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#920 by tva on 09 Feb, 2010 07:05
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How its possible if it is only few km of altitude?
Keep in mind that the orbiter-ET combo is rapidly loosing mass while trust is constant. Combined with that long shallow dive it helps to accelerate. That shallow dive is partly caused of the modest level of trust after SRB separation. The trust level barely maintains 1g for half a minute.
What do u mean with 'overstressing the structure' - pressure which came from changing of acceleration? (Cause there are no aerodynamic stressing above - lets say 80 km of altitude).
Think at the analogy of throwing a stone. When the stone leaves your hand it still will climbs upwards for a while.
Without the shallow dive the stuttle would need to spend longer time in the thicker layers of the atmosphere.Quoteedit: Second question - theoritically could the shuttle climb higher without going to this shallow dive? I mean climb further to point where she would get a required speed. I can imagine that it would cost a lot of fuel but wanna just ensure myself..
Shuttle is inserted in orbit at perigee. After MECO it is coasting (gaining) altitude without burning precious propellant. -
#921 by MKremer on 09 Feb, 2010 09:24
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what is the OMS propellent budget?
assent, circulation, orbit, deorbit, reserve, residual...
Those figures would likely vary depending on the mission and payload mass. (and will also vary depending on the orbiter involved since they don't all have identical masses)
For each mission, the Flight Day Execute Package document will give the best figures for propellant remaining at the start of the flight day, and each PAD burn update will give calculated total orbiter mass.
If you're asking how much propellant is loaded at the beginning of a mission, I believe all tanks are filled completely both front and rear.
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#922 by MikeMi. on 09 Feb, 2010 22:01
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How its possible if it is only few km of altitude?
Keep in mind that the orbiter-ET combo is rapidly loosing mass while trust is constant. Combined with that long shallow dive it helps to accelerate. That shallow dive is partly caused of the modest level of trust after SRB separation. The trust level barely maintains 1g for half a minute.
What do u mean with 'overstressing the structure' - pressure which came from changing of acceleration? (Cause there are no aerodynamic stressing above - lets say 80 km of altitude).
Think at the analogy of throwing a stone. When the stone leaves your hand it still will climbs upwards for a while.
Without the shallow dive the stuttle would need to spend longer time in the thicker layers of the atmosphere.Quoteedit: Second question - theoritically could the shuttle climb higher without going to this shallow dive? I mean climb further to point where she would get a required speed. I can imagine that it would cost a lot of fuel but wanna just ensure myself..
Shuttle is inserted in orbit at perigee. After MECO it is coasting (gaining) altitude without burning precious propellant.
Ok, thanks for answers. One more thing - does someone know a document or page (whatever) where are described in detail all manouvers like this interesting one 5 minutes after launch?
Thanks for help,
Mike -
#923 by Jorge on 09 Feb, 2010 23:02
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what is the OMS propellent budget?
assent, circulation, orbit, deorbit, reserve, residual...
Those figures would likely vary depending on the mission and payload mass. (and will also vary depending on the orbiter involved since they don't all have identical masses)
For each mission, the Flight Day Execute Package document will give the best figures for propellant remaining at the start of the flight day, and each PAD burn update will give calculated total orbiter mass.
If you're asking how much propellant is loaded at the beginning of a mission, I believe all tanks are filled completely both front and rear.
The FRCS tanks are usually filled only 70% to keep the CG in the box.
The ARCS tanks are always loaded full.
The OMS tanks are not always loaded full. For 130 the load is 22761 lbm, which is a couple thousand pounds short of full. -
#924 by Lee Jay on 10 Feb, 2010 03:14
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Why TORVA? Does using twice orbital rate minimize prop usage for the arc? If so, the orbital mechanics there are not intuitive to me.
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#925 by MikeMi. on 10 Feb, 2010 06:55
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One more thing - does someone know a document or page (whatever) where are described in detail all manouvers like this interesting one 5 minutes after launch?
I believe that there exist sth like this..
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#926 by Jorge on 10 Feb, 2010 07:26
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Why TORVA? Does using twice orbital rate minimize prop usage for the arc? If so, the orbital mechanics there are not intuitive to me.
It is a combination of orbital mechanics and the unique arrangement of RCS thrusters on the shuttle. The shuttle's primary RCS thrusters are sized for entry control authority and are quite oversized for orbit ops, especially compared to other (much smaller) ISS visiting vehicles. RCS plume impingement becomes a major concern during shuttle-ISS prox ops.
To minimize plume impingement, the shuttle must use a digital autopilot (DAP) mode called "Low Z" between 1000 and 75 ft which inhibits the +Z (upfiring) thrusters. To perform a +Z translation in Low Z, the DAP fires +X (aft-firing) and -X (forward-firing) thrusters simultaneously. The thrusters are canted slightly such that the X components cancel out and the Z components add, providing a small braking force. A Low Z pulse must fire 11 times as long as a normal Z pulse to provide the same delta-V, so it consumes a correspondingly higher amount of propellant.
It is therefore important that the approach profile be designed to minimize the need for Low Z (+Z) braking, even if this results in more firings in -Z and the other axes. One way to accomplish this for the Rbar to Vbar transition is to increase the rotation rate above the orbital rate. Although the physicist purist in me dislikes the concept of "centrifugal force", the analogy is useful to visualize what's going on. A higher flyaround rate means a higher tangential velocity, which has the tendency to "fling" the orbiter away from the station. This increases the +X and -X delta-V needed to start and stop the flyaround, but it greatly decreases the need for Low Z +Z braking. But this only works up to a point - eventually, the flyaround rate becomes fast enough that no +Z would ever be required, but the +X, -X, and -Z requirements would increase more than enough to balance things out.
It turns out that twice orbital rate is close to optimum for the shuttle. Hence the TORVA. Serendipitously, twice orbital rate also allows a full 360 degree flyaround to be completed during a single orbital daylight pass, so the rate was standardized for both approach and the post-undocking flyaround. -
#927 by tva on 10 Feb, 2010 08:08
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Ok, thanks for answers. One more thing - does someone know a document or page (whatever) where are described in detail all manouvers like this interesting one 5 minutes after launch?
MikeMi,
I am not sure what you mean by "all manoeuvres like this interesting one 5 minutes after launch".
There aren't that much going on at that specific time frame.
SRB staging occurs approx. 2'20"
OMS assist starts right after that
the vehicle rolls heads up at about 5'45"
You can read the entire logg of ascent data for STS-119 attached to that earlier post of mine. -
#928 by MikeMi. on 10 Feb, 2010 08:46
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I am not sure what you mean by "all manoeuvres like this interesting one 5 minutes after launch".
There aren't that much going on at that specific time frame.
Wanna know more about shuttle flight in first 8 minutes (in regards to this graph which I attached one page earlier in this thread), cause I didn't know that there are such manouevers like 'deep shallow dive' after reachin max altitude (109 km) then it goes down to around 102 km. How is this performing (i mean by RCS or ...)?. You see, if we take a look on this graph (attached page earlier) we can see a small hill - trajectory of shuttle (altitude as Y axis, time as X axis).
Just want to know if this situation with 'shallow dive' helps to get rid of ET tank. I suppose that we can have more accurate re-entry place of tank with using that techniq.
And to sum up (with longer answer please) is there really a plus summary energy with that play of trading potential to kinetic energy?
Does Soyuz make also similiar action with 'shallow dive'? I guess not since it has stronger construction..
Next question which came to my mind is if there could be greater g-load without throttling down with SSMEs around 7:22 time of flight.
And here u have that data for sts-130
http://www.cbsnews.com/network/news/space/130/130ascentdata.html -
#929 by Jim on 10 Feb, 2010 08:56
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1. How is this performing (i mean by RCS or ...)?.
2. Does Soyuz make also similiar action with 'shallow dive'? I guess not since it has stronger construction..
3. Next question which came to my mind is if there could be greater g-load without throttling down with SSMEs around 7:22 time of flight.
1. SSME gimbaling
2. no, it is a launch vehicle specific (STS) maneuver driven by unique contraints
3. The throttling is to limit gload -
#930 by MikeMi. on 10 Feb, 2010 09:50
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2. no, it is a launch vehicle specific (STS) maneuver driven by unique contraints
For example?
greetz,
Mike -
#931 by Jim on 10 Feb, 2010 10:04
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2. no, it is a launch vehicle specific (STS) maneuver driven by unique contraints
Abort posturing -
#932 by Lee Jay on 10 Feb, 2010 14:15
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Thanks for the excellent TORVA explanation, Jorge!
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#933 by MikeMi. on 10 Feb, 2010 19:25
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Abort posturing
Okay, thanks!
One more question - does somewhere exists a graph showing aerodynamic drag which works on shuttle during first 9 minutes of flight? (for example graph in function of time)
What is the limit of g-load shuttle could withstand (in theory) - twice, tripple more than 3g? -
#934 by DansSLK on 10 Feb, 2010 20:33
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What is the limit of g-load shuttle could withstand (in theory) - twice, tripple more than 3g?
Has been answered before, a search might turn up a number since my foggy memory can't find it in the old long term storage.
I know its not much more than 3g's, stronger structure tends to mean heavier structure. -
#935 by Hobbs on 10 Feb, 2010 23:52
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Are there any plans for any commemoratory events or anything during STS-133 or are they just going to end the shuttle program quietly?
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#936 by Fequalsma on 11 Feb, 2010 01:35
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3g axial x 1.4 factor of safety (typical for most components,
although FS may be 2 for the crew compartment?).
v/r, F=maWhat is the limit of g-load shuttle could withstand (in theory) - twice, tripple more than 3g?
Has been answered before, a search might turn up a number since my foggy memory can't find it in the old long term storage.
I know its not much more than 3g's, stronger structure tends to mean heavier structure. -
#937 by tminus9 on 11 Feb, 2010 03:40
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Is the docked ISS-shuttle TEA attitude the same for every flight, or is it specific to each shuttle mission? Is there a single TEA, or multiple options to choose from? I recall reading that the primary docked attitude is partially to shield the orbiter's TPS from MMOD damage, but I didn't know how the TEA factors into attitude selection. Any idea what the TEA is for this STS-130?
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#938 by Jorge on 11 Feb, 2010 03:58
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Is the docked ISS-shuttle TEA attitude the same for every flight, or is it specific to each shuttle mission?
It changes a few degrees every mission due to changes in the stack mass properties and drag profile.QuoteIs there a single TEA, or multiple options to choose from? I recall reading that the primary docked attitude is partially to shield the orbiter's TPS from MMOD damage, but I didn't know how the TEA factors into attitude selection.
There are multiple TEAs (technically a TEA, or Torque Equilibrium Attitude, is any attitude where the environmental torques on the stack, mainly gravity gradient and aero, cancel out), but only two of them (biased ISS -XVV and +XVV) meet both shuttle and station thermal and power requirements, and only the -XVV TEA meets shuttle TPS protection criteria. So it is the only one operationally used.QuoteAny idea what the TEA is for this STS-130?
Biased ISS -XVV, as has been standard since STS-107, and is almost certain to remain so for the remaining flights. -
#939 by tminus9 on 11 Feb, 2010 04:36
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Thanks, that makes sense.
Any idea what the TEA is for this STS-130?
Biased ISS -XVV, as has been standard since STS-107, and is almost certain to remain so for the remaining flights.
Does the terminology "biased -XVV" essentially mean start with -XVV (or whatever the particular reference) and rotate predetermined amounts about one or more of the PRY axes?
