SpaceX’s Dragon
“There needs to be an intersection of the set of people who wish to go, and the set
of people who can afford to go.
And that intersection of sets has to be enough to establish
a self-sustaining civilisation.
My rough guess is that for a half-million dollars,
there are enough people that could afford to go and would want to go.
But it’s not going to be a vacation jaunt.
It’s going to be saving up all your money and selling all
your stuff, like when people moved to the early American colonies.”
These are the words of Elon Musk in an interview with Aon Magazine, as he was talking about
Mars Colonization.
In September 2014, NASA announced SpaceX had been awarded a US$2.6 billion Commercial Crew
Transportation Capability (CCtCap) contract for the development of
spacecraft to transport astronauts to the ISS, with a start date of 2017.
For SpaceX, that spacecraft is Dragon.
In 2015, Musk was gearing up to put humans in space, which brought him one step closer
to his ultimate goal: Mars.
It’s an amazing trajectory considering that, less than 15 years previously, Musk had been
on the verge of bankruptcy and the first three Falcon 1 launches had failed.
Aerospace hacks had sharpened their pens and written him off, yet he has been preparing
for humanity’s best shot of getting us to Mars.
Curious to know about Dragon’s design, development and how it’s related to Mars colonization?
KEEP WATCHING!!
The Birth of Space Race:
As early as 1948, von Braun was calculating how to get to Mars and, when he wasn’t busy
working out how to get humans to the Red Planet, he championed the idea of spaceflight,
but the Americans weren’t interested.
Undeterred, von Braun continued his work on a mission
to Mars, the outcome of which was presented on a Walt Disney show to an audience
of 42 million viewers.
Like Musk , von Braun dreamed big.
His Mars mission would send 70 astronauts on 10 spacecraft, with each
vehicle weighing 3,720 tonnes!
Thinking way ahead of his time (this was the 1950s), von
Braun also envisaged a fully reusable launch vehicle that would deliver 25 tonnes of cargo
and 14.5 tonnes of fuel to LEO.
Von Braun’s Project Mars never got off the ground.
In 1957, Sputnik caught the attention of the US and
von Braun was tasked with developing a plan to land Americans on the Moon.
After outlining his proposal for landing men on the Moon,
the Americans were all ears, and so the Space Race was born.
As the creator of the Saturn V, von Braun was the first true visionary
of the American space program.
It was von Braun’s creative genius that propelled the US
to the Moon: without him, there is a good chance Kennedy’s dream of reaching the Moon
before the end of 1969 would have withered and died.
Now we have another visionary in the shape of Elon Musk . Musk has succeeded because
he didn’t wait for the government to deliver the perfect program – he started with the
tools at hand and moved forward.
Aggressively.
One of Musk’s greatest qualities is his extraordinary
ability to believe in his own vision to such an extent that he doesn’t really think that
what he's trying to do is particularly risky.
What he’s trying to do is nothing less than open up an interplanetary era.
It’s real Tony Stark stuff.
And part of the reason he will succeed is because he is willing to take risks.
In the juggernaut industry that is the aerospace world, there is an extraordinary aversion
to risk.
Even when better technology is available, aerospace companies still prefer to use legacy
components, some of which were designed way back in the 1960s.
Take Orbital Sciences as an example.
This company, like SpaceX, has a contract to ferry cargo to the ISS, but their Antares
launcher uses Russian rocket engines (the AJ-26) from the 1960s.
On 28 October 2014, Orbital Sciences suffered a
launch failure, and the finger of suspicion was pointed at that Russian rocket engine.
So what did Orbital Sciences do?
They contracted with the Russians to buy another rocket
engine (the RD-181) – 60 of them, at a cost of US$1 billion!
SpaceX doesn’t go down this road of outsourcing: no subcontracting
or sub-subcontracting for this company, which means their costs are streamlined and
rocket launches have been brought down by a factor of 10.
Designing Dragon:
The business of designing Dragon started at the tail end of 2004.
At the time, SpaceX had decided it would pursue development of the
capsule with its own funds, but that changed in
2005 when NASA announced its Commercial Orbital Transportation Services (COTS) development
program and advertised that it was soliciting proposals for a commercial cargo vehicle which
would replace the Shuttle.
SpaceX submitted Dragon as its proposal in March
2006.
Six months later, NASA awarded SpaceX funding to develop a cargo service to the
International Space Station (ISS), the plan being to fund three demonstration flights
that would be flown between 2008 and 2010.
For this task, SpaceX was awarded US$278 million, provided they met all of NASA’s milestones.
Because Dragon’s primary role was to ferry crews to and from ISS, the capsule didn’t
need to be as roomy as NASA’s five meter- diameter Orion, in contrast, the gum-drop-
shaped Dragon measured just 3.6 meters across.
Visually, the vehicle bears more than a striking resemblance to the Apollo and Orion capsules,
and it sports many of the same features.
The Orion , Dragon, and Apollo spacecraft, each has almost an identical blunt-cone capsule
shape.
In the case of Dragon, a nose-cone cap jettisons after launch and the trunk is equipped with
two solar arrays.
Its heat shield is a proprietary variant of NASA ’s phenolic impregnated carbon ablator
(PICA) material.
The main goal of Dragon is to ferry crew and cargo to and from the ISS and to accomplish
this safely means a really tough and really reliable heat shield is needed.It also helps
the business case if the heat shield can be reused after each flight – remember the
palaver following each Shuttle flight when technicians had to check all those tiles?
This is part of the reason that SpaceX chose an ablator for its Dragon (another reason
is there aren’t many thermal protection systems (TPS) to choose from: if you’re
in the business of designing and building spacecraft,
you can either choose the Shuttle’s TPS or an ablation-based TPS).
Thanks to successes of such high-profile missions as NASA’s
Mars Science Laboratory (MSL), ablative has been the way to go in recent years, but what
is it about ablation that makes it so attractive?
I will answer that, but first you need to know what the term “ablation” means, this
is simply the decay of the spacecraft’s outer layer of
skin caused by the tremendous heating due to re-entry speeds.
This decay occurs due to convection, which in turn is caused by a pyrolyzing
layer that diffuses in the direction of the heated area of the shield.
Here, a boundary layer is created by the pressure of re-entry
and it is this layer that ensures the heat is redirected away from the shield.
What is left is char – basic but effective, and safer than
the Shuttle’s TPS.
While the Shuttle’s TPS was very effective, the one time it failed caused the destruction
of the vehicle and the death of seven crew.
And 1 out of 134 is just not good enough for commercial spaceflight, or any manned spaceflight
endeavor for that matter.
Not only that, but maintaining the Shuttle’s TPS was time-consuming in the extreme, since
each – there were 20,548 high-temperature reusable surface insulation (HRSI) tiles alone
– had to be checked prior to each flight.
So ablative was the default option, but why PICA?
There are a number of reasons.
First, using an ablative system is efficient, because having engineers spending weeks and
weeks checking thousands and thousands of tiles is extremely time consuming.
Secondly, ablatives ensure faster re-entries, because PICA can withstand very high temperatures
– five times higher temperatures (2,760°C) than the Shuttle’s tiles.
And thirdly, ablative systems ensure ease of production.
Yet another attractive feature of PICA is that the material is very, very light – only
slightly heavier than balsa wood!
And for those of you who keep an eye on space records, you will know that PICA has enabled
the fastest re-entry – 12.9 kilometers per second – ever, when NASA ’s Stardust capsule
re-entered Earth’s atmosphere in January 2006.
Despite all these advantages, there was one problem that SpaceX faced when opting to use
PICA as Dragon’s heat shield: cost.
SpaceX wasn’t prepared to pay the price that ARA Ablatives was charging, so SpaceX
being SpaceX, the company decided to build their own heat shield.
The only problem with this approach was that SpaceX didn’t have the very specialized
facilities required to design and test a heat shield, which is why the company turned
to NASA for help.
And that is how PICA-X was developed.
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Dragon’s Name
So far, we’ve talked about the heat shield.
Now let’s get back to the rest of the development and
design but, before we do, some may be wondering how Dragon got its name.
Well, like all of SpaceX’s hardware, there is a story behind
this.
Dragon was named after the creature in the Peter, Paul and Mary song “Puff the
Magic Dragon” for the simple reason that, when
Musk began his space venture, there were many who pronounced his goals beyond reach.
Incidentally, in case you’re wondering, SpaceX’s Falcon rocket was named after the
Millennium Falcon as piloted by Han Solo in the Star Wars series.
This tradition of having cool names for its rockets is in marked contrast
with NASA , which never seems to get much beyond an acronym.
Even the Orion used to be referred to as the Multi-Purpose
Crew Vehicle (MPCV).
And the Space Station?
Well, that’s still known as the ISS.
You would have thought that, after spending US$100
billion building the thing, the orbiting outpost would have deserved a more catchy
name, but that’s the government for you.
Moving on to the reaction control system (RCS), which Dragon needs to maneuver in orbit and
during re-entry.
Dragon’s RCS comprises 12–18 Draco thrusters, which, like just about everything in the SpaceX
inventory, were developed in-house.
Each engine, which is fueled by nitrogen tetroxide as oxidizer and monomethyl-hydrazine, produces
400 newtons of thrust.
Once in orbit, Dragon uses these thrusters to perform elaborate and precise attitude
control and rendezvous maneuvers when approaching and departing the ISS.
And, to ensure those maneuvers are precise, Dragon is fitted with all the necessary navigation
equipment: inertial measurement units (IMUs), GPS, iridium recovery beacons, and star trackers.
As Dragon makes its approach to the ISS, it adjusts its attitude using the IMUs and star
trackers, which enable an accuracy of 0.004° for attitude determination and 0.012° for
attitude control on each axis.
Additionally, while Dragon is in orbit, it must regulate temperatures inside the capsule.
Temperature control must also be very precise, because some of the cargo bound for the
ISS includes biological material and life sciences experiments.
To achieve the necessary temperature regulation, Dragon sports two
pumped fluid cooling loops and radiators mounted to the trunk’s structure.
Internally, air is circulated by fans, while sensors ensure
temperature is maintained within ±1°C. Depending on the type of cargo, temperature can
be adjusted between 10 and 46°C, while humidity can be regulated within 25–75% relative
humidity.
Dragon is pressurized up to 14.9 pounds per square inch and the pressure
can be actively controlled.
Another very important feature while performing those rendezvous maneuvers is
communication and telemetry.
While Dragon can communicate using NASA ’s Tracking
and Data Relay Satellite (TDRS) system, it can also communicate via ground stations.
Since ferrying cargo to and from the ISS is Dragon’s primary role, its payload capacity
is obviously especially important.The pressurized volume of Dragon is 10 cubic meters, but that’s
just the capsule.
Another 14 cubic meters of volume are available for external payloads.
This volume is found in the trunk, which is beneath the capsule.
And, if more cargo needs to be flown, SpaceX has a trunk adapter which increases volume
to 34 cubic meters.
Dragon’s power is provided by two solar arrays that produce up to 2,000 watts and
a peak of up to 4,000 watts.
The arrays are deployed following insertion into orbit and are jettisoned prior to re-entry:
for ascent to orbit and re-entry, Dragon relies on four lithium-polymer batteries.
Other elements of Dragon’s electrical system are two power buses that provide 120 volts
of direct current (VDC) and 28 VDC.
Once Dragon has performed all its necessary maneuvers and has been cleared for final approach
to the ISS, it needs to make use of its sensors and docking mechanism, which can be either
the integral common berthing mechanism (CBM) or the low-impact docking system (LIDS).
Dragon can perform a lifting re-entry to target its ocean landing, which is gentle thanks
to dual drogue parachutes that slow and stabilize the craft before three main parachutes deploy.
The parachute system is fully redundant.
Following splashdown, GPS, and iridium locator beacons can be used to locate the vehicle
if necessary.
Recovery is performed via ship and the capsule enters its refurbishment processing.
The crew dragon docked with the international space station on March 3, 2019, at 3:02 a.m
PST, becoming the first American spacecraft to autonomously dock with the orbiting laboratory.
Red Dragon:
Red Dragon is a variant of the Dragon vehicle that NASA is considering sending to the Red
Planet as part of a sample return mission slated for 2022.
The mission, which would also serve as a precursor to an eventual manned
mission to Mars , has been on the drawing board
of NASA’s Ames Research Center (ARC) for a while.
One of ARC’s goals has been to drill into the Martian subsurface to search for
life.
In 2010, a researcher at Ames reckoned a modified version of Dragon V2 could probably
do the job of landing on Mars and performing the drilling mission.
After a few years studying the Red Dragon concept, the Ames scientists agreed such a
vehicle could execute a propulsive entry, descent, and landing ( EDL ), land two tonnes
of useful payload, and possibly enable a sample return mission.
Thanks for Watching Everyone!
Do you think we can colonize Mars one day?
Do you think that Red Dragon will be ready by 2020?
Did you learn anything new in this video?
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