Author Topic: MCT Speculation and Discussion Thread 4  (Read 626331 times)

Offline nadreck

Re: MCT Speculation and Discussion Thread 4
« Reply #540 on: 09/03/2015 10:35 PM »
Note I don't think they will do any intermediate steps between FH and BFR, however, if they did (and note at one time they definitely were planning to) this is how I think it would go ( while you read this):

So after they have the FH working with the two side cores doing RTLS and the centre core being recovered down range by an ASDS, they develop an alternate 2nd stage with about 2.2 times the current tank volume, probably a 5 meter diameter, and that stage runs with a single Raptor Vac. It masses about 200t.  This would be the workhorse to iron out the design of a Methalox space stage that can re-enter and be reused. As such it might never fly in a configuration that outperformed (in total payload to LEO, GTO, GSO etc) the current FH flight profiles, but while the upper stage would cost a lot more than the existing Falcon upper stage, the goal would be for it to be reusable. It might well drop the price per kilo to orbit somewhat but probably not enough to justify it on its own, but that would not be the main motivation. This stage would allow work on propellant depot/transfer, high energy methalox stage re-entry, and possibly be a working step towards an intermediate man rated vehicle capable of lofting more than 7 but much less than 100 passengers.

Now if you go to that amount of work to build the 5M diameter upper stage running methalox, why not make an intermediate step towards a BFR that is more or less a 5M diameter first stage with the same fineness ratio of an F9 so 5M diameter 70M high first stage with about 2.5x the mass of fuel as the existing first stage and an upper stage that is about twice the mass of the current upper stage so: 1500t take off weight 9 Raptors. This would be destined to become the workhorse to LEO with the new, reusable upper stage that was developed first.

Then what if you did the three, four or five core versions of this? That gets you to BFR size booster. Finally you go with a 10m upper stage replacement, that would be your MCT (and tanker).

This is of course not how things will evolve


Well, many reasons why I believe there will be an incremental approach.
1. SpaceX always did an incremental approach. The didnt start with Falcon 9 1.1 when they developed their first rocket. Same holds true for the BFR. They need to learn to manufacture, launch, etc. such big rockets and thats easier if they dont jump into it with both feat.

And it was also the original path they offered us a few years ago, but have adamantly changed that and insisted it was a straight to BFR in the last 2 years or so.

2. There is a business case. They can probably much more cheaply launch large constellations of satellites. Like one or more of the internet constellations. Maybe even modules of a new space station. Maybe even a commercial space station, serviced by Dragon2 for space tourists.

I don't see a business case that couldn't be met with FH until the BFR is there. Since there is no customer today asking for even 50t to LEO that the FH can do, making a 70 to LEO intermediate step does not show any business case. HOWEVER, whether they create a 70t to LEO NFR or 120t to LEO BFR next, once in place it may develop its own new market.

3. All the key technologies for BFR+MCT can be tested on a smaller rocket with a smaller MCT precursor. That includes:
Sure they can, but they can also be tested with an FH - at most making a new methalox upper stage.

* landing on Mars
Avionics, precursor aerodynamics of shape if not total mass, autonomous operation can all be tested with FH and dragon derived spacecraft.

* large scale energy production on Mars
No this won't happen until enough people get there (>1MW) to layout and maintain solar farm, while it could be done with automated craft, it is no more difficult to get to this level from several 13,000kg craft than several 25,000kg craft)
* water production on Mars
* methane/oxygen production on Mars
as above
* landing, retanking and MCT (precursor) return to Earth
Probably not retanking, though it isn't impossible, just seems too cumbersome, but certainly a 13,000kg lander can have a sample return as part of it (or several can put samples in Mars orbit to be collected by a single return craft that was the SEP testbed).
* flight operations and trajectory execution
* communications
* high bandwidth, high latency internet access on Mars
Already done with the above steps, I expect one of the first SpaceX payloads to Mars from a single FH launch will be the local network for Mars with low latency 150kg satellites in a constellation with one or two larger high latency Earth link satellites. This network needs to be in place to facilitate the automated precursor flights including the first few MCT's.
* booster launch and recovery (using Raptor)
plenty of time to do this to launch and fuel the first MCT. That is 8 flights right there. I am betting on 4 MCT's being launched in the two synods before the first manned flight

* second stage recovery (if any)
As above, but if we made an alternate FH upper stage that was raptor powered maybe it would make sense to work out the major kinks. Note that going from an intermediate MCT re-entering to a full sized one is probably as big a step of development as going from Dragon 2 to the intermediate. Certainly it is not just scaling and will not require significantly less expense because you went through an intermediate step that cost you more than half as much as the last step. I am even afraid that MCT and tanker version upper stages might have enough differences to involve considerable unique costs.

* re-tanking in LEO
This could justify some work on a reusable FH upper stage right there. I think it needs to be done. However, it really can be done with just the planned FH.

* first human on Mars and survivability
* first habitat on Mars

As I mentioned above I think we will see several MCT's sent to Mars once FH based survey efforts have short listed the first settlement sites. The way to start with human presence is permanent, not spend nearly as much on flags and foot prints only to go back with something that costs only a little more to establish a settlement.

IF you are going to do the BFR/MCT and that is your plan for colonization, then that needs to be where you start sending people, not waste nearly as much as the human components for that would cost developing the human components for the intermediate sized vehicles.

* first plant growth on Mars using Mars soil
* first sustainable food growth on Mars


I think that can be done and tested with autonomous 13,000kg landers.

And that are just the biggies. All this needs to be ready for colonization. And all this is easier with a smaller version of BFR/MCT than the ultimate goal noted by Musk.
Once these technologies are in place and tested and ready, a full size MCT makes sense. I would not be surprised that after the logistical hassles are overcome with the first missions, a bigger version of MCT are produced, one that is closer or even capable of 100 humans to Mars. Even though this particular capability would not be used.
4. I dont think that SpaceX will have the funds to do it alone. They will need the help of governments, NASA might not even be enough. When in cooperation with space agencies, pork needs to be provided. That is far easier with a precursor MCTs that focus on technology development and science rather than direct colonization of a naked planet.

While I would suggest that it could be done step wise with an intermediate vehicle, that vehicle would need to have a business case like the F9/FH does right now. If it does not (and it does not right now) then it makes more sense to spend the money once going straight to your Mars vehicles which are as likely to find an alternate business case as the intermediate step vehicle would.
It is all well and good to quote those things that made it past your confirmation bias that other people wrote, but this is a discussion board damnit! Let us know what you think! And why!

Offline Impaler

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Re: MCT Speculation and Discussion Thread 4
« Reply #541 on: 09/04/2015 02:03 AM »
I've done a mass breakdown of my proposed MCT vehicle.

Thermal Protection Airoshell:  5 to 10 kg/m^2 metallic fully reusable, 650 m^2                    5 Mt

Tanks and plumbing:  5% of 300 Mt propellant load                                                            15 Mt

Landing Gear:    10% of landed mass based on F9-R ratio with F9 expendable                   18 Mt

Raptor Engines:    1.5 Mt each based on 150:1 T/W ratio and 2300 KN force x4                   6 Mt

Vernier Engines:    Hover 175 Mt on Mars with 100:1 T/W ratio                                             1 Mt

Miscellaneous:    Transit solar panels, thermal radiators, avionics, cargo handling                5 Mt

Structural Frame:      11% of Entry mass, carbon-fiber skeleton                                           25 Mt

Total  Dry Mass                                                                                                                      75 Mt

Cargo                                                                                                                                   100 Mt

Landing Propellant:   Provide 800 m/s Terminal decent DeltaV                                              40 Mt

Total Entry mass                                                                                                                  215 Mt

Offline guckyfan

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Re: MCT Speculation and Discussion Thread 4
« Reply #542 on: 09/04/2015 05:48 AM »
Needed space per Astronaut. NASA calculates 10m per person as small. Well, 40m for 4 Astronauts is small. But there is economy of scale. 1000m for 100 people is not small IMO.

SpaceX did do evolutionary steps from Falcon 1 and Merlin 1A up to the full thrust version of Merlin 1D and Falcon 9 1.2. That was part of a necessary learning curve. I strongly doubt that there will be a Raptor 1A. It may evolve from a Raptor 1D to a Raptor 1D full thrust and initial payload may go up from 70t to 100t over time. But I don't see them to repeat the whole learning curve on BFR/MCT and Raptor.

I can see them launching BFR from LC-39A with not all Raptor firing or even installed because they can do a lot of testing that way before they need their own full capacity launch pad. But it would be the full BFR/MCT design. They don't have the money and time to do it in smaller steps.

Offline Burninate

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Re: MCT Speculation and Discussion Thread 4
« Reply #543 on: 09/04/2015 06:12 AM »
I've done a mass breakdown of my proposed MCT vehicle.

Thermal Protection Airoshell:  5 to 10 kg/m^2 metallic fully reusable, 650 m^2                    5 Mt

Tanks and plumbing:  5% of 300 Mt propellant load                                                            15 Mt

Landing Gear:    10% of landed mass based on F9-R ratio with F9 expendable                   18 Mt

Raptor Engines:    1.5 Mt each based on 150:1 T/W ratio and 2300 KN force x4                   6 Mt

Vernier Engines:    Hover 175 Mt on Mars with 100:1 T/W ratio                                             1 Mt

Miscellaneous:    Transit solar panels, thermal radiators, avionics, cargo handling                5 Mt

Structural Frame:      11% of Entry mass, carbon-fiber skeleton                                           25 Mt

Total  Dry Mass                                                                                                                      75 Mt

Cargo                                                                                                                                   100 Mt

Landing Propellant:   Provide 800 m/s Terminal decent DeltaV                                              40 Mt

Total Entry mass                                                                                                                  215 Mt

Here's a fully fueled 180mT MCT outbound from LEO (100mT cargo) compared with the launch back from Mars' surface with "only" 25 mT cargo

MCT Dry Wt & Cargo   180   mT
S2 Mass w/MCT   1025   mT  LEO departure.  Mars Return is 75 mT less
S2 Mass w/MCT   2.3   Million LBS
Stage 2 Km/sec    6.48   Km/sec Rocket Equation  LEO
S2 Mars Return 25mT Cargo  8.5Km/sec Rocket Equation

Exponentials help when you reduce the mass.  Just refuel with less propellant to reduce "excess" Km/sec.
The technical challenge is a lightweight MCT vehicle able to withstand Earth re-entry if that is the goal rather than return to some high Earth/moon orbit.

We have a cap of 180-210T on the permanently attached components of the MCT, due to initial Earth launch considerations, what Gwynne Shotwell said about the launch vehicle they were designing.

A BA-2100 should be approximately the right size for 100 people in terms of pressurized volume, and is supposed to weigh 70-100T at launch without consumables or non-essential internal outfitting.  That's a vacuum-only design.  Skylab managed only 1/7th that pressurized volume by using a dry lab, at 77 tons, plus some functions fielded out to the visiting Apollo CSM.

It's hard to extrapolate, but based on that I wouldn't expect a structural aluminum hab with 2000-2500m3 pressurized volume and long-run ECLSS, with thermal isolation from the fuel tanks and heat shields all around, to be below 100 tons, before any 'useful cargo', ISRU gear, surface deployables, rocket stage, or propellant is considered.

I think you need to start much bigger.  Even non-reusable, prelanded-hab/MAV-dependent DRA 5 gives 28 tons for an inflatable transit hab for just 6 crew, plus 13 tons food and a 10 ton return vehicle.

I think we'll probably end up closer to 600 tons at Mars atmospheric interface than 200 tons.
« Last Edit: 09/04/2015 06:25 AM by Burninate »

Offline Impaler

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Re: MCT Speculation and Discussion Thread 4
« Reply #544 on: 09/04/2015 04:48 PM »
Launch Vehicles beyond 200 Mt capacity are hitting all kinds of practical limits such as being transportable by ANY method, having more thrust then any launch pad can handle, being a potentially catastrophic explosion on the pad requiring huge stand-off distances.  Lastly their is the problem of complete impracticality for any use other then launching to Mars, aka the SLS problem but multiplied about 100 fold.

If anything the 225 Mt number for BFR launch mass I'm speculating is aggressive.  I'm concerned about what the 2nd stage recovery cost will be and if this will kill the performance and lower the % of launch mass reaching orbit as philw1776 thought his own analysis looked high in this regard.

Attempts to derived the volume of MCT by calculating the long-duration habitation volume of 100 people is in my opinion flawed, the MCT will hold 100 persons only for brief periods of 3 days or less in something like a train-sleeper-car arrangement which will put it within the range of a 400 m^3 pressurized module placed inside a 500 m^3 cargo bay.  Some kind of large transit vehicle habitat (like BA 2100) will be employed.


As for Vehicle Evolution

I agree with most that the BFR rocket will not evolve significantly, it may see some thrust and performance ingresses, even a bit of a stretch but it will be basically the same vehicle all the way through.  The main focus will be improving the turn-around time to support a rising launch volume and reducing the penalties associated with re-use or the 2nd stage.

The landing vehicle I'm proposing is intended to be used through the whole course of Mars colonization, from the initial human landing all the way to huge volume transport of cargo and people because it is designed to be a rapid-cycling surface to orbit ferry and this actually makes the vehicle easier to design and build then a direct return vehicle.  Avoiding a redesign of the EDL portion of the mission will reduce risk and the delay of re-validating a new system.

I see all the the important system evolution occurring in the interplanetary transit vehicles.  These with be SEP which is a technology advancing by leaps-and-bounds in contrast with chemical propulsion so it makes the most sense to both allow and encourage radical improvement in the mission phase most likely to have the opportunity.  Early transit vehicles would be tugs that move a single lander, later the pace is accelerated by leaving the lander at Mars and using the tugs to haul naked cargo containers or inflatable habitats, finally a large freighter/liner could be created with specialization for cargo or passenger transport as larger vehicles invariably end up being more cost effective.


Offline Burninate

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Re: MCT Speculation and Discussion Thread 4
« Reply #545 on: 09/04/2015 05:37 PM »
If anything the 225 Mt number for BFR launch mass I'm speculating is aggressive.  I'm concerned about what the 2nd stage recovery cost will be and if this will kill the performance and lower the % of launch mass reaching orbit as philw1776 thought his own analysis looked high in this regard.

I think you might have misunderstood me here.  My suggestion is that ~200 tons launched from Earth to LEO seems like the limit, but that limit only has to cover spending on structure & permanently-attached habitat; One adds to that with supplemental launches and reaches ~600 tons at Mars entry, with the extra spent on food, people, ECLSS, ISRU gear, surface equipment, and descent propellent.  Then you factor in propellant for Earth Departure and reach 2000-3000 tons IMLEO (4.5 to 6km/s).

And that buys you a conjunction-class colony-in-a-can mission, for 25 people at least;  And maybe 100 people with prelanded assets.
« Last Edit: 09/04/2015 05:41 PM by Burninate »

Offline Impaler

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Re: MCT Speculation and Discussion Thread 4
« Reply #546 on: 09/04/2015 08:50 PM »
If anything the 225 Mt number for BFR launch mass I'm speculating is aggressive.  I'm concerned about what the 2nd stage recovery cost will be and if this will kill the performance and lower the % of launch mass reaching orbit as philw1776 thought his own analysis looked high in this regard.

I think you might have misunderstood me here.  My suggestion is that ~200 tons launched from Earth to LEO seems like the limit, but that limit only has to cover spending on structure & permanently-attached habitat; One adds to that with supplemental launches and reaches ~600 tons at Mars entry, with the extra spent on food, people, ECLSS, ISRU gear, surface equipment, and descent propellent.  Then you factor in propellant for Earth Departure and reach 2000-3000 tons IMLEO (4.5 to 6km/s).

And that buys you a conjunction-class colony-in-a-can mission, for 25 people at least;  And maybe 100 people with prelanded assets.

I'm having trouble following you, is that 2-3K IMLEO for just a single vehicle landing which carries 100 Mt cargo or it's equivalent in passengers/habs?  Either your describing the total mass needing to be delivered across several vehicles or your singular vehicle is YUUGE!

I've just been talking about a single landing vehicle with mass at mars entry of ~200 Mt and delivering a payload of 100 Mt.  IMLEO for one round trip of said vehicle would be near 1000 Mt even when utilizing SEP.

P.S.  I've always assumed that the landing vehicle will launch with cargo loaded from Earths surface so the landers dry mass is limited to the under 100 Mt as half of the launch mass is cargo.  If your willing to launch the lander and cargo separately then this restriction wouldn't apply.

Offline Hop_David

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Re: MCT Speculation and Discussion Thread 4
« Reply #547 on: 09/07/2015 05:58 AM »
Humm, if I am launching from Mars surface and I want to enter an elliptical hohoman transfer around the sun I need to decrease my heliocentric velocity aka I need to be going slower then Mars itself after having left it's sphere of influence.  Thus gravity loss incurred during escape may actually be beneficial IF it results in the loss in heliocentric velocity that one needs to reach Earth.

This is completely wrong.

For trans earth injection you need to to go slower with regard to the sun. Gravity loss during Mars escape make you go slower wrt Mars.

Mars is moving about 24.16 km/s wrt sun and the aphelion of a mars to earth Hohmann is moving about  21.52 wrt sun. So we need to lose about about 2.64 km/s to drop to a 1 A.U. perihelion. This 2.64 km/s is referred to as Vinf.

To escape from Mars and inject to trans earth orbit you need sqrt(Vescape2 + Vinf2). Someone's already noted Mars escape at surface is about 5 km/s. sqrt(52+2.642) is about 5.7. Without gravity loss we would need about 5.7 km/s to achieve trans earth injection. This is 5.7 km/s with regard to Mars.

Does gravity loss during ascent help us achieve 5.7 km/s? No it does not. It adds to the 5.7.

According to https://en.wikipedia.org/wiki/File%3aDelta-Vs_for_inner_Solar_System.svg you need 5.5 km/s DeltaV to reach escape

Wrong again. The delta V map shows 4.1 from Mars to LMO, another .9 to Phobos transfer, .3 to Deimos transfer and another .2 to reach C3=0. So 5.5 to escape if you make three stops along the way.

From Mars surface, escape is 5.023 km/s (without gravity loss).









« Last Edit: 09/07/2015 06:15 AM by Hop_David »

Offline Impaler

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Re: MCT Speculation and Discussion Thread 4
« Reply #548 on: 09/07/2015 07:15 AM »
I was thinking of something more akin to a gravitational slingshot in which the vehicle is ahead of mars in it's orbit and mars pulls it back, the vehicle loses velocity relative to the sun and mars gains it.

Offline cdleonard

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Re: MCT Speculation and Discussion Thread 4
« Reply #549 on: 09/25/2015 02:46 PM »
I just had a wild idea about the MCT design. What if it was inflatable by itself, without a separate habitat?

Bigelow habitats generally have a solid cylindrical core surrounded by an inflatable shell. But is there any particular reason why a conical shape wouldn't work just as well? Imagine a scaled-up SuperDragon enclosed in a layer of inflatable material which is puffed-up in vacuum.

The capsule would be launched deflated and only inflate once safely out of the atmosphere. When it's time to enter the atmosphere of Mars you can repack all the furniture back into the solid core and deflate the exterior. This pull brings the inflatable portion back behind the heat shield. On the surface of mars you can inflate it again and will end up with a sort of mushroom-shaped habitat. You can mount light-weight flooring inside the inflated region when on the surface..

The "inflatable" portion doesn't have to touch actually the heat shield. You will have side-mounted engines surrounding the heatshield, similar to the current Dragon.

Such a design requires that the skin material have some thermal resistance, similar to the sides of a normal capsule. It would likely need a fairing for flying upwards through the earth's atmosphere. The habitat also needs to support inflation/deflation while people are inside the core. Deflation seems particularly difficult. The simplest way would be to make core itself mostly airtight and pump out the air from the exterior portion.

This design only makes sense for shipping large numbers of people. You give them plenty of space during the transit period and on the surface but pack them closely together for takeoff and landing. It solves the "habitable volume" problem without increasing payload diameter too much.
« Last Edit: 09/25/2015 02:58 PM by cdleonard »

Offline Jimmy Murdok

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Re: MCT Speculation and Discussion Thread 4
« Reply #550 on: 09/25/2015 03:13 PM »
I just had a wild idea about the MCT design. What if it was inflatable by itself, without a separate habitat?

Bigelow habitats generally have a solid cylindrical core surrounded by an inflatable shell. But is there any particular reason why a conical shape wouldn't work just as well? Imagine a scaled-up SuperDragon enclosed in a layer of inflatable material which is puffed-up in vacuum.

The capsule would be launched deflated and only inflate once safely out of the atmosphere. When it's time to enter the atmosphere of Mars you can repack all the furniture back into the solid core and deflate the exterior. This pull brings the inflatable portion back behind the heat shield. On the surface of mars you can inflate it again and will end up with a sort of mushroom-shaped habitat. You can mount light-weight flooring inside the inflated region when on the surface..

The "inflatable" portion doesn't have to touch actually the heat shield. You will have side-mounted engines surrounding the heatshield, similar to the current Dragon.

Such a design requires that the skin material have some thermal resistance, similar to the sides of a normal capsule. It would likely need a fairing for flying upwards through the earth's atmosphere. The habitat also needs to support inflation/deflation while people are inside the core. Deflation seems particularly difficult. The simplest way would be to make core itself mostly airtight and pump out the air from the exterior portion.

This design only makes sense for shipping large numbers of people. You give them plenty of space during the transit period and on the surface but pack them closely together for takeoff and landing. It solves the "habitable volume" problem without increasing payload diameter too much.
Too complicated, this system is designed to break all current limitations. You want to keep it as simple as possible. If there is an inflatable easier to be a docked module until Mars, but I don't think is the case.

Offline hkultala

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Re: MCT Speculation and Discussion Thread 4
« Reply #551 on: 09/25/2015 03:50 PM »
I was thinking of something more akin to a gravitational slingshot in which the vehicle is ahead of mars in it's orbit and mars pulls it back, the vehicle loses velocity relative to the sun and mars gains it.

... and when you are behind mars, the gravity pulls you towards mars. No net gain. This is all calculated into the escape velocity.

You cannot slingshot with the gravity source you are leaving from.


Offline Lars-J

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Re: MCT Speculation and Discussion Thread 4
« Reply #552 on: 09/30/2015 07:10 AM »
I ran across this MCT speculation/article, from the French chapter of the Mars Society: (my apologies if this has already been discussed)

ANALYSIS OF A CONCEPT IN MARCH COLONIZATION TRANSPORTATION (MCT) LAUNCHES TWO [google translation]
http://planete-mars.com/analyse-dun-concept-mars-colonization-transport-mct-a-deux-lancements/

If you have the chrome browser, it will automatically translate the site for you.

Here are some interesting images from the MCT architecture of this article:
Image 1: Two MCT's docking in LMO for propellant transfer
Image 2: Launch abort module interior
Image 3: Launch abort module from behind
Image 4: MCT landed horizontally on Mars
Image 5: MCT interior
Image 6: BFR base
Image 7: BFR/MCT stack

In is an interesting concept, but I'm not sure that horizontal landing is practical. And their MCT seems to be lacking any kind of engines for propulsion. 
« Last Edit: 09/30/2015 07:13 AM by Lars-J »

Offline Lars-J

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Re: MCT Speculation and Discussion Thread 4
« Reply #553 on: 09/30/2015 07:27 AM »
BTW, here is a link to the author's (Richard Heidmann) previous articles on the subject: http://planete-mars.com/author/heidmann/

He has really gone all in on the horizontal landing idea... Anything else doesn't seem to enter his mind as a possibility.

Offline Patchouli

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Re: MCT Speculation and Discussion Thread 4
« Reply #554 on: 09/30/2015 07:43 AM »
I think MCT might resemble the Pegasus VTOL in shape and operation though the denser propellant might eliminate most or all of the drop tanks.
http://www.astronautix.com/lvs/pegvtovl.htm
« Last Edit: 09/30/2015 07:49 AM by Patchouli »

Online Semmel

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Re: MCT Speculation and Discussion Thread 4
« Reply #555 on: 09/30/2015 08:51 PM »
Nice concept. But quite frankly, I like the concept developed in L2 better. Hyperion et al. seem to have a better handle on the subject. Its very interesting to the development though and only good things can come from independent groups tackle the same problem.
« Last Edit: 09/30/2015 08:52 PM by Semmel »

Offline Paul451

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Re: MCT Speculation and Discussion Thread 4
« Reply #556 on: 10/01/2015 04:12 AM »
In a previous article, the same author, Richard Heidmann, seems to have fixed on the idea that BFR is an SSTO, that MCT has no main engine, just belly thrusters for landing. That's led to some weird conclusions, and hence the current article.

Offline Impaler

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Re: MCT Speculation and Discussion Thread 4
« Reply #557 on: 10/01/2015 07:58 AM »
How could anyone think that, it would be non-reusable which is by far the point Musk is most Emphatic on.  If someone showed me a pair of roller-skates and told me that was Musk's MCT design it would be more credible as the vehicle Musk is designing then anything expendable simple because it would fulfill the reusable criteria.
« Last Edit: 10/01/2015 07:59 AM by Impaler »

Offline Oli

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Re: MCT Speculation and Discussion Thread 4
« Reply #558 on: 10/01/2015 08:11 AM »
In a previous article, the same author, Richard Heidmann, seems to have fixed on the idea that BFR is an SSTO, that MCT has no main engine, just belly thrusters for landing. That's led to some weird conclusions, and hence the current article.

Simply not true.

Offline Rocket Surgeon

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Re: MCT Speculation and Discussion Thread 4
« Reply #559 on: 10/02/2015 01:34 AM »
Nice concept. But quite frankly, I like the concept developed in L2 better. Hyperion et al. seem to have a better handle on the subject. Its very interesting to the development though and only good things can come from independent groups tackle the same problem.

I definitely agree, though it is reassuring to see two independent designs that seem to be converging. Really the difference at this point seems to be changes made to base assumptions and what the designers consider to be 'more efficient'

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