Report: DART spacecraft crashed into rendezvous satellite

AP on Yahoo ^ | 5/15/06 | Alicia Chang - ap

[NormsRevenge]

A robotic NASA spacecraft designed to autonomously rendezvous with an orbiting satellite crashed into its target after using too much fuel halfway through its mission, according to a summary of the investigation released Monday.

Investigators blamed the collision on faulty navigational data that caused the DART spacecraft to believe that it was backing away from its target when it was actually bearing down on it.

"The inaccurate perception of its distance and speed ... prevented DART from taking effective action to avoid a collision," the summary said.

The 800-pound Demonstration for Autonomous Rendezvous Technology spacecraft was supposed to rendezvous with a defunct Pentagon satellite during a 24-hour period last year, but the mission ended prematurely.

DART successfully located the target satellite orbiting 472 miles above Earth and moved within 300 feet of it. But problems arose when DART tried to circle the satellite.

Investigators concluded that DART spent too much fuel steering itself toward the satellite. The excessive firings of its engines were caused by inaccurate navigational data from its on-board computer that caused it to reset every three minutes during the mission.

Determining that it wouldn't have enough reserve fuel to complete the mission, DART began shutting down about 11 hours into the mission, but not before crashing into the satellite.

Unbeknownst to engineers at the time, DART's main sensor mistakenly believed it was flying away from the satellite when it was actually moving 5 feet per second toward it, investigators found.

The collision pushed the target satellite into a higher orbit. NASA said neither spacecraft pose a threat to other satellites and both will burn up upon re-entry into the atmosphere.

In addition, the investigation also concluded that DART overestimated how much fuel it consumed, although the remaining amount would not have been enough to complete the mission.

Investigators also raised issues with the mission's management style, saying that lack of training and experience caused the DART design team to shun expert advice. They also found that internal checks and balances were inadequate in uncovering the mission's shortcomings.

The 10-page document summarizing DART's failure comes a year after the spacecraft was launched from Vandenberg Air Force Base in California.

Last month, NASA said it won't release the investigative board's full 70-page report, citing sensitive information protected by International Traffic in Arms Regulations. The summary was prepared by the space agency's exploration systems mission directorate.

Robotic technology plays a critical role in NASA's plan to send humans back to the moon and Mars. The $110 million DART mission was meant to test whether robots can perform some of the tasks astronauts currently must do.

DART was managed by NASA's Marshall Space Flight Center in Huntsville, Ala. It was built by Orbital Sciences Corp.

[NormsRevenge]

This artist rendering released by NASA shows the Demonstration for Autonomous Rendezvous (DART) spacecraft, foreground, as it might appear as it approaches a communications satellite in orbit above Earth. The NASA spacecraft designed to autonomously carry out a series of tasks crashed into its target after using too much fuel halfway through its mission, according to a report summary released Monday, May 15, 2006. Investigators blamed the collision on faulty navigational data that caused the DART spacecraft to believe that it was backing away from its target when it was actually bearing down on it. (AP Photo/HO, NASA)

[clyde asbury]

ping

[kAcknor]

Is it paranoid or hopeful when I imagine that this mission was successful with 'failed test' for a cover story? ;)

[Right Wing Assault]

What kind of sensor would mistake toward and away? That is child's play!

Investigators also raised issues with the mission's management style, saying that lack of training and experience caused the DART design team to shun expert advice. They also found that internal checks and balances were inadequate in uncovering the mission's shortcomings.

Maybe there is an answer here. Children designed it? But where were mom and dad?

[Bones75]

Seems like someone's got pretty good aim to me.

The expanse up there is so vast, and these spacecraft so small, it's stil a pretty impressive feat..

Then again I've always been impressed at the ability to dock spacecraft in orbit.

[catbertz]

Is it paranoid or hopeful when I imagine that this mission was successful with 'failed test' for a cover story? ;)

you're not alone. I thought the sme thing while reading. I'm sure the project was a complete failure *snicker*

[Socratic]

So, did it actually have too little fuel left to complete the mission (when it actually struck its target), or was it faulty sensors which indicated a false fuel reading. Or was it that pesky little sensor which couldn't differentiate between moving toward or away from the target. There are too many explanations for this to be the truth.

[baltodog]

That's exactly what I was thinking...

[Calvin Locke]

What kind of sensor would mistake toward and away?

Uh, French?

Actually, didn't the Japanese have a similar problem trying to land on an asteroid and retrieve material?

Then, of course, there was the Genesis solar wind collection re-entry vehice that slammed in to the desert,
thanks to the parachute deployment sensors being installed upside down.

And the NASA Mars (Polar?) lander that crashed because the design team used English measurements, and that information
didn't get passed to the landing team.

[Drammach]

So, did it actually have too little fuel left to complete the mission (when it actually struck its target), or was it faulty sensors which indicated a false fuel reading.

The article notes that the DART "estimated" how much fuel was left..
I don't understand why they are using software to estimate fuel usage, when a simple physical gas gauge would do the job more efficiently and far more accurately.. ( no "estimation" at all.. actual measurement of fuel left.. )

Likewise, I agree on the sensors issue..
Explanations like that are intuitively disconcerting..
Telemetry alone should have caught any discrepancies immeadiately, unless the person monitoring that activity was on a bathroom break or something.. ( i.e., not doing their job. )

All in all, very disappointing..

[19th LA Inf]

I heard about an engineer, back in the early spacecraft days, who described one that blew up on the pad as a "catastrophic failure". His boss chewed him out royally, saying that every mission was no less than a "partial success". The engineer rewrote his report and said it was a "catastrophic partial success".

[Calvin Locke]

using software to estimate fuel usage,

Maybe there's some technical reason why a "real" fuel/pressure gauge can't be used? The thing is not operating at STP, and
throw in the orientation, micro gravity, and speeding around at roughly 18K mph, in the sunlight for say an hour, behind
the Earth for maybe half an hour, it does present a challenge.

[Drammach]

Maybe there's some technical reason why a "real" fuel/pressure gauge can't be used?

Cheese Whiz.. ( not a commentary, but an example.. ;o)..)

Products in pressurized cans are contained in a pouch..the "propellant" is a pressurized gas in said container, surrounding the pouch..
The gas pressure in the container will decrease as the product, ( cheese ) is dispensed from the container..

The pressure of the gas in the container can be measured, indicating exactly how much product (fuel) is still remaining.

[timer]

The Apollo program landed american astronauts on the moon and returned them back home again 36 years ago. Even Apollo 13 was electronically rescued, has "faster, better, cheaper" gone too far as NASA's philosophy since then? Actually though, AG was discovered/developed years ago, problem is : with everyone in the world having their own magic flying carpet, the entire third world would be landing on your lawn as a plague of locusts(like the mexicans are already).

[supercat]

The pressure of the gas in the container can be measured, indicating exactly how much product (fuel) is still remaining.

Many propellants liquefy under pressure. As long as any propellant remains in liquid form, the pressure will be a function of pressure, rather than of the quantity remaining. This allows things like butane lighters to be constructed very cheaply, since the pressure when nearly full is no greater than the pressure when nearly empty.

[Calvin Locke]

Yeah, but...take the Apollo 11 Moon landing. IIRC, the only indicator, other than a stop watch, was a "low" indicator
that was placed near the bottom of the fuel tank, where the shape changed.

A bladder+"propellant" would only add extra weight when, for the purposes of DART, the problem appeared to be using too
much fuel in the maneuvering for position.

Now that I think about it, when the USSR broke up, the Russians eliminated ($$$) the radar docking system on the
resupply cargo vessels, resulting in at least one collision that I can think of off the top of my head.

[Jeff Gordon]

Another successful test of a satellite killer.

[Ichneumon]

As long as any propellant remains in liquid form, the pressure will be a function of pressure

That seems a pretty safe bet. ;-)

You meant to write, "a function of temperature", of course, but I couldn't resist joking about the inadvertent tautology.

[Drammach]

I am assuming of course, that NASA knows exactly which fuels they are using in their spacecraft, and not guessing or filling them up with random, various fuels that act differently when under pressure..
The characteristics of those fuels should be well known to the engineers ( and rocket scientists ) that designed and built them..

I can't imagine an explosives expert not knowing the properties of his explosives, the burn rate of his fuses, etc..
All of those calculations are supposedly done before the launch date is ever approved..
Weight being a primary consideration, only the necessary amount of fuel for the mission is put on board..
It's designed that way..
Telemetry should be able to tell how much fuel is available..

Likewise, I can't imagine sending a multi-million dollar spacecraft into orbit without knowing exactly how much fuel it has, the burn rate, etc..

My cheese-whiz analogy may not be cost effective, or even scientific, but it points out just one example off the top of my head that could be used to account for fuel usage and remaining capacity..
Please note, the pressurized gas in this instance is not used as a propellant, it only provides pressure for the expulsion of the cheeze whiz.. It's pressure would indeed, remain constant, it never leaves the container..
Sensors could read the positions of microchip tags on the fuel bag to determine remaining volume..
Also, fuel consumption could be determined by measuring the flow of the fuel (or gas) to the engine..
I'm not a scientist, so I may be wrong, but it would seem that there must be some way of determining the ratio of liquid to gas (vapor pressure or boiling point) that would indicate the amount of fuel left in a fuel tank..

Just sayin'...
There must be a dozen ways to determine how much fuel is left, how much has been used, etc..

[supercat]

You meant to write, "a function of temperature", of course, but I couldn't resist joking about the inadvertent tautology.

BTW, on a related note, if a certain amount of heat is added to a fixed-volume container of gas, how would one calculate the peak pressure if none of the heat is allowed to escape and the container does not expand? How about if there is an increase or decrease in the number of moles of gas in the container?

I understand that unlike Boyle's and Charles' laws, the behavior of even ideal gasses under such circumstances depends upon their specific heats, but I don't know exactly how.