 lines][/quote]
Thank you for verifying that you are a technological dunce even about
~C_10 hydrocarbon fuels. Bulk synthesis of cyclobutyl and especially
cyclopropyl polycyclic hydrocarbons affords kerosene liquids even
denser and of higher delivered combustion enthalpies than JP-10 for
their ring strain.
Uncle Al, being of delicate aesthetics, proposes adding 1%
8-exo-formyl-2,6-exo-tricyclo[5.2.1.0^(2,6)]decane to JP-10 for its
having a fresh-green note scent and high stability.
Why isn't NASA eviscerated for its obscene carbon footprint?
--
Uncle Al
http://www.mazepath.com/uncleal/
(Toxic URL! Unsafe for children and most mammals)
http://www.mazepath.com/uncleal/qz4.htm |
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| Sylvia Else... |
| Posted: Mon Nov 02, 2009 12:27 am |
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Guest
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Fred J. McCall wrote:
[quote]3) SSTO or air launched. 'Winged flyback booster' falls in this
category, although the technology there is more difficult than
launching from a manned aircraft. If we want fast cycle times, we
can't just be dropping pieces randomly. Plus having to retrieve them
rather than having them come home on their own increases cycle costs.
[/quote]
Also, not dropping bits off gives you much more flexibility about where
you launch from, particularly if you get the chance of raining burning
debris over inhabited areas down to somewhere around airliner numbers
(whether or not the rest of the mission is that safe).
Sylvia. |
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| Robert Clark... |
| Posted: Mon Nov 02, 2009 3:00 am |
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On Nov 1, 5:46 pm, Pat Flannery <flan... at (no spam) daktel.com> wrote:
[quote]Robert Clark wrote:
Most concepts for such a vehicle centered on hydrogen, since a hydrogen/LOX combination
provides a higher Isp. However, some have argued that dense fuels
should be used since they take up less volume (equivalently more fuel
mass can be carried in the same sized tank) so they incur less air
drag and also since the largest hydrocarbon engines produce greater
thrust they can get to the desired altitude more quickly so they also
incur lower gravity drag loss.
Another key fact is that for dense fuels the ratio of propellant mass
to tank mass is higher, i.e., you need less tank mass for the same
mass of propellant.
You are missing a key point here; Lockheed chose LOX/LH2 for two reasons:
1.) Its superior isp.
2.) The large size of the propellant tankage for it.
VentureStar was to rely on the large volume of the empty propellant
tankage to make the vehicle very light for its size on reentry to
decelerate the spacecraft quickly and reduce the heat loads on the TPS.
Shift to kerosene/LOX and you are going to need a far heavier TPS, and
combined with the lower isp, that is going to make SSTO very difficult
to do, especially with a worthwhile payload.
Pat
[/quote]
The very key aspect of this proposal is that the tanks remain the
*same* size, but at a *lighter* weight. In fact the intent was to keep
the same shape of the X-33 and just switch out the propellant tanks
and engines. So in fact the vehicle becomes lighter for its volume
with hydrocarbon fuels.
When you consider the other benefits of hydrocarbon fuels over
hydrogen, the higher Isp of hydrogen/LOX propellant becomes less of an
advantage.
In fact, kerosene is not necessarily the best hydrocarbon to use,
which I'll discuss in a following post.
Bob Clark |
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| Robert Clark... |
| Posted: Mon Nov 02, 2009 3:11 am |
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On Nov 1, 7:46 pm, Sam Wormley <sworml... at (no spam) mchsi.com> wrote:
[quote]Sylvia Else wrote:
Sam Wormley wrote:
Single Stage to Orbit really limits payload "weight".
Why does that matter? The point of an SSTO is to get down the cost to
orbit per payload kg. An SSTO is likely to mass more than a disposable
multi-stage for a given payload, but that is not in itself a source of
concern.
Sylvia.
http://en.wikipedia.org/wiki/Single-stage-to-orbit#SSTO_Cons
[/quote]
Thanks for that link. It also neatly discuses the reasons why a dense
hydrocarbon fuel can be superior to hydrogen for a SSTO, particularly
for the savings in tank weight and gravity losses:
Dense versus hydrogen fuels.
http://en.wikipedia.org/wiki/Single-stage-to-orbit#Dense_versus_hydrogen_fuels
In regards to the payload to orbit, in my suggested reconfigured
kerosene-fueled VentureStar it would exceed the payload of the Saturn
V, and nearly match that of the Ares V.
And with even more efficient hydrocarbon fuels than kerosene it would
exceed even that of the Ares V.
Bob Clark |
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| Jeff Findley... |
| Posted: Mon Nov 02, 2009 11:13 am |
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Guest
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"Sam Wormley" <swormley1 at (no spam) mchsi.com> wrote in message
news:B_fHm.110690$5n1.67859 at (no spam) attbi_s21...
[quote]Single Stage to Orbit really limits payload "weight".
[/quote]
I think you meant to say that SSTO would limit the mass fraction of the
vehicle which is payload. I'd like to note that is not necessarily a bad
thing, despite the belief of traditional aerospace engineers to the
contrary. What you *really* want to optimize is cost per kg to orbit, not
the payload mass fraction of your vehicle. Since the current launch market
is rather small, there hasn't been much effort made in this area by the
traditional launch providers. But I'd also like to note that some start-ups
have been making some progress in this area, even though they're not
actively pursuing SSTO vehicles.
The development costs for a reusable SSTO would be high and the reality is
that the current launch market just isn't big enough to justify the
investment.
Jeff
--
"Take heart amid the deepening gloom
that your dog is finally getting enough cheese" - Deteriorata - National
Lampoon |
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