What is the Meaning of ATO? the Space Station? Entry?

On Fri, 28 Jul 2006 10:57:08 -0500, George R. Kasica wrote:

After entry interface?

Or, Abort To Orbit and redock with the Space Station if a heat shield
failure has been detected during entry. Like doing a RTLS to the Space
Station instead of KSC.

\Ummmm..not on descent....once the deorbit burn is done, they're
coming down someplace be it on house, farm, field, runway or cow, but
they ARE coming down that's an unchangeable fact of physics. Not
enough propellant to reverse the slowdown.

I would have been writing this post too, a week ago. And really, for the
most part, you and Greg are right. But, often when we hear something over
and over again, we think it true. Must be, or why else would people be
repeating it all the time. We don't even bother to examine a particular
issue. Like, exactly when is the absolute last time the Space Shuttle can
return to the Space Station or Orbit if something is wrong with the
heatshield. We've heard it from everybody, I've even said it myself not
too long ago, but is it really true? Is it an unchangeable fact of
physics?

The question of the Space Shuttle to make it back to the Space Station
after the deorbit burn is really an aerobrake question. Or, really a
question of what happens if the brakes are turned "off", during entry.
Since STS-1, from an aerodynamic standpoint, the Orbiter has only flown
one entry. Well, two if you count Columbia's last mission.
Aerodynamically, they have all been one and the same. Like building an
experimental aircraft, then only flying it at 40 degrees angle of attack.
Keeping the envelope as small as possible, instead of expanding it towards
any of the edges of the envelope.

Forty degrees angle of attack is a high drag/high lift attitude. A useful
attitude for aerobrake too, but not the only one. Maximum Lift/Drag angle
of attack would be important too, especially for plane changes to
rendezvous with an orbiting Space Station. The other one that comes to
mind would be the Minimum Drag attitude (zero angle of attack). Both areas
where the Orbiter has never flown on entry, but very important for
aerobraking to the Space Station for Lunar/Mars returns and the
aero(nobraking) Shuttle Entry Abort To Orbit question.

Currently, the Orbiter plans for and reenters with the lift vector up, at
40 degree angle of attack. This make the deorbit burn larger and the
perigee lower than an entry planned for with the lift vector down. How
much of a difference in the perigee? I'm not sure. If the brakes are
turned "off" (zero angle of attack/roll to heads up) to Abort back into
Orbit, how much OMS fuel (deltaV) would be required to raise perigee up
out of the atmosphere? Not really sure. But, I suspect it's not as much as
most people would think and that the Orbiter has the capability of carry
it.


--
Craig Fink
Courtesy E-Mail Welcome @

"snidely" wrote in message
oups.com...

Herb Schaltegger wrote:
On Fri, 28 Jul 2006 14:04:41 -0500, Jeff Findley wrote
Why don't you tell us the mass of fuel you'd need for an aerobraking
return
to ISS? Do the math and quit your hand waving.

Better yet, quit posting stupid off-the-wall BS when you're apparently
drunk. :-/

There has been an uneven quality to Craig's postings lately....

Bipolar disorder? There are effective treatments for that. I suggest he
head to a mental health professional for an evaluation.

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)

"Craig Fink" wrote in message
news
Currently, the Orbiter plans for and reenters with the lift vector up, at
40 degree angle of attack. This make the deorbit burn larger and the
perigee lower than an entry planned for with the lift vector down. How
much of a difference in the perigee? I'm not sure. If the brakes are
turned "off" (zero angle of attack/roll to heads up) to Abort back into
Orbit, how much OMS fuel (deltaV) would be required to raise perigee up
out of the atmosphere? Not really sure. But, I suspect it's not as much as
most people would think and that the Orbiter has the capability of carry
it.

Hand waving again.

Clearly this depends a lot on the velocity that's been bled off by the
atmosphere and by the original OMS de-orbit burn. Why don't you do us all a
favor and look this up yourself. You're looking for a graph of the
orbiter's altitude and velocity during descent. Also, you'll want to find
out how much reserve OMS fuel is normally in the OMS pods *after* the
de-orbit burn. Come back when you have the answers.

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)

I said earlier in the thread, that a week about I would have agreed with
George, Greg and you. So, obviously, the concept is less that a week old,
unless someone else has done it. Which may very well be the case. You
want to take it a step further, sure, why not. Let put some actual numbers
to it, how about we start with ii)

grabbing nearest envelope in sight

i) Boundary between Orbital and Entry.

After the deorbit burn, what is the minimum drag deltaV (at perigee)
required during the pass through the atmosphere?

That's simply enough atmospheric drag to reduce apogee equal to perigee
while inside the atmosphere. Circular orbit, inside the atmosphere,
with the lift vector pointed down in a high drag attitude (40 degrees
angle of attack). Very close to the deltaV of the OMS-1 burn for a
standard insertion. 250, 300, 350 fps?

So, what is the difference in drag between 0 degrees angle of attack and
40 degrees angle of attack? 30% maybe less? So, passing through the upper
atmosphere at 0 degrees angle of attack would result in an apogee still
above the atmosphere, only losing 100-200 fps due to drag. Orbital. While
the same trajectory in a heads down 40 degree angle of attack would result
in reentry and landing. Entry.

ii) OMS fuel usage ATOSS,

Available Delta_V = 1000 fps (OMS) + ?250? fps (RCS) = +1250
minus Delta_V premeco = 0 fps
minus Delta_V OMS-2 circ = -300 fps
minus Delta_V deorbit = -250 fps
minus Delta_V circ = -300 fps
Subtotal Delta_V available = 400 fps (for drag during atmospheric pass)

So far it looks really good, 400 fps should be plenty to compensate for
drag during a pass thru the upper atmosphere.

iii) Entry heating.

I don't think were talking about a great deal of heating here, resulting
from a pass through the upper atmosphere. It's only 100-200 fps in drag.
It's just not that much drag, energy being dissipated, or atmospheric
heating.

and finally,

iv) Re-Docking at the Space Station

Subtotal Delta_V available = 400 fps
minus DeltaV atmospheric drag = -200 fps

Subtotal Margin for ATOSS = 200 fps

So, the Orbiter would arrive at the Space Station with 200 fps of OMS/RCS
fuel in it's tanks.

--
Craig Fink
Courtesy E-Mail Welcome @

This is what it looks like when someone "actually" uses their filters. If
he says anything of value it'll take someone else (not filtered) to
respond to his posting that has value.

--
Craig Fink
Courtesy E-Mail Welcome @

This is what it looks like when someone "actually" uses their filters. If
he says anything of value it'll take someone else (not filtered) to
respond to his posting that has value.

--
Craig Fink
Courtesy E-Mail Welcome @

This is what it looks like when someone "actually" uses their filters. If
he says anything of value it'll take someone else (not filtered) to
respond to his posting that has value.

--
Craig Fink
Courtesy E-Mail Welcome @

"Craig Fink" wrote in message
news
Subtotal Delta_V available = 400 fps (for drag during atmospheric pass)

So you can only lose less than 300 miles per hour of velocity to drag before
you can no longer "abort" back to orbit. If we assume that you'll lose the
same amount due to drag dropping into the atmosphere that you'd lose while
performing the OMS burn to get out, that's only 150 miles per hour that you
can lose during descent before you have to abort back to orbit.

That's less than one percent of orbital velocity, considering that ISS orbit
is about 17500 miles per hour (from www.nasa.gov).

So, exactly what use is this maneuver again?

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)

--
Danny Dot
www.mobbinggonemad.org

"Craig Fink" wrote in message
news
I said earlier in the thread, that a week about I would have agreed with
George, Greg and you. So, obviously, the concept is less that a week old,
unless someone else has done it. Which may very well be the case. You
want to take it a step further, sure, why not. Let put some actual numbers
to it, how about we start with ii)

grabbing nearest envelope in sight

i) Boundary between Orbital and Entry.

After the deorbit burn, what is the minimum drag deltaV (at perigee)
required during the pass through the atmosphere?

That's simply enough atmospheric drag to reduce apogee equal to perigee
while inside the atmosphere. Circular orbit, inside the atmosphere,
with the lift vector pointed down in a high drag attitude (40 degrees
angle of attack). Very close to the deltaV of the OMS-1 burn for a
standard insertion. 250, 300, 350 fps?

So, what is the difference in drag between 0 degrees angle of attack and
40 degrees angle of attack? 30% maybe less? So, passing through the upper
atmosphere at 0 degrees angle of attack would result in an apogee still
above the atmosphere, only losing 100-200 fps due to drag. Orbital. While
the same trajectory in a heads down 40 degree angle of attack would result
in reentry and landing. Entry.

ii) OMS fuel usage ATOSS,

Available Delta_V = 1000 fps (OMS) + ?250? fps (RCS) = +1250
minus Delta_V premeco = 0 fps
minus Delta_V OMS-2 circ = -300 fps
minus Delta_V deorbit = -250 fps
minus Delta_V circ = -300 fps
Subtotal Delta_V available = 400 fps (for drag during atmospheric pass)

So far it looks really good, 400 fps should be plenty to compensate for
drag during a pass thru the upper atmosphere.

iii) Entry heating.

I don't think were talking about a great deal of heating here, resulting
from a pass through the upper atmosphere. It's only 100-200 fps in drag.
It's just not that much drag, energy being dissipated, or atmospheric
heating.

and finally,

iv) Re-Docking at the Space Station

Subtotal Delta_V available = 400 fps
minus DeltaV atmospheric drag = -200 fps

Subtotal Margin for ATOSS = 200 fps

So, the Orbiter would arrive at the Space Station with 200 fps of OMS/RCS
fuel in it's tanks.

--
Craig Fink
Courtesy E-Mail Welcome @


One thing to consider is at 0 degrees angle of attack, you are not
generating any lift, just drag. I assume you are looking at changing
inclination or something. Or are you looking at protecting for detecting a
big hole in the TPS early in entry, then aborting to station rather than
complete the entry. Is this correct? One problem is the deorbit burn can
normally consume all of the OMS propellant. It would be easy enough to fly
lift vector up and skip back up into the vacuum of space and light the OMS
engines to get back into orbit. But, if this was a planned contingency, the
OMS load would have to carry enough propellant to perform the burn. Today
it does not carry this propellant.

On a skip entry, I tried it once in the NASA simulator. I had been told
that if you skipped, the shuttle would come in so steep on its second entry,
it would burn up. The second entry was very benign actually. The shuttle
never went to high drag on the second entry. If I had OMS propellant, I am
certain I could have used the OMS to get back into orbit. One problem is
the software in the shuttle. After it modes to entry, it can not at this
time go back to orbit operations. This change to the software could be done
I am certain.

Another issue for an about back to station is time to rendezvous and
consumables. It may take days to get back to station, and the shuttle may
not have enough consumables to keep the crew alive.

Danny Dot