| View previous topic :: View next topic |
| Author |
Message |
kT
Guest
|
 Posted: Fri Jun 01, 2007 12:00 am Post subject: Re: NASAspaceflight.com - Censors the John Young - Ares I T |
 |
|
Pat Flannery wrote:
| Quote: |
kT wrote:
Maybe your's isn't, but mine is. You're still living in the 50's.
Show me a technology that gives us a order of magnitude increase in
ISP...because if you can't do that, all you're doing is blowing
rose-smelling farts out of your ass while you're dreaming.
|
Which is why my SSME SSTO test vehicle, the Delta V, routinely gets me
to orbit pulling less than 8 gees with easily attainable mass fractions
and plenty of fuel to spare. SRBs are what produce rose smelling farts.
--
Get A Free Orbiter Space Flight Simulator :
http://orbit.medphys.ucl.ac.uk/orbit.html |
|
| Back to top |
|
 |
| |
Ads |
Advertising
Sponsor
|
|
Guest
|
| Posted: Sat Jun 02, 2007 3:06 am Post subject: Re: NASAspaceflight.com - Censors the John Young - Ares I T |
|
|
On Thu, 31 May 2007 02:24:52 GMT, henry@spsystems.net (Henry Spencer)
wrote:
| Quote: |
there were some important LM changes, notably larger
descent-stage tanks and a stretched descent-engine nozzle.
|
Mr Spencer, what was the reason for larger descent stage tanks? Does
this mean the CM orbitted further away from the moon? what does a
"stretched" descent engine nozzle mean, and what are the advantages? |
|
| Back to top |
|
|
| |
Ads |
Advertising
Sponsor
|
|
Guest
|
| Posted: Sat Jun 02, 2007 3:14 am Post subject: Re: NASAspaceflight.com - Censors the John Young - Ares I T |
|
|
On Thu, 31 May 2007 02:48:39 GMT, henry@spsystems.net (Henry Spencer)
wrote:
| Quote: |
I wrote:
...there were substantial parts of the lunar surface that Apollo
could not reach at all, due to complex interlocking constraints.
|
Granted that Tycho is a very interesting place, is it
| Quote: |
worth one of the few remaining Apollo flights if (for example) you don't
have enough payload to take a rover, so you're limited to exploring the
area the crew can walk to?
|
In these cases, was the CM in the same plane as the Earth and Moon,
ie the simpliest? Or was it maneouvred to change it's orbit?
I'm thinking it would take less overall fuel to keep the CM in the
same plane each mission, and just spend fuel on maneouvring the LM.
Were there places on the moon the LM could not reach?
Thanks, Stan |
|
| Back to top |
|
|
| |
Ads |
Advertising
Sponsor
|
|
Henry Spencer
Guest
|
| Posted: Sat Jun 02, 2007 10:38 am Post subject: Re: NASAspaceflight.com - Censors the John Young - Ares I T |
|
|
In article <pd9163hm96787ldagr7t6p45lcah80rtvb@4ax.com>,
<pstanley55@hotmail.com> wrote:
| Quote: |
there were some important LM changes, notably larger
descent-stage tanks and a stretched descent-engine nozzle.
Mr Spencer, what was the reason for larger descent stage tanks? Does
this mean the CM orbitted further away from the moon?
|
No, and in fact the CSM took the LM down *lower* for the J-series flights,
essentially using CSM fuel instead of LM fuel for the first part of the
descent, to spare still more LM fuel for the later parts. The point of
both that and the bigger descent-stage tanks was more fuel for braking and
landing, to land more equipment and more supplies. Notably, to land a
lightweight rover and enough supplies to give the crew 2-3 days on the
surface.
| Quote: |
what does a
"stretched" descent engine nozzle mean, and what are the advantages?
|
What it means is just what it sounds like: they extended the descent
engine's nozzle. The longer nozzle gave the exhaust gas a little more
time to expand against the nozzle (providing thrust) before leaving the
nozzle. That meant either a bit more thrust for the same fuel flow, or
(the option actually used) a bit less fuel flow for the same thrust. The
net effect was to make each kilogram of fuel go a bit farther, giving the
equivalent of a further increase in available fuel.
(The disadvantage of a longer nozzle was a greater chance of having the
nozzle hit the ground in a hard landing on an uneven surface, something
that had worried the original designers. One reason why people were
willing to consider extending the nozzle was that the early landings
showed that the original predictions about worst-case hard landings were
much too pessimistic.)
--
spsystems.net is temporarily off the air; | Henry Spencer
mail to henry at zoo.utoronto.ca instead. | henry@spsystems.net |
|
| Back to top |
|
|
| |
Ads |
Advertising
Sponsor
|
|
Dave Michelson
Guest
|
| Posted: Sat Jun 02, 2007 12:31 pm Post subject: Re: NASAspaceflight.com - Censors the John Young - Ares I T |
|
|
pstanley55@hotmail.com wrote:
| Quote: |
there were some important LM changes, notably larger descent-stage
tanks and a stretched descent-engine nozzle.
Mr Spencer, what was the reason for larger descent stage tanks? Does
this mean the CM orbitted further away from the moon? what does a
"stretched" descent engine nozzle mean, and what are the advantages?
|
The goal was to get as much additional mass to the lunar surface as
possible.
The extended-stay LM was about 2200 kg heavier than Eagle and Intrepid.
The single largest component of this was the additional propellant in
the enlarged descent stage propellant tanks. The second largest was the
Lunar Rover. A solar power extension package was also considered but
later dropped after the surface stay time was capped at 54 hours. Other
changes included additional batteries, water, LiOH, and oxygen to extend
the surface stay time.
The additional propellant, plus use of the CSM's SPS engine to put the
LM into its descent orbit, allowed a heavier LM to be landed. It also
provided 17 seconds of additional hover time just before landing.
The nozzle extension on the descent stage engine is where the exhaust
gases trade off heat for speed. Stretching the extension increases the
efficiency of the engine by allowing the velocity of the exhaust to
increase just a bit further before it exits the nozzle.
HTH.
--
Dave Michelson
davem@ece.ubc.ca |
|
| Back to top |
|
|
| |
Ads |
Advertising
Sponsor
|
|
Rand Simberg
Guest
|
| Posted: Sat Jun 02, 2007 6:08 pm Post subject: Re: NASAspaceflight.com - Censors the John Young - Ares I T |
|
|
On Fri, 25 May 2007 15:32:59 GMT, in a place far, far away, "Brian
Gaff" <briang1@blueyonder.co.uk> made the phosphor on my monitor glow
in such a way as to indicate that:
| Quote: |
It makes you realise what amazing designs have gone before really.
Besides, if I may proffer my few penneth here, this vision is a Shrub
creation, and thus, I'd imagine that some in Nasa are expecting it to be cut
back or cancelled buy the democrat who gets in next time...
|
There's nothing wrong with the vision. I find it both amusing and
dismaying that so many (apparently ignorant) people have so much
trouble distinguishing between the vision, and Mike Griffin's chosen
means of implementing it. |
|
| Back to top |
|
|
| |
Ads |
Advertising
Sponsor
|
|
kT
Guest
|
| Posted: Sat Jun 02, 2007 7:22 pm Post subject: Re: NASAspaceflight.com - Censors the John Young - Ares I T |
|
|
Rand Simberg wrote:
| Quote: |
It makes you realise what amazing designs have gone before really.
Besides, if I may proffer my few penneth here, this vision is a Shrub
creation, and thus, I'd imagine that some in Nasa are expecting it to be cut
back or cancelled buy the democrat who gets in next time...:-)
There's nothing wrong with the vision. I find it both amusing and
dismaying that so many (apparently ignorant) people have so much
trouble distinguishing between the vision, and Mike Griffin's chosen
means of implementing it.
|
I had a vision once too, but my reality based vision was of 6.5 billion
mammals glued right down to the surface of the planet Earth by gravity.
--
Get A Free Orbiter Space Flight Simulator :
http://orbit.medphys.ucl.ac.uk/orbit.html |
|
| Back to top |
|
|
| |
Ads |
Advertising
Sponsor
|
|
Rand Simberg
Guest
|
| Posted: Sat Jun 02, 2007 8:50 pm Post subject: Re: NASAspaceflight.com - Censors the John Young - Ares I T |
|
|
On Thu, 31 May 2007 11:52:51 -0500, in a place far, far away, Pat
Flannery <flanner@daktel.com> made the phosphor on my monitor glow in
such a way as to indicate that:
| Quote: |
kT wrote:
Maybe your's isn't, but mine is. You're still living in the 50's.
Show me a technology that gives us a order of magnitude increase in
ISP...because if you can't do that, all you're doing is blowing
rose-smelling farts out of your ass while you're dreaming.
|
Nonsense. Isp is not the problem. |
|
| Back to top |
|
|
| |
Ads |
Advertising
Sponsor
|
|
Henry Spencer
Guest
|
| Posted: Sat Jun 02, 2007 10:08 pm Post subject: Re: NASAspaceflight.com - Censors the John Young - Ares I T |
|
|
In article <jV98i.253089$DE1.46689@pd7urf2no>,
Dave Michelson <davem@ece.ubc.ca> wrote:
| Quote: |
...A solar power extension package was also considered but
later dropped after the surface stay time was capped at 54 hours...
|
Actually contrariwise: the surface stay time was capped at 54 hours when
tight funding required canceling the manually-deployed solar array, which
would have stretched the stay a little farther.
--
spsystems.net is temporarily off the air; | Henry Spencer
mail to henry at zoo.utoronto.ca instead. | henry@spsystems.net |
|
| Back to top |
|
|
| |
Ads |
Advertising
Sponsor
|
|
Henry Spencer
Guest
|
| Posted: Sun Jun 03, 2007 1:26 am Post subject: Re: NASAspaceflight.com - Censors the John Young - Ares I T |
|
|
In article <so9163dp7lbomesub6gcvt762lkun0u718@4ax.com>,
<pstanley55@hotmail.com> wrote:
| Quote: |
Granted that Tycho is a very interesting place, is it
worth one of the few remaining Apollo flights if (for example) you don't
have enough payload to take a rover...
In these cases, was the CM in the same plane as the Earth and Moon,
ie the simpliest? Or was it maneouvred to change it's orbit?
|
A counterintuitive but important fact is that for approaching the Moon,
its motion is much more important than its gravity. To a rough first
approximation, the Apollo spacecraft is almost motionless, up near the top
of a highly elliptical transfer orbit, as the relatively-small Moon comes
zipping up behind it. Only when you get quite close is the Moon's gravity
very important. So a fairly small change in the transfer orbit will have
the spacecraft making its closest approach to the Moon over the lunar
equator, over a lunar pole, or anywhere in between. The range of
accessible orbits wasn't unlimited even so, given Apollo's slim fuel
margins, but it was fairly wide.
The plane of each flight's lunar orbit was chosen, roughly speaking, to
pass over the landing site headed due west, so that a dawn landing would
be coming down with a low sun directly behind the LM. This gave the crew
a view of the LM's own shadow for scale, and made even small surface
features highly visible because of their long shadows. So the orbital
inclination (with respect to the Moon's equator) equaled the lunar
latitude of the landing site.
| Quote: |
I'm thinking it would take less overall fuel to keep the CM in the
same plane each mission, and just spend fuel on maneouvring the LM.
|
No, LM fuel reserves were considerably tighter than those of the CSM --
hence the decision in the later flights to use CSM fuel to set up the LM's
descent orbit. In fact, for the flights with long surface stays, quite
noticeable amounts of CSM fuel were burned to rotate the plane of the CSM
parking orbit, to keep it passing directly over the landing site so that
an emergency ascent could be made at any time. (Abort cases quite often
constrained Apollo planning much more than nominal cases.)
| Quote: |
Were there places on the moon the LM could not reach?
|
Yes. Both high latitudes and longitudes well away from the central
meridian were difficult, and the combination could make a landing
impossible. Several constraints interacted, and subtle details of orbital
dynamics could be important given the small margins, so the plot of which
areas were accessible and which weren't was quite complicated. Some areas
were reachable only in winter, or only in summer, or (like the Apollo 17
landing site) only with a night launch.
--
spsystems.net is temporarily off the air; | Henry Spencer
mail to henry at zoo.utoronto.ca instead. | henry@spsystems.net |
|
| Back to top |
|
|
| |
Ads |
Advertising
Sponsor
|
|
Jeff Findley
Guest
|
| Posted: Tue Jun 05, 2007 12:20 am Post subject: Re: NASAspaceflight.com - Censors the John Young - Ares I T |
|
|
"Derek Lyons" <fairwater@gmail.com> wrote in message
news:465fd06c.91365125@news.supernews.com...
| Quote: |
"Greg D. Moore \(Strider\)" <mooregr_deleteth1s@greenms.com> wrote:
Aviation week is stating Orion is already 3,000 pounds over weight. I
don't see how NASA can fix this weight problem without a major reduction
in requirements.
Yeah, generally not a good sign when you start 3000 lbs overweight and you
haven't even bent metal yet.
Yeah. Very few programs ever have weight problems during development
- think how much trouble NASA would have been in had the CSM and LEM
turned out to be overweight.
Oh, wait. They did.
|
Luckily the Saturn V program didn't believe the initial numbers for the CSM
and LEM, so von Braun added quite a hefty margin to the Saturn V design, so
the Apollo program was successful in the end.
Still, there was a weight reduction program needed, especially for the LEM.
Apollo 11 was the first flight that was considered capable of safely landing
and returning to the CSM.
Jeff
--
"They that can give up essential liberty to obtain a
little temporary safety deserve neither liberty nor
safety"
- B. Franklin, Bartlett's Familiar Quotations (1919) |
|
| Back to top |
|
|
| |
Ads |
Advertising
Sponsor
|
|
Pat Flannery
Guest
|
| Posted: Tue Jun 05, 2007 2:16 am Post subject: Re: NASAspaceflight.com - Censors the John Young - Ares I T |
|
|
Jeff Findley wrote:
| Quote: |
Still, there was a weight reduction program needed, especially for the LEM.
Apollo 11 was the first flight that was considered capable of safely landing
and returning to the CSM.
That's still my favorite episode of "From The Earth To The Moon". |
"It'll be easy! Anyone can build something like this with all the time
we have!"
So the Grumman Ironworks turns out something about as sturdily built as
a beer can. :-)
Pat |
|
| Back to top |
|
|
| |
Ads |
Advertising
Sponsor
|
|
Jeff Findley
Guest
|
| Posted: Tue Jun 05, 2007 5:19 pm Post subject: Re: NASAspaceflight.com - Censors the John Young - Ares I T |
|
|
"Pat Flannery" <flanner@daktel.com> wrote in message
news:13693tbdg46t66e@corp.supernews.com...
| Quote: |
Jeff Findley wrote:
Still, there was a weight reduction program needed, especially for the
LEM. Apollo 11 was the first flight that was considered capable of safely
landing and returning to the CSM.
That's still my favorite episode of "From The Earth To The Moon".
"It'll be easy! Anyone can build something like this with all the time we
have!"
So the Grumman Ironworks turns out something about as sturdily built as a
beer can.
|
The LEM pressure vessel walls were pretty thin in places. It wouldn't have
taken much to accidentally put a hole right through the thing.
There is a summary of the LEM weight issues here:
http://www.astronautix.com/craft/lmweight.htm
Jeff
--
"They that can give up essential liberty to obtain a
little temporary safety deserve neither liberty nor
safety"
- B. Franklin, Bartlett's Familiar Quotations (1919) |
|
| Back to top |
|
|
| |
Ads |
Advertising
Sponsor
|
|
|
|
You cannot post new topics in this forum
You cannot reply to topics in this forum
You cannot edit your posts in this forum
You cannot delete your posts in this forum
You cannot vote in polls in this forum
|
222 Attacks blocked
Powered by phpBB © 2001, 2005 phpBB Group
|
FAQ
Search
Memberlist
Usergroups
Register
Profile
Log in to check your private messages
Log in
