Author Topic: Purdue evaluation of ITS proposal  (Read 2362 times)

Offline Dalhousie

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Purdue evaluation of ITS proposal
« on: 04/24/2017 04:41 AM »
A multi-student term project from Purdue University evaluating the SpaceX ITS proposal


This report represents the culmination of an intensive spacecraft design course, AAE 450/EAPS 391, undertaken by seniors during a single semester. The students perform a feasibility study for a specified mission goal, subject to certain constraints. The entire class works as a single team to achieve this goal. They elect a Project Manager and an Assistant Project Manager and organize into specialized groups to study (in this case) CAD (Computer Aided Design) communication and control, human factors, mission design, power and thermal control, propulsion, science, and structures....

In particular, Project Destiny is taking the challenge of Elon Musk—to put one million colonists on Mars within the next hundred years at the cost of $200,000 per colonist—and calculating the numbers....  The ultimate question
that must be answered is: is the Elon Musk plan feasible?


https://engineering.purdue.edu/AAECourses/aae450/2017/spring/docs/AAE%20450-Project%20Destiny.pdf
« Last Edit: 04/24/2017 10:41 PM by Dalhousie »
"There is nobody who is a bigger fan of sending robots to Mars than me... But I believe firmly that the best, the most comprehensive, the most successful exploration will be done by humans" Steve Squyres

Offline rpapo

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Re: Purdue evaluation of ITS proposal
« Reply #1 on: 04/24/2017 10:16 AM »
330 pages!  A lot of "light reading" there...

Nit: the Raptor engine is not a raptor.  Proper noun, not common noun.
« Last Edit: 04/24/2017 10:28 AM by rpapo »
An Apollo fanboy . . . fifty years ago.

Offline Norm38

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Re: Purdue evaluation of ITS proposal
« Reply #2 on: 04/27/2017 04:45 PM »
Quote
2.2 Critical Assumptions
Using these requirements, we needed to apply a set of simplifying assumptions for the entire
mission:
SpaceX ITS architecture is valid: Our feasibility study is not to test whether or not SpaceX can
build their vehicles, but whether or not vehicles with the provided specifications can develop a
million inhabitant colony on Mars surface. As such, we assume the numbers for vehicle
performance, lifetime, and scale are 100% accurate.

So they did bound the scope quite a bit.  They're not evaluating the ITS hardware itself, so much as evaluating the ITS requirements against the colonization goal.

Offline Ludus

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Re: Purdue evaluation of ITS proposal
« Reply #3 on: 04/27/2017 08:58 PM »
A well done class project that explores a lot of aspects of ITS SpaceX hasn't commented on. It includes a lot of work on Cargo variants of the BFS with both a payload faring for large objects like hab modules and a shuttle orbiter like cargo bay version that's piloted with a arm to engage in assembly.

Offline Norm38

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Re: Purdue evaluation of ITS proposal
« Reply #4 on: 04/28/2017 12:19 AM »
I have to admit, that Shuttle version with the docking port in the nose is real sexy.
However, I'm betting for a version like that that just goes to LEO and back, methane fuel cells running on boil off trade better than solar cells (and their batteries).
« Last Edit: 04/28/2017 02:38 AM by Norm38 »

Offline Norm38

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Re: Purdue evaluation of ITS proposal
« Reply #5 on: 04/28/2017 05:58 PM »
This part here doesn't make much sense to me.  Am I missing something or is this fantasy?

Quote
5.2.2 Deployment and use of system
In order to construct the Bigelow Cycler, a significant number of components need to be
transferred from Earth to LEO. Using the ITS-C2, this would require 4 launches minimum just to
get all the needed components for construction into LEO. To avoid the tracking of multiple cycler
elements with individual cycler component launches, we develop a single payload fairing structure
that is launched aboard the first stage booster of the ITS and capable of carrying all of the Bigelow
Cycler’s components. Please see Fig. 5.2.1.4.1 for a sectioned view and side-on view of the
Bigelow Cycler Component Stack in the payload fairing.
The payload fairing itself is approximately 1.33 times the size of the ITS. However, the
first stage is able to launch our payload fairing to Low Earth Orbit (LEO) because it weighs less
than the ITS since it does not have any propellant mass. Once the payload fairing reaches LEO, it
detaches from the booster, separates, and releases the Bigelow Cycler Component Stack seen
above. The first stage booster returns to Earth shortly after launch, where it is loaded with an ITSA,
the construction variant of the ITS. Once the ITS-A is launched and separates from the first
stage booster, it performs a rendezvous with the Bigelow Cycler Component Stack that is orbiting
in LEO.

Offline Jarnis

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Re: Purdue evaluation of ITS proposal
« Reply #6 on: 04/28/2017 07:14 PM »
You are missing the second stage. PLF on top of ITS first stage booster gets your payload to a suborbital trajectory, followed by a splash.
« Last Edit: 04/28/2017 07:15 PM by Jarnis »

Offline Norm38

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Re: Purdue evaluation of ITS proposal
« Reply #7 on: 04/28/2017 07:28 PM »
Yeah, but what second stage?  The ITS is the 1st stage booster and the 2nd stage ship.  If they replace the ship with a giant PLF, are they inventing a new second stage to push it?
I think the kids skipped a few details there.

Offline envy887

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Re: Purdue evaluation of ITS proposal
« Reply #8 on: 04/28/2017 07:34 PM »
You are missing the second stage. PLF on top of ITS first stage booster gets your payload to a suborbital trajectory, followed by a splash.

The ITS booster could indeed act as an SSTO, and bring a large fraction of it's own mass to orbit. I get 190 tonnes as payload to a low 28 degree circular orbit. However, it will never "return to Earth shortly after launch", at least not in one piece and certainly not in any shape to boost another ship to orbit.

It would make for a huge wet lab on orbit though, with 7,000 m^3 of tank volume they could build a whole colony in there. :D

Offline Ludus

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Re: Purdue evaluation of ITS proposal
« Reply #9 on: 04/29/2017 02:24 AM »
This part here doesn't make much sense to me.  Am I missing something or is this fantasy?

Quote
5.2.2 Deployment and use of system
In order to construct the Bigelow Cycler, a significant number of components need to be
transferred from Earth to LEO. Using the ITS-C2, this would require 4 launches minimum just to
get all the needed components for construction into LEO. To avoid the tracking of multiple cycler
elements with individual cycler component launches, we develop a single payload fairing structure
that is launched aboard the first stage booster of the ITS and capable of carrying all of the Bigelow
Cycler’s components. Please see Fig. 5.2.1.4.1 for a sectioned view and side-on view of the
Bigelow Cycler Component Stack in the payload fairing.
The payload fairing itself is approximately 1.33 times the size of the ITS. However, the
first stage is able to launch our payload fairing to Low Earth Orbit (LEO) because it weighs less
than the ITS since it does not have any propellant mass. Once the payload fairing reaches LEO, it
detaches from the booster, separates, and releases the Bigelow Cycler Component Stack seen
above. The first stage booster returns to Earth shortly after launch, where it is loaded with an ITSA,
the construction variant of the ITS. Once the ITS-A is launched and separates from the first
stage booster, it performs a rendezvous with the Bigelow Cycler Component Stack that is orbiting
in LEO.

It seems to be a serious upper level undergrad engineering course so I've gotta assume they did it the math right based on SpaceX specs about the BFR performance. I'd have preferred they were explicit about it because it doesn't intuitively make sense to me either that the BFR Booster can throw this much mass into NEO without any second stage and without entering orbit itself (which it's not designed to do recoverably).

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