Author Topic: MCT Speculation and Discussion Thread 4  (Read 503123 times)

Offline Lars-J

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Re: MCT Speculation and Discussion Thread 4
« Reply #2580 on: 08/09/2016 06:01 PM »
FYI - This may interest people here - first MCT related hardware now exists in pre-production form:  Raptor :D

https://twitter.com/RocketScient1st/status/763063393745940481

Quote
C. G. Niederstrasser ‏@RocketScient1st
Shotwell - just shipped first Raptor engine to Texas last night. #SpaceX #smallsat

No pictures are available yet, but this probably means that Musk will show pictures of real hardware in his September presentation.
« Last Edit: 08/09/2016 06:01 PM by Lars-J »

Offline oldAtlas_Eguy

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Re: MCT Speculation and Discussion Thread 4
« Reply #2581 on: 08/09/2016 06:59 PM »
FYI - This may interest people here - first MCT related hardware now exists in pre-production form:  Raptor :D

https://twitter.com/RocketScient1st/status/763063393745940481

Quote
C. G. Niederstrasser ‏@RocketScient1st
Shotwell - just shipped first Raptor engine to Texas last night. #SpaceX #smallsat

No pictures are available yet, but this probably means that Musk will show pictures of real hardware in his September presentation.
As I mentioned on another thread this is 1 year earlier than we have assumed for such engine and tests. This makes our estimates for NET BFR first launch test conservative by as much as 1 year moving the possibility of  a BFR to exist as early as 2019/2020.

SpaceX is moving faster than we expect. This is surprise number 2 for this year in relation to Mars after the RD mission date.

Offline RonM

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Re: MCT Speculation and Discussion Thread 4
« Reply #2582 on: 08/09/2016 07:14 PM »
FYI - This may interest people here - first MCT related hardware now exists in pre-production form:  Raptor :D

https://twitter.com/RocketScient1st/status/763063393745940481

Quote
C. G. Niederstrasser ‏@RocketScient1st
Shotwell - just shipped first Raptor engine to Texas last night. #SpaceX #smallsat

No pictures are available yet, but this probably means that Musk will show pictures of real hardware in his September presentation.
As I mentioned on another thread this is 1 year earlier than we have assumed for such engine and tests. This makes our estimates for NET BFR first launch test conservative by as much as 1 year moving the possibility of  a BFR to exist as early as 2019/2020.

SpaceX is moving faster than we expect. This is surprise number 2 for this year in relation to Mars after the RD mission date.

One of the advantages of a privately held company is the ability to keep projects secret. No SEC paperwork giving away what's going on.

I bet MCT and Red Dragon are further along than we imagined.

Offline Oersted

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Re: MCT Speculation and Discussion Thread 4
« Reply #2583 on: 08/09/2016 07:15 PM »
A very thorough presentation of ideas for BFR/MCT from "coborop" at Reddit:
https://www.reddit.com/r/spacex/comments/4wks2h/fanmade_mct_and_bfr_architecture_cad_and_math/

Beautiful renders!:
https://imgur.com/a/2k10I

Interesting. Has the upper stage co-fire @ takeoff to increase T/W. Problem with Rvacs there.
What I like is someone not showing some BFR/BFS that is some ridiculous height like past Reddit posts I've seen elsewhere.  A >10m wide BFR gets very heavy quickly with propellant.  I'm confident that the reveal will be short and stout.

Also of interest: N-1-like spherical tanks in the MCT. Nested methalox tanks actually! http://imgur.com/a/pvAh8

In the discussion thread it appears that MCT co-fire may not be necessary, since his concept has a first stage which delivers enough power to give the whole stack a thrust-to-weight similar to Saturn 5/Apollo (around 1:1.15).

Online philw1776

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Re: MCT Speculation and Discussion Thread 4
« Reply #2584 on: 08/09/2016 07:20 PM »
Sea Level ISP 350 seconds seems too high so the BFR will not perform to that level assumed.
On the other hand you don't need the same Km/sec to RTLS as you launched because some of the launch velocity vector is vertical. It's not pure horizontal velocity.  Yes, you need some additional -X delta V to actually fly back.
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Online AncientU

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Re: MCT Speculation and Discussion Thread 4
« Reply #2585 on: 08/10/2016 12:58 AM »
2020 and exomars aren't going to be significantly larger than MSL.

This is a dumb way to argue. Please bring better game.

Fine. 
What evidence is there that MCT will use a HIAD?
There's some indirect evidence that it may be one of several options they'll consider.

I don't disagree that it will be or already was considered; there are many possibilities that will be discarded as not optimum or unworkable.
Certainly no evidence that it will be used on Red Dragon, which would be the obvious opportunity to test it...
It's nearly certain that some sort of deployable drag enhancement device will be used for MCT. None will be used on Red Dragon, which is not at all a reason to think it won't be used on MCT.

I don't have any particular belief that SpaceX will use something like HIAD. I don't envision they will. But you dismiss the possibility far too easily.

GS:
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Figuring out how to do this on Mars is going to be a challenge, part of why we need retro-propulsion on Mars, more predictable than aerodynamics.
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Offline Norm38

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Re: MCT Speculation and Discussion Thread 4
« Reply #2586 on: 08/10/2016 01:37 AM »

Beautiful renders!:
https://imgur.com/a/2k10I

The shuttlecock style interstage is quite interesting. How close do you all feel this is to what we will see in Sept?
Also, is it possible to build control surfaces into that?  How does it give control authority like grid fins?
« Last Edit: 08/10/2016 03:22 AM by Norm38 »

Offline Oersted

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Re: MCT Speculation and Discussion Thread 4
« Reply #2587 on: 08/10/2016 11:04 AM »
Maybe coborop believes that all the control authority needed can come from the main engines and a couple of cold thrusters. I however think that they haven't invested in know-how of grid fins without also using them for the MCT. As I see it they deliver much better targeting ability than the shuttle cock, even though the shuttle cock probably ensures better passive stability.

Online AncientU

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Re: MCT Speculation and Discussion Thread 4
« Reply #2588 on: 08/10/2016 11:18 AM »
Could grid fins (or flaps of some sort) be used forward and aft to control a belly first EDL?
Would give control authority during pop-up maneuver to prepare for landing burn, too.
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Offline envy887

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Re: MCT Speculation and Discussion Thread 4
« Reply #2589 on: 08/10/2016 01:09 PM »
Sea Level ISP 350 seconds seems too high so the BFR will not perform to that level assumed.
On the other hand you don't need the same Km/sec to RTLS as you launched because some of the launch velocity vector is vertical. It's not pure horizontal velocity.  Yes, you need some additional -X delta V to actually fly back.

I think that's 350s for the SL engine operating in vacuum (e.g. booster stage near MECO). SpaceX is proposing 321s at SL and 363s in vacuum for the SL engine, so 350s is probably conservative.

Offline oldAtlas_Eguy

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Re: MCT Speculation and Discussion Thread 4
« Reply #2590 on: 08/10/2016 03:31 PM »
With a prototype Raptor engine going into test the preliminary (concepts/requirements/definition) phase is drawing to a close with the detail design phase starting now. With a good model of what the Raptor will be able to achieve (ISP, thrust, engine bell size, T/W, etc) the specific capabilities of the two elements BFR and BFS will be set by the Sept reveal. Think of that as the PDR for those familiar with US government development program milestones. Although this is a pure commercial development it still has the same phases in its development:
- preliminary (concept/specifications),
- critical (detail design, manufacture "drawings", prototypes, tooling, etc for all elements of the vehicles),
- production of test articles, and
- finally production of flight articles.

And with the drawing of this preliminary design phase to a close so dose this thread's speculation about concepts and capabilities. It will then refocus on the details not revealed in Sept.
« Last Edit: 08/10/2016 03:31 PM by oldAtlas_Eguy »

Online philw1776

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Re: MCT Speculation and Discussion Thread 4
« Reply #2591 on: 08/10/2016 03:43 PM »
Sea Level ISP 350 seconds seems too high so the BFR will not perform to that level assumed.
On the other hand you don't need the same Km/sec to RTLS as you launched because some of the launch velocity vector is vertical. It's not pure horizontal velocity.  Yes, you need some additional -X delta V to actually fly back.

I think that's 350s for the SL engine operating in vacuum (e.g. booster stage near MECO). SpaceX is proposing 321s at SL and 363s in vacuum for the SL engine, so 350s is probably conservative.

Yes, we know that. 
His calculations use 350seconds ISP for the 1st stage BFR, so as I said his BFR model over performs what we know about a SL methalox engine.  The "average" ISP for stage one is most likely under 350s.
“When it looks more like an alien dreadnought, that’s when you know you’ve won.”

Offline envy887

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Re: MCT Speculation and Discussion Thread 4
« Reply #2592 on: 08/10/2016 08:08 PM »
Ugh, not looking forward to half a dozen pages of naming speculation. THE most boring aspect of this whole endeavor.

Does any of the info from Shotwell belong in the MCT source information update thread?

Online oiorionsbelt

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Re: MCT Speculation and Discussion Thread 4
« Reply #2593 on: 08/10/2016 11:47 PM »
2020 and exomars aren't going to be significantly larger than MSL.

This is a dumb way to argue. Please bring better game.

Fine. 
What evidence is there that MCT will use a HIAD?
There's some indirect evidence that it may be one of several options they'll consider.

I don't disagree that it will be or already was considered; there are many possibilities that will be discarded as not optimum or unworkable.
Certainly no evidence that it will be used on Red Dragon, which would be the obvious opportunity to test it...
It's nearly certain that some sort of deployable drag enhancement device will be used for MCT. None will be used on Red Dragon, which is not at all a reason to think it won't be used on MCT.

I don't have any particular belief that SpaceX will use something like HIAD. I don't envision they will. But you dismiss the possibility far too easily.

Are HIADs considered to be a ballute?
 At the 46:00 in the Small Sat keynote address by Qwynne Shotwell, she's says "Retropropulsion is really the answer. As opposed to parachutes, aero foils, ballutes and those things. Atmospheres are much too dynamic. Retroprpulsion really is the answer. In addition it will scale."

Offline OneSpeed

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Re: MCT Speculation and Discussion Thread 4
« Reply #2594 on: 08/11/2016 12:28 PM »
Are HIADs considered to be a ballute?

They probably shouldn't be. Although ballutes are capable of generating drag, they are not capable of generating negative lift. Also they, and parachutes aerofoils only appear to be intended for supersonic and subsonic flight regimes, rather than hypersonic.
« Last Edit: 08/11/2016 09:58 PM by OneSpeed »

Offline envy887

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Re: MCT Speculation and Discussion Thread 4
« Reply #2595 on: 08/11/2016 02:21 PM »
Are HIADs considered to be a ballute?

They probably shouldn't be. Although ballutes are capable of generating drag, they are not capable of generating negative lift. Also they, parachutes and aerofoils only appear to be intended for supersonic and subsonic flight regimes, rather than hypersonic.

HIADs are none of the above, but they do suffer from the same issues when it comes to precision landing.

Also, some airfoils are quite capable of hypersonic flight. The Shuttle, Buran, and a number of lifting body designs were airfoils designed/tested and/or flown at hypersonic reentry speeds.

Offline Lar

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Re: MCT Speculation and Discussion Thread 4
« Reply #2596 on: 08/11/2016 04:21 PM »
Naming is off topic here. I've splitmerged to the naming thread https://forum.nasaspaceflight.com/index.php?topic=35208

Props to Burninate for a heroic copypasta...  which got moved over here https://forum.nasaspaceflight.com/index.php?topic=35208.msg1567939#msg1567939

Wrong idea though, just report to mod (as someone did) and we'll sort it out eventually.

If you think I moved your post incorrectly, PM me. Whether you know my name or not.
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"We're a little bit like the dog who caught the bus" - Musk after CRS-8 S1 successfully landed on ASDS OCISLY

Online AncientU

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Re: MCT Speculation and Discussion Thread 4
« Reply #2597 on: 08/16/2016 08:08 PM »
Carbon fiber bodies/stages instead of aluminum... Advances the state-of-the-art in rocketry.
Helps mass reduction and secondary radiation effects simultaneously.

Quote
SpaceX is switching to carbon fibers from aluminum as it develops heavy rockets for carrying people and large quantities of material. A lighter body would allow more cargo to be loaded, which would cut transport costs.
http://asia.nikkei.com/Business/Deals/Toray-carbon-fiber-to-carry-SpaceX-s-Mars-ambitions

Combined with fast transits, rad problem could be largely mitigated.
PMF could (will) be best ever by far...
« Last Edit: 08/16/2016 08:11 PM by AncientU »
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Offline BobHk

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Re: MCT Speculation and Discussion Thread 4
« Reply #2598 on: 08/17/2016 04:11 PM »
Carbon fiber bodies/stages instead of aluminum... Advances the state-of-the-art in rocketry.
Helps mass reduction and secondary radiation effects simultaneously.

Quote
SpaceX is switching to carbon fibers from aluminum as it develops heavy rockets for carrying people and large quantities of material. A lighter body would allow more cargo to be loaded, which would cut transport costs.
http://asia.nikkei.com/Business/Deals/Toray-carbon-fiber-to-carry-SpaceX-s-Mars-ambitions

Combined with fast transits, rad problem could be largely mitigated.
PMF could (will) be best ever by far...

Quote
Update: On Tuesday evening SpaceX would not confirm that a large deal had been reached. "Toray is one of a number of suppliers we work with to meet our carbon fiber needs for Falcon rocket and Dragon spacecraft production, and we haven’t announced any new agreements at this time," a company spokesman told Ars. "As our business continues to grow, the amount of carbon fiber we use may continue to grow."

http://arstechnica.com/science/2016/08/spacex-reportedly-signs-multibillion-deal-for-carbon-fiber-composites/

meh harrumph

Offline Lar

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Re: MCT Speculation and Discussion Thread 4
« Reply #2599 on: 08/19/2016 01:26 AM »
Sliced out some posts that weren't really MCT to a new thread. When proposing new ideas let's stay focused on what is within the bounds of what we know already... if your idea doesn't fit what has already been said it probably doesn't belong here.

http://forum.nasaspaceflight.com/index.php?topic=40953.0 in SpaceX general ...
"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

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