Author Topic: MCT Speculation and Discussion Thread 4  (Read 610921 times)

Online Lars-J

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Re: MCT Speculation and Discussion Thread 4
« Reply #2960 on: 09/28/2016 05:01 AM »
Might be fun for folks to go back and edit their prediction lists to show how they did (me? not that great)

I don't know if I ever made real "prediction checkbox list", but I have made several posts with the following predictions that came true:
 - spacecraft as integrated 2nd stage
 - biconic/side entry
 - powered by multiple raptors instead of a single one (although I was off on the count, I expected 5)
 - no launch abort capsule (abort the whole thing)

The booster was roughly what I expected, but bigger and lacking landing gear.

To be precise the BFS we were shown is cylindrical with a rounded nose and thick fins that look to hold the landing gear, not bi-conic which would involve the vehicle widening all the way down to the base, the fins can give a false sense that's whats happening but the cut-away is clear the central body is cylindrical.

That said both cylindrical and bi-conic were combined on the questionnaire and the entry profile is indeed horizontal which was the more important distinction.

Really, you of all people nitpicking me on the 'spaceship' predictions?  ;) Cylindrical is indeed what all my previously posted MCT drawings showed... Here are two old sketches of a side re-entering cylindrical MCT, pretty close in the end. (other than size, flipping the propellant and crew/cargo, and engine count)

Offline the_other_Doug

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Re: MCT Speculation and Discussion Thread 4
« Reply #2961 on: 09/28/2016 05:18 AM »
I think perhaps we will need a separate thread shortly on "Launching the ITS from LC-39A", but there is something that is a huge challenge to my understanding, here.

It sounded to me like Elon stated that LC-39A was going to be used to launch F9, FH and ITS.  Not that it would launch F9 and FH until ITS comes on line, and that the pad would then be converted for ITS launches.  No, what I heard Elon say is that all three would be able to launch out of LC-39A.

I understand how LC-39A (and SLC-4 at Vandenberg) can be configured for either Falcon 9 or Falcon Heavy launches; you have three flame holes in the launcher deck, with a set of hold-downs for FH center core/F9 and a set of hold-downs for the FH outer cores.  You just don't engage the outer hold-downs on an F9 flight, since there will be no outer cores over the outer flame holes.  The variations in servicing equipment between F9 and FH are managed within the TEL design for Vandenberg and KSC.

However, you need a much, MUCH larger flame hole for the ITS booster, and much, MUCH larger hold-downs.  The total mass of the ITS on the pad will be huge -- the hold-downs are not big in order to keep 28 million lbs of thrust from tearing them off, they are big in order to not snap at the forces of a 20-million-pound-plus rocket shifting as it lifts off.

Even assuming that ITS will somehow use the existing permanent tower for its servicing equipment (propellant feed lines, etc. -- the stuff the TEL does for the Falcons), will there somehow be an ITS-sized flame hole, launch mounts, hold-downs, etc., and then a "plug" containing the three Falcon flame holes, the Falcon launch mounts, etc., that will be plugged into the ITS flame hole when they wish to launch Falcons?  Or will each type of vehicle have its own "real estate" on the launcher, with the Falcon launch holes (and its hold-downs, etc.) on one side and the ITS launch hole (with all of its associated claptrap) on the other?

I'd have to think the launch pad would be out of commission for weeks, if not months, while converting from one launcher family to another, if a 400-square-meter (or more) slab of launcher deck, complete with launch mounts, hold-downs, electrical, data and fluid connections, etc., etc., has to be removed from the pad every time you need to literally "clear the deck" for a series of ITS launches.  By the same token, I wouldn't think the launcher deck is big enough to have flame holes, launch mounts, hold-downs, etc., for both vehicle families.

Is the talk of launching Falcons and ITS boosters from the same pad more of Elon's off-the-cuff, not-playing-it-out-in-his-head musings, or am I missing something?
« Last Edit: 09/28/2016 05:21 AM by the_other_Doug »
-Doug  (With my shield, not yet upon it)

Online Lars-J

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Re: MCT Speculation and Discussion Thread 4
« Reply #2962 on: 09/28/2016 05:32 AM »
This really belongs in the '39A' thread in the general SpaceX forum, but I see no major problem. FH fits well within the 12 m diameter 'hole' of a BFR launch/landing mount, so a launch mount could be temporarily mounted on top of a BFR launch mount. Plumbing would be an concern, but we should move talk of it to the proper forum.

Offline Impaler

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Re: MCT Speculation and Discussion Thread 4
« Reply #2963 on: 09/28/2016 06:02 AM »

Really, you of all people nitpicking me on the 'spaceship' predictions?  ;) Cylindrical is indeed what all my previously posted MCT drawings showed... Here are two old sketches of a side re-entering cylindrical MCT, pretty close in the end. (other than size, flipping the propellant and crew/cargo, and engine count)

I've seen some other posts claiming the presented vehicle was bi-conic and wanted to clarify, your perdition was indeed for a cylindrical vehicle which is why I though it odd that you wrote bi-conic and that you might have been misinformed by people throwing that word around.

Also I don't see why 'I' of all people should be considered an invalid source of nitpicking even in jest, I did correctly predict nearly everything about the booster in the face of a strong opposing consensus and while I was wrong about the 2nd stage everyone else was basing their prediction on rumors and L2 information that I don't have access too.  And I stick by my opinion that the massive BFS isn't workable and think the design as presented will go the way to the reusable F9 2nd stage.

Online Lars-J

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Re: MCT Speculation and Discussion Thread 4
« Reply #2964 on: 09/28/2016 06:17 AM »

Really, you of all people nitpicking me on the 'spaceship' predictions?  ;) Cylindrical is indeed what all my previously posted MCT drawings showed... Here are two old sketches of a side re-entering cylindrical MCT, pretty close in the end. (other than size, flipping the propellant and crew/cargo, and engine count)

I've seen some other posts claiming the presented vehicle was bi-conic and wanted to clarify, your perdition was indeed for a cylindrical vehicle which is why I though it odd that you wrote bi-conic and that you might have been misinformed by people throwing that word around.

Yes, I meant cylindrical. Although the three "fins" do alter the shape slightly, so I wonder if they have seen some aerodynamic benefit of stretching them so far forward.

Also I don't see why 'I' of all people should be considered an invalid source of nitpicking even in jest, I did correctly predict nearly everything about the booster in the face of a strong opposing consensus and while I was wrong about the 2nd stage everyone else was basing their prediction on rumors and L2 information that I don't have access too.  And I stick by my opinion that the massive BFS isn't workable and think the design as presented will go the way to the reusable F9 2nd stage.

Just to be clear, I'm not an L2 member either.

Offline meekGee

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Re: MCT Speculation and Discussion Thread 4
« Reply #2965 on: 09/28/2016 06:23 AM »
My one BFR speculation was dead on.  Helodriver predicts the future (again)   ;)



A good look at those enormous rainbirds in that photo. Assuming the yellow railing is 4' high, I get a quick-and dirty estimate of the rainbirds at 57'. :o That seems ridiculously big.

Could they be backed off from the rocket far enough that that actually makes sense? Or am I way off on the height?

Pure speculation - These are  oversized for an F9 family vehicle but are right sized for a larger follow on vehicle. 39A is the eventual BFR launch site.

Come on.  You couldn't even predict that you yourself will be at the Grand Mars Reveal.
ABCD - Always Be Counting Down

Offline GORDAP

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Re: MCT Speculation and Discussion Thread 4
« Reply #2966 on: 09/28/2016 11:52 AM »
Well my predictions were a real mixed bag.  Missed on the engine count (27 versus 42) and booster diameter (15 versus 12).  Also really thought BFS would still end up being 'capsule' shaped.

But 'mission profile' was as clean and simple as I'd thought it would be:  No LAS, orbital refueling, BFS goes from Earth orbit, direct entry and lands on Mars, then Mars takeoff and direct entry back at Earth.

Those who insisted (pretty strenuously as I recall) on additional stages, 'pusher stages' for LEO departure, aerocapture (at Mars or Earth), early transition to SEP, and especially Mars orbit refueling were pretty much out to lunch.

Offline jpo234

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Re: MCT Speculation and Discussion Thread 4
« Reply #2967 on: 09/28/2016 11:58 AM »
Those who insisted (pretty strenuously as I recall) on additional stages, 'pusher stages' for LEO departure, aerocapture (at Mars or Earth), early transition to SEP, and especially Mars orbit refueling were pretty much out to lunch.

The aerocapture is on the table (see slide 38 of the presentation):
Quote
From interplanetary space, the ship enters the atmosphere, either capturing into orbit or proceeding directly to landing
You want to be inspired by things. You want to wake up in the morning and think the future is going to be great. That's what being a spacefaring civilization is all about. It's about believing in the future and believing the future will be better than the past. And I can't think of anything more exciting than being out there among the stars.

Offline GORDAP

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Re: MCT Speculation and Discussion Thread 4
« Reply #2968 on: 09/28/2016 12:08 PM »
Those who insisted (pretty strenuously as I recall) on additional stages, 'pusher stages' for LEO departure, aerocapture (at Mars or Earth), early transition to SEP, and especially Mars orbit refueling were pretty much out to lunch.

The aerocapture is on the table (see slide 38 of the presentation):
Quote
From interplanetary space, the ship enters the atmosphere, either capturing into orbit or proceeding directly to landing

Ah, missed this.  Does anyone recall, did Musk's remarks indicate they're leaning one way or another on this?

Offline Helodriver

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Re: MCT Speculation and Discussion Thread 4
« Reply #2969 on: 09/28/2016 01:16 PM »
My one BFR speculation was dead on.  Helodriver predicts the future (again)   ;)



A good look at those enormous rainbirds in that photo. Assuming the yellow railing is 4' high, I get a quick-and dirty estimate of the rainbirds at 57'. :o That seems ridiculously big.

Could they be backed off from the rocket far enough that that actually makes sense? Or am I way off on the height?

Pure speculation - These are  oversized for an F9 family vehicle but are right sized for a larger follow on vehicle. 39A is the eventual BFR launch site.

Come on.  You couldn't even predict that you yourself will be at the Grand Mars Reveal.

Who says I revealed all my predictions in public? ;)

Offline hkultala

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Re: MCT Speculation and Discussion Thread 4
« Reply #2970 on: 09/28/2016 01:25 PM »
a few more teasers before the september reveal:

https://www.washingtonpost.com/news/the-switch/wp/2016/06/10/elon-musk-provides-new-details-on-his-mind-blowing-mission-to-mars/

1 red dragon in 2018, 'at least 2' in 2020, then first flight of MCT in 2022...
Bold mine.

From the article:

Quote
Then in 2022, Musk said he hoped to launch what the company now sometimes refers to as the Mars Colonial Transporter, designed to bring a colony to Mars.

I'm sorry, but this is nuts  somewhat optimistic. You all realize that 2022 is only six years away, right? Regardless of the fact that Dragon v2 hasn't flown yet

Dragon v2 has flown, though not yet to orbit.



Quote
, and regardless of the fact that FH hasn't flown yet; NOTHING concrete about BFR/MCT has even been released, and Musk is talking about launching one in six years. Six. Years.

.. and now after 3 months they have CAD models of their crafts and detailed information of the engine has been released. And it's still 5 years, 10 and half monts until the 2022 launch window.

Quote
Six years to get BFR off the ground, literally. To build a factory on the scale of Michoud (only bigger) for fabrication and assembly of BFR and MCT. To build a huge HIF to handle the 12.5m or 15m cores, or heck even to lease one of the VAB high bays and get it fitted out for BFR. To build all of the ground support infrastructure and ground transportation.

Bigger projects have bene done on shorter timeframe.

Quote
To get the entire Raptor engine (not just components) off of the drawing board and into the test stands and validated.

It's now 3 monts after your post and now an entire raptor engine has gone through it's first test.

Quote

Heck, you guys are still arguing over where the thing will be built and launched from. Do you think that would really be the case if they were going to be rolling off the assembly line in less than six years?


Guys in this forum were arguing but Elon did know that it's going to be launchd from LC-39A.

(lack of) public knowledge on forum is completely different thing than (lack of) detailed plans by Elon/SpaceX.

Offline philw1776

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Re: MCT Speculation and Discussion Thread 4
« Reply #2971 on: 09/28/2016 02:57 PM »
As requested, scoring my mostly way too small predictions. Comments BOLD

Approaching 30 days from what (we hope) is the big reveal, I thought it a good time to revisit and post revised BFR/MCT speculation before any info leaks out.  Trying to stay within the parameters of what Musk has said as I best understand.  A TSTO vehicle launched by a re-useable, single core BFR that puts the BFS a.k.a. the MCT into LEO where it is re-fueled, travels to and lands on Mars where it is again refueled for the journey back to Earth carrying a quarter of the outbound “cargo” mass.  The outbound cargo masses 100 tonnes which I assume means either cargo or people or a combination thereof.  BFS/MCT mass not included in the 100T.

Correct mission profile.  Most here with a few notable exceptions agreed with this, so no great insight.

Myriad unknowns led by the dry mass of the BFS.  Rocket equation dictates various mass assumptions here can produce wildly different answers.

My predictions, metric unless otherwise stated:
1.   Entire launch vehicle BFR+BFS masses under 5,000T.  Guestimate ~4,500T.
WAY off!
2.   BFS dry mass < 100T, my pick is 85T carbon composites BUT heavier than some predictions because ruggedized to allow for minimal maintenance.
WAY off
3.   BFR absolutely > 10m diameter to fit enough engines. Likely between 12.5 and 15m.  My guess 15m.  Allows addition of more engines in the future.
Another miss as I was confident of 12.5m or greater.  Not counting 17m flare outs on ITS craft.
4.   My guestimate BFR+BFS stack <100m height.  Certainly <125m.
Barely made my "certainly under 125m but missed on 15m.  Skinny rocket 12m increased height.
5.   Sticking with the “over 230T” Raptor thrust Elon mentioned, I get 25-27 engines.  My guestimate is 26 with “over 230T” as 235T in my spreadsheet.  Around 13.5 million Lbs force.
Engine # most likely wrong because…
I was right that I was wrong :)
6.   Predict that Raptor engine design goal thrust changed to higher than 230T previously stated, but only by several 10s of tonnes, not hundreds.
Hit! I was confident that more detailed design would increase Raptor SL thrust by several 10s of tonnes. 
It helped that Bezos BE-4 thrust was higher than Elon's earlier 230T for Raptor.  That shall not stand! :)

7.   BFS with 5 Rvac engines
Close but no cigar.
8.   RTLS minimizes cost, turnaround time, effort.  Changed my opinion from max payload ASDS for those reasons.  Just make the BFR bigger. Stages low and slow ~2.2 Km/sec.  “Easy” recovery & re-flight vs F9 GTO flights.
Hit!
9.   Initial BFR test flights likely equipped with less engines and less payload.
Unknown
10.   Large crew volume design >2,000m3.  Initial flights with less people & people space but more cargo space.
I believe crew volume is ~3,000 m3 so this is a hit.  Felt that nuclear sub range 20 something m3 was the goal. Never agreed with those in the 10m3 and under range.  You know who you are.
11.   Initial crewed Mars mission will carry 6-12 people.  10 is my latest #. Why?
NASA & other nations will buy seats. 
http://forum.nasaspaceflight.com/index.php?topic=40683.msg1557261#msg1557261
Unknown
12.   SEP still under development awaits later opposition cargo transits
Scoring as a miss in that not mentioned
13.   BFS will have “exotic” upper mounted engines for rough terrain Mars landing &takeoff (just echoing others’ analysis here)
Big miss.  I am concerned about SX's approach here.
14.   BFS will be a lifting body for EDL, but not a scaled up Dragon capsule shape.  It will look badass.
HIT!
You know we’re totally screwed trying to predict Musk because he already warned us,
“When it looks more like an alien dreadnought, that’s when you know you’ve won.”

I’ve attached a spreadsheet showing different assumptions, BFS mass, etc.

Anyone else want to update their speculations?
« Last Edit: 09/28/2016 03:00 PM by philw1776 »
“When it looks more like an alien dreadnought, that’s when you know you’ve won.”

Offline BSenna

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Re: MCT Speculation and Discussion Thread 4
« Reply #2972 on: 09/28/2016 03:04 PM »
The same specs from Life's Man and Space's mars rocket:
lift-off 10.000 t
LEO cargo 500 t

Arthur C Clarke always choose the numbers.

Offline philw1776

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Re: MCT Speculation and Discussion Thread 4
« Reply #2973 on: 09/28/2016 03:06 PM »
Additional predictions scoring BOLD

1) Overall Launch Architecture
     a)  MCT is composed simply of a BFR 1st stage and BFS 2nd stage/spacecraft
     b)  Boost phase consists of 2 stages, which put the BFS into orbit
     c)  Other: 3rd stage, 'half' stages, drop tanks, etc.

Going with (a)


Hit

2) Number of Raptor Engines on BFR (1st stage)

< 30, my best estimate is 25-27 if thrust stays close to 230 tonnes range

Miss

3) Diameter of BFR (1st stage)

Range 12.5m-15m, best estimate 15m 1st stage

Miss


4) Total Raptor 1st stage thrust (sl)

60 Meganewtons and T/W > 1.3

Miss

5) LAS Architecture
     a) No LAS - BFS is the escape mechanism
     b) Traditional LAS - above BFS and is nominally jettisoned during launch phase
     c) BFS contains smaller 'ejection pod' where humans reside during launch
     d) Other, non-traditional LAS design

Best guess is (a)

HIT!!!

6) Shape and Landing Mode of BFS
     a) Capsule (perhaps elongated), w/ TPS on base
     b) Cylindrical or biconic - horizontal landing
     c) Cylindrical or biconic - vertical landing
     d) Other

Going with (c), definitely no horizontal landing

HIT!!!

7) Mars and Earth return
    a) BFS does direct entry into Mars and Earth atmosphere
     b) BFS does orbital capture before performing entry burn and landing
     c) Same as b, but upon Earth return, stays in orbit for next synod

(a)

HIT

8)  Use of non-chemical thrust
     a) Not part of the plan
     b) Will use SEP for some/all of the big transits
     c) All chemical for now, but plans to incorporate SEP down the road

(c) strongly favor

a seems more correct

Can anyone think of more/better questions?

Predict Musk will miss 1st crewed landing by >= 3 synods
UNKNOWN but too easy
5-6 Rvacs on BFS stage 2
HIT sort of.  Missed on R SL engines.  frakked at self for not seeing that.

Raptor sea level will have 10s of tonnes thrust more than the 230 tonnes mentioned by Elon
HIT!!!
Entire BFR/BFS GLOW masses under 5.000 tonnes; my estimate ~4,500
BIG miss!
Height of BFR/BFS stack under 120m; my estimate <100m
MISS
Cargo version, tanker version, crewed version of BFS
HIT
1st crewed landing on Mars 8-12 humans planned
UNKNOWN
Just over 48 hours until Musk makes fools of us
Got that right!
“When it looks more like an alien dreadnought, that’s when you know you’ve won.”

Offline philw1776

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Re: MCT Speculation and Discussion Thread 4
« Reply #2974 on: 09/28/2016 03:09 PM »
everyone else was basing their prediction on rumors and L2 information that I don't have access too. 

Not so.  Not at all.
« Last Edit: 09/28/2016 03:10 PM by philw1776 »
“When it looks more like an alien dreadnought, that’s when you know you’ve won.”

Offline MikeAtkinson

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Re: MCT Speculation and Discussion Thread 4
« Reply #2975 on: 09/28/2016 05:36 PM »
Yes, I meant cylindrical. Although the three "fins" do alter the shape slightly, so I wonder if they have seen some aerodynamic benefit of stretching them so far forward.

Although I never came out and specifically said so, I've favoured what I called a "semi-lifting body", that is something that gets some lift from its body shape and maybe has small fins but is not a traditional lifting body shape.

It looks like the Ship qualifies as a semi-lifting body.

I was wrong on payload size, I thought a total mass in LEO Ship + payload of about 300 tonnes in expendable mode and about 240 tonnes with a reusable booster.

I guessed at about 140 tonnes dry mass for the Ship and about 90 tonnes for the Tanker variant, close but not a bulls-eye.

Basic mode of operation I got correct, pretty obvious from Elon's original comments I thought. Refuel in LEO, land it all on Mars, then refuel on Mars and do a direct return. I thought aero-capture into LEO was a possibility which would have saved a launch and needed reduced heat shield capability, this looks like it might be the case as the graph showing delta-v does not show landing fuel for the low payloads typical of return flights.

I never expected a LAS.

I underestimated the Tanker fuel load so expected 5-8 Tanker flights to refuel the Ship.

I've seen estimates of crew+cargo space are about 2,200 m3, although I haven't checked that yet. I estimated about 2,100 m3 which would be for crew, cargo or a mixture.

Being miss led by L2 info I upped the diameter from 10-12m to 15m, which meant that my estimates for height were out. I thought about 30 engines, so the larger take-off mass that 42 engines allows also meant that my height estimates were too low.

Musk has several times mentioned 100 tonnes to Mars so a max payload of 450 tonnes was a complete shock.

With full number of crew and full payload I expected a delta-v of 6.5km/s or a bit above, it seems that this is more like 6km/s, but the delta-v of the Ship with 100 tonnes cargo is about 7km/s. I expected the delta-v for return with 25 tonnes cargo to be 9km/s or a bit more, this seems about correct as long as no fuel is reserved for landing.

Like most people I slightly underestimated Raptor, thinking vac Raptor Isp of 380, and sea level Raptor Isp of 330 (SL) and 350 (vac) and a greater mass and size than it appears to be.

I completely missed having only the centre engines on the booster gimbal.

I also considered and discarded having centre SL Raptors on the Ship for landing, instead I thought that they would have mini-Raptors which would also serve for a methane equivalent F9. I never thought that having engines on the sides were a good idea, due to control-ability, cosine losses and vehicle strength issues. It does mean that prepared surfaces will have to be used on Mars after the first few landings.

Electric propulsion was not mentioned so is presumably not included in the architecture, I expected this as it is almost impossible to get SEL to work with short transit times.

Elon has talked about 10 cargo flights for each crew flight, but that was when the payload capacity was 100 tonnes, now it looks like 2-3 cargo flight per crew flight is more likely.

The launch costs were about what I expected for a mature heavily used system. Payload to Mars cost is much better than I expected due to the larger payload capacity. The per person cost to Mars (Musk said under $200,000
at one point) is lower than I expected. At that price both myself and my wife could easily go (about $500k from selling the house), but we would be too old by then.

The optimistic timeline was much as I expected, as is the current number of people working on it. They will almost certainly slip, but the successful Raptor firing and full size Lox tank are indications that the program is so far going well.

The beyond Mars bit was a surprise. Instead I expected to hear about the Moon, LEO's and cis-lunar space which are better prospects for near term revenue and are much easier as well. Nothing was said about Mars' moons either.

The bit about sub-orbital transport I found strange - yes theoretically possible, but immense difficulties in making the system work.

Using the Tanker as a SSTO was also a surprise, payload would be reasonable, but in $/kg would be beaten by the Booster+Ship combination.

I also expected to hear more about Mars surface elements, possibly as a request for others to supply them.


Offline BSenna

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Re: MCT Speculation and Discussion Thread 4
« Reply #2976 on: 09/28/2016 06:21 PM »
Quote
Although I never came out and specifically said so, I've favoured what I called a "semi-lifting body", that is something that gets some lift from its body shape and maybe has small fins but is not a traditional lifting body shape.

It looks like the Ship qualifies as a semi-lifting body.

The shape of the vehicle is related to development, weight and manufacturing costs. I think the actual design is strongly considering this, this bullet looks easier and cheaper to build than a real lifting body.

Other important factors that relate to SpaceX's philosophy are the scaleable design and simplicity - to reduce the number of moving parts and phases of operation to a minimum.

If they show something that looks like a rocket in ten years they will have Deep Space Industries, Google and Facebook's money. Little after, Japan, Europe and tourists paying US$10 million per person for a week in the  moon, just name the first BFS Hilton.
« Last Edit: 09/28/2016 06:23 PM by BSenna »

Offline Burninate

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Re: MCT Speculation and Discussion Thread 4
« Reply #2977 on: 09/28/2016 06:53 PM »

I underestimated the Tanker fuel load so expected 5-8 Tanker flights to refuel the Ship.


Even if dry mass has gone to zero with magical carbon negafiber and infinite TWR - 300 tons of payload can only be accelerated through 2596m/s dV by 300 tons of propellant at 382s.  You're going to require more like 6-10km/s dV for the first half of the mission described.

The video was notional, and chose not to show repetition.
« Last Edit: 09/28/2016 06:54 PM by Burninate »

Offline BSenna

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Re: MCT Speculation and Discussion Thread 4
« Reply #2978 on: 09/28/2016 07:48 PM »
Hummm...

Online Chris Bergin

Re: MCT Speculation and Discussion Thread 4
« Reply #2979 on: 09/28/2016 09:25 PM »
Farewell MCT, hello ITS:

Locked.

Several threads to choose from - Menu:
http://forum.nasaspaceflight.com/index.php?board=72.0

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