Ride on a Shooting Star: Space Fuel

After the decimation suffered during World War II, mankind took a look at all the new technologies he had created to fight the war and turned his gaze towards the stars. From the late 1940’s this onward and upward reach has helped to fuel the engines of our ingenuity, but what has fueled those stellar ambassadors that now dot our solar system and beyond.

654 - Galaxies - Seamless Texture
Creative Commons License photo credit: Patrick Hoesly

To move from the surface of the earth to this new ocean a rocket must be moving about 7 miles per second. That takes a lot of energy. Many different propellants have been used. The very first rocket fuels were a mix of kerosene and liquid oxygen. Alcohol, hydrogen peroxide, and liquid hydrogen have also been used, in addition to solid fuels. They can provide thrust without the need for all the refrigeration and containment equipment that some of the liquid fuels, such as liquid hydrogen and oxygen, require.

Once the probe is beyond the reach of the atmosphere there is no way to change what’s on board.

The probe cannot drop by the local Radio Shack and pick up a fresh pair of AA batteries. While the probe is being built on Earth, the engineers must make sure that they provide a source of power that will give the probe the right amount of power.

Too little power and the scientific instrumentation won’t work; too much power could over heat the probe. On board chemical batteries can be used, but they take space that could be used for scientific instruments. Solar panels can be used, but only up to a certain distance from the sun. Beyond the orbit of Jupiter, probes need an internal power supply that will last for years.

They use the heat from radioactive decay of fissionable isotope.

Sputnik 1 in Orbit Sep 10-4-57
Creative Commons License photo credit: FlyingSinger

Early probes like Sputnik and Explorer 1 used chemical batteries to power their systems. In March of 1958 Vanguard 1, the 4th artificial satellite and the 1st powered by solar power, was launched. Probes with solar panels have more space on board for scientific instruments than probes that use only chemical batteries. Probes sent into the inner solar system (sun to Mars) are almost all powered using solar arrays.

Mariner 2, the first USA probe to Venus, suffered the loss of one of its solar arrays, but because it was closer to the sun, it was able to operate using only one solar array. No American manned space craft have made use of solar arrays yet (the new Multi-Purpose Crew Vehicle may), the Russian Soyuz spacecraft have used them since 1967.

The International Space Station (ISS) is the largest man-made structure outside our atmosphere.

Larger than a football field (but smaller than a football pitch), this outpost orbits the earth every hour and a half. It is also powered completely by solar power. Past the atmosphere, solar power becomes more practical and more consistent (there is no night in space). Because of the orbital path of the ISS, it is eclipsed by the earth for 30 minutes out of every hour and a half. The station makes use of rechargeable batteries to make sure it is never without power.

From a Distance
Creative Commons License photo credit: Undertow851

As the probes go farther and farther away from the sun, the light that can reach them is less and less.

Until August of 2011, no probe to Jupiter had ever been powered just by solar panels. Juno, the latest probe to Jupiter, has the largest solar arrays given to a deep space probe and the first probe to Jupiter to use solar arrays.

Jupiter receives only 4% of the sunlight we enjoy on Earth. Advances in solar technology have now made it practical to use solar panels out 5 Astronomical Units (AUs) from the sun. All other deep space probes have used a radioisotope thermoelectric generator (RTG).

A RTG works by converting the heat from the decay of a radioactive fuel into electricity. American probes have been using Plutonium 238 (an isotope of Plutonium) since the late 1960’s. It has a half life of about 88 years. RTGs have powered all our interplanetary probes (the Voyagers and Pioneers and soon to be New Horizons). However, NASA has begun to run out of fuel for the RTGs and the creation of more is full of political and safety considerations.

There he goes, after an all day long work.
Creative Commons License photo credit: giumaiolini

The technology that we’ve made to go out to the ‘verse with will also help us here on the cool, green hills of earth. RGTs have been used, mainly by Russia, to provide power for off the grid light houses. Advances in solar panels for space are used down here on Terre Firma. With the reliably of solar power in space, there are even attempts to construct orbital solar collectors to beam down electricity. There will be from heaven to Earth more than is dreamt of.

Go Stargazing! September Edition

Venus and Mars have left Saturn behind in the night sky (check out my earlier blog on the position of the planets). You can spot the star Spica in between Mars and Venus during this time of year. (Spica is similar to Mars in brightness and closer to Venus than to Mars). 

 Cloud structure in The Venusian atmosphere,
revealed by ultraviolet observations

September is the last full month to observe Venus at dusk. That’s because Venus has by now come around to Earth’s side of the sun on its faster, inner orbit.  Thus, Venus now begins to overtake the Earth, passing between the Earth and sun on October 29.  We’ll therefore see Venus shift farther to the left of Mars and then drop down below it.  In October, Venus exits the evening sky quite quickly as it shifts back towards the sun.  September and October 2010 is an excellent period for observing Venus’ crescent phase in telescopes.  Anytime Venus is on our side of the sun, more of its night side faces us, resulting in a crescent like appearance when magnified.

Saturn is far to the lower right of Venus and Mars as you face west at dusk.  You’ll need a horizon clear of tall buildings and trees to see it before it sets.  You’ll also need to look early in the month, as Saturn is practically behind the sun by month’s end.  

Jupiter dominates this month’s skies.  On Tuesday morning, September 21, Earth aligns with the sun and Jupiter, bringing Jupiter to opposition (because the sun and Jupiter are then on opposite sides of the Earth).  On the night of September 20-21 we see Jupiter rise at sundown and set at sunup—Jupiter is up literally all night long.  During the whole month, though, Jupiter is visible virtually the whole night.  It outshines all stars in the sky, so it’s easy to find.  Face east in late evening or south southwest at dawn to see it.  The planet Uranus is less than one degree above Jupiter this month; the two planets are closest on September 18.

The Big Dipper is setting in the northwest at dusk; you now need a horizon clear of trees and tall buildings to get a good look at it. You can extend the curve of its handle to ‘arc to Arcturus’, which is in the west at dusk tonight.  Arcturus, by the way, is the fourth brightest star we ever see at night, but the brightest one Americans ever see on a September evening.

As the Dipper gets lower, look for five stars in the shape of an ‘M’ directly across the North Star from the Big Dipper’s handle.  This is Cassiopeia, the Queen—the ‘M’ is the outline of her throne.  Her stars are about as bright as the North Star and the stars of the Big Dipper, so she’s not too hard to find. 

星空下的汗腾格里峰 / Mt. Khan Tengri under Galaxy
Creative Commons License photo credit: livepine

High overhead, look for the enormous Summer Triangle, consisting of the stars Deneb, Vega, and Altair.   This triangle was up all night long from June to early August, hence its name.  Scorpius, the Scorpion, is in the southwest at dusk.  Sagittarius, the Archer, known for its ‘teapot’ asterism, is to its left.  Between these two star patterns is the center of our Milky Way—the brightest part of that band as wee see it.  On a cloudless night far from the big city, see if you notice the Milky Way glow near the ‘teapot’ of Sagittarius. 

Look for the Great Square of Pegasus rising in the east.  The vast stretch of sky under Pegasus is largely devoid of bright stars—ancients called this the ‘Celestial Sea”. 

Moon Phases in September 2010:

Last Quarter                  September 1, 12:22 am, September 30, 10:52 pm

New Moon                       September 8, 5:29 am

1st Quarter                     September 15, 12:49 am 

Full Moon                        September 23, 4:18 am

At 10:13 pm on Wednesday, September 22, the sun is directly overhead at the equator.  As a result, everyone on earth has the same amount of daylight and the same amount of night.  That’s why it is called the equinox (‘equal night’ in Latin).  In the Northern Hemisphere, we’ve seen the days get a little shorter and the midday Sun a little lower each day since June 21.  For us, the season changes from summer to fall at the equinox.  In the Southern Hemisphere, people have seen the days lengthen and the midday Sun get a little higher each day since June.  For them, the season changes from winter to spring.

Go Stargazing! June Edition

Size comparison of terrestrial planets (left to right):
Mercury, Venus, Earth, and Mars

Saturn is now in the south southwest at dusk.  Look just to the west of due south, about 2/3 of the way up from the horizon to the zenith, and you will see Saturn in the sky.

Venus remains high in the evening sky during June.  Face west at dusk and look for a point of light that outshines everything in the sky but the sun and the moon.

Mars is high in the evening sky, although not as bright as it was in winter.  Since January 29, Earth has been pulling ahead of Mars on its faster orbit.  As a result, Mars gets slightly dimmer each night for the rest of 2010.  As June opens, Mars is approaching the star Regulus in Leo from the right.  Mars is right next to the star on June 5, then pulls away from the star to the left after that.  Look high in the west at dusk for a reddish point of light.

Jupiter is in the south-southeast at dawn this month.  It outshines all stars in the sky, so it’s easy to find.

Spring stars are high in the south and west.  A distinct backwards question mark shape outlines the mane and forepaws of Leo, the Lion.  Three stars forming a right triangle are to its upper left; they mark Leo’s hindquarters.  The Big Dipper is as high as it ever gets in the north at dusk. You can extend the curve of its handle to ‘arc to Arcturus’ and then ‘speed on to Spica.’  These stars high in the east and south, respectively, by dusk tonight.  Arcturus, by the way, is the fourth brightest star we ever see at night, but the brightest one Americans ever see in all of June and July.

In the east, look for the enormous Summer Triangle, consisting of the stars Deneb, Vega, and Altair.   This triangle is up all night long in June and July, hence its name.  Scorpius, the Scorpion, is in the southeast at dusk.  Sagittarius, the Archer, known for its ‘teapot’ asterism, rises just after dusk on June 1, but is up by nightfall on June 30.

Moon Phases in June 2010:

Last Quarter                  June 4, 5:13 p.m.

New Moon                      June 12, 6:14 a.m.

First Quarter                  June 18, 11:30 p.m.

Full Moon                        June 26, 6:30 a.m.

It's ba-ack!
Creative Commons License photo credit: ronnie44052

The full moon of Saturday, June 26, will set in partial eclipse.  At 3:55 a.m., the moon first touches the penumbra of the Earth, the region where Earth partially blocks the sun.  The main event starts at 5:16 a.m., when the moon begins to enter the umbra, or the shadow itself.  The moon is not truly aligned with the Earth and sun this time, though, so it will not go all the way into the shadow.  This is why we have only a partial eclipse, with only the north (upper) limb of the moon in shadow.  The moon is still partly inside the umbra as it sets at 6:25 a.m.  (Although we no longer see it, the moon remains partially eclipsed until 8 a.m.)

This eclipse is merely a ‘warm-up’ for the spectacular total lunar eclipse we will have just after midnight on December 21.

At 6:29 a.m. on Monday, June 21, the sun is directly overhead at the Tropic of Cancer. Therefore, this day’s midday sun as high as possible in our skies.  This, then, is the moment of the summer solstice.  Those of us in the Northern Hemisphere enjoy more daylight on this day than on any other day of the year.

Go Stargazing! March Edition

Saturn is up all night long by month’s end.  On Mar. 21, Earth passes between the sun and Saturn.  This alignment is called opposition because it puts Saturn and the sun on opposite sides of the Earth.  As a result, Saturn rises at dusk and sets at dawn on this date.  Look for Saturn to rise due east around 8:00 p.m. tonight. It will rise just a little bit earlier each night.

Venus enters the evening sky by the end of March.  As March opens, Venus is still setting during twilight, making it hard to notice at dusk.  By the end of the month, though, Venus has come out from behind the sun far enough for us to notice it clearly.  Face west at dusk and look for a point of light that outshines everything in the sky but the sun and the moon.

Mars has become an evening object.  It is now already up in the east-northeast by dusk.  On Jan. 29, Mars came to opposition as Earth passed between Mars and the sun, putting Mars in our sky all night long.  Earth is now pulling ahead of Mars on its faster orbit.  As a result, Mars is slightly dimmer each night for the rest of 2010.  However, during March, Mars remains brighter than average, and thus remains easy to see.  Look high in the southeast as dusk (due south by the end of the month) for a reddish point of light sort of in line with the two Dog Stars 

Jupiter is mostly out of sight this month.  Viewers with a very clear east-southeast horizon may notice Jupiter low in the sky at dawn by the end of March.  

STEAL ME FOR YOUR DESKTOP!! (The Bokeh Galaxy)
Creative Commons License photo credit: kevindooley

Dazzling Orion is high in the south.  His belt points up to Aldebaran, the eye of Taurus, the Bull.  The Dog Stars Sirius and Procyon are to Orion’s left.  Sirius is the brightest star we ever see at night.  Gemini, the Twins, are to Orion’s upper left.  Look for two stars of equal brightness less than 5 degrees (three fingers at arms’ length) apart.  These are Castor and Pollux, marking the twins’ heads.  High in the northwest is Capella, the sixth brightest star ever seen at night.  At dusk on March evenings, look below Sirius and a bit to its right for Canopus, the second brightest star we ever see at night. This star is in the keel (bottom) of the legendary ship Argo.  Canopus is so far south that most Americans never get to see it.  We, however, are far enough to the south that it barely rises for us, remaining low on the southern horizon.  

Meanwhile, spring stars are rising in the east.  A distinct backwards question mark shape outlines the mane and forepaws of Leo, the Lion.  Three stars forming a right triangle rise underneath; they mark Leo’s hindquarters.  The Big Dipper is once again fully risen at dusk. Later in the evening, you can extend its handle to ‘arc to Arcturus’ and then ‘speed on to Spica’.  These stars will be along the eastern horizon by 9:30 tonight, and even earlier later in the month.

Transit Lune/Saturne du 22 mai 2007
Creative Commons License photo credit:
ComputerHotline

Moon Phases in March 2010:

Last Quarter                  March 7, 9:43 p.m.

New Moon                      March 15, 4:02 p.m.

First Quarter                  March 23, 5:59 a.m. 

Full Moon                        March 29, 9:25 p.m.

At 12:33 p.m. on Saturday, Mar. 20, the sun is directly overhead at the equator.  This, then, is the vernal equinox. On this date, everyone in the world has the same amount of daylight and the same amount of night.  After this date, daytime is longer than night in the Northern Hemisphere, while night is longer than daytime in the Southern Hemisphere. 

Sunday, Mar. 14, is the second Sunday in March.  Accordingly, we spring forward into Daylight Saving Time at 2 a.m. that morning (1:59:59 a.m. is followed by 3:00:00 a.m.).  Don’t forget to set your clocks forward by one hour before going to bed Saturday night!