- Hi, it's me Tim Dodd, the Everyday Astronaut.
Have you ever accidentally used a tablespoon
instead of a teaspoon?
Or maybe you grabbed a metric wrench
when you were trying to loosen up a 9/16" bolt?
Or maybe you've heard someone say
that something weighs a ton and you have to ask them,
now is that a imperial ton or a metric ton?
Luckily, when most of us mix up units,
it likely just leads to our food tasting bad,
or maybe strips a bolt, or just simply leads
to a really annoying argument between
which is the right measurement system.
But when NASA and Lockheed Martin mixed up
the units for the Mars Climate Orbiter,
it led to the loss of a $327 million mission to Mars.
Welcome to another episode of biggest facepalms
or spaceflight history, otherwise known as spacepalms.
This is where we're going to take a look at a mission
or an event that almost certainly lead to everyone
in Michigan troll collectively facepalming.
Now this one in particular is a very well known story.
One you may have heard your physics professor regale you
with when talking about the importance of units.
But honestly, I don't think I've actually heard
the correct story all the way through
and I definitely didn't know what truly happened
before I made this video.
So today, let's take a look at what was suppose to happen,
what wound up happening and why.
After all, this is a classic lesson
that will be passed down
for generations and generations.
And it's a fun story to tell.
So, let's get started.
Three two one
(upbeat music)
The year 1999, back when websites look like this.
"The Matrix" was released and the Cher song "Believe"
was the number one hit.
NASA was hoping to have a big hit on their hands as well
with an exciting new Mars Orbiter that would study
the Martian climate, known as you guessed it,
the Mars Climate Orbiter.
NASA set new guidelines
for some less expensive and smaller probes
for interplanetary missions after a panel
on small spacecraft technology was formed in 1994.
These new probes would be under 1000 kilograms
with more focused scientific instruments
instead of Swiss Army knife do it all style spacecraft
from years prior.
The first mission in this new program was called
the "Mars Global Surveyor" which launched in 1996,
on top of a Delta II
from SLC-17A Cape Canaveral Space Force Station,
or Cape Canaveral Air Force Station,
as it was known at the time.
This first probe would map
the surface of Mars with more detail than ever before,
which would help pave the way for future Mars landers.
The Mars Climate Orbiter was to follow the success of
the Mars Global Surveyor and would be taking with it some of
the instruments that were originally designed
for the Mars Global Surveyor.
The two would be a mini powerhouse
for studying Mars from orbit.
The spacecraft found up being 2.1 meters wide.
1.6 meters tall and two meters deep.
It would weigh only 638 kilograms making it capable
of being launched on a Delta II
with only four solid rocket boosters,
but despite its small way,
it was still stuffed to the gills
with scientific instruments including
the Mars Orbiter Camera, the Mars Orbiter Laser Altimeter,
the Thermal Emission Spectrometer, a Magnetometer
and electron reflectometer the ultra-stable oscillator
and a Mars Relay signal receiver.
Saying those out loud feels like
I was making half of them up, I probably should
have tried to sneak in the specs on the end line
for the rotary girder to see if any you guys
are actually paying attention.
The vehicle had eight monoprop thrusters each
with 22 Newtons of thrust photo trajectory corrections
and four smaller 0.9 Newton thrusters for attitude control.
Lastly, it had one larger main engine a leros 1B
that provided 640 Newtons of thrust
for the Mars insertion burning.
Mars Climate Orbiter had a unique design.
It only had a single large solar panel off to one side,
which was capable of 500 watts at Mars, which side no
because Mars is 50% further away
from the Sun than the Earth is,
due to the inverse square law, a solar panel on Mars
is about 45% as powerful as it is on Earth.
On December 11th 1998, at 1845 UTC,
the Mars Climate Orbiter took off
from Cape Canaveral Air Force Station SLC-17A beginning
its 10 month journey to Mars.
One of my favorite things about this launch is
the Star-48B spin stabilized solid propellant third stage.
That's right, its spin stabilize
So if there's any minor offset in the thrust,
you can know it out by spinning the stage.
Once the burn is complete,
there's a YoYo Despin mechanism that mostly knows how
the spin, it stuff like this that I think is just so cool.
So the little probe was on its way, everything looking good.
And like all deep space missions,
it's normal to do a few correction burns along the way
to make sure you nail your target.
And that's no big deal I mean, this is done all the time.
There were four course corrections performed
on December 21st 1998, March 4th, July 25th
and September 15th 1999.
There was another optional course correction planned
just one day prior to the Mars insertion burn,
but it was denied by management
because they thought based on prior trajectories
that the probe was on course.
Alongside the course corrections,
the spacecraft also perform something
called angular momentum desaturations or AMDs.
Many spacecraft do this but especially
the Mars Climate Orbiter,
because it had that single sided solar panel.
It experienced more solar pressure on one half of
the spacecraft than the other.
By the way, fun side note, solar pressure is the momentum of
the massless photons exerting pressure on a spacecraft
and it's not solar wind.
Solar wind is composed of particles
with mass ejected by the sun like
nucleons and electrons.
Thanks to Scott Manley and the rest of space Twitter
for helping clarify that for me.
Okay, so your spacecraft is ever so slightly rotating
in a direction you don't want.
And in order to keep the reaction wheels inside
the spacecraft that helped maintain orientation
from having to work overtime,
you can perform an AMD to reset
the spacecraft back to its ideal orientation
and keep those reaction wheels happy and not overworked.
Now each and every single time the spacecraft performs
any desaturation maneuver or any correction burn,
or really any maneuver the exact impulse or the exact amount
of time each and every thruster is fired, is recorded,
and then that's sent back down to earth
so Mission Control can calculate exactly how much
the spacecraft change its trajectory.
Even if it's by the teentiest,
tiniest amount during these corrections.
But now mind you mission control can still track
the probe and its trajectory in deep space
on the way to Mars.
But the primary way of doing so is using Doppler shift
and that's not incredibly accurate
at some portions of the journey,
especially when the changes in velocity
are perpendicular to the vantage point.
Think of it like this Doppler can very precisely tell
if something is speeding up or slowing down,
moving straight, away or towards you.
But it can't really tell if something
is speeding up side to side from Earth's vantage point,
which for a good portion of the journey to Mars,
is exactly what's happening.
So generally guidance teams will precisely calculate
the vehicle's exact trajectory after
the Hohman transfer burn
that sends the probe on its way to Mars.
And so long as any outside force doesn't
act upon the vehicle, which spoiler it's space.
The variables are well accounted for and well known.
The vehicle will end up exactly where it's calculated
to a surprising degree of accuracy.
But this also means that they need to account for each
and every thruster fire as even
those tiny little impulses change
the exact destination of the vehicle.
Even if only a tiny amount, if you do something enough,
it ends up adding up over time to a very drastic change.
Now, of course when you're aiming at a planet
that's over 200 million kilometers away from you,
a tiny error could either mean missing that planet,
or perhaps even worse, smacking right into it.
And NASA was aiming to only miss Mars
by 200 kilometers or so.
So there was very little room for error.
And in general, you want to aim
and get as close as you can safely get to the planet
that you're trying to be captured by.
Now, of course, if you're on a planet
that has an atmosphere,
you need to take that into consideration
and not get too low.
But the closer you are, the less energy
it takes to get captured into orbit.
On September 15th 1999 just one week
prior to the Mars encounter and insertion burn,
NASA performed the fourth and final
trajectory correction maneuver,
which placed its trajectory 226 kilometers
above the surface of Mars.
Perfect for the Mars orbital insertion.
But following that burn,
the navigation team noticed their calculations
and their observations didn't match.
And in fact, the observed trajectory kept getting lower
and lower to the point where
they saw it go all the way down to just 150 kilometers,
but that was still safely above
the minimum altitude of 80 kilometers.
Now if you go below 80 kilometers Mars's atmosphere
will still bite up your fragile little spacecraft
and rip it to shreds.
Just imagine that tiny little fragile solar panel
getting knocked about by the Martian winds.
Oh, humanity.
Just 24 hours before the orbital insertion burn
as the gravitational effects of Mars grew stronger
the newly observed trajectory was putting
the spacecraft at only 100 10 kilometers.
But again, that's still above
the 80 kilometers that's survivable.
So they proceeded despite some vocal opposition
of some of the operators.
At 9 o'clock and 46 seconds UTC on September 23 1999,
the insertion burn began.
Everything was performing as planned at first.
Miss control expected a loss of signal
when the spacecraft went behind Mars,
and they had an exact time they expected that to happen.
The first signs of serious trouble cropped up when
the loss of signal occurred 49 seconds earlier
than expected, and it was even further drilled in by
the fact that signal was not required 21 minutes later
as they expected, despite trying for two full days.
- I'm sorry to report that we have a serious problem
with the Mars Climate Orbiter.
We may in fact be facing a loss of mission.
- So what actually happened?
Was there something wrong with the insertion burn?
Was it that NASA was reading the oxygen kilometers
when the probe was saying miles.
Find out after we hear a word
from this week's sponsor, banana for scale.
- Are you tired of measuring stuff based
on some old guy's feet?
(screaming)
Are you constantly asking Siri how many ounces
are in a pint, only to get the wrong answer?
- Hey Siri, how many ounces are in a pint?
- [Siri] Austin is the capital of Massachusetts?
- Is it just too easy knowing
there's a 1000 milliliters in a litre?
Or perhaps you're measuring horses in hands
and you just (mumbles)
Introducing banana for scale
the one true unit of measure.
- Okay, so the answer each and every time
the spacecraft perform those desaturation maneuvers,
it would report back what it did to correct
for the angular momentum.
Now the internal guidance and control
was performing perfectly fine.
Maintaining control and keeping
proper orientation of the spacecraft no problem.
The problem is what the space craft
was sending back down to earth was Newton seconds.
And the software in the ground station was reading
those results as pound seconds.
And reporting those results to
the guidance and navigation teams off
by a factor of 4.4 or five times.
So in other words, each time
the spacecraft did a desaturation maneuver,
it reported back to the ground what exactly it did.
The data with the wrong unit,
then was put into the model for the spacecraft's trajectory
by the guidance team.
Now since the units were wrong,
the calculated trajectory was also wrong.
Now the funny thing is
because these angular momentum desaturation burns
were so low energy being off
by 4.45 times was hardly noticeable.
So throughout the journey,
every one of those little tiny events
was doing a tiny little bit,
but the estimated trajectory thought
they were doing about 4.45 times more work.
This was compounded by the fact that because
the Mars Climate Orbiter had just a single solar panel,
it had to perform over 10 times more desaturation events
than its sister spacecraft, the Mars Global Surveyor,
which had two solar panels.
So how could this have been prevented?
Well, like most things,
it'd be easy to put blame on one person or group
but in reality, it's kind of a whole swath of small problems
and putting the blame on anyone
doesn't really solve the problem.
The first and most obvious problem and solution
is to make sure all units are the same.
Lockheed Martin took a lot of flack
for delivering units in pounds seconds,
as it was intended to be delivered in Newton's seconds.
But oddly, the blame game continues.
When it was discovered the code given to Lockheed Martin
was in pound seconds in the first place,
and they didn't catch it.
Specifically a set of code called Small forces,
which was wrong from day one.
Well, and then again, that no one caught
the air and quality control at NASA either.
And then you can keep going
and saying it was a management problem,
considering several things factors were overlooked
starting with the initial design of the spacecraft.
Most notably that no one from guidance and navigation
was on the design team, which led to a less than desirable
and hard to navigate spacecraft in the first place.
But then ignoring the requests of
the guidance navigation team to perform
the desaturation maneuvers 180 degrees apart from each other
would have negated the problem before it arose.
By doing asymmetrical burns for the desaturation
also led to imparting additional unwanted velocity.
And lastly, the teams were seeing erroneous data
that didn't line up with our calculated trajectories,
but it was ignored.
This was amplified and actually quite obvious
that something was wrong in the last week of the mission
as the spacecraft got closer to Mars.
A few members of the team spoke up verbally
and wanted to do a t-minus 24 hour correction burn
to raise the approach.
But they were denied because
the concerns weren't filed correctly.
And due to some mis organization of authority.
Those that spoke up were seen as out of line.
So really like all things,
this wasn't a black and white topic.
It's fairly nuanced and has a lot of tiny little things
that added up to one big thing.
And at the end of the day, the thing happened
and the best thing we can do is learn from it
and prevent it from ever happening again.
In fact, the problems discovered
with the Mars Climate Orbiter
was cross checked with the Mars Polar Lander,
which was also on its way to Mars at the exact same time.
And although it didn't have the same problem,
it ended up not touching down softly
for completely different reason.
- Volcom Mars op.
- CFOM, go ahead.
- Yeah, Sam, I'm sorry to report that all we have
is HKTM at this point.
It seemed to have been a nominal no contact MR Pass
- Copy that Mark thanks for,
thank for hanging in there with us.
- But the lesson learned has been passed down
to every new generation of navigators and engineers.
It's a valuable lesson and hopefully a lesson everyone
who designed spacecraft for the first humans going to Mars
has listened to closely.
So to summarize, a spacecraft on its way to Mars
needed to fight off the solar pressure exerted onto
the single sided solar panel by doing
some angular momentum desaturations
with its small attitude thrusters.
Each time the vehicle did a desaturation maneuver,
it recorded what it did and reported it back
down to earth where the recorded thruster firings
were misinterpreted by software as pounds seconds of force
instead of Newton seconds, leading to very tiny deviations
in the calculated trajectory.
These tiny deviations were so small,
they went mostly unnoticed until
the spacecraft encountered Mars at 57 kilometers
in altitude, instead of the calculated 226 kilometers,
which likely made the spacecraft burn up in
the Martian atmosphere, leading to the loss of the mission.
So let's not be so hard on ourselves
when we make little errors.
Or maybe be nicer to each other understanding each
and every single one of us is capable of mistakes.
It's simply part of being human.
So what do you think?
Did you learn something?
Do you think it's just a simple unit error?
Or do you think there's a lot more to it than that?
Let me know your thoughts and why metric is
the better unit of measurement in the comments below.
Now I promise I'll do a few more of these space POM videos
to try and fill the gap between some of my long form videos.
Because trust me, those are getting
a bit ridiculous even for me.
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Thanks everybody.
That's gonna do it for me I'm Tim Dodd,
the everyday astronaut.
Bringing space down to earth for everyday people.
(upbeat music)