Author Topic: MCT Speculation and Discussion Thread 4  (Read 626227 times)

Offline lamontagne

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Re: MCT Speculation and Discussion Thread 4
« Reply #140 on: 06/18/2015 04:14 PM »
From Statements made by SpaceX representatives:
- 100mt payload delivery to Mars
- 1/4 payload SSTO return to Earth from mars surface
- prop density 1m^3 for 1mt (LOX and CH4)
- 15m diameter vehicle (this was hited at not actually specified by SpaceX
- Raptor engines 380-385 vacuum ISP 500klbf

A vehicle like this results:
- Vehicle structure+engines+ shield =40mt
- Max propellant load 900mt
- propulsion section (engines and tanks) cylindircal or nearly cylindrical section at base 15m diameter and 6m tall
- bi-conal payload section (first section 15m to 10m diameter 10m tall) (second section 10m to 0m 10m tall) ~1800m^3 volume
-MCT can be its own 2nd stage on the BFR (BFR is basically just the 1st stage) would have ~7.5km/s delta v capability with a 100mt payload+40mt vehicle dry weight +900mt propellant load
-An MCT tanker variant would be a Cargo MCT without any cargo which could deliver ~150mt of propellant to LEO would have 6km/s delta v capability

In order to get to Mars 6-9 tankers docking in LEO-MEO are required

Edit Added: BTW An MCT cargo used as the 2nd stage going just to LEO would be capable of delivering 180mt of payload. Note the 1st stage needs to be capable of ~3km/s delta v with a fully loaded MCT + 180mt of payload on top ~1120mt MCT+payload GLOW
15m diameter and other such details have not been mentioned. Please cite your sources and put the source quote in the MCT source thread so we know exactly what was said: http://forum.nasaspaceflight.com/index.php?topic=37839.0
I like the quote page, thanks!  the 15m had a qualifying text with it :-)  so I'm keeping with my own ideas for a 10m core for the moment.  Although the 15m core is a tempting design basis.

Offline R7

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Re: MCT Speculation and Discussion Thread 4
« Reply #141 on: 06/18/2015 04:16 PM »
Except the Vac-optimized Raptors may not have enough thrust to get it off the ground nor the Isp to get to orbit. Just because it might conceivably get 9km/s in free space doesn't mean it is a SSTO.

Btw how would MCT land on Earth if it had vac-Raptors?
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Offline MikeAtkinson

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Re: MCT Speculation and Discussion Thread 4
« Reply #142 on: 06/18/2015 04:22 PM »
Except the Vac-optimized Raptors may not have enough thrust to get it off the ground nor the Isp to get to orbit. Just because it might conceivably get 9km/s in free space doesn't mean it is a SSTO.

5 Raptors probably would not have enough thrust for Earth launch (depending on what their SL thrust is), but landing on Earth would need a SL engine so at least one of them might have altitude compensation.

I'm really sceptical myself, if SpaceX could really bring in an MCT at 40 tonnes, they would be able to achieve what I have long considered impossible using near term technology - an economically viable reusable SSTO.

Offline Impaler

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Re: MCT Speculation and Discussion Thread 4
« Reply #143 on: 06/18/2015 04:23 PM »
I was just thinking, what if the side-boosters of Falcon Heavy are used a boosters to the BFR (like 8-10 of them).  Like any rocket you need more liftoff thrust then you need to sustain and the side-boosters would simply drop off and do the normal return to launch site or down-range landing as that would be a well established practice by then (I'd imagine they don't all drop off at once, early drops RTLS, late ones land down range). 

The side-booster would continue to use Kerolox and 9 Merlin engines which means you would be using two fuels but Kerosine is easy to handle.  Structural attachment to the core might prove tricky and the reintegration of the overall vehicle also be annoying and far short of 'gas-and-go' so it might be much like Atlas V, the rocket can launch without boosters but adding them gives higher payload which would allow SpaceX to design a smaller launcher that is more economical for small launches while still performing the few actual launches of massive vehicle while being fully reusable.
« Last Edit: 06/18/2015 09:27 PM by Impaler »

Offline Lobo

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Re: MCT Speculation and Discussion Thread 4
« Reply #144 on: 06/18/2015 04:31 PM »
The MCT is not a small vehicle. It could conceivably reach Earth orbit as an SSTO with a  little payload about 20mt.

20 tonnes to LEO is not a little payload.

If the MCT could really achieve a dry mass of 40 tonnes it would make a very useful reusable SSTO.

Now this is an interesting bit, if accurate.  For those looking at commonality with MCT to replace Falcon, here you have it.  Not a new Raptor powered SFR.  The MCT spacecraft acting as a SSTO LV.
Of course, most unmanned paylaods are not just going to LEO, so a kick stage or something would need to be used for BLEO trajectories.  And that kick stage would need to be significantly cheaper than F9US to make any economic advantage over F9R or FHR.
But interesting, nontheless.

Except the Vac-optimized Raptors may not have enough thrust to get it off the ground nor the Isp to get to orbit. Just because it might conceivably get 9km/s in free space doesn't mean it is a SSTO.

If there was a cluster of 5 Raptors, they could do something clever like making the four outer engines sea level Raptors, and just the central engine vacuum Raptor.  The outer booster engines would be shut down at the optimal point during ascent and the rest of ascent done on just the central vacuum Raptor.  By that point enough propellant would likely have been burned so that the single 500klb upper stage engine can finish the job.

Again, unless only going to LEO, I don't know that this gains anything over Falcon.  But interesting.

Offline Bynaus

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Re: MCT Speculation and Discussion Thread 4
« Reply #145 on: 06/18/2015 04:32 PM »
Quote
15m diameter vehicle (this was hited at not actually specified by SpaceX

How and where (by whom) was this "hinted at"? What was the actual wording?
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Offline lamontagne

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Re: MCT Speculation and Discussion Thread 4
« Reply #146 on: 06/18/2015 04:35 PM »
I have just noticed this year's number for the raptor engine, at 230 tonnes rather than 820 tonnes (Raptor engine Wikipedia article).  As this is a direct quote from Musk, it seems cannon.  That means something like 28+ engines for the fully fuelled ship on Earth.  That probably doesn't fit on a 10m core.  So the single core design would have to be larger, leading to a very short rocket, 35 to 40 m high for a 15m core, for example.  Is that the present consensus, more or less?

Offline MikeAtkinson

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Re: MCT Speculation and Discussion Thread 4
« Reply #147 on: 06/18/2015 04:38 PM »
Now this is an interesting bit, if accurate.  For those looking at commonality with MCT to replace Falcon, here you have it.  Not a new Raptor powered SFR.  The MCT spacecraft acting as a SSTO LV.
Of course, most unmanned paylaods are not just going to LEO, so a kick stage or something would need to be used for BLEO trajectories.  And that kick stage would need to be significantly cheaper than F9US to make any economic advantage over F9R or FHR.
But interesting, nontheless.

As I said above, not likely to be feasible in my opinion, as 40 tonnes seems too little mass for MCT. However, if it was possible, it would be in a universe of propellant transfer in LEO (probably from a depot) and so ability to only get to LEO would be no handicap, no kick stage needed.

Offline Lobo

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Re: MCT Speculation and Discussion Thread 4
« Reply #148 on: 06/18/2015 04:53 PM »
From Statements made by SpaceX representatives:
- 100mt payload delivery to Mars
- 1/4 payload SSTO return to Earth from mars surface
- prop density 1m^3 for 1mt (LOX and CH4)
- 15m diameter vehicle (this was hited at not actually specified by SpaceX
- Raptor engines 380-385 vacuum ISP 500klbf

A vehicle like this results:
- Vehicle structure+engines+ shield =40mt
- Max propellant load 900mt
- propulsion section (engines and tanks) cylindircal or nearly cylindrical section at base 15m diameter and 6m tall
- bi-conal payload section (first section 15m to 10m diameter 10m tall) (second section 10m to 0m 10m tall) ~1800m^3 volume
-MCT can be its own 2nd stage on the BFR (BFR is basically just the 1st stage) would have ~7.5km/s delta v capability with a 100mt payload+40mt vehicle dry weight +900mt propellant load
-An MCT tanker variant would be a Cargo MCT without any cargo which could deliver ~150mt of propellant to LEO would have 6km/s delta v capability

In order to get to Mars 6-9 tankers docking in LEO-MEO are required

Edit Added: BTW An MCT cargo used as the 2nd stage going just to LEO would be capable of delivering 180mt of payload. Note the 1st stage needs to be capable of ~3km/s delta v with a fully loaded MCT + 180mt of payload on top ~1120mt MCT+payload GLOW
Thanks, this is a great summary.   I guess this means not much water based radiation shielding?  And if as Guckyfan proposes there is no final injection burn, not much fuel at the end for radiation protection either?

One item I forgot to mention was the number of Raptors on MCT would be 5 to give a 3g liftoff at Mars with immediate 1 engine out continue mission capability. Later in Mars launch even 2 engines out would still enable continue mission. A very low risk value for mission success results from this.

Edit added: GLOW at Mars liftoff would be 965mt or 2.135Mlb more than 2x the GLOW of the F9v1.0. (65mt dry weight [40mt vehicle 25mt payload]). The MCT is not a small vehicle. It could conceivably reach Earth orbit as an SSTO witha  little payload about 20mt.

Atlas,

Hmmm...this all looks pretty familiar.  :-)

Thanks for fleshing that concept of mine out a bit more.  Putting some numbers with concept is interesting.

I too have been speculating the advantages of a 5-engine cluster on MCT, for reasons of engine-out.  It would basically allow for an engine out during Earth ascent to LEO (although an engine out then would likely result in that MCT being recalled and mission aborted).  Obviously it'd allow for engine out during TMI.  It would allow for an engine out during Mars liftoff and ascent, or at TEI burn.
And -if- MCT were to land on Raptor vs. dedicated landing thrusters, it would allow various engine out contingency options during EDL.

Seems like a good bit of backup.

I do agree that 40mt is probably too optimistic.  The S-II stage was about 45mt dry, and it had a volume of ~1800m^3 as well.  If SpaceX were making an equivalent expendable stage to the S-II, I'm sure they could make it lighter, given modern methods and materials.  But Making it a reusable spacecraft I think it would be at least somewhat heavier.
If it's dry mass were 100mt (as has been often guestimated as a nice round number in this thread), what would the performance numbers be then?  Just to make a more conservative number, for the sake of discussion?


Offline MikeAtkinson

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Re: MCT Speculation and Discussion Thread 4
« Reply #149 on: 06/18/2015 04:55 PM »
I have just noticed this year's number for the raptor engine, at 230 tonnes rather than 820 tonnes (Raptor engine Wikipedia article).  As this is a direct quote from Musk, it seems cannon.  That means something like 28+ engines for the fully fuelled ship on Earth.  That probably doesn't fit on a 10m core.  So the single core design would have to be larger, leading to a very short rocket, 35 to 40 m high for a 15m core, for example.  Is that the present consensus, more or less?

Note Elon said "Thrust to weight is optimizing for a surprisingly low thrust level, even when accounting for the added mass of plumbing and structure for many engines. Looks like a little over 230 metric tons (~500 klbf) of thrust per engine, but we will have a lot of them :)"

Don't read into it more than he said. There are other things to optimise, including cost, reliability, maintainability and manufacturing. When these and other factors are taken into account they may decide to go for a bigger engine.

That said my opinion is that they will end up with a slightly larger engine at maybe 250-270 tonnes. The size will be driven mainly by using 5 (which would give the best balance or T/W and engine out IMHO) of them on the MCT.

A short stubby BFR seems to be the consensus, with MCT on top it is still going to be pretty tall, perhaps 60-70m in total.

Offline oldAtlas_Eguy

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Re: MCT Speculation and Discussion Thread 4
« Reply #150 on: 06/18/2015 05:13 PM »
For an MCT that has a vehicle weight of 90mt (the heavy pessimistic version vs the light weight optimistic version)

-Mars liftoff GLOW 1265mt (1150mt of propelant)
-Earth liftoff GLOW (on top of BFR 1st stage) 1340mt with a delta v of 7.3km/s (which is still > 6.5km/sec needed on top of the 1st stage 3km/s capability to reach LEO + margins)

Would need ~8 tankers to load prop for Mars departure in 100mt increments. Needs additional prop to do the remaining 5.8km/s delta v that its residual prop capability of about 1km/s cannot meet the 6.8km/s for TMI (using direct entry no orbiting Mars).

As for the 15m diameter this was established because of the bell size (calculated from the rocket equation for 1atm) of a 500klbf Raptor and the number of them required (~31) in order to get ~200mt into LEO. 12m is just not big enough. Plus for this heavier MCT (90mt vehicle dry weight) a diameter of 20m would work better giving it a 20m diameter and 30m height in capsule like shape where it would have up to 2500m^3 of payload volume. A 15m diameter  lighter MCT would have only about 1500m^3 of payload volume.

BTW a Earth SSTO version (90mt dry weight) with 5 340 ISP Raptors and 15mt of payload could do ~8.5km/s. A very minimal orbit that would quickly decay. A 2mt kick motor would turn this vehicle into a F9R sized payload vehicle.

Offline nadreck

Re: MCT Speculation and Discussion Thread 4
« Reply #151 on: 06/18/2015 05:27 PM »
From Statements made by SpaceX representatives:
- 100mt payload delivery to Mars
- 1/4 payload SSTO return to Earth from mars surface
- prop density 1m^3 for 1mt (LOX and CH4)
- 15m diameter vehicle (this was hited at not actually specified by SpaceX
- Raptor engines 380-385 vacuum ISP 500klbf

A vehicle like this results:
- Vehicle structure+engines+ shield =40mt
- Max propellant load 900mt
- propulsion section (engines and tanks) cylindircal or nearly cylindrical section at base 15m diameter and 6m tall
- bi-conal payload section (first section 15m to 10m diameter 10m tall) (second section 10m to 0m 10m tall) ~1800m^3 volume
-MCT can be its own 2nd stage on the BFR (BFR is basically just the 1st stage) would have ~7.5km/s delta v capability with a 100mt payload+40mt vehicle dry weight +900mt propellant load
-An MCT tanker variant would be a Cargo MCT without any cargo which could deliver ~150mt of propellant to LEO would have 6km/s delta v capability

In order to get to Mars 6-9 tankers docking in LEO-MEO are required

Edit Added: BTW An MCT cargo used as the 2nd stage going just to LEO would be capable of delivering 180mt of payload. Note the 1st stage needs to be capable of ~3km/s delta v with a fully loaded MCT + 180mt of payload on top ~1120mt MCT+payload GLOW
That gives you and MCT with a ΔV of 7.475 km/s (380 isp) I am under the impression that ΔV budget of 4.5km/s worst case for LEO-Mars TMI and that variably we have been discussing needs in the order of 1kms for EDL presuming Aerocapture/braking.  That leave us with a need for about 5.5km/s, since making LEO as a 2nd stage for F9 needs about 5.9, I am happy with making 6.2km/s the round number leaving a healthy margin of fuel for Earth EDL.  At 6.2km/s and 380isp I see the amount of propellant needed for the dry weight and payload you mentioned being 600t at launch, and 472t leaving LEO.
However, personally, even with the smaller propellant load, I would presume MCT's dry weight (which includes potentially some active cooling for propellant and/or sun shades/reflectors, solar power, a higher proportion of RCS than your average US, and several other systems not seen on upper stages) is 60t.
I see it launching with less than full cargo though and having a full tank for the TMI burn.

Can you tell me where your 7.475km/s came from (or where I might have made an assumption about your vehicle concept that reduces its ΔV)
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 oldAtlas_Eguy

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Re: MCT Speculation and Discussion Thread 4
« Reply #152 on: 06/18/2015 05:41 PM »
From Statements made by SpaceX representatives:
- 100mt payload delivery to Mars
- 1/4 payload SSTO return to Earth from mars surface
- prop density 1m^3 for 1mt (LOX and CH4)
- 15m diameter vehicle (this was hited at not actually specified by SpaceX
- Raptor engines 380-385 vacuum ISP 500klbf

A vehicle like this results:
- Vehicle structure+engines+ shield =40mt
- Max propellant load 900mt
- propulsion section (engines and tanks) cylindircal or nearly cylindrical section at base 15m diameter and 6m tall
- bi-conal payload section (first section 15m to 10m diameter 10m tall) (second section 10m to 0m 10m tall) ~1800m^3 volume
-MCT can be its own 2nd stage on the BFR (BFR is basically just the 1st stage) would have ~7.5km/s delta v capability with a 100mt payload+40mt vehicle dry weight +900mt propellant load
-An MCT tanker variant would be a Cargo MCT without any cargo which could deliver ~150mt of propellant to LEO would have 6km/s delta v capability

In order to get to Mars 6-9 tankers docking in LEO-MEO are required

Edit Added: BTW An MCT cargo used as the 2nd stage going just to LEO would be capable of delivering 180mt of payload. Note the 1st stage needs to be capable of ~3km/s delta v with a fully loaded MCT + 180mt of payload on top ~1120mt MCT+payload GLOW
That gives you and MCT with a ΔV of 7.475 km/s (380 isp) I am under the impression that ΔV budget of 4.5km/s worst case for LEO-Mars TMI and that variably we have been discussing needs in the order of 1kms for EDL presuming Aerocapture/braking.  That leave us with a need for about 5.5km/s, since making LEO as a 2nd stage for F9 needs about 5.9, I am happy with making 6.2km/s the round number leaving a healthy margin of fuel for Earth EDL.  At 6.2km/s and 380isp I see the amount of propellant needed for the dry weight and payload you mentioned being 600t at launch, and 472t leaving LEO.
However, personally, even with the smaller propellant load, I would presume MCT's dry weight (which includes potentially some active cooling for propellant and/or sun shades/reflectors, solar power, a higher proportion of RCS than your average US, and several other systems not seen on upper stages) is 60t.
I see it launching with less than full cargo though and having a full tank for the TMI burn.

Can you tell me where your 7.475km/s came from (or where I might have made an assumption about your vehicle concept that reduces its ΔV)

The higher values are for worst case scenarios etc in departures other than the lowest delta v departure dates + the vehicles capabilities was based on using an ISP of 385 (upgraded version of Raptor) to see how much it could do). The 380 ISP values is much less delta V capability for same prop amounts. The real key is the amount of delta  v required to leave Mars surface and head for earth, nearly 9km/s. That is what governs the MCT prop load amounts. Use as its own 2nd stage needs less propellant load so the extra propellant increases the delta v capability as a 2nd stage. So size the propellant load to get the vehicle off Mars and headed back to Earth. The 2nd stage required amount is actually less.

Offline Robotbeat

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Re: MCT Speculation and Discussion Thread 4
« Reply #153 on: 06/18/2015 05:57 PM »
Mars surface to earth is much less than 9km/s. More like 7-7.5km/s.
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Offline BobHk

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Re: MCT Speculation and Discussion Thread 4
« Reply #154 on: 06/18/2015 05:57 PM »
Except the Vac-optimized Raptors may not have enough thrust to get it off the ground nor the Isp to get to orbit. Just because it might conceivably get 9km/s in free space doesn't mean it is a SSTO.

Btw how would MCT land on Earth if it had vac-Raptors?

By designing both into one engine:  https://en.wikipedia.org/wiki/Expanding_nozzle

Hard to make it work but beneficial if you can.

Offline oldAtlas_Eguy

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Re: MCT Speculation and Discussion Thread 4
« Reply #155 on: 06/18/2015 06:09 PM »
Mars surface to earth is much less than 9km/s. More like 7-7.5km/s.

But still the largest delta v requirement. At some point for growing vehicle dry weight other delta v requirements become larger. A 90mt vehicle weight may even be beyond that point. But leaving Mars surface it would be prudent to have significantly more capability than just the minimum. The item here is that use as 2nd stage to LEO, use as EDS and the use as direct return all have close to the same propellant requirements. The vehicle dry weight minus the payload weight drives which one is the driver for the amount the MCT must hold.

My values gives the information that it is doable and the reasoning behind some of the speculation on what the MCT would do.  For Earth departure you just keep filling the tanks until you get enough prop. Note here is that you need also prop for the landing phase on Mars of ~1km/s or more based on the vehicle shape and weight.

Edit: Difference between 2nd stage or EDS and Mars liftoff is payload size 100mt vs 25mt.
« Last Edit: 06/18/2015 06:12 PM by oldAtlas_Eguy »

Offline Lobo

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Re: MCT Speculation and Discussion Thread 4
« Reply #156 on: 06/18/2015 06:23 PM »
So, a few thoughts on MCT's TPS system.  Impaler has made the point that if coming in from interplanetary speeds, a metallic heat-absorption type TPS probably won't be able to handle that direct entry head load without the heat bleeding through and melting the structure.  And that the shuttle had ground support equipment to circulate cooling behind the TPS to prevent this from happening, which MCT won't have on Mars....at least for some time.

Now if you look at the SpaceX F9US-R concept, and the Rocketplane Kistler K-1 concept, they both only had a heat shield on a blunted nose.  Presumably that'd be an ablator as it'd be a relatively small surface area to take a large heat load.  But presumably enough engineering went into both to give the idea that the concept would work.

So, what if MCT basically looked like F9US-R and the K-1 (as I've speculated in the past), with a replaceable ablator on the nose, but fully reusable metallic TPS around everything else, which would pretty much compromise the skin.  Rather than the traditional biconic concepts with the TPS on just one half, this metallic would wrap the entire vehicle.  The ablator nose would take the severe heat load, but after a certain amount of deceleration, MCT would pitch over and start to "fly" like a biconic as it continued to decelerate.  That way the metallic TPS wouldn't get overheated for it's head absorption capacity.  Also, the primary reentry forces would be transferred directly along the axis, where a pressurized cylinder is the strongest, and not have the bending forces subjected to it like for a full "belly" reentry.

Moreover, for this we'd put the crew/cargo at the bottom, between the engine and the bottom of the tanks. in this way, the metallic TPS is backed by the tank skin all the way to very back of the vehicle, which has cryogenic temp residual liquids in it, which could absorb excess heat bleeding through the TPS system, and vent off the boiloff gasses, or collect it and use it for the RCS thrusters.  (Obviously you must be sure to not boiloff too much so there's enough liquid propellant to land).  So it'd be hard to soak enough heat into the structural tank to cause a problem because of the cold liquids and gases on the other side, I would think.
And the ablator on the nose would be backed by the pressurized tank dome, rather than by an unpressurized cargo hold or a crew cabin.  So it'd have a nice, evenly distributed support behind it from that.  Not mention the advantages of having the crew/cargo down at that bottom once on the surface.

Possibly, if there's a full wrap around engine skirt so the engines would be protected on all sides, if needed, perhaps MCT could roll over during EDL do actually distribute the heating evenly around the full circumference.  Do a "rotisserie" maneuver as the Apollo astronauts called what they did with the CSM during the transits.  (The crew may not be a fan of that however, heh)

The metallic panels would be attached to the cryogenic tank wall as part of an integrated airframe concept, as talked about in this paper which can be Googled to find...the link is too long to post.

AIAA 2002-0502
Metallic Thermal Protection System
Technology Development: Concepts,
Requirements And Assessment Overview

Quote
The TPS is attached to the tanks and intertank structures through the TPSS. Depending on the tank structural concept and stiffening arrangement, the TPSS may be attached to external stiffeners, such as ring frames and longerons, or to the outer skin of a sandwich tank structure.

So something like that.

Finally, if MCT were a symetrical cylinder with a bunt nosed ablator on top, that means theoretically, all such metallic TPS panels would be identical.  If you had a multi sloped biconic or triconic, or an asymmetrical biconic or lifting body of some sort, you'd have tiles of various shapes depending on their location...not unlike the Shuttle's.  But if you just have a basic cylinder, every tile should be the same shape no matter where it goes.  Which would make fabrication and repair much cheaper and more simple between missions, or possibly even on Mars.

Bottom pic is the 5-engine Raptor cluster on MCT with wrap around protective skirt.

« Last Edit: 06/18/2015 06:32 PM by Lobo »

Offline Robotbeat

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Re: MCT Speculation and Discussion Thread 4
« Reply #157 on: 06/18/2015 06:30 PM »
Yeah, I agree it probably I the largest delta-v requirement. Although 100-120 day Earth to Mars transits are pretty brutal, it helps a lot if you fill up last at high orbit like EML1/2.
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Offline Robotbeat

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Re: MCT Speculation and Discussion Thread 4
« Reply #158 on: 06/18/2015 06:34 PM »
MCT will only be reused 15-30 times (once each for Mars entry and Earth entry), so for the crew version, PICA-X may be fine, perhaps with TPS replacement every decade or so. Metallic TPS probably doesn't make sense for MCT, except for perhaps a tanker or cargo version that would just travel to LEO but could be reused hundreds or even thousands of times and which isn't as mass-sensitive.

PICA-X should be just fine for MCT, though, if it works as good as SpaceX says it does. metallic would be suboptimal except for tanker/cargo duty.
« Last Edit: 06/18/2015 06:38 PM by Robotbeat »
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Offline Lobo

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Re: MCT Speculation and Discussion Thread 4
« Reply #159 on: 06/18/2015 06:36 PM »
As a note, it occured to me where Rocketplane Kistler must have gotten then idea for the shape of the K-1.

;-)


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