Starship Asterisk*

gingerd wrote:
Is it a smoke plume or a steam plume (or a mixture of both)?

http://www.airspacemag.com/flight-today/Plume-Power.html wrote:

Discovery on STS-131. Credit: James Vernacotola

---

<<Photographer James Vernacotola had stood on the Palm Valley Bridge, which crosses the Intracoastal Waterway near Jacksonville, Florida, to capture night, dawn, and dusk launches from NASA’s Kennedy Space Center, more than a hundred miles to the south. Most recently, he had come in the middle of the night on February 8, 2010, where he nailed an awe-inspiring time exposure of the space shuttle Endeavour rising from the launch pad 115 miles away (see “Sightings” Jun./Jul. 2010). That 4:14 a.m. launch was the last scheduled night launch of the shuttle program. Vernacotola went back a couple months later for the 6:21 a.m. launch of Discovery on STS-131. With the sky brightening in the east, and no moon or stars in the frame, it wouldn’t quite rival the STS-130 shot.

Think again. Six and a half minutes into the ascent, with the solid rocket boosters having long since fallen away but with its three main engines still cooking, the orbiter was suddenly high enough in the northeastern sky to be in sunlight. This revealed a gossamer plume of water vapor expelled by the burning of the liquid hydrogen and liquid oxygen propellants. The exhaust instantly condensed to ice crystals in the frigid vacuum of near-space almost a hundred miles high. Vernacotola swiveled his camera on its tripod and made this 15-second exposure (see a larger version here). “That’s the first time I’d ever seen anything like it,” he says. “When we first saw it, we were wondering if something was wrong. Now I suppose the vapor trail is always there, but maybe I’ve never seen it because it was never backlit by the sun like that.”

Four-time shuttle flier Tom Jones confirms these suspicions. He says that the [water vapor] plume gets lost in the fiery booster exhaust during the first two minutes, and would be too diffuse to be seen in daylight or darkness anyway. But the main engines continue to produce it until they shut down about eight and a half minutes after liftoff. Jones has seen the plume from inside the shuttle during ascent. “The steam from the nozzles, at high vacuum [occurring at high altitude] begins to creep up the side of the stack,” he says. “With no ambient pressure, the plume expands to engulf the [external fuel] tank and orbiter sides, so much so that the crew can see the flickering of the steam plume reflecting the luminosity at the engine nozzle through the top windows in the flight deck. The pulsing plume gets your attention—is it a fire?!!! Is everything OK back there? But it’s normal. Just unexpected to see your exhaust racing along with you.”>>

hpfeil wrote:Solid booster engines: smoke.
Fuel: Aluminum powder.
Oxidizer: Ammonium perchlorate.
Binding: Elastomer.

http://science.ksc.nasa.gov/shuttle/tec ... f/srb.html
http://en.wikipedia.org/wiki/Space_Shut ... et_Booster

The shuttle engines burn hydrogen from the main fuel tank (liquid oxygen + liquid hydrogen).

What is the chemical composition of the aluminum smoke?

http://www.aero.org/publications/crosslink/summer2000/01.html wrote:
Rockets and the Ozone Layer
Martin N. Ross and Paul F. Zittel

[img3="Most chlorine emerges from solid-propellant rocket motors as hydrogen chloride (HCl). Some of the HCl is converted into reactive chlorine atom (Cl) and molecule (Cl2) by downstream chemical processes called "afterburning." Computer models are used to predict how much of the chlorine is in the reactive form as a function of distance away from the motor nozzle. Here, a model predicts that about one-third of the HCl leaving the nozzle is converted into Cl and Cl2 in the plume of an Athena II rocket as it flies through the ozone layer."]http://www.aero.org/publications/crossl ... /01_04.gif[/img3]

Rocket engine exhaust contains chemical compounds that react with ozone in the stratosphere. A new measurement program suggests that current space transportation activities only minimally affect Earth's protective ozone layer.

Ozone concentration measured across the plume wakes of four different launch vehicles, all obtained about one hour after the different launches. Red represents data obtained while the WB-57F aircraft was inside the exhaust plume. The total amounts of chlorine emitted by the Titan IVA, Atlas IIAS, space shuttle, and Delta II SRMs at the altitude of these measurements are about 2, 0.2, 4, and 0.3 tons per kilometer of altitude. Despite such large differences in chlorine emission rates among the four rocket types, the ozone losses in the plumes are comparable. The data were obtained by J. Benbrook and W. Sheldon of the University of Houston.

---

<<Both solid and liquid rocket-propulsion systems emit a variety of gases and particles directly into the stratosphere. A large percentage of these emissions are inert chemicals such as carbon dioxide that do not directly affect ozone levels. Emissions of other gases, such as hydrogen chloride and water vapor, though not highly reactive, indirectly affect ozone levels by participating in chemical reactions that determine the concentrations of the ozone-destroying radicals in the global stratosphere. A small percentage of rocket- engine emissions, however, are highly reactive radical compounds that immediately attack and deplete ozone in the plume wake following launch. Aerosol emissions, such as alumina particles, carbon (soot) particles, and water droplets, can also act as reactive compounds when heterogeneous chemical reactions take place on the surface of these particles.

Rocket emissions have two distinct effects on ozone: short-term and long-term. Following launch, rapid chemical reactions between plume gases and particles and ambient air that has been drawn into the plume wake cause immediate changes in the composition of the local atmosphere. During this phase, which lasts for several hours, the concentrations of radicals in the plume can be thousands of times greater than the concentrations found in the undisturbed stratosphere, and the ozone loss is dramatic.

Long-term effects occur as gas and particulate emissions from individual launches become dispersed throughout the global stratosphere and accumulate over time. The concentrations of emitted compounds reach an approximate global steady state as exhaust from recent launches replaces exhaust removed from the stratosphere by natural atmospheric circulation.

The theory of reactive chlorine production in SRM plumes was proved during a WB-57F mission through the plume wake of a Titan IVA. The concentration of chlorine molecule (Cl2) was measured as the aircraft flew through the eight-kilometer-wide plume 40 minutes after launch. Because Cl2 is not present in the undisturbed stratosphere, all of the measured Cl2 could be attributed to the Titan IVA SRMs.>>