Author Topic: MCT Speculation and Discussion Thread 4  (Read 624485 times)

Online Bynaus

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Re: MCT Speculation and Discussion Thread 4
« Reply #2840 on: 09/23/2016 08:24 AM »
...A figure shown by a user on twitter showing essentially the BFR-boosted BFS flying to Mars, refueling there and flying back to Earth entry was commented by him to be the best representation of the MCT to date...

Anyone have that image or a link to it? That's something I would like to see!

I remember seeing this, was this it? It looks like Elon's comment about it being the closest guess he's seen so far is above the linked tweet and is actually about a diagram of a Hyperloop track. I don't see a reply from Elon about the MCT diagram.

That is definetly the image I was thinking of. but I can't find Elon's tweet/comment on it. Perhaps it was deleted. The best I can come up with is a blog entry repeating what the tweet said (including the picture):

https://rocketry.wordpress.com/2013/07/15/spacex-f9-next-generation-booster-gets-full-duration-burn/

"Pretty close to what I have in mind". So its not the Hyperloop tweet, although the content is similar.
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Re: MCT Speculation and Discussion Thread 4
« Reply #2841 on: 09/23/2016 12:30 PM »
Hi Everyone, this is a concept of a monolithic BFS: http://imgur.com/gallery/fGzkH

Nice one, wouldn't be surprised if the final thing looked a lot like this, but landing this thing vertically doesn't look practical.
It's just a hunch, but I think it's gonna land horizontally, using a separate set of smaller engines. I don't think the MCT/ITS/whatever will have more than 2-3 Raptors and they will be used for orbital stuff, not landing. Oh, and deployable skids on the sides of the thermal shielding would be more robust than current F9 legs for the same mass.

Well, only 4 days left until, hopefully, we know more.
« Last Edit: 09/23/2016 12:30 PM by jsgirald »
"For every expert, there is an equal and opposite expert".

Offline BSenna

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Re: MCT Speculation and Discussion Thread 4
« Reply #2842 on: 09/23/2016 02:05 PM »
Not specified, they look thin but ithis concept is more about the layout of the components and the general idea.
Landing legs for such a rig would be a major component and the general idea (of anything spaceflight, let alone an ITS) would be to comply with laws of physics and waltz your design around the constraints they impose.

Do you know why people find rockets beautiful?
I've done this prevously, I thought a little about the system, but I simply didn't mind to put on the final renderings.
Uh... it's better, but only marginally... I suggest you try to thoughtfully brake some things in your spare time. All kinds of things, of different materials, sizes and shapes. Also, try to be creative with how you apply the force needed to brake a thing - fast, slow, point, area, etc. While you are at it, remember that force has a vector and try to visualize it.



Of course is science fiction. I took more time on these first concepts, before the "put the entire thing on the surface of mars" rumour, I guess.

http://imgur.com/a/EtH8F

http://imgur.com/a/15fO2

As long I have no STEM background, the only part I could seriously work is on the cabin accommodations. Please look it just as a layout, not a engineering proposal.

Online Pipcard

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Re: MCT Speculation and Discussion Thread 4
« Reply #2843 on: 09/23/2016 02:05 PM »
Hi Everyone, this is a concept of a monolithic BFS: http://imgur.com/gallery/fGzkH

Nice one, wouldn't be surprised if the final thing looked a lot like this, but landing this thing vertically doesn't look practical.
It's just a hunch, but I think it's gonna land horizontally, using a separate set of smaller engines. I don't think the MCT/ITS/whatever will have more than 2-3 Raptors and they will be used for orbital stuff, not landing. Oh, and deployable skids on the sides of the thermal shielding would be more robust than current F9 legs for the same mass.

Well, only 4 days left until, hopefully, we know more.
While a horizontal lander would be better for cargo access, the MCT/ITS would need to launch from the surface of Mars, so the main thrust would need to be along the longitudinal axis for better aerodynamics during ascent, and there would be extra weight and complexity to support the loads of the vehicle landing on its side in addition to the loads along the vehicle's longitudinal axis.

But I would guess that the MCT/ITS would be a lifting body like in BSenna's link (see also: HYFLEX) and enter Mars's atmosphere on its side in order to take advantage of aerobraking a huge mass with a larger surface area before switching to hypersonic retropropulsion for the final descent sequence.

(Mars EDL becomes harder with larger masses because of the square-cube law in relation to the surface area exposed during entry into the thin atmosphere.)
« Last Edit: 09/23/2016 02:29 PM by Pipcard »

Offline BSenna

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Re: MCT Speculation and Discussion Thread 4
« Reply #2844 on: 09/23/2016 02:13 PM »
Hi Everyone, this is a concept of a monolithic BFS: http://imgur.com/gallery/fGzkH

Nice one, wouldn't be surprised if the final thing looked a lot like this, but landing this thing vertically doesn't look practical.
It's just a hunch, but I think it's gonna land horizontally, using a separate set of smaller engines. I don't think the MCT/ITS/whatever will have more than 2-3 Raptors and they will be used for orbital stuff, not landing. Oh, and deployable skids on the sides of the thermal shielding would be more robust than current F9 legs for the same mass.

Well, only 4 days left until, hopefully, we know more.

Its really puzzling. If you ask me I would think about a 20 years test programme with SEP, expandable disposable habitats, etc. But the rumour mill quasi-consensus point other way. On the Mars landing field, I agree, but other engines would add mass just for landing, and there is the coming back problem, the need to reorient the ship for take-off.

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Re: MCT Speculation and Discussion Thread 4
« Reply #2845 on: 09/23/2016 02:15 PM »
While a horizontal lander would be better for cargo access, the MCT/ITS would need to launch from the surface of Mars, and there would be extra weight and complexity to support the loads of the vehicle landing on its side in addition to the loads generated by the main engine's thrust along the vehicle's longitudinal axis.

Your objections are quite reasonable, but the operational advantages when you need to operate without ground infrastructure should not be underestimated. Anyway, as I said, just a hunch.
"For every expert, there is an equal and opposite expert".

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Re: MCT Speculation and Discussion Thread 4
« Reply #2846 on: 09/23/2016 02:31 PM »
Its really puzzling. If you ask me I would think about a 20 years test programme with SEP, expandable disposable habitats, etc. But the rumour mill quasi-consensus point other way. On the Mars landing field, I agree, but other engines would add mass just for landing, and there is the coming back problem, the need to reorient the ship for take-off.

Think of smallish engines in nacelles placed high on both sides of the ship. You could use the side engines for take off and fire the big ones (Raptors) high in the atmosphere. The mass argument is reasonable, but this alternative provides for a more flexible design. Also, smaller engines far from the ground would prevent damage from dust or rocks blasted off. Several small motors provide redundancy, so a single damaged engine would not risk the whole mission. Add a detachable nose and a ramp like some cargo planes or ferries and you get an easy to operate roll-on roll-of ship.

Just a thought anyway.
"For every expert, there is an equal and opposite expert".

Offline BSenna

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Re: MCT Speculation and Discussion Thread 4
« Reply #2847 on: 09/23/2016 03:10 PM »
Its really puzzling. If you ask me I would think about a 20 years test programme with SEP, expandable disposable habitats, etc. But the rumour mill quasi-consensus point other way. On the Mars landing field, I agree, but other engines would add mass just for landing, and there is the coming back problem, the need to reorient the ship for take-off.

Think of smallish engines in nacelles placed high on both sides of the ship. You could use the side engines for take off and fire the big ones (Raptors) high in the atmosphere. The mass argument is reasonable, but this alternative provides for a more flexible design. Also, smaller engines far from the ground would prevent damage from dust or rocks blasted off. Several small motors provide redundancy, so a single damaged engine would not risk the whole mission. Add a detachable nose and a ramp like some cargo planes or ferries and you get an easy to operate roll-on roll-of ship.

Just a thought anyway.

My approach was to reduce the number of moving parts for risk reduction. The 6 raptors and 6 legs are also redundancy.

Offline 2552

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Re: MCT Speculation and Discussion Thread 4
« Reply #2848 on: 09/23/2016 04:55 PM »
...A figure shown by a user on twitter showing essentially the BFR-boosted BFS flying to Mars, refueling there and flying back to Earth entry was commented by him to be the best representation of the MCT to date...

Anyone have that image or a link to it? That's something I would like to see!

I remember seeing this, was this it? It looks like Elon's comment about it being the closest guess he's seen so far is above the linked tweet and is actually about a diagram of a Hyperloop track. I don't see a reply from Elon about the MCT diagram.

That is definetly the image I was thinking of. but I can't find Elon's tweet/comment on it. Perhaps it was deleted. The best I can come up with is a blog entry repeating what the tweet said (including the picture):

https://rocketry.wordpress.com/2013/07/15/spacex-f9-next-generation-booster-gets-full-duration-burn/

"Pretty close to what I have in mind". So its not the Hyperloop tweet, although the content is similar.

Maybe it actually was deleted, I just found this reddit comment that has a screenshot of John Gardi's MCT diagram and Elon's reply to it saying it's "pretty close to what I have in mind."

Also, this Google+ post has a direct link to Elon's tweet, but the tweet doesn't exist anymore.

Online Pipcard

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Re: MCT Speculation and Discussion Thread 4
« Reply #2849 on: 09/23/2016 07:22 PM »
...A figure shown by a user on twitter showing essentially the BFR-boosted BFS flying to Mars, refueling there and flying back to Earth entry was commented by him to be the best representation of the MCT to date...

Anyone have that image or a link to it? That's something I would like to see!

I remember seeing this, was this it? It looks like Elon's comment about it being the closest guess he's seen so far is above the linked tweet and is actually about a diagram of a Hyperloop track. I don't see a reply from Elon about the MCT diagram.

That is definetly the image I was thinking of. but I can't find Elon's tweet/comment on it. Perhaps it was deleted. The best I can come up with is a blog entry repeating what the tweet said (including the picture):

https://rocketry.wordpress.com/2013/07/15/spacex-f9-next-generation-booster-gets-full-duration-burn/

"Pretty close to what I have in mind". So its not the Hyperloop tweet, although the content is similar.

Maybe it actually was deleted, I just found this reddit comment that has a screenshot of John Gardi's MCT diagram and Elon's reply to it saying it's "pretty close to what I have in mind."

Also, this Google+ post has a direct link to Elon's tweet, but the tweet doesn't exist anymore.
The overall idea behind that makes sense if the goal is simple reusability operations. However, "no refueling" in Earth orbit is not an option unless you want the second stage to require SSTO-like delta-v performance or have extremely low mass margins. There will probably be MCTs/ITSs acting as tankers in the plan.
« Last Edit: 09/23/2016 07:24 PM by Pipcard »

Online Bynaus

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Re: MCT Speculation and Discussion Thread 4
« Reply #2850 on: 09/23/2016 07:35 PM »
...A figure shown by a user on twitter showing essentially the BFR-boosted BFS flying to Mars, refueling there and flying back to Earth entry was commented by him to be the best representation of the MCT to date...

Anyone have that image or a link to it? That's something I would like to see!

I remember seeing this, was this it? It looks like Elon's comment about it being the closest guess he's seen so far is above the linked tweet and is actually about a diagram of a Hyperloop track. I don't see a reply from Elon about the MCT diagram.

That is definetly the image I was thinking of. but I can't find Elon's tweet/comment on it. Perhaps it was deleted. The best I can come up with is a blog entry repeating what the tweet said (including the picture):

https://rocketry.wordpress.com/2013/07/15/spacex-f9-next-generation-booster-gets-full-duration-burn/

"Pretty close to what I have in mind". So its not the Hyperloop tweet, although the content is similar.

Maybe it actually was deleted, I just found this reddit comment that has a screenshot of John Gardi's MCT diagram and Elon's reply to it saying it's "pretty close to what I have in mind."

Also, this Google+ post has a direct link to Elon's tweet, but the tweet doesn't exist anymore.
The overall idea behind that makes sense if the goal is simple reusability operations. However, "no refueling" in Earth orbit is not an option unless you want the second stage to require SSTO-like delta-v performance or have extremely low mass margins. There will probably be MCTs/ITSs acting as tankers in the plan.

Well, the "no refueling" part is actually the only point that is contradicted by something Elon said himself (that there will be re-fueling before departure). So its a safe bet that this point is (among others, perhaps) why he said "pretty close" and not "spot on".
More of my thoughts: www.final-frontier.ch (in German)

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Re: MCT Speculation and Discussion Thread 4
« Reply #2851 on: 09/23/2016 07:39 PM »
Well, the "no refueling" part is actually the only point that is contradicted by something Elon said himself (that there will be re-fueling before departure). So its a safe bet that this point is (among others, perhaps) why he said "pretty close" and not "spot on".
Oh yeah, he did say that. (9:40 in video)

Quote from: Elon Musk
I mean, if you do a densified liquid methalox rocket with on-orbit refueling, so like you load the spacecraft into orbit and then you send a whole bunch of refueling missions to fill up the tanks and you have the Mars colonial fleet - essentially - that gets built up during the time between Earth-Mars synchronizations, which occur every 26 months, then the fleet all departs at the optimal transfer point.
« Last Edit: 09/23/2016 07:42 PM by Pipcard »

Offline Chris_Pi

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Re: MCT Speculation and Discussion Thread 4
« Reply #2852 on: 09/24/2016 03:28 AM »
Of course is science fiction. I took more time on these first concepts, before the "put the entire thing on the surface of mars" rumour, I guess.

AE-35 unit? I'm Sorry Dave, They won't let you fly that. :D

I don't have anything else to add, Just couldn't pass that one up.

Offline GORDAP

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Re: MCT Speculation and Discussion Thread 4
« Reply #2853 on: 09/24/2016 01:03 PM »
Well, this didn't get the traction that I'd hoped, but I'm still wondering if anyone would like to 'put their money where their mouth is' and declare their positions on the (hopefully) upcoming reveal details.  Only a few days left!  I'll start with my guesses:

1-a, 2-31, 3-15m, 4-17.5Mlbs, 5a, 6a, 7a, 8c



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

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

3) Diameter of BFR (1st stage)

4) Total Raptor 1st stage thrust (sl)

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

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

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

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


Offline Snake

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Re: MCT Speculation and Discussion Thread 4
« Reply #2854 on: 09/24/2016 01:38 PM »
Re: GORDAP's Poll

1) a
2) 36
3) 15 m
4) 36 x 2,300 kN = 82,800 kN  (18.6 Mlbs)
5) c
6) a
7) b
8) c

Also:

6 Raptors and 16 SuperDragons on BFS.
BFS revealed as being Benjamin Franklin Class Ship.
« Last Edit: 09/24/2016 01:58 PM by Snake »

Offline BSenna

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Re: MCT Speculation and Discussion Thread 4
« Reply #2855 on: 09/24/2016 07:31 PM »
Re: GORDAP's Poll

1- C, drop tanks on BFS
2- 33 Raptors
3- 15m
4- 75,900 kN  (17.1 Mlbs)
5- A, BFS escape is like Dragon 2
6- C, Biconic, vertical landing
7- B, Orbital capture, then landing.
8- C, Chemical, soon SEP.

BFS will be called Master Cylinder type. (Mars bound only).



Offline Lar

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Re: MCT Speculation and Discussion Thread 4
« Reply #2856 on: 09/24/2016 08:38 PM »
Fun exercise. I don't know the numbers that well so just gave ranges. These ideas all seem like well received ones in the threads.

1- C - Mostly option A, in that BFS is the second stage and comes in three variants: Tanker, cargo and crew, but for special purpose missions there will be a tanker variant that can fling an expendable third stage and fairly light payload on a high energy, possibly even interstellar, trajectory, and return to a rendezvous point with dry tanks. This may be just hinted at.
2- 30-36 Raptors
3- 15m
4- 17-20 Mlbs
5- A, ala Dragon 2
6- C, Biconic, vertical landing
7- D, all of the above are possible but A (direct return) and C (stay in orbit) are primary variants, crew return usually A but sometimes cargo or tanker may stay in orbit after capture (C) instead of landing. B rarely executed because pointless compared to A if returning. Some Cs turn into Bs (vessel completes orbital transfers and then deorbits for maintenance or downmass). Use of C will grow over time. Especially cargo, long term, may transfer to other vessels for different destinations, and as on orbit capability grows there may be more and more transshipment. Again, this may be just hinted at. Everything may be A initially.
8- C, Chemical, soon SEP. Cyclers are not ruled out eventually, but won't be used initially.
« Last Edit: 09/24/2016 08:41 PM by Lar »
"I think it would be great to be born on Earth and to die on Mars. Just hopefully not at the point of impact." -Elon Musk
"We're a little bit like the dog who caught the bus" - Musk after CRS-8 S1 successfully landed on ASDS OCISLY

Offline dror

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Re: MCT Speculation and Discussion Thread 4
« Reply #2857 on: 09/24/2016 09:00 PM »

1) a
2) 9-12 engines
3) 8.5-10 m diameter
4)
5)c) BFS contains smaller 'ejection pod' where humans reside during launch
6)
7) a)direct entry
8.) c) All chemical for now, but plans to incorporate SEP down the road

I hope it will be called Bender 8)
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Offline knowles2

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Re: MCT Speculation and Discussion Thread 4
« Reply #2858 on: 09/24/2016 10:59 PM »
Lot of talk here seem to be about a single vehicle that will launch from earth, land on mars, and then return to earth.

Musk isn't one to waste things, surely he will be using Red Dragon vehicle to handle the Mars orbit to ground bit and the IST will just handle the Earth to Mars bit?

It seems a bit risky to me to design a vehicle capable of being launch from earth with dozens of passengers and all their supplies sent to land to Mars and expect the same vehicle to do the reverse again.

Offline knowles2

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Re: MCT Speculation and Discussion Thread 4
« Reply #2859 on: 09/24/2016 11:10 PM »
Well, this didn't get the traction that I'd hoped, but I'm still wondering if anyone would like to 'put their money where their mouth is' and declare their positions on the (hopefully) upcoming reveal details.  Only a few days left!  I'll start with my guesses:

1-a, 2-31, 3-15m, 4-17.5Mlbs, 5a, 6a, 7a, 8c

Quote

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


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

27 engines.


Quote
3) Diameter of BFR (1st stage)

15-20 meters

Quote
4) Total Raptor 1st stage thrust (sl)
Don't know.


Quote
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

   d) Other, non-traditional LAS design

Quote
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

Capsule, will probably be a human rated Red Dragon.

Quote
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
 

c) Same as b, but upon Earth return, stays in orbit for next synod


Quote
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, all chemical for now, but will probably look into electrical engines once the technology has developed.

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