ApolloHoax.net
Apollo Discussions => The Reality of Apollo => Topic started by: Mag40 on February 24, 2013, 05:35:10 PM
-
.....a Saturn V had taken off due East from Florida?
I know the mechanism whereby an object in orbit goes around in a large circle......so I'm interested to understand how the rocket would be drawn into that large circle from what starts off as segmental orbit.
-
I'm not sure I understand you. By taking off due east from Cape Canaveral, a rocket is following a great circle route. It doesn't maintain this due east orientation, however, any more than a ship or aircraft on a long voyage maintains a constant compass heading all the way to the destination even if it does follow a single great circle route.
-
.....a Saturn V had taken off due East from Florida?
It's S-II center engine would cut-off early and the CM would suffer an oxygen tank explosion.
http://history.nasa.gov/SP-4029/Apollo_18-21_Earth_Orbit_Data.htm
;D
-
I'm not sure I understand you. By taking off due east from Cape Canaveral, a rocket is following a great circle route. It doesn't maintain this due east orientation, however, any more than a ship or aircraft on a long voyage maintains a constant compass heading all the way to the destination even if it does follow a single great circle route.
Are there any directions that that a rocket could not use to launch into orbit? No just the Saturn V, but any hypothetical rocket.
-
I'm not sure I understand you. By taking off due east from Cape Canaveral, a rocket is following a great circle route. It doesn't maintain this due east orientation, however, any more than a ship or aircraft on a long voyage maintains a constant compass heading all the way to the destination even if it does follow a single great circle route.
Are there any directions that that a rocket could not use to launch into orbit? No just the Saturn V, but any hypothetical rocket.
I was under the impression that most launches start off by pitching in an easterly direction because they are utilising the rotation speed of the earth. At the Cape, the rotational speed of the earth is about 1400 kph. Launching and pitching toward the west would be problematic as you would be working against the earth's rotation so you would need more fuel plus longer burns to achieve the same orbit (retrograde)
Of course, more fuel means more weight which in turn means more fuel. I would think the weight+fuel impact of needing to find an extra 2,800 kph* to achieve orbit would be significant, because that is around 10% of LEO speed.
* its 2800 kph because you need to make up the 1400 kph you lose by not going eastwards, plus an extra 1400 kph to make up for going against the earth's rotation.
-
Are there any directions that that a rocket could not use to launch into orbit? No just the Saturn V, but any hypothetical rocket.
Roughly half of them, assuming you start from ground level. Possibly less depending on surrounding terrain.
-
I'm not sure I understand you. By taking off due east from Cape Canaveral, a rocket is following a great circle route. It doesn't maintain this due east orientation, however, any more than a ship or aircraft on a long voyage maintains a constant compass heading all the way to the destination even if it does follow a single great circle route.
Florida is at 28 degrees latitude.....if a rocket flies due East and maintains(or at least tries to hold) that direction.....it is following a path 5 degrees North of the tropic of Cancer. That is not a great circle.
I'm just interested in the orbital mechanics that 'force' the craft into a large circle. Is it a greater gravitational force to its starboard side?
-
Are there any directions that that a rocket could not use to launch into orbit? No just the Saturn V, but any hypothetical rocket.
Roughly half of them, assuming you start from ground level. Possibly less depending on surrounding terrain.
Very funny but don't give up your day job just yet. Orbital mechanics humor doesn't have a very large audience.
-
I'm not sure I understand you. By taking off due east from Cape Canaveral, a rocket is following a great circle route. It doesn't maintain this due east orientation, however, any more than a ship or aircraft on a long voyage maintains a constant compass heading all the way to the destination even if it does follow a single great circle route.
Florida is at 28 degrees latitude.....if a rocket flies due East and maintains(or at least tries to hold) that direction.....it is following a path 5 degrees North of the tropic of Cancer. That is not a great circle.
I'm just interested in the orbital mechanics that 'force' the craft into a large circle. Is it a greater gravitational force to its starboard side?
Sorry, I didn't mean to jump in on your question. It is one I have been wondering about too.
-
Florida is at 28 degrees latitude.....if a rocket flies due East and maintains(or at least tries to hold) that direction.....it is following a path 5 degrees North of the tropic of Cancer. That is not a great circle.
I'm just interested in the orbital mechanics that 'force' the craft into a large circle. Is it a greater gravitational force to its starboard side?
Gravitational force is toward the center of the planet, and objects orbit the center of the planet. No matter what direction you start out in, once in freefall, gravity will curve your trajectory around toward the center, resulting in a trajectory within the plane defined by the center of the planet and the initial direction. Every such plane intersects the surface on a great circle.
-
Rockets can be launched into orbit in any direction, north, east, south or west, as long as you don't care what or who it flies over. (This is true for more countries than you might think.)
However, you can't directly reach every orbit this way from every launch site. The lowest inclination (the angle the northbound orbit makes with the equator) that can be directly reached without an expensive dogleg or plane change is equal to the latitude of the launch site.
For example, Cape Canaveral is at 28.5N. Launching due east gives an orbit with a 28.5 degree inclination. Launching due northor south (correcting for Coriolis forces) will give a 90 degree inclination.
Since geostationary orbit has zero inclination, launch sites close to the equator have the advantage. Here you can't beat Sea Launch, which launches their rockets from a converted oil drilling platform that they put in the middle of the Pacific Ocean directly on the equator.
-
You should also read up on the concept of a "great circle route". This applies to ships and airplanes as well as rockets.
-
Florida is at 28 degrees latitude.....if a rocket flies due East and maintains(or at least tries to hold) that direction.....
The guidance system will guide the rocket to follow a great circle path during launch. If you tried to keep it at 28 N until it reached orbital velocity it would be like conducting a constant plane change maneuver and plane changes require a lot of fuel. If you could keep it at 28 N and reach orbital velocity, as soon as the rocket shuts off it will then orbital around the center of mass of the Earth and follow the typical path you see in orbit diagrams.
-
Florida is at 28 degrees latitude.....if a rocket flies due East and maintains(or at least tries to hold) that direction.....
The guidance system will guide the rocket to follow a great circle path during launch. If you tried to keep it at 28 N until it reached orbital velocity it would be like conducting a constant plane change maneuver and plane changes require a lot of fuel. If you could keep it at 28 N and reach orbital velocity, as soon as the rocket shuts off it will then orbital around the center of mass of the Earth and follow the typical path you see in orbit diagrams.
Exactly. Mag40, remember the principle that (absent outside influences) an object in orbit always passes through the point of its last powered maneuver.
-
On any rocket built so far, you'd run out of juice relatively quickly . . .
-
I'm just interested in the orbital mechanics that 'force' the craft into a large circle. Is it a greater gravitational force to its starboard side?
If I'm understanding the question correctly, you'd continually be at the "top" (that is, the highest latitude) of an orbit, in this sense - if you cut the engines at any point, the craft would follow an orbit that stayed within 28 N and 28 S. You'd need to be continually be thrusting towards the north, or your trajectory will immediately start to "fall" to a lower latitude.
-
OK, here's another way to think about it.
If you are travelling in a circle directly about 28 N, you are constantly accelerating around a point on the earth's axis, which is r*sin(28) (argument taken in degrees, make the appropriate conversion for radians) north of the centre of the earth. Earth's gravity is constantly accelerating you towards the centre of the earth.
So to maintain this "orbit", you need to be constantly applying acceleration which is equal to the vector pointing towards the axis north of the earth's centre, minus the vector pointing to the centre (i.e., the difference between the acceleration you need and the acceleration you get for free from the earth). This difference needs to point north, but it could also point "inward" towards the earth, or "outward", depending on how fast you are going.
I think the minimum acceleration needed to maintain this trajectory is probably parallel to the surface of the earth, i.e., along a great circle pointing from your present position towards the north pole. However, I haven't done the calculations to support that yet, so it might be wrong.
-
Some calculations.
It's easiest (for me at least) to use x/y/z coordinates where z=0 is the plane containing the equator. Then the desired orbit is
x = r*cos(w*t)*cos(alpha)
y = r*sin(w*t)*cos(alpha)
z = r*sin(alpha)
where r is the distance from the centre of the earth, and alpha is the desired constant latitude. w is related to orbital speed, and t is the time. The acceleration needed to maintain this is
x'' = -r*w*w*cos(w*t)*cos(alpha)
y'' = -r*w*w*sin(w*t)*cos(alpha)
z'' = 0
The acceleration you get from gravity is
x'' = -r*beta*cos(w*t)*cos(alpha)
y'' = -r*beta*sin(w*t)*cos(alpha)
z'' = -r*beta*sin(alpha)
where beta depends on the earth's mass, the gravitational constant, stuff like that. What you need is the difference,
x'' = r*(beta-w*w)*cos(w*t)*cos(alpha)
y'' = r*(beta-w*w)*sin(w*t)*cos(alpha)
z'' = r*beta*sin(alpha)
Assuming you have a fixed altitude in mind, then r would be fixed, so the acceleration "north", parallel to the earth's axis, is fixed. However, the acceleration which is perpendicular to the earth's axis can be controlled by adjusting your speed (which is related to w). The total acceleration needed is the smallest in magnitude if you choose w to be the square root of beta, and x'' and y'' are zero then.
So my initial intuition was wrong - the minimum acceleration needed, when the speed is just right, is parallel to the earth's axis, not parallel to the surface just beneath you.
-
One more thought - the acceleration needed to hover straight above the north pole would be r*beta. To keep travelling in a circle just above 28 N, you're going to need at least 46.9% of that amount of acceleration, if you get the speed just right (and more if you don't).
So maintaining this type of orbit is going to be pretty tough. If you get far away from earth, then beta will get a lot smaller, and it will become easier, although we have to think about what "above 28 N" means in this case - in the same plane the circle of latitude lies in, or "above" from the perspective of a person standing on the surface of the earth. The latter case is the one that would require more fuel.
-
So my initial intuition was wrong - the minimum acceleration needed, when the speed is just right, is parallel to the earth's axis, not parallel to the surface just beneath you.
This makes sense, as you're forcing the orbital plane to continually precess around the earth's axis, i.e., to constantly change the RAAN. To make a gyroscope precess around a given axis, you apply a force parallel to that axis. Think of a toy gyroscope spinning on a stand in gravity.
I seem to recall some serious theoretical proposals to do just this, to make it possible to have geostationary satellites over some latitude other than the equator. Obviously this can't be done with conventional reaction engines, but it might be possible with a solar sail. Probably a really big one.
-
I am thinking of it this way. Is this more or less right.
A hypothetical launches due east from a point 5 degrees south of the north pole. It is relatively easy to visualize that the track that stays on a line east from the launch site is not going to stay on the rather tight curve of the 85th parallel, which will be be moving away to the north with the curve of the earth as the rocket climbs. As rises along the same line it will ultimately end up in a orbit with an 85 degree inclination.
-
I used Google Earth to illustrate: The line starts at Pad 39A and goes due east on heading 090.
(http://i46.tinypic.com/qq7ar8.png)
Looking straight down on the line, we can see that it is straight; yet on the globe we can see that it follows the great circle route and goes south of the equator.
Hope this helps.
-
I get the impression the OP is OK with the idea of a great circle, and is aware that the proposed trajectory isn't one. I interpreted it to mean, what kind of thrust would you have to apply to maintain this circular but non-great-circle trajectory.
-
I seem to recall some serious theoretical proposals to do just this, to make it possible to have geostationary satellites over some latitude other than the equator. Obviously this can't be done with conventional reaction engines, but it might be possible with a solar sail. Probably a really big one.
Yes, it was a bit of an eye-opener for me to realise that it is not some small course correction which is needed, but something quite powerful. Unless you deviate from the equator only slightly.
Do we have satellites which stay over a fixed line of longitude, but which oscillate back and forth between north and south? A few of those at almost the same longitude would have the effect of keeping a satellite somewhat close to overhead (from a fixed point on the surface) all of the time. Just not the same satellite at all times.
-
Do we have satellites which stay over a fixed line of longitude, but which oscillate back and forth between north and south?
Some orbits can hover over an area but they make figure 8s; they can't stay over a longitude. See Tundra orbit (http://en.wikipedia.org/wiki/Tundra_orbit)
-
Do we have satellites which stay over a fixed line of longitude, but which oscillate back and forth between north and south?
Yes, but as Chew points out they actually follow a figure-8 pattern around the longitude line. This is usually close enough.
This happens automatically when geostationary satellites run out of stationkeeping fuel. Perturbations from the sun and moon cause the inclination to slowly increase to a maximum and then decrease again. They also tend to migrate east or west to one of several "gravity wells" at specific longitudes due to the earth's lumpy gravity field.
These old satellites are often available cheap to those who can use them because they're pretty much useless for direct broadcasting or other applications with large numbers of mechanically fixed antennas. Broadcasters doing point-to-point feeds usually have antennas that can track, so they can use them. I believe Qualcomm's Omnitracs system makes use of such satellites because their truck antenna patterns are broad enough in elevation to cover the entire orbital path.
Another use of old satellites in inclined orbits is to provide polar coverage. The geostationary arc can't be seen at all from the poles, but a satellite in an inclined orbit may rise above the horizon for a few hours every day. This is how the South Pole Station has gotten its Internet connection for quite a few years now; for a long time they used TDRSS-1, the original one launched on STS-6 I think, plus a couple of old Air Force experimental satellites. They didn't have 24 hour coverage, nor was it terribly fast, but it was better than nothing. When the Internet was young, before it was walled off by firewalls, I often demonstrated pinging spole.gov to visitors, most of whom had never seen the Internet before.
-
See Tundra orbit (http://en.wikipedia.org/wiki/Tundra_orbit)
I actually chose Sirius because of this; I like to patronize companies with clever new ideas.
Sirius chose the tundra orbit so that its active satellites could be seen at much higher elevation angles over its service area, the continental United States, than conventional communications satellites. Their thinking was that this would better illuminate urban canyons without an expensive terrestrial repeater network filling in lots of holes. It didn't quite work out this way, but it does help.
-
For information, if you path has constant track, it's called a rhumb line.
-
Some orbits can hover over an area but they make figure 8s; they can't stay over a longitude. See Tundra orbit (http://en.wikipedia.org/wiki/Tundra_orbit)
Yes, I guess they couldn't stay over the same longitude. The beginning of the idea, but I failed to think it all the way through :-[
This happens automatically when geostationary satellites run out of stationkeeping fuel. Perturbations from the sun and moon cause the inclination to slowly increase to a maximum and then decrease again. They also tend to migrate east or west to one of several "gravity wells" at specific longitudes due to the earth's lumpy gravity field.
These old satellites are often available cheap to those who can use them because they're pretty much useless for direct broadcasting or other applications with large numbers of mechanically fixed antennas. Broadcasters doing point-to-point feeds usually have antennas that can track, so they can use them. I believe Qualcomm's Omnitracs system makes use of such satellites because their truck antenna patterns are broad enough in elevation to cover the entire orbital path.
Would these be omnidirectional? Or is the system for keeping them oriented separate from the system for keeping them in a particular orbit?
Another use of old satellites in inclined orbits is to provide polar coverage. The geostationary arc can't be seen at all from the poles, but a satellite in an inclined orbit may rise above the horizon for a few hours every day. This is how the South Pole Station has gotten its Internet connection for quite a few years now; for a long time they used TDRSS-1, the original one launched on STS-6 I think, plus a couple of old Air Force experimental satellites. They didn't have 24 hour coverage, nor was it terribly fast, but it was better than nothing. When the Internet was young, before it was walled off by firewalls, I often demonstrated pinging spole.gov to visitors, most of whom had never seen the Internet before.
So you used their limited bandwidth on a ping :) Pretty cool though. But maybe not quite as cool as the other end of the ping.
-
I actually chose Sirius because of this; I like to patronize companies with clever new ideas.
Bugger, I can't remember what satellite radio service I had in my car when I lived in North America (and when I had a car). I seem to recall that there were two main services - was this one of them? (Maybe there are more than two now?)
-
I used Google Earth to illustrate: The line starts at Pad 39A and goes due east on heading 090.
(http://i46.tinypic.com/qq7ar8.png)
Looking straight down on the line, we can see that it is straight; yet on the globe we can see that it follows the great circle route and goes south of the equator.
Hope this helps.
From what I have read.....from the moment powered flight stops, the craft will start falling around the great circle. It is a very hard subject for a complete layman to understand. The hardest part to grasp I suppose, is that even though it sets off East....that tendency to fall around the centre of mass is what swings it south(even during powered flight)...away from 5 degrees above the Tropic of Cancer. So even if a bizarre trajectory was chosen to force it to hold East(with thrusters or whatever), it would still curve around into a SE trajectory once it started to orbit.
Thanks for the replies :)
-
So let me try to think this figure-8 orbit thing through here . . .
A circular orbit in the z=0 plane with earth's centre at the origin (axis orientation left deliberately vague at this point) follows
x = r*cos(w*t)
y = r*sin(w*t)
z = 0
Rotate the y and z axes to give it some inclination. (Unlike my earlier prime symbols, these primes just indicate alternate coordinates.)
x' = x = r*cos(w*t)
y' = y*cos(theta)-z*sin(theta)=r*cos(theta)*sin(w*t)
z' = y*sin(theta)+z*cos(theta)=r*sin(theta)*sin(w*t)
If this was all done so that z'=0 includes the equator, then
lon = atan(y'/x') = atan[tan(w*t)/cos(theta)]
lat = atan(z'/sqrt(x'^2+y'^2))=atan[sin(theta)*sin(w*t)/sqrt(cos^2(w*t)+cos^2(theta)*sin^2(w*t))]
But this is coordinate system of a non-rotating planet. So we need
lon = atan[tan(w*t)/cos(theta)]-k*t
lat = atan[sin(theta)*sin(w*t)/sqrt(cos^2(w*t)+cos^2(theta)*sin^2(w*t))]
and it will be periodic if k=w. Looks like some simplification is possible, but I need to go do something else right now.
-
It doesn't maintain this due east orientation, however, any more than a ship or aircraft on a long voyage maintains a constant compass heading all the way to the destination even if it does follow a single great circle route.
...unless that great circle happens to be the equator or a meridian.
Very funny but don't give up your day job just yet. Orbital mechanics humor doesn't have a very large audience.
That's not even orbital mechanics humor, it's "big honkin' planet in your way" humor.
-
I guess "lithobraking" is orbital mechanics humour.
-
"It didn't crash. It impacted with the ground prematurely."
"Oh, meltdown. It's one of those annoying buzzwords. We prefer to call it an unrequested fission surplus."
-
I used Google Earth to illustrate: The line starts at Pad 39A and goes due east on heading 090.
(http://i46.tinypic.com/qq7ar8.png)
Looking straight down on the line, we can see that it is straight; yet on the globe we can see that it follows the great circle route and goes south of the equator.
Hope this helps.
From what I have read.....from the moment powered flight stops, the craft will start falling around the great circle. It is a very hard subject for a complete layman to understand. The hardest part to grasp I suppose, is that even though it sets off East....that tendency to fall around the centre of mass is what swings it south(even during powered flight)...away from 5 degrees above the Tropic of Cancer. So even if a bizarre trajectory was chosen to force it to hold East(with thrusters or whatever), it would still curve around into a SE trajectory once it started to orbit.
Well, on a mercator-progection map, it may look like its curving to the SE, but as you can see in the above image, it actually goes straight (or rather, the orbit is a circle/ellipse on a flat plane, and (like you said) the plane bisects the Earth right through its center-of-mass).
-
I used Google Earth to illustrate: The line starts at Pad 39A and goes due east on heading 090.
(http://i46.tinypic.com/qq7ar8.png)
Looking straight down on the line, we can see that it is straight; yet on the globe we can see that it follows the great circle route and goes south of the equator.
Hope this helps.
From what I have read.....from the moment powered flight stops, the craft will start falling around the great circle. It is a very hard subject for a complete layman to understand. The hardest part to grasp I suppose, is that even though it sets off East....that tendency to fall around the centre of mass is what swings it south(even during powered flight)...away from 5 degrees above the Tropic of Cancer. So even if a bizarre trajectory was chosen to force it to hold East(with thrusters or whatever), it would still curve around into a SE trajectory once it started to orbit.
Thanks for the replies :)
One layman to another, here's a point that may make it easier to picture:
There's a thought experiment called Newton's Cannonball. Imagine a very large cannon on top of a very tall mountain, aimed in a direction parallel with Earth's surface. If you fire a cannonball at, say, a velocity of 2000 m/s it will travel a certain distance in a path that curves down to strike the ground (assume no air resistance). If you fire another one at 4000 m/s it will follow a similar path, striking ground further away.
Now. If you fire one with enough velocity - about 7300 m/s - the downward curve of its trajectory is equal to or less than the curvature of the Earth and although the cannonball continues to fall it will never strike the ground; it continues to fall around the Earth.
And this is the key to basic orbital mechanics for the layman. The plane of any free orbit by necessity passes through the center of the planet because the satellite is always falling toward the planet with only its tangential velocity keeping it from ever striking the ground. Hence the term "free-fall".
If that was confusing, just ignore it. We now return you to the Astrodynamics Channel.
;)
-
Would these be omnidirectional? Or is the system for keeping them oriented separate from the system for keeping them in a particular orbit?
The satellite antennas or Omnitracs?
The satellite antennas are always directional. Usually it's a highly complex array with a custom-designed pattern shaped to cover the service area from the assigned longitude. One pattern is used with the continental USA, another for Europe, another for Japan, etc. The perspective of earth that the satellite sees from an inclined orbit usually doesn't change so much that the service area changes significantly, but east-west drift might be a problem depending on the assigned longitude.
Omnitracs uses an asymmetric "taco-shell" Ku-band horn with azimuth tracking only, necessary on a moving truck. The antenna pattern is narrow in azimuth but wide in elevation. This renders elevation tracking unnecessary and makes an inclined satellite orbit almost irrelevant. The only requirement is that the user links (both up and down) be vertically polarized, so only half the transponders on any one satellite can be used.
So you used their limited bandwidth on a ping :) Pretty cool though. But maybe not quite as cool as the other end of the ping.
Nobody seemed to mind...
-
Bugger, I can't remember what satellite radio service I had in my car when I lived in North America (and when I had a car). I seem to recall that there were two main services - was this one of them? (Maybe there are more than two now?)
Sirius and XM. Sirius uses three satellites in tundra orbits, with two usually in service at any given time. There's a 4-second delay between the two, giving receivers a better chance of filling in gaps when driving under overpasses (yet it often didn't work with my receiver, for some reason.)
XM uses several conventional geostationary satellites named "Rock", "Roll", "Rhythm" and "Blues" or something like that. They may have more now.
Both services operate in a large chunk stolen from the 2300-2450 MHz (13 cm) amateur radio band (grrr...) Not much is left of it now since WiFi has taken over 2400-2450.
When the spectrum was first assigned to direct satellite radio broadcasting, the FCC insisted on at least two competing services. Sirius and XM accepted this condition. Just a few years later they were back, begging permission to merge and claiming they would both go bankrupt soon if they weren't allowed to do so.
So now we have "Sirius XM". The infrastructure of the two services remains much the same, with two independent constellations of satellites operating on different portions of the band with incompatible modulation methods. They now duplicate the same set of program channels, wasting half the spectrum and doubling the cost of their infrastructure without any compensating redundancy advantages since each receiver can only receive one system.
Grrr.
-
"It didn't crash. It impacted with the ground prematurely."
I've always liked "spontaneous disassembly".
"Oh, meltdown. It's one of those annoying buzzwords. We prefer to call it an unrequested fission surplus."
Which is technically inaccurate, at least in western reactors like TMI and Fukushima. A so-called meltdown is caused by the residual decay heat of the fission products after shutdown, not by a "fission surplus".
Chernobyl, on the other hand, was a true unrequested fission surplus. The power spiked to hundreds of gigawatts due to criminally incompetent mishandling by the operators.
-
And I suppose a fire could be called an 'exothermic oxidization event'. ;D
I am rather partial to 'lithobreaking' myself. It has a nice ring to it.
-
From what I have read.....from the moment powered flight stops, the craft will start falling around the great circle.
Not from the moment powered flight stops, but all during flight unless the rocket deliberately changes course by yawing (turning) left or right. That's sometimes necessary to avoid flying over land or dropping spent stages on peoples' heads, but it's always inefficient.
Ideally a rocket flies on a perfectly straight course from the moment it begins its roll and pitch maneuver after leaving the launch pad. Once on that course it may roll to point antennas at various ground stations, and it will gradually pitch down to the horizontal (or even below) as it climbs above the atmosphere, but yaw (left-right) changes are avoided whenever possible.
-
I am rather partial to 'lithobreaking' myself. It has a nice ring to it.
Agreed. Though the canonical spelling should probably be lithobraking, I suppose lithobreaking is an acceptable variation.
But this word is suitable only for terrestrial moons and planets, i.e., those with rocky surfaces. Can we come up with a variant applicable to gas giants? How about surfaces made of ice rather than silicate rock?
And space launchers never actually fail, they simply achieve geostationary orbits with subterranean perigees. After the second Ariane launch dropped our satellite into the Atlantic, I suggested that the next launch should carry a communications satellite in its payload fairing and have an undersea fiber optic cable tied to its tail. That way, one of the two communications systems will work.
-
lithobraking
lithobreaking
subterranean perigees
Orbital mechanics humor is richer than I imagined.
-
Orbital mechanics humor is richer than I imagined.
Yes. Don't forget the "trench" in the Apollo Mission Control Center and all the colorful characters who worked there. Their mascot was Captain REFSMMAT, the ideal flight controller, and according to Gene Kranz (who admitted he knew much more about spacecraft systems than orbital mechanics) everybody who worked in it had a characteristic, uh, "attitude".
My favorite story from him concerns the controller who hurriedly parked his car on the sidewalk when late for work, resulting in the suspension of his parking privileges. Until he got them restored, he parked across from the entrance to MSFC, opened up a trailer, and rode his horse up to the building, tying it off while he worked. Apparently nobody in NASA security thought to require permits for horses.
-
Agreed. Though the canonical spelling should probably be lithobraking, I suppose lithobreaking is an acceptable variation.
They both actually seem fairly accurate, they just describe different aspects of the process :)
-
And space launchers never actually fail, they simply achieve geostationary orbits with subterranean perigees. After the second Ariane launch dropped our satellite into the Atlantic, I suggested that the next launch should carry a communications satellite in its payload fairing and have an undersea fiber optic cable tied to its tail. That way, one of the two communications systems will work.
A hedged postion :)
-
My favorite story from him concerns the controller who hurriedly parked his car on the sidewalk when late for work, resulting in the suspension of his parking privileges. Until he got them restored, he parked across from the entrance to MSFC, opened up a trailer, and rode his horse up to the building, tying it off while he worked. Apparently nobody in NASA security thought to require permits for horses.
Well if NASA had been anything like the US Army, not only would they have been required to give him a permit for his horse, but the quartermaster would have been compelled to provide his horse with feed and bedding!!!
-
Agreed. Though the canonical spelling should probably be lithobraking, I suppose lithobreaking is an acceptable variation.
They both actually seem fairly accurate, they just describe different aspects of the process :)
Ok, I'll bite. lithobreaking was a mistake, as I intended to write lithobraking. Euphemisms aside though, the latter could be said to be a valid manoeuvre for such space probes as Luna 9, Opportunity and Spirit.
-
Agreed. Though the canonical spelling should probably be lithobraking, I suppose lithobreaking is an acceptable variation.
They both actually seem fairly accurate, they just describe different aspects of the process :)
Ok, I'll bite. lithobreaking was a mistake, as I intended to write lithobraking. Euphemisms aside though, the latter could be said to be a valid manoeuvre for such space probes as Luna 9, Opportunity and Spirit.
Ah yes, in those cases, lithobreaking would be the result of unsuccessful lithobraking.
As the craft descended towards the planetary surface, the tension mounted and pulses raced. Nobody spoke, yet each knew the thoughts of the others - lithobraking, or lithobreaking?
-
Euphemisms aside though, the latter could be said to be a valid manoeuvre for such space probes as Luna 9, Opportunity and Spirit.
Wikipedia agrees (http://en.wikipedia.org/wiki/Lithobraking).
-
Euphemisms aside though, the latter could be said to be a valid manoeuvre for such space probes as Luna 9, Opportunity and Spirit.
Likewise for some of the Rangers, though in a different sense.
-
As the craft descended towards the planetary surface, the tension mounted and pulses raced. Nobody spoke, yet each knew the thoughts of the others - lithobraking, or lithobreaking?
Now we have a first line of a orbital mechanics romance novel? Or perhaps an entry in the Bulwer-Lytton Fiction Contest?
-
Euphemisms aside though, the latter could be said to be a valid manoeuvre for such space probes as Luna 9, Opportunity and Spirit.
Likewise for some of the Rangers, though in a different sense.
Slamming a spacecraft into the moon at around 10,000 km/h is a somewhat severe form of lithobraking!
In fact, it could be better described by raven's earlier term; "Lithobreaking"
-
Well, they decelerated when they encountered the lithosphere. That counts as braking in my book. :)
-
Luna 2 also preformed this manoeuvre. In fact, it was the first to do so, though Luna 1 was intended to but missed the moon and instead entered solar orbit.
I guess flying really is the art of throwing yourself at the ground and missing! ;D
-
Luna 2 also preformed this manoeuvre. In fact, it was the first to do so, though Luna 1 was intended to but missed the moon and instead entered solar orbit.
I guess flying really is the art of throwing yourself at the ground and missing! ;D
"Falling with style."
-
My favorite story from him concerns the controller who hurriedly parked his car on the sidewalk when late for work, resulting in the suspension of his parking privileges. Until he got them restored, he parked across from the entrance to MSFC, opened up a trailer, and rode his horse up to the building, tying it off while he worked. Apparently nobody in NASA security thought to require permits for horses.
Well if NASA had been anything like the US Army, not only would they have been required to give him a permit for his horse, but the quartermaster would have been compelled to provide his horse with feed and bedding!!!
That's correct. Until the early 1980s, the Manual of Air Force Law (Australia) said that Officers were required to be provided with Batmen to tender their needs and look after their horse!
Even today, our law actually says that no ADF aircraft, vessel, vehicle, whatever, can be charged a toll for passage through or use of Australian soil. Of course, our wimpy politicians give in and pay airport charges, etc, as well as ADF vehicles being charged tolls on motorways, etc.
-
That's correct. Until the early 1980s, the Manual of Air Force Law (Australia) said that Officers were required to be provided with Batmen to tender their needs and look after their horse!
Even today, our law actually says that no ADF aircraft, vessel, vehicle, whatever, can be charged a toll for passage through or use of Australian soil. Of course, our wimpy politicians give in and pay airport charges, etc, as well as ADF vehicles being charged tolls on motorways, etc.
"Somebody's gotta go back and get a whole shitloada rooboys!"