I was impressed by the fireball at ignition. Seems like a lot of transient hydrogen around the base. Also, it appeared there was some flame around the edges of the base as it initially climbed out. Seemed strange.
14 seconds before T-0, the Radially Outward Firing Initiators (ROFIs) ignited beneath the three Main Engines to burn residual Hydrogen that was released during the fuel-rich start-up of the RS-68.
Employing a slightly modified ignition sequence, the Terminal Countdown Sequencer of the Delta IV assumed control of the countdown at T-10 seconds. At T-7 seconds, the Main Fuel Valve of the starboard RS-68 Engine was opened as the engine started its ignition sequence. This single engine was started earlier in order to reduce of the Hydrogen flame that is known to erupt from the launch table during engine start. At T-5 seconds, the Main Oxidizer Valve on the starboard engine opened and the RS-68 soared to life. At the same time, the remaining two engines started their ignition sequence by opening their Main Fuel Valves. Visually, the hydrogen flame engulfing the Delta IV appeared smaller than during previous launches, indicating that the staggered ignition sequence achieved its goal.
Something I always wondered, do you ever have to adjust trim because lots of passengers are moving to one side if the plane? I've wondered if they simulate an event like that with ballast barrels.
No, even if every passenger moved to one side, they are only moving a little ways in relation to the center line so their collective arm wouldn't be very long. Fuel, on the other hand weighs a lot and could potentially have a long arm depending on fuel level in the wings. But only under rare circumstances (think engine failure) would there be an opportunity for a fuel imbalance. Fortunately the ailerons are way out there and have a very long arm so it takes a relatively small aileron trim change to keep the plane from turning under that condition. On my aircraft the limitation for fuel imbalance in flight is 1100 pounds. So left side could weigh 7000 pounds and right side could weigh as much as 8100 pounds. Seems like a lot but the plane weighs over 50000 pounds. Interestingly the for/aft balance limitations are always measured in inches and my aircraft has to maintain a balance within 31 inches at all times even though the whole plane is nearly 100 feet long.
No, even if every passenger moved to one side, they are only moving a little ways in relation to the center line so their collective arm wouldn't be very long. Fuel, on the other hand weighs a lot and could potentially have a long arm depending on fuel level in the wings. But only under rare circumstances (think engine failure) would there be an opportunity for a fuel imbalance. Fortunately the ailerons are way out there and have a very long arm so it takes a relatively small aileron trim change to keep the plane from turning under that condition. On my aircraft the limitation for fuel imbalance in flight is 1100 pounds. So left side could weigh 7000 pounds and right side could weigh as much as 8100 pounds. Seems like a lot but the plane weighs over 50000 pounds. Interestingly the for/aft balance limitations are always measured in inches and my aircraft has to maintain a balance within 31 inches at all times even though the whole plane is nearly 100 feet long.
I find it interesting about your specs. My aircraft weighs up to 85,000 lbs yet can only have a max fuel imbalance of 800 lbs. maybe it has to do with the spoilerons and aleron systems. Different wing designs?
To get contrails, you must achieve water saturation at some point. At water saturation (RHw=100%) in our current atmosphere there are cloud condensation nuclii present, so condensation ensues. In the proposed perfectly clean atmosphere with no aerosols what so ever you need to get to quite high super saturation before it will occur spontaneously... 120% 130% 140%. You would still get them but that mixing line has to be deep into the saturated )cloud) zone. https://www.metabunk.org/threads/us...mages-and-infographics.1007/page-2#post-59756
Other stuff (not water) in the jet exhaust does help the freezing and condensing processes to an extent, but these are not essential. Those will occur anyway.
The main problem would be to achieve high enough super saturation with respect to water during mixing of exhaust with environment to get condensation to occur in the absence of CCN (in the proposed perfectly clean atmosphere).
I'm a little confused Ross because it's ice nuclei that are required and I've seen you state that the air is essentially clean of these which is how ISSRs can exist. Can you clarify please?
I was impressed by the fireball at ignition. Seems like a lot of transient hydrogen around the base. Also, it appeared there was some flame around the edges of the base as it initially climbed out. Seemed strange.
There would be all of those strange manifestations you so closely observed.
The fuel is passed through the rocket housing and enters the chamber through perforations so that a liquid film travels down the inside surface of the motor in an unburnt state. If the actual flame contacted the inside surface of the chamber it would be game over.
I'm a little confused Ross because it's ice nuclei that are required and I've seen you state that the air is essentially clean of these which is how ISSRs can exist. Can you clarify please?
Homogeneous vs. Heterogeneous nucleation (for both condensation and deposition)
Ice supersaturation vs. Water supersaturation.
Ice nuclei vs. Water nuclei (cloud condensation nuclei).
Ice nuclei and water nuclei (CCN) have different physical properties. Ice will deposit on ice nuclei, but not on water nuclei
Ice nuclei are are not required at -40C, as water freezes without them (homogenous nucleation of ice within liquid water). However you need some liquid water to start off with.
For a normal contrail, you'd need RHw > 100 % (temporarily), and the water condenses on the CNN, this then freezes as it's -40C, which then gives you ice, which is an ice deposition nuclei.
If there are no CCN, then the water will still condense out homogeneously at very high supersaturations.
ISSR can exist with lots of CCN but no ice deposition nuclei.
Then I think there's also a distinction between an ice deposition nuclei and a ice freezing nuclei?
This is why it's hard to explain contrails in depth to the chemtrail folk. These distinctions are inaccessible to their understanding.
The partially-burnt fuel molecules and soot particles in fanjet exhausts contribute countless billions of seeding instances per meter of forward flight. There's no need to get very worked-up about whether it's ice or water in any particular circumstance. There will always be an excess of "seeds".
You can bet your boots that a formed trail is falling through air that is busily reducing its saturation to below 100%.
I find it interesting about your specs. My aircraft weighs up to 85,000 lbs yet can only have a max fuel imbalance of 800 lbs. maybe it has to do with the spoilerons and aleron systems. Different wing designs?
Sorry, 50000 is a general OWE (what we used to call BOW). MTOW is actually 99500. As the total fuel on board drops below 21000#s the max imbalance drops to 600 in flight. And the whole wing is different than any RJ, much larger and more spoilerons.
Homogeneous vs. Heterogeneous nucleation (for both condensation and deposition)
Ice supersaturation vs. Water supersaturation.
Ice nuclei vs. Water nuclei (cloud condensation nuclei).
Ice nuclei and water nuclei (CCN) have different physical properties. Ice will deposit on ice nuclei, but not on water nuclei
Ice nuclei are are not required at -40C, as water freezes without them (homogenous nucleation of ice within liquid water). However you need some liquid water to start off with.
For a normal contrail, you'd need RHw > 100 % (temporarily), and the water condenses on the CNN, this then freezes as it's -40C, which then gives you ice, which is an ice deposition nuclei.
If there are no CCN, then the water will still condense out homogeneously at very high supersaturations.
ISSR can exist with lots of CCN but no ice deposition nuclei.
Then I think there's also a distinction between an ice deposition nuclei and a ice freezing nuclei?
This is why it's hard to explain contrails in depth to the chemtrail folk. These distinctions are inaccessible to their understanding.
The formation of cloud droplets and cloud ice crystals is associated with suspended aerosols, which are produced by natural processes as well as human activities and are ubiquitous in Earth’s atmosphere. In the absence of such aerosols, the spontaneous conversion of water vapour into liquid water or ice crystals requires conditions with relative humidities much greater than 100 percent, with respect to a flat surface of H2O. The development of clouds in such a fashion, which occurs only in a controlled laboratory environment, is referred to as homogeneous nucleation. Air containing water vapour with a relative humidity greater than 100 percent, with respect to a flat surface, is referred to as being supersaturated. In the atmosphere, aerosols serve as initiation sites for the condensation or deposition of water vapour. Since their surfaces are of discrete sizes, aerosols reduce the amount of supersaturation required for water vapour to change its phase and are referred to as cloud condensation nuclei.
The larger the aerosol and the greater its solubility, the lower the supersaturation percentage required for the aerosol to serve as a condensation surface. Condensation nuclei in the atmosphere become effective at supersaturations of around 0.1 to 1 percent (that is, levels of water vapour around 0.1 to 1 percent above the point of saturation). The concentration of cloud condensation nuclei in the lower troposphere at a supersaturation of 1 percent ranges from around 100 per cubic centimetre (approximately 1,600 per cubic inch) in size in oceanic air to 500 per cubic centimetre (8,000 per cubic inch) in the atmosphere over a continent. Higher concentrations occur in polluted air.
Aerosols that are effective for the conversion of water vapour to ice crystals are referred to as ice nuclei. In contrast to cloud condensation nuclei, the most effective ice nuclei are hydrophobic (having a low affinity for water) with molecular spacings and a crystallographic structure close to that of ice.
While cloud condensation nuclei are always readily available in the atmosphere, ice nuclei are often scarce. As a result, liquid water cooled below 0 °C (32 °F) can often remain liquid at subfreezing temperatures because of the absence of effective ice nuclei. Liquid water at temperatures less than 0 °C is referred to as supercooled water. Except for true ice crystals, which are effective at 0 °C, all other ice nuclei become effective at temperatures below freezing. In the absence of any ice nuclei, the freezing of supercooled water droplets of a few micrometres in radius, in a process called homogeneous ice nucleation, requires temperatures at or lower than −39 °C (−38 °F). While a raindrop will freeze near 0 °C, small cloud droplets have too few molecules to create an ice crystal by random chance until the molecular motion is slowed as the temperature approaches −39 °C. When ice nuclei are present, heterogeneous ice nucleation can occur at warmer temperatures.
Ice nuclei are of three types: deposition nuclei, contact nuclei, and freezing nuclei. Deposition nuclei are analogous to condensation nuclei in that water vapour directly deposits as ice crystals on the aerosol. Contact and freezing nuclei, in contrast, are associated with the conversion of supercooled water to ice. A contact nucleus converts liquid water to ice by touching a supercooled water droplet. Freezing nuclei are absorbed into the liquid water and convert the supercooled water to ice from the inside out.
Examples of cloud condensation nuclei include sodium chloride (NaCl) and ammonium sulfate ([NH4]2 SO2), whereas the clay mineral kaolinite is an example of an ice nuclei. In addition, naturally occurring bacteria found in decayed leaf litter can serve as ice nuclei at temperatures of less than about −4 °C (24.8 °F). In a process called cloud seeding, silver iodide, with effective ice-nucleating temperatures of less than −4 °C, has been used for years in attempts to convert supercooled water to ice crystals in regions with a scarcity of natural ice nuclei.
One thing I don't think I've ever quite managed to grasp is the continued growth (not the spread) subsequent to the the formation of the contrail. As I understand it the ice crystals grow and fall and are replaced by new crystals using up the available water vapour, but how are these new crystals forming? Or have I picked that up completely wrong?
One thing I don't think I've ever quite managed to grasp is the continued growth (not the spread) subsequent to the the formation of the contrail. As I understand it the ice crystals grow and fall and are replaced by new crystals using up the available water vapour, but how are these new crystals forming? Or have I picked that up completely wrong?
Yah, it's the same number of particles. There is a stupendous number of them per cu cm. The particles are growing in size with WV depositing on them (while the supersaturation gradually reduces). The optical depth (= visibility) remains more or less the same even though the trail is being stretched in the vertical by precipitation (falling) and in the horizontal by wind shear through the depth (vertical dimension) of the trail.
One thing I don't think I've ever quite managed to grasp is the continued growth (not the spread) subsequent to the the formation of the contrail. As I understand it the ice crystals grow and fall and are replaced by new crystals using up the available water vapour, but how are these new crystals forming? Or have I picked that up completely wrong?
They aren't "replaced". They just grow. Eventually they fall into warmer air where they sublime back to vapor, generally. As Ross says, it's the same number of particles. They begin with a microscopic size - far too small to see. And as Mick says they fall at a rate proportional to their size.
In slightly more detail, the ice crystals are in dynamic disequilibrium when they are growing, in dynamic equilibrium when they stop growing, and in dynamic disequilibrium (the other way!) when they shrink. Water vapor molecules are traveling both ways at all times. (Sticking and unsticking).
In slightly more detail, the ice crystals are in dynamic disequilibrium when they are growing, in dynamic equilibrium when they stop growing, and in dynamic disequilibrium (the other way!) when they shrink. Water vapor molecules are traveling both ways at all times. (Sticking and unsticking).
Yeah, it's like the next level up in understanding, to consider what is actually going on at a molecular level. It's especially important in understanding condensation and evaporation - the dynamic constant exchange of molecules was a bit of an eye opener for me.
Is it the same for deposition and sublimation though? It would seem like you'd get a lot fewer molecules exchanged with ice/air than water/air at equilibrium (saturated vapor pressure)
Is it the same for deposition and sublimation though? It would seem like you'd get a lot fewer molecules exchanged with ice/air than water/air at equilibrium (saturated vapor pressure)
I'm sure you're right about a difference in rates.
Crystals form the way they do because of the electrostatic potential differences (water molecules have an asymmetric potential). I don't know which shape (sphere or crystal) favors deposition or sublimation/evaporation in either case. It's on the limits of my understanding, being a designer, neither a researcher nor a theoretician in this field.
There is a considerable difference between a snowflake and those hexagonal prisms that are formed at high altitudes and low temperatures. But the number six features in both.
I suppose that a part-formed crystal is "stickier" where it is incomplete... ...and that prisms are formed in less chaotically-moving air... ...perhaps...
Distant chink of a penny dropping. I'd been thinking of the ice crystals 'growing' in the wrong way. It's existing ones getting larger rather than new ones forming.
Yeah, it's like the next level up in understanding, to consider what is actually going on at a molecular level. It's especially important in understanding condensation and evaporation - the dynamic constant exchange of molecules was a bit of an eye opener for me.
Is it the same for deposition and sublimation though? It would seem like you'd get a lot fewer molecules exchanged with ice/air than water/air at equilibrium (saturated vapor pressure)
