Dawn Spacecraft Fires Past Record for Speed Change (w/ Video)

Jun 08, 2010
NASA's Dawn spacecraft, illustrated in this artist's concept, is propelled by ion engines. Image credit: NASA/JPL

(PhysOrg.com) -- Deep in the heart of the asteroid belt, on its way to the first of the belt's two most massive inhabitants, NASA's ion-propelled Dawn spacecraft has eclipsed the record for velocity change produced by a spacecraft's engines.

The previous standard-bearer for velocity change, NASA's Deep Space 1, also impelled by , was the first interplanetary spacecraft to use this technology. The Deep Space 1 record fell on Saturday, June 5, when the Dawn spacecraft's accumulated acceleration over the mission exceeded 4.3 kilometers per second (9,600 miles per hour).

"We are using this amazing ion-engine technology as a stepping-stone to orbit and explore two of the asteroid belt's most mysterious objects, Vesta and Ceres," said Robert Mase, Dawn project manager from NASA's Jet Propulsion Laboratory in Pasadena, Calif.

A spacecraft's change in velocity refers to its ability to change its path through space by using its own rocket engines. This measurement of change begins only after the spacecraft exits the last stage of the that hurled it into space.

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To get to where it is in both the record books and the , the Dawn spacecraft had to fire its three engines - one at a time-- for a cumulative total of 620 days. In that time, it has used less than 165 kilograms (363 pounds) of xenon propellant. Over the course of its eight-plus-year mission, Dawn's three are expected to accumulate 2,000 days of operation -- 5.5 years of thrusting -- for a total change in velocity of more than 38,620 kilometers per hour (24,000 miles per hour).

"I am delighted that it will be Dawn that surpasses DS1's record," said Marc Rayman, chief engineer for the Dawn mission and a previous project manager for Deep Space 1."It is a tribute to all those involved in the design and operations of this remarkable spacecraft."

At first glance, Dawn's pedal-to-the-metal performance is a not-so-inspiring 0-to-97 kilometers per hour (0-to-60 miles per hour) in four days. But due to its incredible efficiency, it expends only 37 ounces of xenon propellant during that time. Then take into consideration that after those four days of full-throttle thrusting, it will do another four days, and then another four. By the end of 12 days, the spacecraft will have increased its velocity by more than 290 kilometers per hour (180 miles per hour), with more days and weeks and months of continuous thrusting to come. In one year's time, Dawn's ion propulsion system can increase the spacecraft's speed by 8,850 kilometers per hour (5,500 miles per hour), while consuming the equivalent of only 16 gallons of fuel.

"This is a special moment for the spacecraft team," said Dawn's principal investigator, Chris Russell of the University of California Los Angeles. "In only 407 days, our minds will be on another set of records, the data records that Dawn will transmit when we enter Vesta orbit."

Dawn's 4.8-billion-kilometer (3-billion-mile) odyssey includes exploration of asteroid Vesta in 2011 and 2012, and the dwarf planet Ceres in 2015. These two icons of the asteroid belt have been witness to much of our solar system's history. By using the same set of instruments at two separate destinations, scientists can more accurately formulate comparisons and contrasts. Dawn's science instrument suite will measure shape, surface topography and tectonic history, elemental and mineral composition, as well as seek out water-bearing minerals. In addition, the way the orbits both Vesta and Ceres will be used to measure the celestial bodies' masses and gravity fields.

While Dawn surpassed Deep Space 1's record for velocity change, Deep Space 1 will continue to reign as holder for the longest duration of powered spaceflight for another few months. Dawn is expected to take over that record on about August 10 of this year.

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User comments : 11

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jsa09
5 / 5 (3) Jun 08, 2010
Looking forward to pictures of Ceres and Vesta when this little beauty reaches them.
bg1
not rated yet Jun 08, 2010
"In one year's time, Dawn's ion propulsion system can increase the spacecraft's speed by 8,850 kilometers per hour (5,500 miles per hour), while consuming the equivalent of only 16 gallons of fuel."

What mass at the beginning and end of this acceleration?
Sonhouse
5 / 5 (2) Jun 09, 2010
Well, at 37 ounces in 4 days, That's 9.25 ounces per day, times 28 is about 260 grams per day. So times 365 = 94,500 odd grams per year, 94.5 Kg is about 207 pounds per year if you must. So whatever the mass is at the beginning, which I don't know, just subract 207 pounds and you know. Or 95 Kg, whatever. Someone know the mass of the probe after it is on its own?
Sonhouse
not rated yet Jun 09, 2010
Also, 0 to 60 mph in 4 days is 88 feet per second per 345,600 seconds is about 2.5 E-4 feet/second/second or about 7.6 micro G's of acceleration. Not exactly going to knock you to your feet:)
TAz00
4 / 5 (1) Jun 09, 2010
Years of continuous thrusting, zing!
Mr_Frontier
5 / 5 (1) Jun 09, 2010
Sir, the possibility of successfully navigating an asteroid field is approximately 3,720 to 1.
LuckyBrandon
1 / 5 (2) Jun 09, 2010
9600 mph does NOT sound impressive whatsoever...our shuttles beat that easily...I know this thing uses less fuel, but seriously, 9600mph being touted as if its something big...
That is extremely fast, but in my opinion, nobody should brag about their speed unless they are beating the speed of all other "vehicles" out there...
colinnwn
not rated yet Jun 09, 2010
@LuckyBrandon

The shuttle does not beat that easily, Dawn handily whoops the shuttle. This is only the change in speed after the last stage of the launch vehicle.

Since the launch vehicle of the shuttle includes the external tank, none of the speed increase provided by the main engines or SRBs can be included. You can only include the speed change from the OMS engines.

The OMS engines can provide a max of 680 mph of speed change for the shuttle, or only 7% of what Dawn has attained.

http://abyss.uore...c23.html
LuckyBrandon
1 / 5 (1) Jun 11, 2010
shuttles go what, around 17-18k mph...9600 does not meet that mark...
I understand this line "The Deep Space 1 record fell on Saturday, June 5, when the Dawn spacecraft's accumulated acceleration over the mission exceeded 4.3 kilometers per second (9,600 miles per hour)." to mean not a change in speed, but as it states, the accumulated acceleration...sorry, but 17k-9.5k = a big difference in speed....

Don't get me wrong, I'm all for this technology, but would be way more interested in hearing "it topped 30k mph"....that would be impressive...
Eikka
5 / 5 (1) Jun 13, 2010
Yeah, but Dawn got 4000 m/s on top of the speed that was required to climb to earth orbit.

So it is travelling faster than the shuttle ever has.
colinnwn
not rated yet Jun 15, 2010
Once again LuckyBrandon,

You can't count any of the acceleration attained by the shuttle to get it into orbit around the Earth to compare it to Dawn's Earth departure speed. This is because relative to the Earth as a central body, the shuttle is going ZERO mph, not 17k mph. From that point, the shuttle can add or subtract a maximum of 680 mph.

When DAWN was launched, it too had a orbital velocity provided by its launcher of about 17k mph around the earth. From that point, it has accelerated away from Earth at over 9k mph. The shuttle never even leaves Earth orbit.

If you want to incorrectly add both types of acceleration together, then the shuttle has about 17,680 mph of acceleration, and Dawn wins hands down with 22,600 mph of acceleration.