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SpaceX Dragon



 
 
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  #1  
Old March 15th 07, 02:48 PM posted to sci.space.policy
are
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Default SpaceX Dragon

Per SpaceX, the Dragon capsule carries 1200 kg propellant, which
"supports a safe mission profile from sub-orbital insertion to ISS
rendezvous to reentry." Questions:

1. What is the propellant?
2. Why the reference to "sub-orbital" insertion? Falcon 9 would
perform full orbital insertion. Is that a back-up capability provided
in the event of sub-nominal performance of the launch vehicle? I'd
have thought that the Furthermore, the second Dragon mission is
intended to demonstrate rendezvous with the Falcon 9's second stage,
suggesting that at least on that mission, the second stage will make
it all the way to orbit.
3. SpaceX used to claim that both stages of the Falcon 9 would be
reusable, though it was never clear to me precisely how the upper
stage was to be recovered. I see no mention of re-usability on the
website now. Has re-usability been dropped?

  #2  
Old March 20th 07, 12:40 PM posted to sci.space.policy
are
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Posts: 47
Default SpaceX Dragon

Have I received no replies because my questions are too stoopid or
because nobody knows?

  #3  
Old March 20th 07, 04:29 PM posted to sci.space.policy
are
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Default SpaceX Dragon

OK, spaceglobal.com says the propellant is MMH/NTO, same as for the
attitude-control system. Isn't it a bit 20th-century to be using a
relatively toxic propellants like that?

The same site says that both stages are to be recovered by parachute.
Coulda guessed that -- but what about the other details of bringing
the second stage back from orbit?

  #4  
Old March 21st 07, 01:17 AM posted to sci.space.policy
Pat Flannery
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Default SpaceX Dragon



are wrote:
OK, spaceglobal.com says the propellant is MMH/NTO, same as for the
attitude-control system. Isn't it a bit 20th-century to be using a
relatively toxic propellants like that?

The same site says that both stages are to be recovered by parachute.
Coulda guessed that -- but what about the other details of bringing
the second stage back from orbit?


They've been keeping details pretty close to their chest, which is
probably pretty wise.
http://www.thespacereview.com/article/682/1
http://en.wikipedia.org/wiki/SpaceX

Pat
  #5  
Old March 21st 07, 05:06 AM posted to sci.space.policy
John Schilling
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Default SpaceX Dragon

On 20 Mar 2007 08:29:33 -0700, "are" wrote:

OK, spaceglobal.com says the propellant is MMH/NTO, same as for the
attitude-control system. Isn't it a bit 20th-century to be using a
relatively toxic propellants like that?


The 21st century is not yet old enough, nor Elon Musk rich enough,
to have completely reinvented all of rocketry from scratch. Unless
you're planning on putting space on hold for the next twenty years,
you are going to have to accept that rockets are going to go up with
a whole lot of 20th-century stuff in them that the builders didn't
feel they absolutely positively had to redesign.

As the 20th century left us with a lot of very good, very reliable
MMH/NTO thrusters and even cumbersome but proven techniques for
handling MMH and NTO, there are going to be a lot of rocketeers
who focus their limited R&D capability elsewhere and fly MMH/NTO.

There will also be people who focus on green-propellant engines,
but the rest of the industry isn't going to A: wait on them before
going ahead with its own plans, or B: wager their plans against
the green-propellant folks being ready when needed.


--
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*Member:AIAA,NRA,ACLU,SAS,LP * is worth doing for money" *
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  #6  
Old March 25th 07, 03:29 AM posted to sci.space.policy
Henry Spencer
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Default SpaceX Dragon

In article .com,
are wrote:
OK, spaceglobal.com says the propellant is MMH/NTO, same as for the
attitude-control system. Isn't it a bit 20th-century to be using a
relatively toxic propellants like that?


It's six of one and half a dozen of the other. The trouble with MMH/NTO
and its immediate relatives is toxicity, and the resulting handling
hassles. But the good part is that proven, reliable hardware to use them
is available off the shelf.

Pick most anything else, and you may have solved the toxicity problem, but
now you've got to develop a lot of the hardware from scratch. And that's
not necessarily a simple exercise; the alternatives all have their own
special problems, of one kind or another.

So if you were trying to go after a bunch of NASA money -- like the COTS
contract that SpaceX won -- it's not ridiculous to decide that at least
the Mark 1 should use RCS/OMS hardware you can buy right now, even if it's
costly and a hassle to use. It makes your proposal look less risky, and
that may be more important than reducing operating costs later.
--
spsystems.net is temporarily off the air; | Henry Spencer
mail to henry at zoo.utoronto.ca instead. |
  #7  
Old March 25th 07, 12:19 PM posted to sci.space.policy
Craig Fink
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Posts: 1,858
Default SpaceX Dragon

Yes, and the way to go after a bunch of NASA money is to increase recurring
costs. Plain and simple, and it works. Using Toxic fuel will probably drive
them up, making development, testing, ground handling, safety more complex
and increase turn around time. Clear the area while we do something with
this toxic stuff. Ops, downtime, clean up that mess. Much higher recurring
costs, and in the end, probably higher up front costs too.

It also limits the multiple use of a heavy item, which SpaceX has been doing
some of, with their innovative Falcon 1. Kerosine fuel and hydraulic fluid,
Helium pressurization, roll control, attitude thrusters. You can't breath
the stuff like other combinations (one that includes Oxygen). So, the
choice just added a bunch of weight and complexity to another separate
system. Handling it in space may also not be the best of ideas, leaks
spewing toxic stuff, which limits another use operationally, offloading
excess fuel and oxidizer at a space station/or space hotel. They might
actually want any extra Oxygen and probably Hydrogen too, might actually be
willing to pay for it. They may not be in the market for deltaV. So, he's
limiting his future revenue streams, along with future business
opportunities.

As activities at a future Space Hotels, Space Stations, Space depots, Space
industries complex, Space junkyards and Orbital transfer facility become a
reality, the usefulness of cryogenic oxygen, hydrogen, nitrogen, methane,
carbon dioxide (solid) will be obvious. They are simply commodities in a
new Space Market Place. People will probably have to pay to recycle their
excess MMH/NTO, rather than getting payed for their excess Oxygen,
Hydrogen ...

I agree, it's not ridiculous to decide to use the toxic stuff, but makes me
wonder why it's not ridiculous. It's probably driven by NASA and some of
their requirements in the contract. NASA is famous for writing contract
requirements to get what they want, but not necessarily what they need.
They simply need mass transportation and crew transportation to the
Station, but should not be telling them how to do it in the requirements.
The Tar Baby is holding a carrot, grab the carrot and the Tar Baby grabs
you. That why my simplified model of where SpaceX is going has a -1 for
such interactions.

I also agree, it is a bit 20th-century thinking to use it in the
21st-century. But, NASA seems to be stuck in the 20th with their "Apollo on
Steroids", the sequel, exploration plan.

--
Craig Fink
Courtesy E-Mail Welcome @
--

Henry Spencer wrote:

In article .com,
are wrote:
OK, spaceglobal.com says the propellant is MMH/NTO, same as for the
attitude-control system. Isn't it a bit 20th-century to be using a
relatively toxic propellants like that?


It's six of one and half a dozen of the other. The trouble with MMH/NTO
and its immediate relatives is toxicity, and the resulting handling
hassles. But the good part is that proven, reliable hardware to use them
is available off the shelf.

Pick most anything else, and you may have solved the toxicity problem, but
now you've got to develop a lot of the hardware from scratch. And that's
not necessarily a simple exercise; the alternatives all have their own
special problems, of one kind or another.

So if you were trying to go after a bunch of NASA money -- like the COTS
contract that SpaceX won -- it's not ridiculous to decide that at least
the Mark 1 should use RCS/OMS hardware you can buy right now, even if it's
costly and a hassle to use. It makes your proposal look less risky, and
that may be more important than reducing operating costs later.


 




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