Title: Out-of-control SpaceX Falcon 9 on collision course with the moon
Did you guys hear the news? A SpaceX rocket is on a collision
course with the moon. This is insane, right?
What is happening over there? More amazingly, this piece of
the rocket is going to crash after spending almost seven years hurtling through space!
It will arrive on the moon the next month, after being launched from Florida in Feb. 2015,
as a part of a mission, an interplanetary one: the NOAA's Deep Space Climate Observatory.
But after completing a long burn of its engines and sending the satellite
on its way to the Lagrange Point, the rocket's second stage became derelict.
It wandered for seven years, following very strange paths, very unusual orbits given by the
studying of chaotic systems in our solar system. In particular, he can be considered as a small
body in the gravitational field of the Moon, Earth, and Sun. Such objects in
such systems behave in a weird way, and what is happening now is that the rocket's orbit will
intersect the moon. That's why we are going to have a crash after seven years.
Space observers believe the rocket – about four metric tonnes of “space
junk” – is on course to intersect with the moon at a velocity of about 2.58km/s in a matter of weeks.
Follow me in this video to get to know more about it!
Bill Gray, who writes software to track near-Earth objects, asteroids, minor planets, and comets,
has said the Falcon 9’s upper stage will very likely hit the far side of the moon,
near the equator, on 4 March. Scientists will hopefully use this impact as an opportunity
to better study uncharacterized parts of the moon.
It isn't an everyday thing to get a free unwanted impact to study the moon's surface!
But who is Bill Gray?
And what do we exactly mean when we say that a Falcon 0's upper stage will hit the moon?
Let's start with the guy.
Bill Gray is a data analyst involved in the so-called Project Pluto.
Project Pluto supplies astronomical software, both commercial and freeware,
to amateur and professional astronomers.
The orbit determination software of Project Pluto, called Find Orb, can take a set of positional
measurements of an asteroid, comet, or natural or artificial satellite, and determine its orbit.
So basically what Project Pluto and Gray do, is the determination of orbital parameters.
This makes the guy one of the most reliable sources of information since
his measurements are really precise. Bill Gray said that the object made a
closer lunar flyby on January 5th, but it will make a certain impact on March 4th.
This will be the first unintentional case of space junk hitting the moon of which we are aware.
Not let's get to the Falcon 9. Let's see how it is made.
The Falcon 9 rocket is something that looks like this:
As you can see from the picture,
it is made of various stages and the one on the left is called the first stage.
First stage When we say that Falcon 9 is a reusable rocket,
we mean that we can recover and bring the primary stage down to earth again,
and prepare it for another launch. Reusability allows SpaceX to refly
the most expensive parts of the rocket, which in turn drives down the cost of space access.
Falcon 9’s first stage incorporates nine Merlin engines and aluminium-lithium alloy
tanks containing liquid oxygen and rocket-grade kerosene propellant.
Falcon 9 generates more than 1.7 million pounds of thrust at sea level.
SECOND STAGE The second stage, powered by a single
Merlin Vacuum Engine, delivers Falcon 9’s payload to the desired orbit. The second stage engine
ignites a few seconds after stage separation and can be restarted multiple times to place multiple
payloads into different orbits. Interstage
The interstage is a composite structure that connects the first and second stages
and houses the pneumatic pushers that allow the first and second stages to separate during flight.
Falcon 9 is equipped with four hypersonic grid fins positioned at the base of the interstage.
They orient the rocket during reentry by moving the centre of pressure.
PAYLOAD Then there is the payload.
Made of a carbon composite material, the fairing protects satellites on their
way to orbit. The fairing is jettisoned approximately 3 minutes into the flight,
and SpaceX continues to recover fairings for reuse on future missions.
========================================================== Due to the cylindrical form of the second
space, Falcon 9's orbital computation is not as easy as it may seem.
In fact, it is usually more difficult to predict the orbit for a spherical object,
than for a cylindrical one and results may differ in orders of magnitude.
That's why the exact spot the rocket will hit remains obscure.
One of the main uncertainties we have is the one due to the Sun.
The sun pushes on the rocket by means of its radiation pressure, and this
gives us an ambiguity in measuring rotation periods, which may slightly alter its orbit.
Even if these effects are very small, they will accumulate between now and March 4.
This means that we will require further observations to refine
the precise time and location of the impact.
You may find that this anim­ation showing the
motion of the object during 2022 gives you a better idea of what's going on.
This shows the path as seen from the "side" of the earth-moon system and a little above it.
In the animation, the moon is on the white trail that mostly repeats in a nice, regular ellipse,
and there are some changes because the sun is pulling on it gently.
Below, you can see the path of the object between January 1
and the impact on March 4. The green circle shows the orbit of the moon;
the earth is the red circle at the centre, and the black track shows where the DSCOVR stage is going.
Will this collision be viewed from Earth?
Well, it will happen on the far side, which means the dark side of the moon.
The bulk of the moon is in the way, and even if it were on the near side, the impact occurs
a couple of days after New Moon, which makes it really hard, almost impossible, to observe.
Space enthusiasts believe the impact could provide valuable data.
I bet you think this news is amazing. But the amazing fact is that this is not
the first time something crashed on our Moon. We, humans, have intentionally crashed some
of our spacecraft into the moon. During many of the Apollo missions, for example,
NASA crashed the rocket booster stages (the S-IVBs) into the moon for scientific reasons.
It allowed them to take seismic measurements to help them characterize the lunar interior.
Intentional crashes into the moon or other worlds
in our solar system also are useful because they eliminate space debris.
If you scan this list of artificial objects on the moon, you can see that a great many
of them were intentionally crashed. But one of the most important examples
of intentional crashes is the one obtained with the LCROSS mission.
LCROSS was designed to collect and relay data from the impact and debris plume resulting from
the launch vehicle's spent Centaur upper stage striking the crater Cabeus near
the south pole of the Moon. Centaur had a nominal impact mass of
2,305 kg (5,081 lb), and an impact velocity of about 9,000 km/h (5,600 mph),
releasing the kinetic energy equivalent of detonating approximately 2 tons of TNT.
Centaur impacted successfully on October 9, 2009.
Scientists thought that they would have seen some trace of
water coming out of the impact's ejected plume. The Shepherding Spacecraft descended through
Centaur's ejected plume, collected and relayed data. Contrary to media reports at the time,
neither the impact nor its dust cloud could be seen from Earth,
using the naked eye or telescopes. NASA was therefore sceptical about the presence
of water, but in the end, they confirmed traces of it in the data from spectrographic measurements,
which measure light absorbed at different wavelengths, revealing different compounds
of the Centaur stage crater and the two-part debris plume the impact created.
The signature of water was seen in both infrared and ultraviolet spectroscopic measurements.
Amazingly, they saw evidence for the water in two different instruments,
an infrared and an ultraviolet one. And that's what makes us really
confident in our findings right now. What might we learn from this impact?
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Gray thinks we will not observe the impact. This is what he writes on his blog:
“I know a fair bit about computing orbits, but not much more than the next guy about
which satellites orbiting the moon can do what. I do know that the Lunar Reconnaissance Orbiter
(LRO) and Chandrayaan-2 are in low orbits; the odds that they'll be overhead at the
right time are pretty lousy. So I don't expect them to see the actual impact”
However, if we can tell the LRO and/or Chandrayaan folks exactly where the crater is,
they'll eventually pass over that spot and be able to see a very fresh impact crater
and probably learn something about the geology - well better calling it
selenology - of that part of the moon. We know the mass of an empty Falcon 9 booster,
and that it will hit at 2.58 km/s; the known momentum and energy of the object making the
crater ought to help in calibrating the crater size versus the energy function.
This means that we could do real science,
starting from an unwanted collisional event. What a time to be alive!
"This video ends here! Thanks for watching everyone! What do you think about this
crazy collision event? Do you think we will observe it? Let us know in the comments below,
be sure to subscribe, and I'll see you next time on the channel!"
C