Author Topic: Speculation thread: intermediate-lift Raptor-derived RLV  (Read 12709 times)

Offline sevenperforce

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There's no way of knowing for sure whether the Mars Colonization plans will ever come to fruition, or whether BFR will ever fly. Raptor, on the other hand, seems to be spinning along quite well, and SpaceX is already testing composite tanks. Whether BFS flies or not, it's reasonable to speculate that SpaceX might eventually field a fully-reusable launch system in the same class as Falcon 9 or Falcon Heavy, either as a test bed for the Mars ship, or to supplement the Mars colonization program, or as a scaled-back approach (if BFR never comes to anything).

Several other threads have touched on this subject (see here, here, and here), but having a consolidated thread seemed like a good idea.

So, what fully-reusable two-stage launch vehicle in the same class as Falcon 9 could SpaceX realistically field? Specifically, what architecture would they use? Would the second stage have a ballistic re-entry with a small heat shield, or a biconic lifting re-entry with TPS spread across a stiffened body? How would it land? If it was designed for reuse from the ground up, would it still use a payload fairing, or would it opt for a more easily-recoverable payload bay arrangement? And what, if any, would be the plan for a manned/crewed version, for sending a handful of people to orbit rather than the 100+ carrying capacity of the ITS? Would it have a separate capsule or an integrated capsule?

I've got my own ideas but I wanted to see what people might come up with.

Online guckyfan

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Re: Speculation thread: intermediate-lift Raptor-derived RLV
« Reply #1 on: 04/23/2017 06:40 AM »
For a long time I did not believe in a methane upper stage for Falcon.

But now, given the latest announcement I have changed my mind. First there was the announcement for the FH maiden launch, doing a test with slow chance of success. That will be mainly a reentry stability test with the present S2.

Then the reusable upper stage end of next year will be a methane stage for both F9 and FH. Increasing capability enough that with most orbits reuse will give the same capabilities as expendable US now. Landing burn will be done with the methane RCS thrusters or a variant of them.

Composite airframe, self pressurized, recoverable conventional fairing. Loss of payload capacity with a connected cargo space would probably be too high. Steering during reentry with flaps, similar to ITS and IXV.

Lifting body?

Edit: This would test many of the technologies needed for ITS. Maybe even refuelling, which might enable cargo moon landing.
« Last Edit: 04/23/2017 06:41 AM by guckyfan »

Offline mikelepage

I'm curious in general about how feasible it is to put a single full-size, vacuum-optimised engine on the rear end of a second stage, and a small-scale, sea-level/supersonic-retropropulsion-optimised engine on the forward end? (all using the same fuel/oxidiser tanks - no flip and burn maneuvers - land it "upside down").

I just figure if boost stage engines and vacuum engines have their own optimisations, surely supersonic retropropulsion/landing engines would have their own, separate optimisations.

Online guckyfan

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Re: Speculation thread: intermediate-lift Raptor-derived RLV
« Reply #3 on: 04/23/2017 10:55 AM »
I'm curious in general about how feasible it is to put a single full-size, vacuum-optimised engine on the rear end of a second stage, and a small-scale, sea-level/supersonic-retropropulsion-optimised engine on the forward end? (all using the same fuel/oxidiser tanks - no flip and burn maneuvers - land it "upside down").

I am continuous baffled by that idea. You need one end with a heat shield to reenter. How would an engine survive there without complex mechanisms to protect it, which are failure points and added complexities?

I just figure if boost stage engines and vacuum engines have their own optimisations, surely supersonic retropropulsion/landing engines would have their own, separate optimisations.

Yes. Separate engines very likely. There is plenty of space for small landing thrusters, ideally using the same propellant as the main engine. Unlike the first stage which is packed full of engines. But I don't see the rationale in placing the landing engines and landing legs on the other end. Enough to place the pressure tanks there for the pressure fed landing engines to change the center of mass somewhat for reentry stability.

Offline Jimmy Murdok

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Re: Speculation thread: intermediate-lift Raptor-derived RLV
« Reply #4 on: 04/23/2017 11:46 AM »
The easiest way is to use a slightly modified ITS with sea nozzles acting as a booster. The passenger and cargo replaced by an empty bay with top doors a la shuttle (same external ITS shape). During launch, at certain altitude, doors open to deploy a 2nd stage with 1 raptor + payload without fairing. After deployment, booster close doors and return to launch site.

Would have around 28-29MN compared to the 23 of FH, allow to test the infrastructure for Mars with revenue using a configuration very close to the well known F9.

Specific developments are the fairing-doors, the deployment mechanism and the 2nd stage. The commonality advantages with the Mars architecture are huge, allow for testing small scale without an entire new vehicle.

But not sure about the commercial case if FH is successful except for big diameter payloads.
« Last Edit: 04/23/2017 12:01 PM by Jimmy Murdok »

Offline Oli

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Re: Speculation thread: intermediate-lift Raptor-derived RLV
« Reply #5 on: 04/23/2017 12:21 PM »
I'm curious in general about how feasible it is to put a single full-size, vacuum-optimised engine on the rear end of a second stage

A single vacuum-optimized Raptor would take up a lot of space in the back of a correspondingly downsized ITS.

Offline Lar

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Re: Speculation thread: intermediate-lift Raptor-derived RLV
« Reply #6 on: 04/23/2017 12:25 PM »
The easiest way is to use a slightly modified ITS with sea nozzles acting as a booster. The passenger and cargo replaced by an empty bay with top doors a la shuttle (same external ITS shape). During launch, at certain altitude, doors open to deploy a 2nd stage with 1 raptor + payload without fairing. After deployment, booster close doors and return to launch site.

Opening doors while ballistic to release a second stage? Seems like everything has to work in a very delicate, highly choreographed, series of actions or else you lose the booster or the second stage or both. (I'm assuming with a door failure to open the booster can't land, not enough fuel remaining)

I confess I'm highly dubious of any intermediate vehicles, with the possible exception of a raptor second stage for F9/FH (which I am still dubious of but not highly dubious :) )... but we'll find out soon, maybe.
« Last Edit: 04/23/2017 12:26 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 sevenperforce

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Re: Speculation thread: intermediate-lift Raptor-derived RLV
« Reply #7 on: 04/23/2017 06:15 PM »
Composite airframe, self pressurized, recoverable conventional fairing. Loss of payload capacity with a connected cargo space would probably be too high. Steering during reentry with flaps, similar to ITS and IXV.

Lifting body?

Edit: This would test many of the technologies needed for ITS. Maybe even refuelling, which might enable cargo moon landing.
Yeah, that's precisely what I was thinking...though also considering a methalox first stage.

The easiest way is to use a slightly modified ITS with sea nozzles acting as a booster. The passenger and cargo replaced by an empty bay with top doors a la shuttle (same external ITS shape). During launch, at certain altitude, doors open to deploy a 2nd stage with 1 raptor + payload without fairing. After deployment, booster close doors and return to launch site.

Would have around 28-29MN compared to the 23 of FH, allow to test the infrastructure for Mars with revenue using a configuration very close to the well known F9.

Specific developments are the fairing-doors, the deployment mechanism and the 2nd stage. The commonality advantages with the Mars architecture are huge, allow for testing small scale without an entire new vehicle.
Oh, that's tremendous. Just like Falcon 1's first stage essentially became the Falcon 9 second stage. It would give them a lot of good experience, though I'm not entirely sure about the payload bay approach. I am not sure that second-stage reuse would be particularly feasible with that design, either.

Another issue would be thrust. The ITS second stage can barely pull 1.1 gees at sea level if you replace the RVacs with SL Raptors. So while it might have plenty of dV, lifting a large enough second stage could be problematic.

Opening doors while ballistic to release a second stage? Seems like everything has to work in a very delicate, highly choreographed, series of actions or else you lose the booster or the second stage or both. (I'm assuming with a door failure to open the booster can't land, not enough fuel remaining)

I confess I'm highly dubious of any intermediate vehicles, with the possible exception of a raptor second stage for F9/FH (which I am still dubious of but not highly dubious :) )... but we'll find out soon, maybe.
How is a payload-door-based staging significantly different than ordinary staging? If stages fail to separate, you lose the booster and the second stage. Opening doors before deploying the stage might be a little more complex, but it's done in exoatmospheric free-fall and there's plenty of time.

SpaceX has always wanted to go fully-reusable, and since they are presently developing the Raptor with that goal in mind, I can definitely see a methalox upper stage for FH, if nothing else. The isp advantage is just ridiculous, and even if everything goes as planned with ITS, the planet is still going to need a launch vehicle capable of taking people to orbit in groups smaller than 100+. SpaceX would almost definitely want this to be reusable.

Offline sevenperforce

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Re: Speculation thread: intermediate-lift Raptor-derived RLV
« Reply #8 on: 04/23/2017 06:46 PM »
The unsolved problem for full reuse deals mostly with second stage recovery, since SpaceX seems to have first stage recovery down and is unlikely to change anything there. Recovering the second stage is tricky. With ITS, the plan is to include SL engines on the second stage (which help with TWR right after launch) and land it in much the same way as the booster, albeit after a biconic lifting-body re-entry. That might work for a monster like the ITS Spaceship, but the design doesn't really scale down well.

SpaceX is, however, planning to develop hot-gas methane-oxy thrusters for RCS on the ITS. In a Reddit AMA, they were confirmed at 10 metric tonnes vacuum thrust each. So if we need auxiliary landing thrusters, these might work.

It would also be nice to be able to use the upper stage as an SSTO for Martian missions or lunar missions, so that's another consideration.

I mentioned in the OP that I had my own idea for a fully-reusable RLV, so here goes:



Looks a little like the ITS, right? But it would be 4 meters wide with the same booster height as Falcon 9, so the booster would still be road-transportable.

Two full-size SL Raptor engines on the first stage, plus six auxiliary thrusters; four landing legs:



The upper stage is where it gets really interesting. It's the same monocoque design as the ITS Spaceship/Tanker, but it uses two vacuum-optimized 1000-kN development Raptors, and it has two winglet extensions instead of three:



Notional staging velocity is 1.5-2.5 km/s, depending on payload. Booster carries enough propellant for RTLS on every mission, and lands on its auxiliary thrusters.

The second stage re-enters on its belly using split flaps for attitude control, like the ITS Spaceship and Tanker. However, it has no landing legs near its tail, and no tail auxiliary thrusters. Instead, panels on the underside open up, both serving as landing skids and exposing auxiliary landing thrusters for a propulsive belly-first landing:



I've worked out all the specs...filled up about three Excel spreadsheets doing so, too.

First stage dry mass: 17 tonnes
First stage propellant: 421 tonnes
First stage mass ratio: 24:1
Thrust at launch: 6,266 kN

Second stage dry mass: 6.6 tonnes
Second stage propellant: 141 tonnes
Total vacuum thrust: 2,292 kN

Reusable payload to LEO: 24 tonnes
Reusable payload to GTO: 6.8 tonnes
Downmass from LEO: 22 tonnes

This is obviously plenty of margin to have a crewed version, which would use the same tank and body as the rest of the orbiter but have a crew cabin in place of the cargo bay. Payload capacity is high enough that the crew cabin could carry at least a dozen crew members plus unpressurized cargo and still have independent LES and re-entry capability (lifeboat).

Upper stage landing would look like something out of Star Wars, because it drops straight down, winglets open, and it lands on the wingtips with rocket propulsion.

Know what else is great? Due to the vertically-oriented thrusters, the upper stage could both land on and take off from the Moon or from the surface of Mars without needing a launch pad. On Mars, it would need to be refueled on the Martian surface; the lower gravity means that the thrusters have enough thrust to lift it off the ground so the main engines could be fired up. For lunar missions, simply being refueled once in LEO would give it ample dV to fly to the moon, land, SSTO, and return to LEO.

I kept the thrusters behind the landing panels to protect them from re-entry -- I can't imagine that plasma is healthy for engines -- but there might be a way to have them exposed but not directly in the plasma stream, which would allow them to be used for RCS control as well. It should be noted that the dry mass of the first stage is actually significantly lower than the dry mass of the Falcon 9 first stage, due to the use of a slightly greater diameter to hold more propellant for less mass, and the use of composites.

I try not to succumb to Rule of Cool too often, but I couldn't resist this. Mostly because it does genuinely offer some real advantages. And, good grief, who doesn't want to see a sleek spaceship rise straight off the lunar pad on thrusters, rotate gently to orient properly, and then fire up its big engines in the back to blast into orbit? It's exactly how the Millennium Falcon takes off.

I set the total auxiliary engine thrust high enough to allow the same vertical takeoff on Mars, which (coincidentally) is precisely what you need for a nice tight landing on Earth with a good bit of downmass.

One thing I'm unsure of is the pressurization issues for the auxiliary thrusters. They are autogenously pressurized off the main Raptors, so I'm not sure how much dV they can push before they start to lose tank pressure.

With an adapted interstage, this upper stage could be used with Falcon Heavy as well.
« Last Edit: 04/23/2017 06:47 PM by sevenperforce »

Offline wes_wilson

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Re: Speculation thread: intermediate-lift Raptor-derived RLV
« Reply #9 on: 04/23/2017 08:39 PM »
I'm curious in general about how feasible it is to put a single full-size, vacuum-optimised engine on the rear end of a second stage, and a small-scale, sea-level/supersonic-retropropulsion-optimised engine on the forward end? (all using the same fuel/oxidiser tanks - no flip and burn maneuvers - land it "upside down").

I am continuous baffled by that idea. You need one end with a heat shield to reenter. How would an engine survive there without complex mechanisms to protect it, which are failure points and added complexities?


Like they're doing with Dragon?  Sloped form with small engines behind the shield through geometry.  Cosine losses may even be helpful.  I've speculated on a re-appearance of pressure fed Kestrels using this model in other threads.
@SpaceX "When can I buy my ticket to Mars?"

Offline mikelepage

The second stage re-enters on its belly using split flaps for attitude control, like the ITS Spaceship and Tanker. However, it has no landing legs near its tail, and no tail auxiliary thrusters. Instead, panels on the underside open up, both serving as landing skids and exposing auxiliary landing thrusters for a propulsive belly-first landing:



I've worked out all the specs...filled up about three Excel spreadsheets doing so, too.

First stage dry mass: 17 tonnes
First stage propellant: 421 tonnes
First stage mass ratio: 24:1
Thrust at launch: 6,266 kN

Second stage dry mass: 6.6 tonnes
Second stage propellant: 141 tonnes
Total vacuum thrust: 2,292 kN

Reusable payload to LEO: 24 tonnes
Reusable payload to GTO: 6.8 tonnes
Downmass from LEO: 22 tonnes

Cool factor is high :) but how did you work out the second stage dry mass?  Wouldn't the lower surface area of a smaller craft during reentry mean higher g-forces, greater loads, and more need for structural reinforcement?  Seems a little light to me...

EDIT ps: talking to the Armadillo Aerospace guys 10 years ago at XPrize cup 2007 I asked why they went with VTVL rather than VTHL (dreamchaser type vehicles), and the answer they gave was mainly along the lines of "you wouldn't believe how much extra mass you add when the airframe has to support/propel itself in two different orientations".  I was reminded of that during the ITS presentation - the ship performs entry and descent on its belly, but flips up to land on its tail... seems like a risky maneuver that you wouldn't make unless it was absolutely necessary.
« Last Edit: 04/24/2017 04:11 AM by mikelepage »

Offline sevenperforce

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Re: Speculation thread: intermediate-lift Raptor-derived RLV
« Reply #11 on: 04/24/2017 04:17 AM »
The second stage re-enters on its belly using split flaps for attitude control, like the ITS Spaceship and Tanker. However, it has no landing legs near its tail, and no tail auxiliary thrusters. Instead, panels on the underside open up, both serving as landing skids and exposing auxiliary landing thrusters for a propulsive belly-first landing.

I've worked out all the specs...filled up about three Excel spreadsheets doing so, too.

First stage dry mass: 17 tonnes
First stage propellant: 421 tonnes
First stage mass ratio: 24:1
Thrust at launch: 6,266 kN

Second stage dry mass: 6.6 tonnes
Second stage propellant: 141 tonnes
Total vacuum thrust: 2,292 kN

Reusable payload to LEO: 24 tonnes
Reusable payload to GTO: 6.8 tonnes
Downmass from LEO: 22 tonnes

Cool factor is high :) but how did you work out the second stage dry mass?  Wouldn't the lower surface area of a smaller craft during reentry mean higher g-forces, greater loads, and more need for structural reinforcement?  Seems a little light to me...
I used the dry mass of the ITS Tanker, subtracting projected engine mass and accounting for square-cube losses, then adding back the engine mass again, with conservatism built in at each step. I can dig up the numbers tomorrow. Lower surface area does mean somewhat higher g-forces, but that's what the wing extensions are for. Also, it's longer and thinner, aspect-ratio-wise, than the ITS. So as long as it isn't so long that there are bending moment stresses, it has less structural susceptibility than the ITS.

Quote
EDIT ps: talking to the Armadillo Aerospace guys 10 years ago at XPrize cup 2007 I asked why they went with VTVL rather than VTHL (dreamchaser type vehicles), and the answer they gave was mainly along the lines of "you wouldn't believe how much extra mass you add when the airframe has to support/propel itself in two different orientations".  I was reminded of that during the ITS presentation - the ship performs entry and descent on its belly, but flips up to land on its tail... seems like a risky maneuver that you wouldn't make unless it was absolutely necessary.
I think the primary reason they have it landing tail-first is so it can proceed to SSTO from Mars after refilling its tanks. I neatly avoided this by using biaxial auxiliary thrusters...rule of cool, yes, but also a lot safer.

I also hate anything that makes egress difficult.

Offline Semmel

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Re: Speculation thread: intermediate-lift Raptor-derived RLV
« Reply #12 on: 04/24/2017 06:41 AM »
I think the reason for vertical us the load structure. During EDL, the load is distributed over the entire surface which is not so problematic as landing on discrete points like legs.

Offline Jimmy Murdok

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Re: Speculation thread: intermediate-lift Raptor-derived RLV
« Reply #13 on: 04/24/2017 09:28 AM »
Opening doors while ballistic to release a second stage? Seems like everything has to work in a very delicate, highly choreographed, series of actions or else you lose the booster or the second stage or both. (I'm assuming with a door failure to open the booster can't land, not enough fuel remaining)

I confess I'm highly dubious of any intermediate vehicles, with the possible exception of a raptor second stage for F9/FH (which I am still dubious of but not highly dubious :) )... but we'll find out soon, maybe.

I can imagine doors facing down, pneumatic impulse to the second stage from the ITS and cold gas thrusters until ignition. I agree is the most delicate part.

I´m also dubious about mid size developments as per FH, that´s the only stuff that make sense to me because is part of the development pathway of ITS, provides cash and allow for early test. Kind of the way Elon likes to do things. But it assumes FH has short expiration date because of the complexity of the 3 cores which I don't think is the case.

Offline Jimmy Murdok

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Re: Speculation thread: intermediate-lift Raptor-derived RLV
« Reply #14 on: 04/24/2017 10:18 AM »
Another option is a second stage for FH as a half scaled ITS. 6m diameter, 24m long, 1 raptor and 3 flavours:
1- Cargo version with integrated fairing (crocodile style) to deploy satellites
2- Mini crewed ITS launched as FH: minibus of 20 PAX to LEO, 10 PAX to moon vicinity and 5 to asteroids or even Phobos. Crewed part is 6m diameter, 9m long with around 180m3. Could copy-paste beefed up ECLSS systems from Dragon and become a very polyvalent spaceship.
3 - Tanker version

That would be the spaceship that NASA needs for BLEO and would match beautifully with the SLS. But I guess reminds too much the shuttle. Would delay too much the bigger brother, but a very good exploration spaceship.

edit: removed extra raptors on ITS
« Last Edit: 04/24/2017 11:50 PM by Jimmy Murdok »

Offline spacenut

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Re: Speculation thread: intermediate-lift Raptor-derived RLV
« Reply #15 on: 04/24/2017 11:13 AM »
SpaceX has said Falcon Heavy is "hard".  A 9 Raptor engine 7m diameter reusable first stage, with a single engine vacuum Raptor second stage.  Add a few small landing thrusters for second stage after re-entry.  This single stick two stage rocket would replace Falcon Heavy and be able to test all factors of in a reduced scale.  Like the previous poster, possibly a mini-ITS half scale, but with a single stick 9 engine raptor first stage.  This would make for a completely reusable two stage vehicle.  F9/FH is too small a diameter and too tall for a good mini-ITS.  After sea level Raptor is developed, a single stick upscaled F9 to 7m diameter shouldn't be a problem except location of the manufacturing facility. 

This new rocket would be slightly more powerful than BO's New Glenn, and be fully reusable. 

Offline FishInferno

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Re: Speculation thread: intermediate-lift Raptor-derived RLV
« Reply #16 on: 04/24/2017 11:58 AM »
SpaceX has said Falcon Heavy is "hard".  A 9 Raptor engine 7m diameter reusable first stage, with a single engine vacuum Raptor second stage.  Add a few small landing thrusters for second stage after re-entry.  This single stick two stage rocket would replace Falcon Heavy and be able to test all factors of in a reduced scale.  Like the previous poster, possibly a mini-ITS half scale, but with a single stick 9 engine raptor first stage.  This would make for a completely reusable two stage vehicle.  F9/FH is too small a diameter and too tall for a good mini-ITS.  After sea level Raptor is developed, a single stick upscaled F9 to 7m diameter shouldn't be a problem except location of the manufacturing facility. 

This new rocket would be slightly more powerful than BO's New Glenn, and be fully reusable.

Would such a booster be able to land on the launch cradle like the ITS booster?
Comparing SpaceX and SLS is like comparing paying people to plant fruit trees with merely digging holes and filling them.  - Robotbeat

Offline envy887

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Re: Speculation thread: intermediate-lift Raptor-derived RLV
« Reply #17 on: 04/24/2017 12:48 PM »
SpaceX has said Falcon Heavy is "hard".  A 9 Raptor engine 7m diameter reusable first stage, with a single engine vacuum Raptor second stage.  Add a few small landing thrusters for second stage after re-entry.  This single stick two stage rocket would replace Falcon Heavy and be able to test all factors of in a reduced scale.  Like the previous poster, possibly a mini-ITS half scale, but with a single stick 9 engine raptor first stage.  This would make for a completely reusable two stage vehicle.  F9/FH is too small a diameter and too tall for a good mini-ITS.  After sea level Raptor is developed, a single stick upscaled F9 to 7m diameter shouldn't be a problem except location of the manufacturing facility. 

This new rocket would be slightly more powerful than BO's New Glenn, and be fully reusable.

A 6 Raptor booster would slightly more powerful than New Glenn. A 9 Raptor version considerably more so.

I do think that mini-ITS on FH is feasible, though, since I believe the biggest structural issue with Falcon Heavy is how fast it goes in the dense lower atmosphere. A heavier upper stage means Max-Q and trans-sonic regions are higher up in thinner atmosphere with less dynamic stress, and the rocket goes through high altitude wind shear much slower. It also means that staging is lower and slower so it's easier to get the boosters back.

Offline OneSpeed

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Re: Speculation thread: intermediate-lift Raptor-derived RLV
« Reply #18 on: 04/24/2017 12:57 PM »
A 6 Raptor booster would slightly more powerful than New Glenn. A 9 Raptor version considerably more so.

I do think that mini-ITS on FH is feasible, though, since I believe the biggest structural issue with Falcon Heavy is how fast it goes in the dense lower atmosphere. A heavier upper stage means Max-Q and trans-sonic regions are higher up in thinner atmosphere with less dynamic stress, and the rocket goes through high altitude wind shear much slower. It also means that staging is lower and slower so it's easier to get the boosters back.

Agreed, both are feasible. Perhaps a logical development path would be half scale BFS on FH first, then half scale BFS on half scale BFR, and once they are making money from that system, full scale of both.

Offline Oli

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Re: Speculation thread: intermediate-lift Raptor-derived RLV
« Reply #19 on: 04/24/2017 02:56 PM »
Another option is a second stage for FH as a half scaled ITS. 6m diameter, 24m long, 1 raptor and 3 flavours:
1- Cargo version with integrated fairing (crocodile style) to deploy satellites
2- Mini crewed ITS launched as FH: minibus of 20 PAX to LEO, 10 PAX to moon vicinity and 5 to asteroids or even Phobos. Crewed part is 6m diameter, 9m long with around 180m3. Could copy-paste beefed up ECLSS systems from Dragon and become a very polyvalent spaceship.
3 - Tanker version

That would be the spaceship that NASA needs for BLEO and would match beautifully with the SLS. But I guess reminds too much the shuttle. Would delay too much the bigger brother, but a very good exploration spaceship.

It would be similar in size to NASA's Mid-L/D Mars lander design for the Evolvable Mars Campaign. Although I guess some of the tanking (and Raptor) would have to be removed to make room for the payload. It would be "landing only".

I bet Blue Origin has plans for something like that.
« Last Edit: 04/24/2017 02:59 PM by Oli »

Offline sevenperforce

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Re: Speculation thread: intermediate-lift Raptor-derived RLV
« Reply #20 on: 04/24/2017 05:34 PM »
A 6 Raptor booster would slightly more powerful than New Glenn. A 9 Raptor version considerably more so.

I do think that mini-ITS on FH is feasible, though, since I believe the biggest structural issue with Falcon Heavy is how fast it goes in the dense lower atmosphere. A heavier upper stage means Max-Q and trans-sonic regions are higher up in thinner atmosphere with less dynamic stress, and the rocket goes through high altitude wind shear much slower. It also means that staging is lower and slower so it's easier to get the boosters back.
Agreed, both are feasible. Perhaps a logical development path would be half scale BFS on FH first, then half scale BFS on half scale BFR, and once they are making money from that system, full scale of both.
Yeah, I definitely like this idea. Build a fully-reusable methalox upper stage that can be tested on Falcon Heavy as a flying testbed for Raptor and ITS, then either go straight to ITS or go to a single-stick methalox first stage.

My concept, posted earlier, could be dropped in on FH easily. It would need a custom interstage but it would still have pretty solid performance.

I think the reason for vertical us the load structure. During EDL, the load is distributed over the entire surface which is not so problematic as landing on discrete points like legs.
With the wing extensions, the load is distributed across most of the stage.

Another option is a second stage for FH as a half scaled ITS. 6m diameter, 24m long, 1 raptor and 3 flavours:
1- Cargo version with integrated fairing (crocodile style) to deploy satellites
2- Mini crewed ITS launched as FH: minibus of 20 PAX to LEO, 10 PAX to moon vicinity and 5 to asteroids or even Phobos. Crewed part is 6m diameter, 9m long with around 180m3. Could copy-paste beefed up ECLSS systems from Dragon and become a very polyvalent spaceship.
3 - Tanker version

That would be the spaceship that NASA needs for BLEO and would match beautifully with the SLS. But I guess reminds too much the shuttle. Would delay too much the bigger brother, but a very good exploration spaceship.

It would be similar in size to NASA's Mid-L/D Mars lander design for the Evolvable Mars Campaign. Although I guess some of the tanking (and Raptor) would have to be removed to make room for the payload. It would be "landing only".

I bet Blue Origin has plans for something like that.
Oh, neat -- that looks a lot like my reusable second stage (though without the whole "single use" thing).
« Last Edit: 04/24/2017 05:44 PM by sevenperforce »

Offline dror

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Re: Speculation thread: intermediate-lift Raptor-derived RLV
« Reply #21 on: 04/24/2017 06:04 PM »

The second stage re-enters on its belly using split flaps for attitude control, like the ITS Spaceship and Tanker. However, it has no landing legs near its tail, and no tail auxiliary thrusters. Instead, panels on the underside open up, both serving as landing skids and exposing auxiliary landing thrusters for a propulsive belly-first landing:



I've worked out all the specs...filled up about three Excel spreadsheets doing so, too.

First stage dry mass: 17 tonnes
First stage propellant: 421 tonnes
First stage mass ratio: 24:1
Thrust at launch: 6,266 kN

Second stage dry mass: 6.6 tonnes
Second stage propellant: 141 tonnes
Total vacuum thrust: 2,292 kN

Reusable payload to LEO: 24 tonnes
Reusable payload to GTO: 6.8 tonnes
Downmass from LEO: 22 tonnes

 
Quote
Upper stage landing would look like something out of Star Wars, because it drops straight down, winglets open, and it lands on the wingtips with rocket propulsion.

Know what else is great? Due to the vertically-oriented thrusters, the upper stage could both land on and take off from the Moon or from the surface of Mars without needing a launch pad.
 

To see that thing land, it would be mindblowing. Very cool stuff indeed. The ultimate space shuttle.
I hope some SpaceXer is reading this.
They could also arrange to show this launch technique on earth if they can manage to fly with ~ 2/3 empty tanks.

I do want to ask:
how and why did you opt for 4 meter diameter for both stages?
With this diameter you put a harder constraint on the payloads' diameter and volume than F9.
It also seems that most posters think that more performance is needed.
A three-engine version would be too big for most payloads, but will be big enogh for all.

Offline sevenperforce

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Re: Speculation thread: intermediate-lift Raptor-derived RLV
« Reply #22 on: 04/24/2017 07:18 PM »
To see that thing land, it would be mindblowing. Very cool stuff indeed. The ultimate space shuttle.
I hope some SpaceXer is reading this.
They could also arrange to show this launch technique on earth if they can manage to fly with ~ 2/3 empty tanks.
Yeah, they could easily do manned or unmanned hypersonic flight tests using the VTOL mechanism with the vacuum engines swapped out for SL-expanded mini-Raptors. Would also be a fantastic antipodal high-speed transport.

Quote
I do want to ask:
how and why did you opt for 4 meter diameter for both stages?
With this diameter you put a harder constraint on the payloads' diameter and volume than F9.
It also seems that most posters think that more performance is needed.
A three-engine version would be too big for most payloads, but will be big enogh for all.
The four-meter diameter is just seven inches wider in every direction than F9, which is all I need to make the first stage identical in height to the Falcon 9 first stage. That's a 19% increase in volume while the stage remains entirely road-transportable and still capable of using many of the systems already in place for Falcon 9. Might even be able to use the same grid fins and landing legs.

The upper stage could also drop in to the Falcon Heavy using only a small modification to the interstage.

If we were sticking with an aluminum first stage, then you'd need three Raptors to get decent performance. But with a composite first stage and the auxiliary landing thrusters, two Raptors is plenty.
« Last Edit: 04/24/2017 07:19 PM by sevenperforce »

Offline dror

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Re: Speculation thread: intermediate-lift Raptor-derived RLV
« Reply #23 on: 04/24/2017 07:44 PM »

The four-meter diameter is just seven inches wider in every direction than F9, which is all I need to make the first stage identical in height to the Falcon 9 first stage. That's a 19% increase in volume while the stage remains entirely road-transportable and still capable of using many of the systems already in place for Falcon 9. Might even be able to use the same grid fins and landing legs.

The upper stage could also drop in to the Falcon Heavy using only a small modification to the interstage.
So you went for 4 meters based on booster road-transportability and kept it to the upper stage, thus making a 4 meter faring.
Wouldn't you be able to make a 5.4 meter upper stage  like the Falcon fairing?

Offline GWH

The upper stage could also drop in to the Falcon Heavy using only a small modification to the interstage.

Could it not drop onto a Block 5 F9 as well?  At a glance it looks like full stage mass is only a hair over F9, and therefore within acceptable TWR. 

Curious as well what the performance of this mini ITS would be with either F9 or FH booster rather than the methalox single stick.
« Last Edit: 04/24/2017 07:51 PM by GWH »

Offline sevenperforce

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Re: Speculation thread: intermediate-lift Raptor-derived RLV
« Reply #25 on: 04/24/2017 08:28 PM »

The four-meter diameter is just seven inches wider in every direction than F9, which is all I need to make the first stage identical in height to the Falcon 9 first stage. That's a 19% increase in volume while the stage remains entirely road-transportable and still capable of using many of the systems already in place for Falcon 9. Might even be able to use the same grid fins and landing legs.

The upper stage could also drop in to the Falcon Heavy using only a small modification to the interstage.
So you went for 4 meters based on booster road-transportability and kept it to the upper stage, thus making a 4 meter faring.
Wouldn't you be able to make a 5.4 meter upper stage  like the Falcon fairing?
Upper-stage dimensions are more flexible. It could be 4 meters, or it could be 5.4 meters with a taper to 4 meters at the rear. I prefer 4 meters because it allows some commonality with the first stage, just like Falcon 9 has. I didn't set a specific height limit. The whole front end would probably need to come in several variants depending on whether it was crewed or not.

Note that the upper stage has 165% the dry mass of the Falcon 9 upper stage, while the first stage has only 77% the dry mass of the Falcon 9 first stage. So it is even more balanced toward the upper stage than the Falcon 9.

With the mini-vacuum-Raptors swapped out for SL raptors, the upper stage would have the following specs:

Dry mass: 6.4 tonnes
Propellant capacity: 141 tonnes
Total vacuum thrust: 2,166 kN
Vacuum isp: 360 s

It could make orbit as an SSTO with about 700 kg of payload and enough margin for recovery. That's if it launches vertically, with full fuel tanks. Obviously the landing thrusters don't have enough umph to get it off the ground with full tanks.

The upper stage could also drop in to the Falcon Heavy using only a small modification to the interstage.

Could it not drop onto a Block 5 F9 as well?  At a glance it looks like full stage mass is only a hair over F9, and therefore within acceptable TWR. 

Curious as well what the performance of this mini ITS would be with either F9 or FH booster rather than the methalox single stick.
Full second-stage mass at liftoff is 149.4 tonnes without payload, which is rather high compared to Falcon 9's 111.5 tonnes. F9 FT has 775 tonnes thrust, so TWR is lower but acceptable.

Based on this calculator and assuming 21.6 tonnes of residuals for first stage recovery, I get 22.6 tonnes to LEO, fully reusable. That's with the second stage delivering 6.1 km/s, which allows staging to occur at less than 2 km/s.

Looks like they wouldn't need Falcon Heavy to test it after all. They could fly every Falcon Heavy mission with full reuse and first-stage RTLS, single-stick.

Offline GWH

Looks like they wouldn't need Falcon Heavy to test it after all. They could fly every Falcon Heavy mission with full reuse and first-stage RTLS, single-stick.

I'm thinking that while it may have lower refurbishment costs the methalox booster would have pretty slim margins of cost reduction vs. Block 5 F9's & FH's.

Offline sevenperforce

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Re: Speculation thread: intermediate-lift Raptor-derived RLV
« Reply #27 on: 04/24/2017 09:04 PM »
Looks like they wouldn't need Falcon Heavy to test it after all. They could fly every Falcon Heavy mission with full reuse and first-stage RTLS, single-stick.

I'm thinking that while it may have lower refurbishment costs the methalox booster would have pretty slim margins of cost reduction vs. Block 5 F9's & FH's.
I think you're right. The methalox booster is higher-performing, but clearly not needed. Not when F9FT + methalox upper stage can already do as much as FH.

Offline GWH

One huge advantage of this architecture that I can think of is Lunar or Mars missions could be performed quite economically through reuse without any use of ISRU tech and actually getting the stage back.
If each upper stage could be used as little as several times before performing a one way trip and landing the hardware cost for those missions should be very low. 

Offline sevenperforce

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Re: Speculation thread: intermediate-lift Raptor-derived RLV
« Reply #29 on: 04/24/2017 09:49 PM »
One huge advantage of this architecture that I can think of is Lunar or Mars missions could be performed quite economically through reuse without any use of ISRU tech and actually getting the stage back.
If each upper stage could be used as little as several times before performing a one way trip and landing the hardware cost for those missions should be very low.
SpaceX could build a tanker variant to be sent up on Falcon Heavy easily enough, for refueling on-orbit. I get 41.2 tonnes of fuel to LEO with full reuse, off Falcon Heavy with booster RTLS and center-core recovery. No crossfeed necessary.

I can't remember if I already said this here, but with full fuel tanks in LEO, the methalox upper stage would be able to burn from LEO to the moon, land on the moon, and return to lunar orbit, all without refueling. It would need to refuel in cislunar space to get back home, though. Of course it could take off fully fueled from the lunar surface on its side thrusters easily.

Online Bynaus

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Re: Speculation thread: intermediate-lift Raptor-derived RLV
« Reply #30 on: 04/25/2017 01:40 PM »
I like your idea, sevenperforce, but aren't you forgetting something? Namely, the payload. To first order, a rocket must launch satellites. How would you deploy them with that upper stage? Does your upper stage have an internal compartment with cargo bay doors? How would the satellites then be deployed? Using a robotic arm? Or rather "crocodile"-style? But then what about the joints being exposed to re-entry heating? Or does it have a front adapter onto which the satellite and normal fairings could be mounted? (but your drawing suggests otherwise)

Offline gospacex

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Re: Speculation thread: intermediate-lift Raptor-derived RLV
« Reply #31 on: 04/25/2017 02:05 PM »
The four-meter diameter is just seven inches wider in every direction than F9, which is all I need to make the first stage identical in height to the Falcon 9 first stage. That's a 19% increase in volume while the stage remains entirely road-transportable and still capable of using many of the systems already in place for Falcon 9.

Even though it is only +30 cm, it is likely to cause all sorts of headache at the existing F9 factory. All those 3.7m fixtures need to be remade.
Welding machines need to be readjusted - if you are lucky. If you are not, you need different welding machines.
And if there is a door frame which is just a bit too narrow for 4m? Need to change that too. Let's hope that wouldn't require walls to be moved...
And if you want to continue building F9s, you need to support both at once.

At which point you ask yourself, "maybe it's easier to just build a separate factory and don't mess with the existing one". "And while we are at it, why not build this new factory in a location where road transport is not a limitation".

IOW: a small diameter change probably is not worth it. If you go for a diameter change, got for a big one.

Offline sevenperforce

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Re: Speculation thread: intermediate-lift Raptor-derived RLV
« Reply #32 on: 04/25/2017 02:39 PM »
I like your idea, sevenperforce, but aren't you forgetting something? Namely, the payload. To first order, a rocket must launch satellites. How would you deploy them with that upper stage? Does your upper stage have an internal compartment with cargo bay doors? How would the satellites then be deployed? Using a robotic arm? Or rather "crocodile"-style? But then what about the joints being exposed to re-entry heating? Or does it have a front adapter onto which the satellite and normal fairings could be mounted? (but your drawing suggests otherwise)
Originally, I was thinking that the single bay door shown in the drawings could hinge up (or, if that was difficult to achieve, it could be split and open like the cargo bay doors on the shuttle) and the payload would be deployed perpendicular to the long axis of the satellite.



As you can see, the payload adapter would need to wrap about the body to some degree in order to transfer force to the main axis. This design would keep seams outside of the re-entry plasma stream. Of course, that's not necessarily a huge concern; there will need to be seams in the TPS anyway for the landing skids/landing engine ports, but there were seams in the Shuttle's TPS for its landing gear, and the seams in the ITS Spaceship (for landing legs) are not entirely out of the plasma stream.

If seams turn out to be nonproblematic, it can also open up at the nose, like this:



There are a few ways it can work. I have some structural concerns about the difference between the crewed and uncrewed versions. Because this configuration (low forward cross-section for launch, high belly cross-section for re-entry, perpendicular thrusters for propulsive landing) is highly advantageous for landing on Mars or on the Moon, we definitely want manned capability.

But then the differences between manned and unmanned flights become tricky. Ideally, you could manufacture the entire back end of the spacecraft exactly the same 100% of the time, and fit the front end with either the payload deployment/recovery module or a crew cabin. In theory you could even swap out the front module between flights. But getting the structure to work with this is tricky, particularly if you have landing propulsion on the front end, as I've depicted.

Online guckyfan

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Re: Speculation thread: intermediate-lift Raptor-derived RLV
« Reply #33 on: 04/25/2017 03:02 PM »
At which point you ask yourself, "maybe it's easier to just build a separate factory and don't mess with the existing one". "And while we are at it, why not build this new factory in a location where road transport is not a limitation".
............
IOW: a small diameter change probably is not worth it. If you go for a diameter change, got for a big one.

That would be true for a new booster stage. If you want a new upper stage that can be launched on mostly existing ground support hardware you go for the diameter that can be supported on a TEL. 4m is exactly what I was thinking about. Enough volume increase to have at least the same propellant weight, making good use of methalox propellant. Prove a lot of technology by using carbon composite, Raptor, self pressurization, even refuelling in orbit. As was shown in this thread the system would be very capable. keeping the existing payload capability or even increasing it slightly and have full reusability of the system. They may use a conventional fairing. No problem with reusing the fairing too.

Offline sevenperforce

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Re: Speculation thread: intermediate-lift Raptor-derived RLV
« Reply #34 on: 04/25/2017 03:16 PM »
At which point you ask yourself, "maybe it's easier to just build a separate factory and don't mess with the existing one". "And while we are at it, why not build this new factory in a location where road transport is not a limitation".
............
IOW: a small diameter change probably is not worth it. If you go for a diameter change, got for a big one.

That would be true for a new booster stage. If you want a new upper stage that can be launched on mostly existing ground support hardware you go for the diameter that can be supported on a TEL. 4m is exactly what I was thinking about. Enough volume increase to have at least the same propellant weight, making good use of methalox propellant. Prove a lot of technology by using carbon composite, Raptor, self pressurization, even refuelling in orbit. As was shown in this thread the system would be very capable. keeping the existing payload capability or even increasing it slightly and have full reusability of the system. They may use a conventional fairing. No problem with reusing the fairing too.
Yeah, after seeing how capable a double-dev-Raptor US would be, there is absolutely no reason to add a new booster. Falcon 9 would be able to lift a double-dev-Raptor composite upper stage with no trouble whatsoever.

Offline GWH

How much payload to LEO would this be upper stage MITS (mini-ITS) be capable of with a fully expendable Falcon Heavy, and the more pertinent number what mass to TMI, (and maybe TLI for fun).
I suspect this FH-MITS number would be well above SLS block 1.

Now I know what you are thinking "But why expendable? This system is reusable!" However I think there is SOME merit to a single lift straight from pad to Mars, and there is no reason whatsoever why this type of mission would be flown with brand new cores.  I also suspect that there would be "maintenance intervals", where after say 9* flights the Merlins may need to be stripped down for a complete refurbishment.  At this point the cost of building new cores amortized over 10 flights may be less than the operating cost of distributed lift**, and the economical choice would be to fly those used cores expendable for max payload.

*The 9 flight number is just pulled out thin air as an example.  Could be anything.
**Another strategy could be to ALWAYS fly the FH-MITS variant when launching sats to GTO and transfer over excess prop to awaiting MITS in circular LEO orbit before making the GTO burn and returning.  Launch costs generally go down on a per-kg basis with larger launch vehicles and this averages out those costs considerably. Could be a future optimization. 

Offline envy887

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Re: Speculation thread: intermediate-lift Raptor-derived RLV
« Reply #36 on: 04/25/2017 05:29 PM »
How much payload to LEO would this be upper stage MITS (mini-ITS) be capable of with a fully expendable Falcon Heavy, and the more pertinent number what mass to TMI, (and maybe TLI for fun).
I suspect this FH-MITS number would be well above SLS block 1.

Now I know what you are thinking "But why expendable? This system is reusable!"...

I am thinking that, and I am right. FH is never going to match even SLS Block 1A without LEO refueling. With LEO refueling, it easily beats SLS Block 2 to any BLEO orbit. The only way LEO refueling makes sense is with reuse.

With LEO refueling, a 5 to 6 meter mini-ITS on reusable FH could send about 50t all the way to the surface of Mars or the Moon. Refueled on Mars via ISRU (or a combination of ISRU and delivered fuel), it could send at least 30t back to land on Earth.

Offline sevenperforce

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Re: Speculation thread: intermediate-lift Raptor-derived RLV
« Reply #37 on: 04/25/2017 06:12 PM »
How much payload to LEO would this be upper stage MITS (mini-ITS) be capable of with a fully expendable Falcon Heavy, and the more pertinent number what mass to TMI, (and maybe TLI for fun).
I suspect this FH-MITS number would be well above SLS block 1.

Now I know what you are thinking "But why expendable? This system is reusable!" However I think there is SOME merit to a single lift straight from pad to Mars, and there is no reason whatsoever why this type of mission would be flown with brand new cores.  I also suspect that there would be "maintenance intervals", where after say 9* flights the Merlins may need to be stripped down for a complete refurbishment.  At this point the cost of building new cores amortized over 10 flights may be less than the operating cost of distributed lift**, and the economical choice would be to fly those used cores expendable for max payload.
Flying expendable doesn't make much sense for this system, as envy points out, because you've got the dry mass of the recovery system tacked on there, which hurts it quite a bit.

But I'll go ahead and crunch the numbers for a few things. How's this: current Falcon 9 upper stage, a hypothetical one-dev-Raptor flying with the exact same current Falcon 9 upper stage (other than a shifted common bulkhead), and my proposed mini-ITS; to be flown on F9 and FH in each possible configuration?

Offline GWH

Flying expendable doesn't make much sense for this system, as envy points out, because you've got the dry mass of the recovery system tacked on there, which hurts it quite a bit.

But I'll go ahead and crunch the numbers for a few things. How's this: current Falcon 9 upper stage, a hypothetical one-dev-Raptor flying with the exact same current Falcon 9 upper stage (other than a shifted common bulkhead), and my proposed mini-ITS; to be flown on F9 and FH in each possible configuration?
Payload to LEO with expendable Falcon Heavy boosters is just a "what-if" measuring stick since most rockets are compared by LEO payload. 

More interested in just the TMI number for the expendable FH scenario, as if one were trying to land volume+mass on Mars as soon as possible it would probably be the fastest path forward.
The scenario where expendable booster 3-cores of Falcon Heavy might launch this mini-ITS direct to Mars would be where: in space prop transfer isn't developed yet, but one really wants to get a test of the system to land on Mars with at least some meaningful payload, so you expend some used FH cores. 

Its a matter of phased development, with in space cryo fluid transfer being one of the low TRL sticking points for people when discussing feasibility of the ITS.  From spreadsheets I've done on re-use its actually quite sound economically on a $/kg basis if there is a concern of high periodic refurbishment costs.  That's not to say reuse doesn't make sense and go off on THAT tangent, just that if you actually look at the cost vs capability it is a non-trivial improvement if refurb costs are high and stage life limited.

Offline envy887

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Re: Speculation thread: intermediate-lift Raptor-derived RLV
« Reply #39 on: 04/25/2017 07:30 PM »
Flying expendable doesn't make much sense for this system, as envy points out, because you've got the dry mass of the recovery system tacked on there, which hurts it quite a bit.

But I'll go ahead and crunch the numbers for a few things. How's this: current Falcon 9 upper stage, a hypothetical one-dev-Raptor flying with the exact same current Falcon 9 upper stage (other than a shifted common bulkhead), and my proposed mini-ITS; to be flown on F9 and FH in each possible configuration?
Payload to LEO with expendable Falcon Heavy boosters is just a "what-if" measuring stick since most rockets are compared by LEO payload. 

More interested in just the TMI number for the expendable FH scenario, as if one were trying to land volume+mass on Mars as soon as possible it would probably be the fastest path forward.
The scenario where expendable booster 3-cores of Falcon Heavy might launch this mini-ITS direct to Mars would be where: in space prop transfer isn't developed yet, but one really wants to get a test of the system to land on Mars with at least some meaningful payload, so you expend some used FH cores. 

Its a matter of phased development, with in space cryo fluid transfer being one of the low TRL sticking points for people when discussing feasibility of the ITS.  From spreadsheets I've done on re-use its actually quite sound economically on a $/kg basis if there is a concern of high periodic refurbishment costs.  That's not to say reuse doesn't make sense and go off on THAT tangent, just that if you actually look at the cost vs capability it is a non-trivial improvement if refurb costs are high and stage life limited.
Mars is 6,000 m/s past LEO; if you bring the upper stage tanks and propulsion along all the way to the surface the payload drops to about what Red Dragon can do with a fully expendable FH - roughly 2,000 kg.

Cryo prop transfer is really, really important if we want to go to Mars or anywhere else. It's not that hard, compared to landing on Mars and making fuel there. It's something that could easily be flight-ready before the rest of a mini-ITS system.

Offline sevenperforce

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Re: Speculation thread: intermediate-lift Raptor-derived RLV
« Reply #40 on: 04/25/2017 07:54 PM »
Payload to LEO with expendable Falcon Heavy boosters is just a "what-if" measuring stick since most rockets are compared by LEO payload.

More interested in just the TMI number for the expendable FH scenario, as if one were trying to land volume+mass on Mars as soon as possible it would probably be the fastest path forward.
The scenario where expendable booster 3-cores of Falcon Heavy might launch this mini-ITS direct to Mars would be where: in space prop transfer isn't developed yet, but one really wants to get a test of the system to land on Mars with at least some meaningful payload, so you expend some used FH cores.
Right, makes perfect sense.

Here's the table showing payloads. Everything is listed in tonnes.

_LEO|GTO|TMI
Falcon 9 FT (RTLS)18.3|5.7|2.7
Falcon 9 FT (droneship)19.2|6.6|3.3
Falcon 9 FT (expended)22.3|8.1|4.4
Falcon H (recovered)31.6|11.7|6.7
Falcon H (core expended)39.3|15.4|9.3
Falcon H (expended)51.5|20.6|12.9
Falcon 9M (RTLS)19.9|7.4|4.0
Falcon 9M (droneship)21.9|8.4|4.7
Falcon 9M (expended)25.5|10.2|6.1
Falcon HM (recovered)37.3|14.5|8.9
Falcon HM (core expended)46.4|19.0|12.1
Falcon HM (expended)59.51|25.1|16.3
Falcon 9M+ (RTLS)22.0|7.8|1.4
Falcon 9M+ (droneship)23.8|8.8|2.1
Falcon 9M+ (expended)27.0|10.4|3.3
Falcon HM+ (recovered)42.4|16.9|7.7
Falcon HM+ (core expended)50.2|20.8|10.6
Falcon HM+ (expended)64.8|27.0|14.9

"Falcon 9 FT" and "Falcon H" represent the current incarnations with expendable kerolox upper stages. Standard recovery for Falcon Heavy is RTLS for the boosters and droneship for the core; "core expended" means droneship recovery for the boosters.

"Falcon 9M" and "Falcon HM" represent the current configuration with an expendable methalox upper stage powered by a single vacuum-optimized devRaptor. Upper stage material and dimensions are the same, with a shifted common bulkhead.

"Falcon 9M+" and "Falcon HM+" represent the replacement of the current upper stage with my two-engine reusable composite upper stage, including landing thrusters and recovery margins. LEO missions have enough margin for bringing the full payload back to Earth (e.g., crewed missions), GTO missions have enough margin for bringing the stage back empty, and TMI missions have enough margin to land the full payload on Mars.

Not shown in the table is the theoretical maximum performance to LEO (e.g., upper stage fully expended, with plan to refuel in LEO); this is 65.7 tonnes. However, these are all Falcon 9 FT numbers, with Falcon Heavy based on this. SpaceX is currently projecting Falcon Heavy (based on Block 5 cores) at an expendable payload of 63.8 tonnes to LEO, while my table has it at 51.5 tonnes to LEO. So the true theoretical maximum performance could be significantly higher, maybe as high as 75 tonnes.

Not sure how Block 5 FH can make 63.8 tonnes to orbit, though. That's a jump far larger than what thrust increases alone can manage. Maybe specific impulse is coming up too?

Mars is 6,000 m/s past LEO; if you bring the upper stage tanks and propulsion along all the way to the surface the payload drops to about what Red Dragon can do with a fully expendable FH - roughly 2,000 kg.

Cryo prop transfer is really, really important if we want to go to Mars or anywhere else. It's not that hard, compared to landing on Mars and making fuel there. It's something that could easily be flight-ready before the rest of a mini-ITS system.
Actually, I got 15 tonnes to the Martian surface with a direct ascent on fully-expendable Falcon Heavy. And this number, like the rest of the numbers, is based on the FT Heavy, not the Block 5 Heavy.

But you're right, orbital prop transfer is super important. A reusable methalox upper stage for Falcon 9 and Falcon Heavy would be a fantastic test bed for this.
« Last Edit: 04/25/2017 08:03 PM by sevenperforce »

Offline envy887

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Re: Speculation thread: intermediate-lift Raptor-derived RLV
« Reply #41 on: 04/25/2017 08:26 PM »
Mars is 6,000 m/s past LEO; if you bring the upper stage tanks and propulsion along all the way to the surface the payload drops to about what Red Dragon can do with a fully expendable FH - roughly 2,000 kg.

Cryo prop transfer is really, really important if we want to go to Mars or anywhere else. It's not that hard, compared to landing on Mars and making fuel there. It's something that could easily be flight-ready before the rest of a mini-ITS system.
Actually, I got 15 tonnes to the Martian surface with a direct ascent on fully-expendable Falcon Heavy. And this number, like the rest of the numbers, is based on the FT Heavy, not the Block 5 Heavy.
Your mass fractions are also extremely optimistic. 6.6/(6.6+141) = 4.5%. SpaceX is claiming 7.1% dry mass for the  ITS ship, which presumably includes a pressure vessel for crew and ECLSS equipment but no consumables. The ITS tanker is at 3.5%, but I have seen no indication that it has anything needed for flight beyond LEO like a high velocity heatshield, solar panels, payload adapter, or cargo doors.

I was assuming 4.5 km/s for TMI and 1.5 km/s for landing, which is probably conservative. A slower transfer could be done for 5 km/s total, which even with more realistic mass fractions does get 5 to 10 tonnes to the surface.

But with refueling and very conservative mass fractions it's straightforward to get 40 or 50 tonnes landed. There's just no comparison to direct launch, so LEO refueling is going to be one of the first things validated by any serious Mars architecture.

Offline sevenperforce

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Re: Speculation thread: intermediate-lift Raptor-derived RLV
« Reply #42 on: 04/25/2017 08:27 PM »
Here's the table showing payloads. Everything is listed in tonnes.

Falcon H (expended)51.5|20.6|12.9

Falcon heavy expedable is 63.8 tonnes to LEO, 26.7 tonnes to GTO and 16.8 tonnes to TMI. So your numbers are way off.
My numbers are based on the Full Thrust Falcon Heavy, before the planned Block 5 uprating. We don't yet have enough numbers to model the performance of Block 5 Falcon Heavy. SpaceX does, and that's why SpaceX's website has those higher numbers.

As I said before, I'm not sure how they are able to get those numbers. Shotwell said the primary change is more powerful engines but they would have to be hella powerful to get that much of a boost.

Offline envy887

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Re: Speculation thread: intermediate-lift Raptor-derived RLV
« Reply #43 on: 04/25/2017 08:33 PM »
Here's the table showing payloads. Everything is listed in tonnes.

Falcon H (expended)51.5|20.6|12.9

Falcon heavy expedable is 63.8 tonnes to LEO, 26.7 tonnes to GTO and 16.8 tonnes to TMI. So your numbers are way off.
My numbers are based on the Full Thrust Falcon Heavy, before the planned Block 5 uprating. We don't yet have enough numbers to model the performance of Block 5 Falcon Heavy. SpaceX does, and that's why SpaceX's website has those higher numbers.

As I said before, I'm not sure how they are able to get those numbers. Shotwell said the primary change is more powerful engines but they would have to be hella powerful to get that much of a boost.

Maybe they are bringing crossfeed back :D

Offline gospacex

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Re: Speculation thread: intermediate-lift Raptor-derived RLV
« Reply #44 on: 04/25/2017 08:33 PM »
At which point you ask yourself, "maybe it's easier to just build a separate factory and don't mess with the existing one". "And while we are at it, why not build this new factory in a location where road transport is not a limitation".
............
IOW: a small diameter change probably is not worth it. If you go for a diameter change, got for a big one.

That would be true for a new booster stage. If you want a new upper stage that can be launched on mostly existing ground support hardware you go for the diameter that can be supported on a TEL. 4m is exactly what I was thinking about. Enough volume increase to have at least the same propellant weight, making good use of methalox propellant. Prove a lot of technology by using carbon composite, Raptor, self pressurization, even refuelling in orbit. As was shown in this thread the system would be very capable.

I' not disputing the capability. I'm disputing than going to 4m core makes most sense. Why not just go for a new factory and 6m core, for example?

Offline GWH

That chart is phenomenal work.

Mars is 6,000 m/s past LEO; if you bring the upper stage tanks and propulsion along all the way to the surface the payload drops to about what Red Dragon can do with a fully expendable FH - roughly 2,000 kg.
Actually, I got 15 tonnes to the Martian surface with a direct ascent on fully-expendable Falcon Heavy. And this number, like the rest of the numbers, is based on the FT Heavy, not the Block 5 Heavy.

The mini-ITS can deliver something that a Dragon can't however: volume. And if the hinged nose cone is used mobile equipment can be deployed direct to surface without the added mass of a crane.

Offline sevenperforce

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Re: Speculation thread: intermediate-lift Raptor-derived RLV
« Reply #46 on: 04/25/2017 08:38 PM »
I' not disputing the capability. I'm disputing than going to 4m core makes most sense. Why not just go for a new factory and 6m core, for example?
There's a limit to what is readily road-transportable that's right around 4-5 meters.

But in any case, as the numbers above demonstrate, there is really no need for a new booster core. Falcon Heavy can take the methalox upper stage anywhere it needs to go. Having to pipe in both methane and kerosene kinda sucks, but oh well.

The upper stage size is flexible; I made it 4 meters to match the 4-meter booster core I was proposing, but since that's not gonna happen, it could be larger if necessary. My guess is that the ideal size will depend on what will have the best drag characteristics for mating to Falcon Heavy. You don't want it to be too much taller than the existing stack.
« Last Edit: 04/25/2017 08:41 PM by sevenperforce »

Offline gospacex

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Re: Speculation thread: intermediate-lift Raptor-derived RLV
« Reply #47 on: 04/25/2017 08:44 PM »
I' not disputing the capability. I'm disputing than going to 4m core makes most sense. Why not just go for a new factory and 6m core, for example?

There's a limit to what is readily road-transportable that's right around 4-5 meters.

If you go for a new factory, you plan to have it where water transportation is possible. And/or build it close to the pad.

Offline envy887

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Re: Speculation thread: intermediate-lift Raptor-derived RLV
« Reply #48 on: 04/25/2017 08:51 PM »
That chart is phenomenal work.

Mars is 6,000 m/s past LEO; if you bring the upper stage tanks and propulsion along all the way to the surface the payload drops to about what Red Dragon can do with a fully expendable FH - roughly 2,000 kg.
Actually, I got 15 tonnes to the Martian surface with a direct ascent on fully-expendable Falcon Heavy. And this number, like the rest of the numbers, is based on the FT Heavy, not the Block 5 Heavy.

The mini-ITS can deliver something that a Dragon can't however: volume. And if the hinged nose cone is used mobile equipment can be deployed direct to surface without the added mass of a crane.

Agreed that volume and landed height are useful, but I don't think such a vehicle is worth designing and building to launch direct with no refueling. If you're going through that much effort to build a vehicle that capable, it's a very small additional  step to refuel it in LEO.

And I'll pit the mass of a crane against the additional structure and propulsion required for horizontal landing any day. A simple unloading ramp probably has more mass than a crane. The operational simplicity is definitely nice though.

Offline sevenperforce

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Re: Speculation thread: intermediate-lift Raptor-derived RLV
« Reply #49 on: 04/25/2017 09:01 PM »
As I said before, I'm not sure how they are able to get those numbers. Shotwell said the primary change is more powerful engines but they would have to be hella powerful to get that much of a boost.

Maybe they are bringing crossfeed back :D
Even if I switch up the numbers to factor in 6-engine crossfeed, it only goes up to 57.6 tonnes.

Of course, it might be that the calculator I've been using is not handling the boosters properly.

Offline sevenperforce

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Re: Speculation thread: intermediate-lift Raptor-derived RLV
« Reply #50 on: 04/25/2017 09:30 PM »
I got 15 tonnes to the Martian surface with a direct ascent on fully-expendable Falcon Heavy. And this number, like the rest of the numbers, is based on the FT Heavy, not the Block 5 Heavy.
Your mass fractions are also extremely optimistic. 6.6/(6.6+141) = 4.5%. SpaceX is claiming 7.1% dry mass for the  ITS ship, which presumably includes a pressure vessel for crew and ECLSS equipment but no consumables. The ITS tanker is at 3.5%, but I have seen no indication that it has anything needed for flight beyond LEO like a high velocity heatshield, solar panels, payload adapter, or cargo doors.
Here, I can break down my numbers.

I'm putting the Raptor's SL TWR at 200:1, which makes its mass 1.55 tonnes. There are nine of these on the ITS Tanker and Spaceship, but I'll go ahead and kick the engine mass up to a total of 15.5 tonnes to account for the mass of the vacuum nozzle extensions.

The dry mass of the ITS tanker is projected at 90 tonnes, which includes the monocoque tanks/body, the intertanks, the RCS thrusters, the TPS, the engines, and the landing legs. Subtract the engine mass, and that's 74.5 tonnes for the tanker's 2,500 tonnes of propellant, or a mass ratio of 33.6:1.

To account for some square-cube losses, I projected my structural mass ratio at 29:1 to get a base structural mass of 4.88 tonnes for the 141 tonnes of propellant I wanted. I added back 1.28 tonnes for the two dev Raptor engines and 405 kg for the eight landing thrusters.

I didn't include payload encapsulation in my overall dry mass because I'd want a monocoque pressure vessel for the crewed version. The payload fairings on the Falcon 9 mass 1.75 tonnes total so that's a good estimate for the cargo bay mass. The actual downmass to Mars on a FH-expendable direct ascent is probably closer to 13 tonnes, then. That's reserving 2.9 tonnes of propellant for the landing burn, which gives about 448 m/s of dV. That should be enough, I think; if I need more it would decrease the downmass slightly but not by much.

Agreed that volume and landed height are useful, but I don't think such a vehicle is worth designing and building to launch direct with no refueling. If you're going through that much effort to build a vehicle that capable, it's a very small additional  step to refuel it in LEO.

And I'll pit the mass of a crane against the additional structure and propulsion required for horizontal landing any day. A simple unloading ramp probably has more mass than a crane. The operational simplicity is definitely nice though.
I would certainly support refueling. But there is really very little additional structure or propulsion required for horizontal landing. Composites have better biaxial rigidity than aluminum, you need biaxial strength for the biconic re-entry anyway, and you need the thrusters regardless because of TWR issues.

You might still need an arm or crane or some other mechanism for getting the payload out, but it is a LOT easier than trying to do it with a capsule.
« Last Edit: 04/25/2017 09:33 PM by sevenperforce »

Offline envy887

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Re: Speculation thread: intermediate-lift Raptor-derived RLV
« Reply #51 on: 04/26/2017 01:04 AM »
I got 15 tonnes to the Martian surface with a direct ascent on fully-expendable Falcon Heavy. And this number, like the rest of the numbers, is based on the FT Heavy, not the Block 5 Heavy.
Your mass fractions are also extremely optimistic. 6.6/(6.6+141) = 4.5%. SpaceX is claiming 7.1% dry mass for the  ITS ship, which presumably includes a pressure vessel for crew and ECLSS equipment but no consumables. The ITS tanker is at 3.5%, but I have seen no indication that it has anything needed for flight beyond LEO like a high velocity heatshield, solar panels, payload adapter, or cargo doors.
Here, I can break down my numbers.

I'm putting the Raptor's SL TWR at 200:1, which makes its mass 1.55 tonnes. There are nine of these on the ITS Tanker and Spaceship, but I'll go ahead and kick the engine mass up to a total of 15.5 tonnes to account for the mass of the vacuum nozzle extensions.

The dry mass of the ITS tanker is projected at 90 tonnes, which includes the monocoque tanks/body, the intertanks, the RCS thrusters, the TPS, the engines, and the landing legs. Subtract the engine mass, and that's 74.5 tonnes for the tanker's 2,500 tonnes of propellant, or a mass ratio of 33.6:1.

To account for some square-cube losses, I projected my structural mass ratio at 29:1 to get a base structural mass of 4.88 tonnes for the 141 tonnes of propellant I wanted. I added back 1.28 tonnes for the two dev Raptor engines and 405 kg for the eight landing thrusters.

I didn't include payload encapsulation in my overall dry mass because I'd want a monocoque pressure vessel for the crewed version. The payload fairings on the Falcon 9 mass 1.75 tonnes total so that's a good estimate for the cargo bay mass. The actual downmass to Mars on a FH-expendable direct ascent is probably closer to 13 tonnes, then. That's reserving 2.9 tonnes of propellant for the landing burn, which gives about 448 m/s of dV. That should be enough, I think; if I need more it would decrease the downmass slightly but not by much.

This makes sense, except that you're comparing to the ITS tanker. As I pointed out already, the tanker isn't designed to fly to Mars. It most likely doesn't have TPS for an interplanetary entry, which will probably mass about twice as much as TPS for Earth LEO entry. It probably doesn't have significant solar power, operating mostly off batteries for the few hours it's in LEO. And it probably doesn't have active or passive cooling to keep the landing fuel from boiling off during a 6 month transit, which is how long a mass-optimized transfer to Mars takes. I'd figure dry mass of at least 5% of wet, before payload.

And it will need at least 1000 m/s to land. Terminal velocity is going to be Mach 2-ish.

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Agreed that volume and landed height are useful, but I don't think such a vehicle is worth designing and building to launch direct with no refueling. If you're going through that much effort to build a vehicle that capable, it's a very small additional  step to refuel it in LEO.

And I'll pit the mass of a crane against the additional structure and propulsion required for horizontal landing any day. A simple unloading ramp probably has more mass than a crane. The operational simplicity is definitely nice though.
I would certainly support refueling. But there is really very little additional structure or propulsion required for horizontal landing. Composites have better biaxial rigidity than aluminum, you need biaxial strength for the biconic re-entry anyway, and you need the thrusters regardless because of TWR issues.

You might still need an arm or crane or some other mechanism for getting the payload out, but it is a LOT easier than trying to do it with a capsule.
What Isp and TWR are you assuming for the thrusters? I haven't seen any reliable info on them other than fuel and thrust. I'd be surprised if it's over 340 sec for a low pressure methalox RCS thruster.

Vertical landing allows the more efficient Raptors to null 99% of the velocity with thrusters handling only terminal thrust. And you only need about 1 g worth of terminal thrust instead of 3 to 4 gees. So with vertical landing you some structure mass, some thruster mass, and some fuel mass thanks to being lighter AND more efficient.

Offline TheKutKu

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Re: Speculation thread: intermediate-lift Raptor-derived RLV
« Reply #52 on: 04/26/2017 01:42 PM »
Why does the second stage need to have 2 engines? One single Vacuum Raptor-dev (assuming it is at 1/3rd of the thrust, and doesn't have much less TWR compared to the full sized one) could push the full second stage well enough, you don't need a 1 TWR (on earth) for a second stage or even a mars/moon lander.

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And it will need at least 1000 m/s to land. Terminal velocity is going to be Mach 2-ish.

I may be wrong but since it is both a lifting body and it is quite light (<15 tons), i've read that in this case mars EDL delta v could be as low as 800 m/s.

Offline sevenperforce

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Re: Speculation thread: intermediate-lift Raptor-derived RLV
« Reply #53 on: 04/26/2017 03:06 PM »
I'm putting the Raptor's SL TWR at 200:1, which makes its mass 1.55 tonnes. There are nine of these on the ITS Tanker and Spaceship, but I'll go ahead and kick the engine mass up to a total of 15.5 tonnes to account for the mass of the vacuum nozzle extensions.

The dry mass of the ITS tanker is projected at 90 tonnes, which includes the monocoque tanks/body, the intertanks, the RCS thrusters, the TPS, the engines, and the landing legs. Subtract the engine mass, and that's 74.5 tonnes for the tanker's 2,500 tonnes of propellant, or a mass ratio of 33.6:1.

To account for some square-cube losses, I projected my structural mass ratio at 29:1 to get a base structural mass of 4.88 tonnes for the 141 tonnes of propellant I wanted. I added back 1.28 tonnes for the two dev Raptor engines and 405 kg for the eight landing thrusters.

I didn't include payload encapsulation in my overall dry mass because I'd want a monocoque pressure vessel for the crewed version. The payload fairings on the Falcon 9 mass 1.75 tonnes total so that's a good estimate for the cargo bay mass. The actual downmass to Mars on a FH-expendable direct ascent is probably closer to 13 tonnes, then. That's reserving 2.9 tonnes of propellant for the landing burn, which gives about 448 m/s of dV. That should be enough, I think; if I need more it would decrease the downmass slightly but not by much.

This makes sense, except that you're comparing to the ITS tanker. As I pointed out already, the tanker isn't designed to fly to Mars. It most likely doesn't have TPS for an interplanetary entry, which will probably mass about twice as much as TPS for Earth LEO entry. It probably doesn't have significant solar power, operating mostly off batteries for the few hours it's in LEO. And it probably doesn't have active or passive cooling to keep the landing fuel from boiling off during a 6 month transit, which is how long a mass-optimized transfer to Mars takes. I'd figure dry mass of at least 5% of wet, before payload.
See, this is just the sort of engineering counter-analysis I was hoping for with this thread! Thanks. The points regarding high-velocity TPS, cooling, and power are good ones. I hadn't considered that. However, even if there is some dry mass growth on my upper stage, it's not catastrophic. Payload with full reuse is already very high, and this is not a SSTO where a 10% increase in dry mass results in negative payload fraction.

It was difficult to get a good estimate of tankage/structural fraction on the ITS Spaceship, because I don't know how much to subtract for the crew cabin and cargo hold. But after some consideration, I think we have a way we can at least place an upper bound on it.

The ITS Tanker and ITS Spaceship have identical external form lines, so we can say with relative confidence that if the tanker DID have all the TPS and cooling and power systems of the spaceship, it would still have a lower dry mass than the spaceship, since the crew cabin and ECLSS and cargo hold are heavier than monocoque tanks of equivalent size. So we can divide the structural dry mass of the ITS Spaceship (150 tonnes minus 15 tonnes of engine) by the propellant capacity of the ITS Tanker (2,500 tonnes) to get a structural/tankage/body fraction of 5.4%. This, I think, is generous and conservative. Even if there are square-cube losses to factor in, they are greatly outweighed by the fact that we are including the crew cabin and cargo hold and ECLSS dry mass, which we definitely don't need. And the ITS Spaceship dry mass already includes the additional mass of landing legs, control surfaces, RCS, and additional outer mold lines, so I don't need to add anything in to compensate for that.

Add it up, and the dry mass of my second-stage vehicle climbs from 6.56 tonnes to 9.32 tonnes, which means payload is simply reduced by a little under three tonnes. However, my reusable upper stage already beats the Falcon 9 upper stage for all LEO payloads by more than 3 tonnes when lofted on F9FT and it beats the Falcon 9 upper stage for all payloads period when lofted on Falcon Heavy...and that, again, is with full reuse. So it is by no means a dealbreaker.

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I would certainly support refueling. But there is really very little additional structure or propulsion required for horizontal landing. Composites have better biaxial rigidity than aluminum, you need biaxial strength for the biconic re-entry anyway, and you need the thrusters regardless because of TWR issues.

You might still need an arm or crane or some other mechanism for getting the payload out, but it is a LOT easier than trying to do it with a capsule.
What Isp and TWR are you assuming for the thrusters? I haven't seen any reliable info on them other than fuel and thrust. I'd be surprised if it's over 340 sec for a low pressure methalox RCS thruster.

Vertical landing allows the more efficient Raptors to null 99% of the velocity with thrusters handling only terminal thrust. And you only need about 1 g worth of terminal thrust instead of 3 to 4 gees. So with vertical landing you some structure mass, some thruster mass, and some fuel mass thanks to being lighter AND more efficient.
Ah, but here's the problem: we're dealing with an upper stage, not a first stage; we can't use vacuum-expanded dev Raptors for landing at sea level. So for Earth entry we must have the thrusters handle the landing burn.

Not to mention that terminal velocity on Earth will be far lower for a blunt lifting body than for a tail-first descent, and the structural mass really doesn't go up because, again, you're already using a biconic re-entry.

Good catch about the isp of the landing engines. They are ten-metric-tonne thrusters, which is overpowered for RCS on a craft of this size, but great for landing. I did already factor in a decreased thrust due to SL expansion. Ten metric tonnes of vacuum thrust is 98.1 kN, but since these are going to need to be sea-level-expanded, underexpansion will decrease vacuum thrust to around 92 kN and SL thrust will be around 86 kN. 

I had been projecting vacuum isp for the landing engines at 360 seconds and SL isp at 330 seconds, forgetting that pressure-feeding decreases their efficiency. But by how much? The pressure-fed methalox thruster tested by NASA recently had a projected vacuum specific impulse of 348 seconds; for SL-expanded thrusters this translates to a vacuum isp of around 326 s and a SL isp of 305 s.

So that's going to increase landing fuel somewhat. But again, I have a LOT of margin, so it's not catastrophic.
Why does the second stage need to have 2 engines? One single Vacuum Raptor-dev (assuming it is at 1/3rd of the thrust, and doesn't have much less TWR compared to the full sized one) could push the full second stage well enough, you don't need a 1 TWR (on earth) for a second stage or even a mars/moon lander.
I tried it with a single dev Raptor first, but I didn't like it. TWR would be under half a gee for crewed missions, which is not really ideal; you end up needing an aggressively lofted trajectory, which really hurts your ability to safely abort. And FFSC gives you a really good TWR; removing one of the dev Raptors would only save you 640 kg of dry mass while cutting your vehicle TWR in half.

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And it will need at least 1000 m/s to land. Terminal velocity is going to be Mach 2-ish.

I may be wrong but since it is both a lifting body and it is quite light (<15 tons), i've read that in this case mars EDL delta v could be as low as 800 m/s.
You need 1000 m/s for a capsule, but not for a biconic lifting body. Even 800 m/s is an overestimate, I think. The Mid-L/D MAV concept allocates 650 m/s for the landing burn, and my upper vehicle would be much fluffier (higher-drag, lower-mass) than the Mid-L/D. Speaking of which, the re-entry profile is quite similar:



I designed this from the ground up as an Earth-based reusable upper stage, but the adjustments to make it work equally well for Mars or the moon are really, really minor. The few tweaks merely make it a more capable spacecraft for Earth missions.
« Last Edit: 04/26/2017 03:22 PM by sevenperforce »

Offline envy887

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Re: Speculation thread: intermediate-lift Raptor-derived RLV
« Reply #54 on: 04/26/2017 03:58 PM »
... a structural/tankage/body fraction of 5.4%. ... second-stage vehicle climbs from 6.56 tonnes to 9.32 tonnes...

Sounds about right.

Ah, but here's the problem: we're dealing with an upper stage, not a first stage; we can't use vacuum-expanded dev Raptors for landing at sea level. So for Earth entry we must have the thrusters handle the landing burn.

Not to mention that terminal velocity on Earth will be far lower for a blunt lifting body than for a tail-first descent, and the structural mass really doesn't go up because, again, you're already using a biconic re-entry.

Musk said they plan to test the dev Raptor with a 150:1 nozzle, so it can probably operate at max thrust in Earth's atmosphere and still get about 375s Isp in vacuum.

On Earth, the terminal velocity is low enough to permit the flip to tail-first at a low altitude, so the final velocity is roughly the same. But the terminal velocity is also low enough that the Isp difference is almost negligible.

But you are right that you have margins, especially if refueled. Landing at Mars on 326s vs 375s engines eats only a tonne of the 40t or more payload capacity. Since this design is likely volume-limited, that's not a issue - and horizontal exit to the Mars surface is definitely worth the payload difference.

You need 1000 m/s for a capsule, but not for a biconic lifting body. Even 800 m/s is an overestimate, I think. The Mid-L/D MAV concept allocates 650 m/s for the landing burn, and my upper vehicle would be much fluffier (higher-drag, lower-mass) than the Mid-L/D. Speaking of which, the re-entry profile is quite similar:




Interesting that they have a supersonic drag coefficient over 3.0 at a 55 degree AoA, I'd expected that to be half that, at best. The higher drag can get the terminal velocity under 500 m/s, allowing the landing burn to be under 650 m/s. Nice.

I'd love to see some simulations of this vehicle doing EDL at Earth and Mars. Maybe OneSpeed can work something up similar to his ITS sims.

Offline sevenperforce

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Re: Speculation thread: intermediate-lift Raptor-derived RLV
« Reply #55 on: 04/26/2017 04:49 PM »
To follow up on the one devRaptor vs two devRaptor question:

Assume launching on a Falcon 9 FT with droneship recovery of the first stage and recovery of the upper stage:

engines|LEO payload|LEO payload up/down (crew)|GTO payload
one vacuum dev Raptor|27 tonnes|25 tonnes|8.8 tonnes
two vacuum dev Raptors|25 tonnes|22 tonnes|9.0 tonnes

Dropping to a single engine can give you an advantage for lower-payload GTO flights, because your vehicle TWR isn't so bad at staging, but the GTO gains are very small and the LEO losses are large. Plus, it may no longer be able to SSTO from Mars. So I don't think it is a good tradeoff, especially because of the abort mode problems I mentioned before.

That's just for reference; the above numbers are based on the old dry mass and thruster impulse. Going to go ahead and generate new numbers to get an idea of what sort of performance it would really have with the additional conservatism suggested by envy.

Ah, but here's the problem: we're dealing with an upper stage, not a first stage; we can't use vacuum-expanded dev Raptors for landing at sea level. So for Earth entry we must have the thrusters handle the landing burn.
Musk said they plan to test the dev Raptor with a 150:1 nozzle, so it can probably operate at max thrust in Earth's atmosphere and still get about 375s Isp in vacuum.

On Earth, the terminal velocity is low enough to permit the flip to tail-first at a low altitude, so the final velocity is roughly the same. But the terminal velocity is also low enough that the Isp difference is almost negligible.

But you are right that you have margins, especially if refueled. Landing at Mars on 326s vs 375s engines eats only a tonne of the 40t or more payload capacity. Since this design is likely volume-limited, that's not a issue - and horizontal exit to the Mars surface is definitely worth the payload difference.
Since we are dealing with the main propulsion engines, we want to squeeze out all the vacuum specific impulse we can get, especially if this is going BLEO. And the landing thrusters are simple; I'm projecting their mass at just 45 kg each or thereabouts, so we'd be talking about a savings of maybe 200 kg max if we went to vertical, main-engine-assisted landing instead of horizontal-attitude landing. You're gonna lose more than 200 kg of payload by cutting isp from 381 to 375.

Horizontal attitude on Mars is definitely a big advantage. If the nose opens up as I showed above, then the payload could be an ISRU unit on an arm that extends a few meters out of the nose and then drops a drill straight down. Hit rock? No worries; simply take off on remaining fuel, fly to another site, and try again. One of the possible Mars mission architectures I'm looking at is using an ISRU-equipped mini-ITS to fill up on the Martian surface and then head to orbit. The crewed vehicle would aerocapture and rendezvous, then refuel fully in Martian orbit before descending; this avoids the need to do propellant transfer on the surface and allows you to abort to Earth if there's a problem.

I would argue that horizontal attitude on Earth is also worth the payload difference, particularly when you're dealing with a manned vehicle. Tipover or hard landing is way way less of a problem.

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Interesting that they have a supersonic drag coefficient over 3.0 at a 55 degree AoA, I'd expected that to be half that, at best. The higher drag can get the terminal velocity under 500 m/s, allowing the landing burn to be under 650 m/s. Nice.

I'd love to see some simulations of this vehicle doing EDL at Earth and Mars. Maybe OneSpeed can work something up similar to his ITS sims.
I'm going to try to get someone with KSP+RSS and procedural parts to do a mockup and simulation, though it wouldn't be as nice as other sims.

Offline sevenperforce

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Re: Speculation thread: intermediate-lift Raptor-derived RLV
« Reply #56 on: 04/26/2017 09:51 PM »
Here's a build request I did over at the KSP forums -- I'll see what I can get people to do.

I promised I would get some revised payload numbers based on the adjusted dry mass and corrected landing isp, so here we go! First, some landing fuel fractions:

Earth (255 m/s @ 305 s): 8.12%
Mars (650 m/s @ 325 s): 18.46%
Luna (1600 m/s @ 381 s, then 200 m/s @ 326 s): 38.81%

This gives me a starting point.

_|LEO|GTO|ISS|
Falcon 9FT (RTLS)|20.6|4.0|5.5|
Falcon 9FT (OCISLY)|22.4|5.0|7.2|
Falcon 9FT (expended)|25.7|6.7|10.1|
Falcon H (recovered)|41.0|13.1|23.0|
Falcon H (core expended)|49.1|16.2|30.3|
Falcon H (expended)|61.4|23.2|41.0|

LEO and GTO are for payload launches only, factoring in the weight of the cargo bay, cargo bay doors, and deployment system. All launches are with full upper stage recovery, as recovery penalty for an upper stage is about the same regardless of whether it is coming in from GTO or coming in from LEO.

ISS represents the payload capabilities of a manned shuttle-style variant, with an ejectable crew cabin containing seats for up to 10 passengers, ECLSS, LES, and independent re-entry/lifeboat capability. Passenger weight, equipment, and consumables must be deducted from listed payload. In all cases, the vehicle has sufficient reserves to return at least 5.5 tonnes of its payload (crew, cargo, or both) to the surface. Dry mass of the crew cabin variant is 20.5 tonnes.

A crewed flight to LEO without going to the ISS will have slightly higher payload margins.

Tomorrow, if I get a chance, I'll run some numbers to see what kind of direct-ascent cislunar, lunar-surface, TMI, and Martian-surface performance I can get. Then I'll look into what it can do with LEO refueling.

One neat idea I saw somewhere was that if SpaceX started flying something like this, it could fly comsat missions with more reserves than necessary (e.g., flying with FH instead of F9, or flying F9 with droneship recovery rather than RTLS recovery) and rendezvous with a tanker variant in LEO before deploying the payload. In this way, the tanker would end up accumulating propellant without requiring dedicated launches.

For reference, a tanker variant the same size as the standard vehicle would have a dry mass of 11.1 tonnes and be able to carry 174 tonnes of propellant. Launched on Falcon Heavy with full recovery, it would reach LEO with a little under 40 tonnes of propellant, plus its own landing reserves.

Online hkultala

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Re: Speculation thread: intermediate-lift Raptor-derived RLV
« Reply #57 on: 04/27/2017 04:36 AM »
Before running more (incorrect) numbers for different trajectories, you should try to match your numbers with the ACTUAL numbers released by spaceX.

Offline dror

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Re: Speculation thread: intermediate-lift Raptor-derived RLV
« Reply #58 on: 04/27/2017 06:50 AM »

This makes sense, except that you're comparing to the ITS tanker. As I pointed out already, the tanker isn't designed to fly to Mars. It most likely doesn't have TPS for an interplanetary entry, which will probably mass about twice as much as TPS for Earth LEO entry. It probably doesn't have significant solar power, operating mostly off batteries for the few hours it's in LEO. And it probably doesn't have active or passive cooling to keep the landing fuel from boiling off during a 6 month transit, which is how long a mass-optimized transfer to Mars takes. I'd figure dry mass of at least 5% of wet, before payload.

A little OT -
I figured that orbital refuel will be done first to one of the tankers on orbit, and than from the refueled tanker to a crewed spaceship. That means the tanker will stay longer on orbit and will act as a fuel depot for the spaceship.
The spaceship will have it's fuel ready on orbit when it is launched thus increasing crew safty.
For that to happen, at least one of three tankers, if not all, need to have built in cooling and power to act as a depot.

Offline JamesH65

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Re: Speculation thread: intermediate-lift Raptor-derived RLV
« Reply #59 on: 04/27/2017 10:36 AM »
I'm putting the Raptor's SL TWR at 200:1, which makes its mass 1.55 tonnes. There are nine of these on the ITS Tanker and Spaceship, but I'll go ahead and kick the engine mass up to a total of 15.5 tonnes to account for the mass of the vacuum nozzle extensions.

The dry mass of the ITS tanker is projected at 90 tonnes, which includes the monocoque tanks/body, the intertanks, the RCS thrusters, the TPS, the engines, and the landing legs. Subtract the engine mass, and that's 74.5 tonnes for the tanker's 2,500 tonnes of propellant, or a mass ratio of 33.6:1.

To account for some square-cube losses, I projected my structural mass ratio at 29:1 to get a base structural mass of 4.88 tonnes for the 141 tonnes of propellant I wanted. I added back 1.28 tonnes for the two dev Raptor engines and 405 kg for the eight landing thrusters.

I didn't include payload encapsulation in my overall dry mass because I'd want a monocoque pressure vessel for the crewed version. The payload fairings on the Falcon 9 mass 1.75 tonnes total so that's a good estimate for the cargo bay mass. The actual downmass to Mars on a FH-expendable direct ascent is probably closer to 13 tonnes, then. That's reserving 2.9 tonnes of propellant for the landing burn, which gives about 448 m/s of dV. That should be enough, I think; if I need more it would decrease the downmass slightly but not by much.

This makes sense, except that you're comparing to the ITS tanker. As I pointed out already, the tanker isn't designed to fly to Mars. It most likely doesn't have TPS for an interplanetary entry, which will probably mass about twice as much as TPS for Earth LEO entry. It probably doesn't have significant solar power, operating mostly off batteries for the few hours it's in LEO. And it probably doesn't have active or passive cooling to keep the landing fuel from boiling off during a 6 month transit, which is how long a mass-optimized transfer to Mars takes. I'd figure dry mass of at least 5% of wet, before payload.
See, this is just the sort of engineering counter-analysis I was hoping for with this thread! Thanks. The points regarding high-velocity TPS, cooling, and power are good ones. I hadn't considered that. However, even if there is some dry mass growth on my upper stage, it's not catastrophic. Payload with full reuse is already very high, and this is not a SSTO where a 10% increase in dry mass results in negative payload fraction.

It was difficult to get a good estimate of tankage/structural fraction on the ITS Spaceship, because I don't know how much to subtract for the crew cabin and cargo hold. But after some consideration, I think we have a way we can at least place an upper bound on it.

The ITS Tanker and ITS Spaceship have identical external form lines, so we can say with relative confidence that if the tanker DID have all the TPS and cooling and power systems of the spaceship, it would still have a lower dry mass than the spaceship, since the crew cabin and ECLSS and cargo hold are heavier than monocoque tanks of equivalent size. So we can divide the structural dry mass of the ITS Spaceship (150 tonnes minus 15 tonnes of engine) by the propellant capacity of the ITS Tanker (2,500 tonnes) to get a structural/tankage/body fraction of 5.4%. This, I think, is generous and conservative. Even if there are square-cube losses to factor in, they are greatly outweighed by the fact that we are including the crew cabin and cargo hold and ECLSS dry mass, which we definitely don't need. And the ITS Spaceship dry mass already includes the additional mass of landing legs, control surfaces, RCS, and additional outer mold lines, so I don't need to add anything in to compensate for that.

Add it up, and the dry mass of my second-stage vehicle climbs from 6.56 tonnes to 9.32 tonnes, which means payload is simply reduced by a little under three tonnes. However, my reusable upper stage already beats the Falcon 9 upper stage for all LEO payloads by more than 3 tonnes when lofted on F9FT and it beats the Falcon 9 upper stage for all payloads period when lofted on Falcon Heavy...and that, again, is with full reuse. So it is by no means a dealbreaker.

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I would certainly support refueling. But there is really very little additional structure or propulsion required for horizontal landing. Composites have better biaxial rigidity than aluminum, you need biaxial strength for the biconic re-entry anyway, and you need the thrusters regardless because of TWR issues.

You might still need an arm or crane or some other mechanism for getting the payload out, but it is a LOT easier than trying to do it with a capsule.
What Isp and TWR are you assuming for the thrusters? I haven't seen any reliable info on them other than fuel and thrust. I'd be surprised if it's over 340 sec for a low pressure methalox RCS thruster.

Vertical landing allows the more efficient Raptors to null 99% of the velocity with thrusters handling only terminal thrust. And you only need about 1 g worth of terminal thrust instead of 3 to 4 gees. So with vertical landing you some structure mass, some thruster mass, and some fuel mass thanks to being lighter AND more efficient.
Ah, but here's the problem: we're dealing with an upper stage, not a first stage; we can't use vacuum-expanded dev Raptors for landing at sea level. So for Earth entry we must have the thrusters handle the landing burn.

Not to mention that terminal velocity on Earth will be far lower for a blunt lifting body than for a tail-first descent, and the structural mass really doesn't go up because, again, you're already using a biconic re-entry.

Good catch about the isp of the landing engines. They are ten-metric-tonne thrusters, which is overpowered for RCS on a craft of this size, but great for landing. I did already factor in a decreased thrust due to SL expansion. Ten metric tonnes of vacuum thrust is 98.1 kN, but since these are going to need to be sea-level-expanded, underexpansion will decrease vacuum thrust to around 92 kN and SL thrust will be around 86 kN. 

I had been projecting vacuum isp for the landing engines at 360 seconds and SL isp at 330 seconds, forgetting that pressure-feeding decreases their efficiency. But by how much? The pressure-fed methalox thruster tested by NASA recently had a projected vacuum specific impulse of 348 seconds; for SL-expanded thrusters this translates to a vacuum isp of around 326 s and a SL isp of 305 s.

So that's going to increase landing fuel somewhat. But again, I have a LOT of margin, so it's not catastrophic.
Why does the second stage need to have 2 engines? One single Vacuum Raptor-dev (assuming it is at 1/3rd of the thrust, and doesn't have much less TWR compared to the full sized one) could push the full second stage well enough, you don't need a 1 TWR (on earth) for a second stage or even a mars/moon lander.
I tried it with a single dev Raptor first, but I didn't like it. TWR would be under half a gee for crewed missions, which is not really ideal; you end up needing an aggressively lofted trajectory, which really hurts your ability to safely abort. And FFSC gives you a really good TWR; removing one of the dev Raptors would only save you 640 kg of dry mass while cutting your vehicle TWR in half.

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And it will need at least 1000 m/s to land. Terminal velocity is going to be Mach 2-ish.

I may be wrong but since it is both a lifting body and it is quite light (<15 tons), i've read that in this case mars EDL delta v could be as low as 800 m/s.
You need 1000 m/s for a capsule, but not for a biconic lifting body. Even 800 m/s is an overestimate, I think. The Mid-L/D MAV concept allocates 650 m/s for the landing burn, and my upper vehicle would be much fluffier (higher-drag, lower-mass) than the Mid-L/D. Speaking of which, the re-entry profile is quite similar:



I designed this from the ground up as an Earth-based reusable upper stage, but the adjustments to make it work equally well for Mars or the moon are really, really minor. The few tweaks merely make it a more capable spacecraft for Earth missions.

How does the lander get vertical again, for takeoff? Once fueled the landing engines will not be enough to get it off the ground will they?

Offline DOCinCT

How does the lander get vertical again, for takeoff? Once fueled the landing engines will not be enough to get it off the ground will they?
Obviously lwith just an appropriate application of levers. ;) 
(Image from Colliers Magazine April 30, 1954 as reproduced in Horizons Vol 39 Issue 2 Sept/Oct 2013, used with permission)

Offline sevenperforce

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Re: Speculation thread: intermediate-lift Raptor-derived RLV
« Reply #61 on: 04/27/2017 03:28 PM »
This makes sense, except that you're comparing to the ITS tanker. As I pointed out already, the tanker isn't designed to fly to Mars. It most likely doesn't have TPS for an interplanetary entry, which will probably mass about twice as much as TPS for Earth LEO entry. It probably doesn't have significant solar power, operating mostly off batteries for the few hours it's in LEO. And it probably doesn't have active or passive cooling to keep the landing fuel from boiling off during a 6 month transit, which is how long a mass-optimized transfer to Mars takes. I'd figure dry mass of at least 5% of wet, before payload.
A little OT -
I figured that orbital refuel will be done first to one of the tankers on orbit, and than from the refueled tanker to a crewed spaceship. That means the tanker will stay longer on orbit and will act as a fuel depot for the spaceship.
The spaceship will have it's fuel ready on orbit when it is launched thus increasing crew safty.
For that to happen, at least one of three tankers, if not all, need to have built in cooling and power to act as a depot.
Yes, that's what I've assumed as well. It doesn't make sense for the crewed spaceship to just sit around for 5+ tanker launches; much more sense if the tanker goes up and acts as a fuel depot. If they can hit their mass fractions, it's not gonna be too tough to get 380 tonnes to orbit each launch, or maybe even a little bit more.

In any case I'll keep my mass fractions for conservatism.
Before running more (incorrect) numbers for different trajectories, you should try to match your numbers with the ACTUAL numbers released by spaceX.
Errrr...what? What SpaceX numbers am I missing?

You need 1000 m/s for a capsule, but not for a biconic lifting body. Even 800 m/s is an overestimate, I think. The Mid-L/D MAV concept allocates 650 m/s for the landing burn, and my upper vehicle would be much fluffier (higher-drag, lower-mass) than the Mid-L/D. Speaking of which, the re-entry profile is quite similar:



I designed this from the ground up as an Earth-based reusable upper stage, but the adjustments to make it work equally well for Mars or the moon are really, really minor. The few tweaks merely make it a more capable spacecraft for Earth missions.

How does the lander get vertical again, for takeoff? Once fueled the landing engines will not be enough to get it off the ground will they?
Ah, see, that's the beautiful thing. Providing enough thrust for aggressive, efficient SL landing on Earth means that the landing thrusters are able to push a total of 736 kN in the lower-pressure Martian atmosphere. That's enough to lift 198 tonnes on Mars, meaning it could theoretically take up to 45 tonnes of payload to Martian orbit.
« Last Edit: 04/27/2017 03:31 PM by sevenperforce »

Offline sevenperforce

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Re: Speculation thread: intermediate-lift Raptor-derived RLV
« Reply #62 on: 04/27/2017 03:58 PM »
Notionally, consider the following plan for a Mars Sample Return mission:

Two-tonne rover capable of acquiring samples is launched to LEO in the cargo-variant upper stage. A tanker-variant upper stage is also launched to LEO. Both are fully refueled in orbit and exit together on TMI. After the TMI burn, the mission spacecraft has 35 tonnes of propellant remaining; the tanker has 55 tonnes of propellant remaining.

Immediately after the TMI burn, the two upper stages rendezvous and the tanker transfers 53 tonnes of propellant to the mission spacecraft, then adjusts its trajectory to perform a Martian free-return. It will have enough residuals for high-energy Earth EDL after its loop around Mars. The mission spacecraft is now 62% fueled, with 88 tonnes of propellant.

The mission spacecraft performs a high-energy entry and landing on Mars, reaching the surface on its auxiliary thrusters with 69 tonnes of propellant. The rover exits and picks up a series of samples, then returns to the mission spacecraft.

The mission spacecraft lifts off on its thrusters, fires its main engines, and rockets toward the solset on a direct ascent to Earth Injection. It performs a high-energy entry and lands on Earth with 5 tonnes of propellant to spare.

Fully-reusable Mars Sample Return with no ISRU required, at the cost of only two reusable Falcon-family launches plus refueling runs.

EDIT:

Adapting the same mission plan as before, but for a crewed lunar mission:

Fully-fueled manned vehicle (dry mass 20.5 tonnes, payload 4 tonnes including crew) and tanker head for TLI out of LEO together as before, with the tanker transferring its propellant reserves to the manned vehicle immediately after the TLI burn and coming back on a free-return trajectory to land. Manned vehicle reaches cislunar space with 112.8 tonnes of propellant, executes orbital entry, deorbit, and landing to reach New Tranquility Base with 48.8 tonnes of propellant remaining.

After the mission (which can last quite a while, given that total delivered payload is the same as the entire gross mass of the Apollo Lunar Ascent Module), the manned vehicle lifts off on its thrusters, ignites its main engines, and heads on a direct ascent to Earth. EDL is completed with a whopping 10.2 tonnes of propellant to spare.
« Last Edit: 04/27/2017 04:23 PM by sevenperforce »

Offline rakaydos

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Re: Speculation thread: intermediate-lift Raptor-derived RLV
« Reply #63 on: 04/27/2017 04:32 PM »

This makes sense, except that you're comparing to the ITS tanker. As I pointed out already, the tanker isn't designed to fly to Mars. It most likely doesn't have TPS for an interplanetary entry, which will probably mass about twice as much as TPS for Earth LEO entry. It probably doesn't have significant solar power, operating mostly off batteries for the few hours it's in LEO. And it probably doesn't have active or passive cooling to keep the landing fuel from boiling off during a 6 month transit, which is how long a mass-optimized transfer to Mars takes. I'd figure dry mass of at least 5% of wet, before payload.

A little OT -
I figured that orbital refuel will be done first to one of the tankers on orbit, and than from the refueled tanker to a crewed spaceship. That means the tanker will stay longer on orbit and will act as a fuel depot for the spaceship.
The spaceship will have it's fuel ready on orbit when it is launched thus increasing crew safty.
For that to happen, at least one of three tankers, if not all, need to have built in cooling and power to act as a depot.
That's what EVERYONE figures... but that's not what SpaceX is actually saying.

It's always been "send the interplanetary craft up, then refuel it, and if that takes more than a week, send the crew after."

this "take out EVERYTHING that isnt absolutely essential to short-stay LEO refueling to increase fuel capacity" idea explains the seemingly-obvous disconnect between the "right" thing and what spaceX is saying. And since SpaceX has run the REAL numbers, I'd say they probably have the right of it.

Offline rakaydos

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Re: Speculation thread: intermediate-lift Raptor-derived RLV
« Reply #64 on: 04/27/2017 04:45 PM »
Notionally, consider the following plan for a Mars Sample Return mission:

Two-tonne rover capable of acquiring samples is launched to LEO in the cargo-variant upper stage. A tanker-variant upper stage is also launched to LEO. Both are fully refueled in orbit and exit together on TMI. After the TMI burn, the mission spacecraft has 35 tonnes of propellant remaining; the tanker has 55 tonnes of propellant remaining.

Immediately after the TMI burn, the two upper stages rendezvous and the tanker transfers 53 tonnes of propellant to the mission spacecraft, then adjusts its trajectory to perform a Martian free-return. It will have enough residuals for high-energy Earth EDL after its loop around Mars. The mission spacecraft is now 62% fueled, with 88 tonnes of propellant.

The mission spacecraft performs a high-energy entry and landing on Mars, reaching the surface on its auxiliary thrusters with 69 tonnes of propellant. The rover exits and picks up a series of samples, then returns to the mission spacecraft.

The mission spacecraft lifts off on its thrusters, fires its main engines, and rockets toward the solset on a direct ascent to Earth Injection. It performs a high-energy entry and lands on Earth with 5 tonnes of propellant to spare.

Fully-reusable Mars Sample Return with no ISRU required, at the cost of only two reusable Falcon-family launches plus refueling runs.

EDIT:

Adapting the same mission plan as before, but for a crewed lunar mission:

Fully-fueled manned vehicle (dry mass 20.5 tonnes, payload 4 tonnes including crew) and tanker head for TLI out of LEO together as before, with the tanker transferring its propellant reserves to the manned vehicle immediately after the TLI burn and coming back on a free-return trajectory to land. Manned vehicle reaches cislunar space with 112.8 tonnes of propellant, executes orbital entry, deorbit, and landing to reach New Tranquility Base with 48.8 tonnes of propellant remaining.

After the mission (which can last quite a while, given that total delivered payload is the same as the entire gross mass of the Apollo Lunar Ascent Module), the manned vehicle lifts off on its thrusters, ignites its main engines, and heads on a direct ascent to Earth. EDL is completed with a whopping 10.2 tonnes of propellant to spare.
We may be overestimating the capability of the tanker. That dry mass is amazing, but it's got to come from somewhere... and SpaceX has gone out of their way never to claim  the tanker has the endurance to be a fuel depot. Instead it's always "send the spaceship, refuel with tankers, and if that takes too long, send (another spaceship with) crew after. Batteries, insulation, probably more- the tanker's going to be shaved to the bone to squeeze in more fuel.

Cutting the heat shield back to being able to barely handle LEO is another way to save on dry mass... and one synergestic with other dry mass reductions, as a lighter tanker (with the same aerodynamic footprint) has less reentry stress. Does a hollow carbon fiber tube even need heat shielding?

But while this improves the tanker's ability to do it's primary task, it means any cargo or fuel depot has to use the SPACESHIP's dry mass numbers.

Offline sevenperforce

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Re: Speculation thread: intermediate-lift Raptor-derived RLV
« Reply #65 on: 04/27/2017 04:55 PM »
We may be overestimating the capability of the tanker. That dry mass is amazing, but it's got to come from somewhere... and SpaceX has gone out of their way never to claim  the tanker has the endurance to be a fuel depot. Instead it's always "send the spaceship, refuel with tankers, and if that takes too long, send (another spaceship with) crew after. Batteries, insulation, probably more- the tanker's going to be shaved to the bone to squeeze in more fuel.

Cutting the heat shield back to being able to barely handle LEO is another way to save on dry mass... and one synergestic with other dry mass reductions, as a lighter tanker (with the same aerodynamic footprint) has less reentry stress. Does a hollow carbon fiber tube even need heat shielding?

But while this improves the tanker's ability to do it's primary task, it means any cargo or fuel depot has to use the SPACESHIP's dry mass numbers.
Yeah, envy pointed this out a page back or so, and I redid my dry mass numbers to adjust. My dry mass, for the cargo and tanker and crew variants, are all based on the ITS Spaceship's dry mass numbers.

By that, I mean that I used the dry mass of the spaceship (less projected engine mass) divided by the propellant capacity of the tanker, and used that to find my structural/tankage mass fraction. The two ships have the same external dimensions.

Offline spacenut

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Re: Speculation thread: intermediate-lift Raptor-derived RLV
« Reply #66 on: 04/27/2017 05:46 PM »
With a horizontal landing, what about dust and debris hitting the heat shield material landing on Mars?  Will it be strong enough to take some "pings"?  Can it be repaired while waiting for refueling?  Can longer landing legs work? 

Offline sevenperforce

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Re: Speculation thread: intermediate-lift Raptor-derived RLV
« Reply #67 on: 04/27/2017 06:31 PM »
With a horizontal landing, what about dust and debris hitting the heat shield material landing on Mars?  Will it be strong enough to take some "pings"?  Can it be repaired while waiting for refueling?  Can longer landing legs work?
The landing thrusters are set in the wing extensions, rather high off the ground...maybe 4 meters up? With the low air pressure on Mars, the plume is going to be really diffuse by the time it hits the ground, so debris impingement should be low or nonexistent. Same with landings on the moon.

For Earth return, landing would be on a pad, so no worries there.

This is a problem for the ITS; I don't really know how they are going to handle it. The engines are going to be directly in the debris impingement zone even if the heat shield is not.

Offline dror

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Re: Speculation thread: intermediate-lift Raptor-derived RLV
« Reply #68 on: 04/27/2017 10:07 PM »
With a horizontal landing, what about dust and debris hitting the heat shield material landing on Mars?  Will it be strong enough to take some "pings"?  Can it be repaired while waiting for refueling?  Can longer landing legs work?
The landing thrusters are set in the wing extensions, rather high off the ground...maybe 4 meters up? With the low air pressure on Mars, the plume is going to be really diffuse by the time it hits the ground, so debris impingement should be low or nonexistent. Same with landings on the moon.

For Earth return, landing would be on a pad, so no worries there.

You may be able to further improve by gimbaling the thrusters out a bit at the last second of landing so that debris will be diverted away
« Last Edit: 04/27/2017 10:09 PM by dror »

Offline sevenperforce

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Re: Speculation thread: intermediate-lift Raptor-derived RLV
« Reply #69 on: 04/27/2017 10:34 PM »
The landing thrusters are set in the wing extensions, rather high off the ground...maybe 4 meters up? With the low air pressure on Mars, the plume is going to be really diffuse by the time it hits the ground, so debris impingement should be low or nonexistent. Same with landings on the moon.

For Earth return, landing would be on a pad, so no worries there.

You may be able to further improve by gimbaling the thrusters out a bit at the last second of landing so that debris will be diverted away

Oh, good idea. I was planning on having the thrusters fixed rather than gimballed, to reduce dry mass, since their placement allows total pitch and roll authority with differential thrust alone. But gimballing could also add yaw authority in addition to protecting the heat shield on landing.

Another possibility would be having the landing panels open up in the opposite direction, protecting the underside of the ship. Not quite as stable, though.

Offline sevenperforce

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Re: Speculation thread: intermediate-lift Raptor-derived RLV
« Reply #70 on: 05/01/2017 12:58 PM »
Another option is a second stage for FH as a half scaled ITS. 6m diameter, 24m long, 1 raptor and 3 flavours:
1- Cargo version with integrated fairing (crocodile style) to deploy satellites
2- Mini crewed ITS launched as FH: minibus of 20 PAX to LEO, 10 PAX to moon vicinity and 5 to asteroids or even Phobos. Crewed part is 6m diameter, 9m long with around 180m3. Could copy-paste beefed up ECLSS systems from Dragon and become a very polyvalent spaceship.
3 - Tanker version

That would be the spaceship that NASA needs for BLEO and would match beautifully with the SLS. But I guess reminds too much the shuttle. Would delay too much the bigger brother, but a very good exploration spaceship.


Landing is a problem here. You'd need auxiliary thrusters for touchdown. And protecting that Raptor Vac would be tough.

Offline Jimmy Murdok

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Re: Speculation thread: intermediate-lift Raptor-derived RLV
« Reply #71 on: 05/01/2017 03:12 PM »
Landing is a problem herd. You'd need auxiliary thrusters for touchdown. And protecting that Raptor Vac would be tough.
SL Raptor has around 300tons, throttle at advertised 20% and you are at 60 tones for a 2nd stage of FH + spaceship all in one and on a hoverslam. I guess should work.
Regarding the nozzle extension either disposable or retractable.
I don't know, the ITS full system is such a giant leap forward that we all look at logical intermediate steps to make it "chewable". My guess is that from Elon perspective, this might make sense as a good cost/benefit step, allow test and become a good solution itself, but I'm far from being convinced. In few weeks we might have a hint about if mid stage in the architecture. If so, Zubrin will breath ;D

Offline dror

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Re: Speculation thread: intermediate-lift Raptor-derived RLV
« Reply #72 on: 05/01/2017 03:21 PM »
Landing is a problem herd. You'd need auxiliary thrusters for touchdown. And protecting that Raptor Vac would be tough.
SL Raptor has around 300tons, throttle at advertised 20% and you are at 60 tones for a 2nd stage of FH + spaceship all in one and on a hoverslam. I guess should work.
Regarding the nozzle extension either disposable or retractable.
I don't know, the ITS full system is such a giant leap forward that we all look at logical intermediate steps to make it "chewable". My guess is that from Elon perspective, this might make sense as a good cost/benefit step, allow test and become a good solution itself, but I'm far from being convinced. In few weeks we might have a hint about if mid stage in the architecture. If so, Zubrin will breath ;D
I fear that from Elon perspective the ITS is a chewable intermadiate step...

Offline dror

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Re: Speculation thread: intermediate-lift Raptor-derived RLV
« Reply #73 on: 05/01/2017 03:42 PM »
This is obviously plenty of margin to have a crewed version, which would use the same tank and body as the rest of the orbiter but have a crew cabin in place of the cargo bay. Payload capacity is high enough that the crew cabin could carry at least a dozen crew members plus unpressurized cargo and still have independent LES and re-entry capability (lifeboat).

Can you please elaborate on the crew cabin?
Surely you have a sketch of it  ;)
If you want it to have independent LES and re-entry capability then it is basically a Dragon2
« Last Edit: 05/01/2017 03:45 PM by dror »

Offline sevenperforce

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Re: Speculation thread: intermediate-lift Raptor-derived RLV
« Reply #74 on: 05/01/2017 04:24 PM »
Landing is a problem herd. You'd need auxiliary thrusters for touchdown. And protecting that Raptor Vac would be tough.
SL Raptor has around 300tons, throttle at advertised 20% and you are at 60 tones for a 2nd stage of FH + spaceship all in one and on a hoverslam. I guess should work.
Regarding the nozzle extension either disposable or retractable.
I don't know, the ITS full system is such a giant leap forward that we all look at logical intermediate steps to make it "chewable". My guess is that from Elon perspective, this might make sense as a good cost/benefit step, allow test and become a good solution itself, but I'm far from being convinced. In few weeks we might have a hint about if mid stage in the architecture. If so, Zubrin will breath ;D

I don't see jettisoned or retractable nozzle extensions as likely; either one would hurt the 380+ second specific impulse that the Raptor Vacuum can boast. So I'm pretty sure landing on the main engine is right out. 60 tonnes is a LOT of dry mass compared to the 4-tonne dry mass of the current upper stage. With any reasonable fuel fraction you'd be getting to the upper limits of what Falcon Heavy can lift. In order to maintain a launch TWR of 1.36:1, the lower limit for F9, the upper stage and payload cannot exceed 400 tonnes.

The reason I think a dev-Raptor-powered composite methalox upper stage is promising is that the Air Force helped fund Raptor based on the promise of a methalox upper stage. This would be a perfect test bed for composite staging, upper-stage reuse, and BLEO operation.
This is obviously plenty of margin to have a crewed version, which would use the same tank and body as the rest of the orbiter but have a crew cabin in place of the cargo bay. Payload capacity is high enough that the crew cabin could carry at least a dozen crew members plus unpressurized cargo and still have independent LES and re-entry capability (lifeboat).

Can you please elaborate on the crew cabin?
Surely you have a sketch of it  ;)
If you want it to have independent LES and re-entry capability then it is basically a Dragon2
Yes, the idea was basically to have the same overall systems as a Dragon 2. That's what my dry mass considerations were based on, just for conservatism.

No sketch at present but I've attached outer and cutaway line drawings. Essentially a Dragon 2, but turned on its side. Re-entry is not particularly pretty and probably close to ballistic, but that's for emergencies only, so I'm not too worried.

As I've depicted it, there are two pressurized regions -- a "trunk" with its own docking port on top and a fair bit of volume for pressurized cargo, and the forward crew cabin. In a launch abort, solids between the fore and aft sections activate and push the upper section free by itself; recovery is via chute. As you can see, the heat shield on the overall craft doubles as the heat shield for the crew compartment if the stage is damaged and the crew must perform an emergency lifeboat re-entry. Unlike Dragon 2, crew-capsule-only landing is NOT nominal, so sacrificial elements are okay.

Offline GWH

IMO it would be a more efficient use of resources to go with a blunt nosed stubby mini-ITS for launching Dragon on top. Then not going to the trouble of developing a fully integrated crew man rated crew cabin for what is essentially a stepping stone program with a short life.  Or just keep crew on a Merlin based upper stage and rendezvous in orbit.

Still would retain the in flight abort ability, independent reentry - so a suicide burn landing is acceptable.
Mars Ascent Vehicle would just be a dragon in a fairing where the fairing is ditched after landing on Mars.

I'd been meaning to post this strategy on Robotbeat's humans to Mars in 2020, I think a cargo MITS + Dragon 2 could be a workable architecture in the short term.

Offline sevenperforce

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Re: Speculation thread: intermediate-lift Raptor-derived RLV
« Reply #76 on: 05/01/2017 05:07 PM »
IMO it would be a more efficient use of resources to go with a blunt nosed stubby mini-ITS for launching Dragon on top. Then not going to the trouble of developing a fully integrated crew man rated crew cabin for what is essentially a stepping stone program with a short life.  Or just keep crew on a Merlin based upper stage and rendezvous in orbit.

Still would retain the in flight abort ability, independent reentry - so a suicide burn landing is acceptable.
Mars Ascent Vehicle would just be a dragon in a fairing where the fairing is ditched after landing on Mars.

I'd been meaning to post this strategy on Robotbeat's humans to Mars in 2020, I think a cargo MITS + Dragon 2 could be a workable architecture in the short term.
While I think a reusable methalox upper stage/MITS is probable, I know this particular configuration is less so. That being said, it represents my own personal wish-fulfillment fantasy for a fully-reusable LEO crew shuttle.

The trouble, as always, is recovery mode. If your stage loses its front end, how does it shield itself from heat on re-entry? And while suicide burns may be possible without crew, landing on the vacuum engine(s) is not, so you still need landing thrusters. Biconic re-entry makes a lot of sense, so biconic landing should as well.

I'm not sure I am picturing your MAV proposal correctly....

Offline GWH

The heat shield "stubby nose" would need to be under the Dragon trunk, and it may need an expendable stage adapter to smooth out the airflow. 
For the MAV, take your sketch of the hinged nose cone and place a dragon under the cone, with the trunk mounted in the upper half of the payload section.  Add a tapered skirt if necessary for aerodynamics, which is less of a concern as an MAV.

Offline GWH


Landing is a problem here. You'd need auxiliary thrusters for touchdown. And protecting that Raptor Vac would be tough.
[/quote]

If the center core interstage was shortened significantly with the Raptor Vac being shoved up inside the MITS rather than dangling below, or at least wrapped in a 120+degree shield/flaps then re-entry damage wouldn't be a problem

Offline sevenperforce

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Re: Speculation thread: intermediate-lift Raptor-derived RLV
« Reply #79 on: 05/01/2017 05:47 PM »
The heat shield "stubby nose" would need to be under the Dragon trunk, and it may need an expendable stage adapter to smooth out the airflow. 

For the MAV, take your sketch of the hinged nose cone and place a dragon under the cone, with the trunk mounted in the upper half of the payload section.  Add a tapered skirt if necessary for aerodynamics, which is less of a concern as an MAV.
Dragon doesn't have nearly enough dV to be an MAV, though.

The crewed version I've outlined above would be able to do a Mars EDL and return to orbit with any ratio better than 26.3% (that's including losses for the thruster burns), so if you send a tanker into Martian orbit ahead of (or along with) your lander, you can manage easily.

Offline GWH

Dragon doesn't have nearly enough dV to be an MAV, though.
Not at all what I was suggesting, although some derivative with a substantial trunk mounted propulsion COULD, such as one might want for a lunar lander/ascent vehicle, which itself is a tall order. 

Using the MITS as a SSTO booster and dragon as a payload would be the idea: 
One Dragon as crewed Earth launch docks in LEO to MITS based transit habitat, then acts as Mars descent vehicle.  One Dragon acting as a payload on a MITS as the MAV's crew capsule, dock in orbit to MITS based transit habitat, then used to land crew on Earth.   Add a tanker in Martian orbit for the dV.
A lot less cost effective in the long run than a true MITS based crew vehicle, but I think that would be an effective trade off when considering the MITS architecture to fast-track crew missions to Mars pre-ITS.

MITS in my opinion would be best as a cargo vehicle, at least at first, so it can be fast-tracked easier than a fully integrated crewed spacecraft like the ITS.
« Last Edit: 05/01/2017 07:17 PM by GWH »

Offline sevenperforce

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Re: Speculation thread: intermediate-lift Raptor-derived RLV
« Reply #81 on: 05/01/2017 08:45 PM »
Dragon doesn't have nearly enough dV to be an MAV, though.
Not at all what I was suggesting, although some derivative with a substantial trunk mounted propulsion COULD, such as one might want for a lunar lander/ascent vehicle, which itself is a tall order. 

Using the MITS as a SSTO booster and dragon as a payload would be the idea: 
One Dragon as crewed Earth launch docks in LEO to MITS based transit habitat, then acts as Mars descent vehicle.  One Dragon acting as a payload on a MITS as the MAV's crew capsule, dock in orbit to MITS based transit habitat, then used to land crew on Earth.   Add a tanker in Martian orbit for the dV.
A lot less cost effective in the long run than a true MITS based crew vehicle, but I think that would be an effective trade off when considering the MITS architecture to fast-track crew missions to Mars pre-ITS.

MITS in my opinion would be best as a cargo vehicle, at least at first, so it can be fast-tracked easier than a fully integrated crewed spacecraft like the ITS.
I think a methalox F9/FH upper stage is reasonably likely, but I think if they DO make one, it's likely that they would go for full reuse from the very beginning. If they are going for full reuse, I see them doing a fixed payload bay rather than fairings; if you're bringing it all back, why not do it at once? And so the rest of the design kind of emerges from that.

Making it man-rated would be tough, I admit.

Online guckyfan

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Re: Speculation thread: intermediate-lift Raptor-derived RLV
« Reply #82 on: 05/01/2017 08:51 PM »
A fixed payload bay instead of a fairing would be nice. But would a methane upper stage that is designed to be interchangeably used with the Merlin upper stage have enough payload capacity to GTO? The full weight of that payload bay would come out of the GTO capacity. That's a big loss, assuming no refuelling for GTO flights.

Edit: If that were their plan then why would they develop fairing reuse now, just for the interim?
« Last Edit: 05/01/2017 08:53 PM by guckyfan »

Offline sevenperforce

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Re: Speculation thread: intermediate-lift Raptor-derived RLV
« Reply #83 on: 05/01/2017 09:02 PM »
A fixed payload bay instead of a fairing would be nice. But would a methane upper stage that is designed to be interchangeably used with the Merlin upper stage have enough payload capacity to GTO? The full weight of that payload bay would come out of the GTO capacity. That's a big loss, assuming no refuelling for GTO flights.

Edit: If that were their plan then why would they develop fairing reuse now, just for the interim?
They still plan to fly Falcon 9 and Falcon Heavy with the kerolox upper stage for quite some time, so fairing recovery can still save them money now.

In any case, there's not a significant payload hit for a fixed fairing. With recovery, it can take up to 5 tonnes of payload to GTO if it is launched on Falcon 9 with ASDS recovery and 13.1 tonnes to GTO if it is launched on Falcon Heavy with all three cores recovered. That's factoring the fixed fairing/payload bay into the stage dry mass.

Offline Norm38

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Re: Speculation thread: intermediate-lift Raptor-derived RLV
« Reply #84 on: 05/01/2017 09:16 PM »
This rendering is from the Purdue University study (http://forum.nasaspaceflight.com/index.php?topic=42790.0), which they call ITS-A.  It's based on the full size ITS, but includes cargo bay and would be optimized for LEO operation. It's basically Space Shuttle 2.0. A fully reusable TSTO.  Payload may be FH class, not sure.  The Purdue students designed it specifically to assemble a Mars Cycler, but it could also launch satellites and assemble/service space hotels, commercial labs, fuel depot, etc.

Now it's not subscale, it is full scale.  But what this does is give the 1st stage booster a way to earn money.  It allows the second stage to make money by starting with smaller payloads and working its way up.
By that I mean that at first TPS and landing systems could be overdesigned.  Plenty of fuel margin allocated.  No solar arrays to start, or much smaller and simpler, disposable even.  They should have plenty of performance margin and still be able to launch everything in sight and expand the market.  Fuel is cheap, so if the system is fully reusable, why not go full scale?

And this then grows into the Mars rated ITS.  Development craft can spend 6 months in LEO testing out life support and other systems.  It can extend and retract the solar arrays a hundred times to test that mechanism.  Whatever it needs to do.
NASA can use it for ISS (or whatever comes after ISS).  Bigelow can use it.  With the Shuttle retired, we need a new space truck.
« Last Edit: 05/01/2017 09:22 PM by Norm38 »

Offline sevenperforce

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Re: Speculation thread: intermediate-lift Raptor-derived RLV
« Reply #85 on: 05/01/2017 09:23 PM »
This rendering is from the Purdue University study (http://forum.nasaspaceflight.com/index.php?topic=42790.0), which they call ITS-A.  It's based on the full size ITS, but includes cargo bay and would be optimized for LEO operation. It's basically Space Shuttle 2.0. A fully reusable TSTO.  Payload may be FH class, not sure.  The Purdue students designed it specifically to assemble a Mars Cycler, but it could also launch satellites and assemble/service space hotels, commercial labs, fuel depot, etc.

Now it's not subscale, it is full scale.  But what this does is give the 1st stage booster a way to earn money.  It allows the second stage to make money by starting with smaller payloads and working its way up.
By that I mean that at first TPS and landing systems could be overdesigned.  Plenty of fuel margin allocated.  No solar arrays to start, or much smaller and simpler, disposable even.  They should have plenty of performance margin and still be able to launch everything in sight and expand the market.  Fuel is cheap, so if the system is fully reusable, why not go full scale?

And this then grows into the Mars rated ITS.  Development craft can spend 6 months in LEO testing out life support and other systems.  It can extend and retract the solar arrays a hundred times to test that mechanism.  Whatever it needs to do.
NASA can use it for ISS (or whatever comes after ISS).  Bigelow can use it.  With the Shuttle retired, we need a new space truck.
Landing leg placement is all wrong, but otherwise, beautiful!

Online Lars-J

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Re: Speculation thread: intermediate-lift Raptor-derived RLV
« Reply #86 on: 05/01/2017 09:46 PM »
Yes, this kind of ITS-cargo vehicle is assumed by most (myself included) to be an obvious development that would earn the bills between Mars launch windows.

Offline spacenut

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Re: Speculation thread: intermediate-lift Raptor-derived RLV
« Reply #87 on: 05/02/2017 12:25 AM »
Could a mini-ITS and an intermediate Raptor booster do Mars using fuel depots, SEP tugs, and maybe a reusable lander (mini-ITS) stationed only at Mars to take SEP cargo to the surface, refuel, and bring more down to the surface?

From earth launch cargo on a mini-its, offload to SEP tugs, and return to earth for more cargo. 

A refueled mini-ITS could take passengers direct to shorten the trip.  Say 20-50 passengers instead of the 100. 

The Martian mini-ITS can also bring up argon derived from the Mars atmosphere for a SEP tug to return to earth for more cargo. 

SEP tugs could be refueled with Falcon Heavies from earth for return trip to Mars.

Offline Robotbeat

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Re: Speculation thread: intermediate-lift Raptor-derived RLV
« Reply #88 on: 05/02/2017 01:39 AM »
Auxiliary methane thrusters will be needed for the booster anyway. Might as well use them on a scaled BFS.
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Offline M.E.T.

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Re: Speculation thread: intermediate-lift Raptor-derived RLV
« Reply #89 on: 05/02/2017 11:10 AM »
This rendering is from the Purdue University study (http://forum.nasaspaceflight.com/index.php?topic=42790.0), which they call ITS-A.  It's based on the full size ITS, but includes cargo bay and would be optimized for LEO operation. It's basically Space Shuttle 2.0. A fully reusable TSTO.  Payload may be FH class, not sure.  The Purdue students designed it specifically to assemble a Mars Cycler, but it could also launch satellites and assemble/service space hotels, commercial labs, fuel depot, etc.

Now it's not subscale, it is full scale.  But what this does is give the 1st stage booster a way to earn money.  It allows the second stage to make money by starting with smaller payloads and working its way up.
By that I mean that at first TPS and landing systems could be overdesigned.  Plenty of fuel margin allocated.  No solar arrays to start, or much smaller and simpler, disposable even.  They should have plenty of performance margin and still be able to launch everything in sight and expand the market.  Fuel is cheap, so if the system is fully reusable, why not go full scale?

And this then grows into the Mars rated ITS.  Development craft can spend 6 months in LEO testing out life support and other systems.  It can extend and retract the solar arrays a hundred times to test that mechanism.  Whatever it needs to do.
NASA can use it for ISS (or whatever comes after ISS).  Bigelow can use it.  With the Shuttle retired, we need a new space truck.

This makes so much sense that it seems almost inevitable, if the ITS is to go ahead. In fact, the general cargo ITS seems like it should be the very first version of the ITS variants designed, before the crew spaceship and tanker versions are built.

Such a cargo vessel would immediately render Falcon Heavy obsolete, and since it is fully reusable, might even make F9 obsolete, other than perhaps for minimal payloads that allow F9 RTLS. And even then, I'm not sure which would be cheaper, given that full reusability of F9 still seems unlikely, unlike the ITS cargo.

In any case, this would give ITS an immediate income stream, and allow the booster and upper stage to fly dozens of times a year before any manned flight needs to be risked. The massive financial benefits from such a reusable bulk cargo transporter would then go a long way in funding the development of the crew and tanker ITS variants.

It seems the logical progression to follow. And would provide the smoothest transition from the current Falcon based business model to a new ITS based architecture.

« Last Edit: 05/02/2017 11:27 AM by M.E.T. »

Offline rsdavis9

Quote
Such a cargo vessel would immediately render Falcon Heavy obsolete, and since it is fully reusable, might even make F9 obsolete, other than perhaps for minimal payloads that allow F9 RTLS. And even then, I'm not sure which would be cheaper, given that full reusability of F9 still seems unlikely, unlike the ITS cargo.

and why is a mini version better than just the full sized ITS with a cargo version?
bob

Offline M.E.T.

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Re: Speculation thread: intermediate-lift Raptor-derived RLV
« Reply #91 on: 05/02/2017 11:55 AM »
Quote
Such a cargo vessel would immediately render Falcon Heavy obsolete, and since it is fully reusable, might even make F9 obsolete, other than perhaps for minimal payloads that allow F9 RTLS. And even then, I'm not sure which would be cheaper, given that full reusability of F9 still seems unlikely, unlike the ITS cargo.

and why is a mini version better than just the full sized ITS with a cargo version?

Sorry if I misinterpreted something, but my reading of the rendering from the Purdue study above is that it IS a full sized ITS cargo version, not a mini version. It is the full size one that I am saying is the logical next step, not a mini sized version at all.
« Last Edit: 05/02/2017 11:56 AM by M.E.T. »

Offline rsdavis9

Quote
Such a cargo vessel would immediately render Falcon Heavy obsolete, and since it is fully reusable, might even make F9 obsolete, other than perhaps for minimal payloads that allow F9 RTLS. And even then, I'm not sure which would be cheaper, given that full reusability of F9 still seems unlikely, unlike the ITS cargo.

and why is a mini version better than just the full sized ITS with a cargo version?

Sorry if I misinterpreted something, but my reading of the rendering from the Purdue study above is that it IS a full sized ITS cargo version, not a mini version. It is the full size one that I am saying is the logical next step, not a mini sized version at all.

It might be me who has misinterpreted something. I guess I am questioning what the reasons are that ITS is not the right vehicle for earth based payload launches. Why do we need a completely different vehicle to do cargo to near earth orbit?
bob

Offline M.E.T.

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Re: Speculation thread: intermediate-lift Raptor-derived RLV
« Reply #93 on: 05/02/2017 12:11 PM »
Quote
Such a cargo vessel would immediately render Falcon Heavy obsolete, and since it is fully reusable, might even make F9 obsolete, other than perhaps for minimal payloads that allow F9 RTLS. And even then, I'm not sure which would be cheaper, given that full reusability of F9 still seems unlikely, unlike the ITS cargo.

and why is a mini version better than just the full sized ITS with a cargo version?

Sorry if I misinterpreted something, but my reading of the rendering from the Purdue study above is that it IS a full sized ITS cargo version, not a mini version. It is the full size one that I am saying is the logical next step, not a mini sized version at all.

It might be me who has misinterpreted something. I guess I am questioning what the reasons are that ITS is not the right vehicle for earth based payload launches. Why do we need a completely different vehicle to do cargo to near earth orbit?

I can think of two reasons off hand. Make that three.

1. ITS has a lot of internal space dedicated to crew accommodation, which cannot be used for bulk cargo purposes.

2. ITS does not have large enough cargo doors to deliver a payload that utilizes most of its internal space.

3. ITS has a lot of expensive hardware related to life support and other long range Mars colonization activities which make it less efficient as a pure cargo carrier.

Consider for example that if you could use the entire payload to LEO capability of the ITS for large bulk cargo, you could come close to lofting the entire 400 ton ISS to LEO in one launch.

EDIT

The cargo ITS could then be the "Dragon", while the eventual crew ITS could be the "Dragon 2, crew version" which is built upon the foundation of the cargo ship.
« Last Edit: 05/02/2017 12:17 PM by M.E.T. »

Offline spacenut

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Re: Speculation thread: intermediate-lift Raptor-derived RLV
« Reply #94 on: 05/02/2017 12:27 PM »
I think the Mini-ITS would cost less overall to develop and can be developed more quickly.  Infrastructure for one.  A Mini-ITS can use existing pad 39A or B and would cost less to modify than a whole new launch pad.  Transportation from any factory along the waterways would be easier. 

I reading so much, I don't really know which ITS version is going to be developed.  The 12m version can take advantage of the existing river and intercoastal waterways, so factory doesn't have to be at or near the launch pad.  However, a new pad and facilities would have to be developed. 

Mini-ITS to me would be about 7-8m in diameter and be able to launch 75 tons to LEO fully reusable. 

Offline M.E.T.

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Re: Speculation thread: intermediate-lift Raptor-derived RLV
« Reply #95 on: 05/02/2017 12:55 PM »
I think the Mini-ITS would cost less overall to develop and can be developed more quickly.  Infrastructure for one.  A Mini-ITS can use existing pad 39A or B and would cost less to modify than a whole new launch pad.  Transportation from any factory along the waterways would be easier. 

I reading so much, I don't really know which ITS version is going to be developed.  The 12m version can take advantage of the existing river and intercoastal waterways, so factory doesn't have to be at or near the launch pad.  However, a new pad and facilities would have to be developed. 

Mini-ITS to me would be about 7-8m in diameter and be able to launch 75 tons to LEO fully reusable.

But then you would still need to develop a separate full size cargo version, full size crew version and full size tanker version. Whereas if you went straight for a full size cargo version, it would likely be significantly less complex than the full size crew version, with less required functionality, no life support, far simpler internal design and far more cargo capability.

And it would then retire the mini version, making all of that interim development work a wasted exercise.

Offline rsdavis9

I think the Mini-ITS would cost less overall to develop and can be developed more quickly.  Infrastructure for one.  A Mini-ITS can use existing pad 39A or B and would cost less to modify than a whole new launch pad.  Transportation from any factory along the waterways would be easier. 

I reading so much, I don't really know which ITS version is going to be developed.  The 12m version can take advantage of the existing river and intercoastal waterways, so factory doesn't have to be at or near the launch pad.  However, a new pad and facilities would have to be developed. 

Mini-ITS to me would be about 7-8m in diameter and be able to launch 75 tons to LEO fully reusable.

But then you would still need to develop a separate full size cargo version, full size crew version and full size tanker version. Whereas if you went straight for a full size cargo version, it would likely be significantly less complex than the full size crew version, with less required functionality, no life support, far simpler internal design and far more cargo capability.

And it would then retire the mini version, making all of that interim development work a wasted exercise.

Yes this was actually my point which I failed to articulate properly.
As far as I understand it the falcon is the biggest rocket(3.6m) that can get road transported. All bigger stages require barge/train. So what is the advantage of the mini?
bob

Offline M.E.T.

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Re: Speculation thread: intermediate-lift Raptor-derived RLV
« Reply #97 on: 05/02/2017 03:45 PM »
I think the Mini-ITS would cost less overall to develop and can be developed more quickly.  Infrastructure for one.  A Mini-ITS can use existing pad 39A or B and would cost less to modify than a whole new launch pad.  Transportation from any factory along the waterways would be easier. 

I reading so much, I don't really know which ITS version is going to be developed.  The 12m version can take advantage of the existing river and intercoastal waterways, so factory doesn't have to be at or near the launch pad.  However, a new pad and facilities would have to be developed. 

Mini-ITS to me would be about 7-8m in diameter and be able to launch 75 tons to LEO fully reusable.

But then you would still need to develop a separate full size cargo version, full size crew version and full size tanker version. Whereas if you went straight for a full size cargo version, it would likely be significantly less complex than the full size crew version, with less required functionality, no life support, far simpler internal design and far more cargo capability.

And it would then retire the mini version, making all of that interim development work a wasted exercise.

Yes this was actually my point which I failed to articulate properly.
As far as I understand it the falcon is the biggest rocket(3.6m) that can get road transported. All bigger stages require barge/train. So what is the advantage of the mini?

And furthermore, it seems the whole road transport limitation is something that will have to be overcome in the end if we are to go to heavy lift vehicles of the future. So just go and build the entire factory at Boca Chica, and end the transport problem for good.

Offline sevenperforce

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Re: Speculation thread: intermediate-lift Raptor-derived RLV
« Reply #98 on: 05/02/2017 04:10 PM »
Could a mini-ITS and an intermediate Raptor booster do Mars using fuel depots, SEP tugs, and maybe a reusable lander (mini-ITS) stationed only at Mars to take SEP cargo to the surface, refuel, and bring more down to the surface?

From earth launch cargo on a mini-its, offload to SEP tugs, and return to earth for more cargo. 

A refueled mini-ITS could take passengers direct to shorten the trip.  Say 20-50 passengers instead of the 100. 

The Martian mini-ITS can also bring up argon derived from the Mars atmosphere for a SEP tug to return to earth for more cargo. 

SEP tugs could be refueled with Falcon Heavies from earth for return trip to Mars.
Yes, precisely. But it's even better than this; you don't need an intermediate raptor booster, since a mini-ITS could launch on Falcon 9 or Falcon Heavy just as easily. As long as you have orbital refueling, the mini-ITS alone (or combinations thereof) could do pretty much all the Mars missions you can think of. A couple of pages back I outlined a fully-reusable 2020 Mars Sample Return for the cost of just two reusable Falcon Heavy launches plus refueling runs. Getting crew to Mars requires a transhab, which is a little more challenging, but I think doable.

No SEP required.

Auxiliary methane thrusters will be needed for the booster anyway. Might as well use them on a scaled BFS.
Makes landing a lot easier, and allows you to avoid the lossy step of including a SL Raptor.

I think the Mini-ITS would cost less overall to develop and can be developed more quickly.  Infrastructure for one.  A Mini-ITS can use existing pad 39A or B and would cost less to modify than a whole new launch pad.  Transportation from any factory along the waterways would be easier. 

I reading so much, I don't really know which ITS version is going to be developed.  The 12m version can take advantage of the existing river and intercoastal waterways, so factory doesn't have to be at or near the launch pad.  However, a new pad and facilities would have to be developed. 

Mini-ITS to me would be about 7-8m in diameter and be able to launch 75 tons to LEO fully reusable.

But then you would still need to develop a separate full size cargo version, full size crew version and full size tanker version. Whereas if you went straight for a full size cargo version, it would likely be significantly less complex than the full size crew version, with less required functionality, no life support, far simpler internal design and far more cargo capability.

And it would then retire the mini version, making all of that interim development work a wasted exercise.

Yes this was actually my point which I failed to articulate properly.
As far as I understand it the falcon is the biggest rocket(3.6m) that can get road transported. All bigger stages require barge/train. So what is the advantage of the mini?
You can get up to around 4 meters of diameter onto the road; length is more an issue.

Offline OneSpeed

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Re: Speculation thread: intermediate-lift Raptor-derived RLV
« Reply #99 on: 05/03/2017 11:26 AM »
You can get up to around 4 meters of diameter onto the road; length is more an issue.

Are you sure? The US highway standards are: Vertical clearance: Minimum vertical clearance under overhead structures (including over the paved shoulders) of 16 feet (4.9 m) in rural areas and 14 feet (4.3 m) in urban areas. The F9 appears to be over 5 metres already.

Offline gospacex

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Re: Speculation thread: intermediate-lift Raptor-derived RLV
« Reply #100 on: 05/03/2017 11:38 AM »
You can get up to around 4 meters of diameter onto the road; length is more an issue.

Are you sure? The US highway standards are: Vertical clearance: Minimum vertical clearance under overhead structures (including over the paved shoulders) of 16 feet (4.9 m) in rural areas and 14 feet (4.3 m) in urban areas. The F9 appears to be over 5 metres already.

They can use a different way to mount it, which sits lower. There is some ~1.5 m of space under it on the current trailer.

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Re: Speculation thread: intermediate-lift Raptor-derived RLV
« Reply #101 on: 05/03/2017 11:56 AM »
Roads are not flat...  They probably can't  lower the stage much, if at all...

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Offline rsdavis9

I personally think spacex has maxed out road transportable size with the F9 architecture.
How about short ballistic hops to transport stages from coast to coast?
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Offline spacenut

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Re: Speculation thread: intermediate-lift Raptor-derived RLV
« Reply #103 on: 05/03/2017 02:18 PM »
Four meter diameter can do a Guppy flight from the existing factory.  Surely there is a plane that can do 5m in diameter and can take off from the airport near the factory.  Don't know the maximum length, but an upper stage is shorter and could be made wider for use as an upper stage replacement on FH.  This would improve FH performance. 

Another thing is to cluster about 7 F9 cores (like Saturn IB), with a one or two Raptor engines on each core, maybe one in the center core for landing and fuel enough remaining for landing.  This strapped together would act as a complete first stage.  It would land with the center Raptor.  This would be 13 Raptors.  This would approach Saturn V thrust.  The strapping together could be done at the Cape and still use 39a.  It would require some equipment changes at the Cape. 

Then for a second stage, use 3 second stages strapped together with one Raptor vacuum on the middle.  A large interstage would have to be assembled on top of the 7 cores to encompass the Raptor vacuum and the three core second stage.

Then a larger 5m diameter payload could be placed on top. 

I know it would be a kludge, but it would max out the existing manufacturing. 

Then a new manufacturing facility and a wider first stage with say 18 raptors  would be far more efficient.  Less capable than ITS, but probably more economically likely.   

Offline macpacheco

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Re: Speculation thread: intermediate-lift Raptor-derived RLV
« Reply #104 on: 05/03/2017 02:44 PM »
Lets think rationally.
Most SpaceX launches today are to GTO. The 2nd most common destination is ISS. Then we have LEO constellations.
An upper stage that can travel all the way to Mars and land with massive payload capability should be able to deliver a boatload of satellites to GSO or near GEO spots.
If SpaceX ITS launch costs are 10% of a partial reuse F9, using ITS to GEO becomes a proposition no one can pass.
ITS is perfect for the ISS too, a single flight can deliver a year's worth of cargo and cycle the entire ISS crew. Perhaps with cheap large scale crew+cargo missions ISS can operate at double the current crew.
And of course, if ITS can deliver a lot of satellites to GTO directly, LEO delivery is a snap.
The sole question that remains is if the standard ITS can be used for multi satellite delivery or if a separate upper stage will have to be custom built for satellite delivery.
This would end any justification to use chemical propulsion for faster orbital raising. Same day delivery to GTO justifies waiting a month for enough payloads to be ready at the same time. In fact, SpaceX will have so much spare capacity, it will always be able to pick up last minute sign ups (as long as satellite is compatible with the ITS satellite delivery system).

There is no point in keeping merlin rockets once Raptor is fully tested, it doesn't matter if a new pad and a new rocket must be built.

SpaceX and Musk thinks big. The smaller they will think is a pure methane mini ITS. But when I say mini, I mean still much larger than FH or D4H 1/3 scale mini ITS, still an SLS class rocket payload capability even with full reuse performance hits.

Whatever the schedule SpaceX can create the proposed upper stage, with 1-2 years more, they can do the complete ITS/mini ITS platform.

Just saying.
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Offline dror

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Re: Speculation thread: intermediate-lift Raptor-derived RLV
« Reply #105 on: 05/03/2017 05:57 PM »
I think the Mini-ITS would cost less overall to develop and can be developed more quickly.  Infrastructure for one.  A Mini-ITS can use existing pad 39A or B and would cost less to modify than a whole new launch pad.  Transportation from any factory along the waterways would be easier. 

I reading so much, I don't really know which ITS version is going to be developed.  The 12m version can take advantage of the existing river and intercoastal waterways, so factory doesn't have to be at or near the launch pad.  However, a new pad and facilities would have to be developed. 

Mini-ITS to me would be about 7-8m in diameter and be able to launch 75 tons to LEO fully reusable.

(A)But then you would still need to develop a separate full size cargo version, full size crew version and full size tanker version. (B)Whereas if you went straight for a full size cargo version, it would likely be significantly less complex than the full size crew version, with less required functionality, no life support, far simpler internal design and far more cargo capability.

(C)And it would then retire the mini version, making all of that interim development work a wasted exercise.

I think not.
(A) you wouldnt NEED to develope any arbitrary size. 75 tons is more than enough for any of the suggested uses. IF there will still be a need for bigger loads, it will be so much later that a seconed generation will be designed anyway.
(B) I totaly agree that a cargo version will be easier than a crew version, that goes without saying. But that means nothing about full size vs smaller size. I think that the sheer size of ITS is its biggest hurdle.
(C) big rockets don't retire smaller ones unless they are better or cheaper at the job. 747 dont retire 737.

Offline rsdavis9

I think the Mini-ITS would cost less overall to develop and can be developed more quickly.  Infrastructure for one.  A Mini-ITS can use existing pad 39A or B and would cost less to modify than a whole new launch pad.  Transportation from any factory along the waterways would be easier. 

I reading so much, I don't really know which ITS version is going to be developed.  The 12m version can take advantage of the existing river and intercoastal waterways, so factory doesn't have to be at or near the launch pad.  However, a new pad and facilities would have to be developed. 

Mini-ITS to me would be about 7-8m in diameter and be able to launch 75 tons to LEO fully reusable.

(A)But then you would still need to develop a separate full size cargo version, full size crew version and full size tanker version. (B)Whereas if you went straight for a full size cargo version, it would likely be significantly less complex than the full size crew version, with less required functionality, no life support, far simpler internal design and far more cargo capability.

(C)And it would then retire the mini version, making all of that interim development work a wasted exercise.

I think not.
(A) you wouldnt NEED to develope any arbitrary size. 75 tons is more than enough for any of the suggested uses. IF there will still be a need for bigger loads, it will be so much later that a seconed generation will be designed anyway.
(B) I totaly agree that a cargo version will be easier than a crew version, that goes without saying. But that means nothing about full size vs smaller size. I think that the sheer size of ITS is its biggest hurdle.
(C) big rockets don't retire smaller ones unless they are better or cheaper at the job. 747 dont retire 737.

But full reusable big rockets do retire not fully reusable smaller ones.(cheaper)
bob

Online Lars-J

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Re: Speculation thread: intermediate-lift Raptor-derived RLV
« Reply #107 on: 05/03/2017 08:35 PM »
I think the Mini-ITS would cost less overall to develop and can be developed more quickly.  Infrastructure for one.  A Mini-ITS can use existing pad 39A or B and would cost less to modify than a whole new launch pad.  Transportation from any factory along the waterways would be easier. 

I reading so much, I don't really know which ITS version is going to be developed.  The 12m version can take advantage of the existing river and intercoastal waterways, so factory doesn't have to be at or near the launch pad.  However, a new pad and facilities would have to be developed. 

Mini-ITS to me would be about 7-8m in diameter and be able to launch 75 tons to LEO fully reusable.

(A)But then you would still need to develop a separate full size cargo version, full size crew version and full size tanker version. (B)Whereas if you went straight for a full size cargo version, it would likely be significantly less complex than the full size crew version, with less required functionality, no life support, far simpler internal design and far more cargo capability.

(C)And it would then retire the mini version, making all of that interim development work a wasted exercise.

I think not.
(A) you wouldnt NEED to develope any arbitrary size. 75 tons is more than enough for any of the suggested uses. IF there will still be a need for bigger loads, it will be so much later that a seconed generation will be designed anyway.
(B) I totaly agree that a cargo version will be easier than a crew version, that goes without saying. But that means nothing about full size vs smaller size. I think that the sheer size of ITS is its biggest hurdle.
(C) big rockets don't retire smaller ones unless they are better or cheaper at the job. 747 dont retire 737.

But full reusable big rockets do retire not fully reusable smaller ones.(cheaper)

It all depends on the cargo model. Smaller is not necessarily cheaper. It is cheaper to fly cross country on a large commercial jet than to lease/rent a small aircraft.

Offline dror

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Re: Speculation thread: intermediate-lift Raptor-derived RLV
« Reply #108 on: 05/03/2017 09:59 PM »
I think the Mini-ITS would cost less overall to develop and can be developed more quickly.  Infrastructure for one.  A Mini-ITS can use existing pad 39A or B and would cost less to modify than a whole new launch pad.  Transportation from any factory along the waterways would be easier. 

I reading so much, I don't really know which ITS version is going to be developed.  The 12m version can take advantage of the existing river and intercoastal waterways, so factory doesn't have to be at or near the launch pad.  However, a new pad and facilities would have to be developed. 

Mini-ITS to me would be about 7-8m in diameter and be able to launch 75 tons to LEO fully reusable.

(A)But then you would still need to develop a separate full size cargo version, full size crew version and full size tanker version. (B)Whereas if you went straight for a full size cargo version, it would likely be significantly less complex than the full size crew version, with less required functionality, no life support, far simpler internal design and far more cargo capability.

(C)And it would then retire the mini version, making all of that interim development work a wasted exercise.

I think not.
(A) you wouldnt NEED to develope any arbitrary size. 75 tons is more than enough for any of the suggested uses. IF there will still be a need for bigger loads, it will be so much later that a seconed generation will be designed anyway.
(B) I totaly agree that a cargo version will be easier than a crew version, that goes without saying. But that means nothing about full size vs smaller size. I think that the sheer size of ITS is its biggest hurdle.
(C) big rockets don't retire smaller ones unless they are better or cheaper at the job. 747 dont retire 737.

But full reusable big rockets do retire not fully reusable smaller ones.(cheaper)
Thats right, but all of the sugestions within this thread were fully reusable.

Offline gospacex

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Re: Speculation thread: intermediate-lift Raptor-derived RLV
« Reply #109 on: 05/04/2017 07:56 AM »
Roads are not flat...  They probably can't  lower the stage much, if at all...

You can have an adjustable bogie, and maximally lower the cargo only for the locations where in needs to pass under an obstacle. (Of course, nothing is free - they might be more expensive, or even non-existent and SpaceX would need to design and make them themselves).
« Last Edit: 05/04/2017 07:57 AM by gospacex »

Offline gospacex

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Re: Speculation thread: intermediate-lift Raptor-derived RLV
« Reply #110 on: 05/04/2017 08:04 AM »
I personally think spacex has maxed out road transportable size with the F9 architecture.

We can't know that until some info leak from SpaceX.

I would like to remind you that at the time when F9 diameter was chosen, Musk was not at all sure the entire enterprise is going to work, much less he could know how wildly Tom Mueller would succeed in uprating Merlins. Musk could not clearly foresee that F9 diameter would be such a serious limiter to its further evolution, and thus had no reason to scrape the barrel for the last half a meter of stage width. He could choose a somewhat more conservative width, to have less pain with transportation.

This is a photo of first F9 launch. Note how stubby it is compared to latest version.

Offline macpacheco

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Re: Speculation thread: intermediate-lift Raptor-derived RLV
« Reply #111 on: 05/04/2017 08:54 AM »
I think the Mini-ITS would cost less overall to develop and can be developed more quickly.  Infrastructure for one.  A Mini-ITS can use existing pad 39A or B and would cost less to modify than a whole new launch pad.  Transportation from any factory along the waterways would be easier. 

I reading so much, I don't really know which ITS version is going to be developed.  The 12m version can take advantage of the existing river and intercoastal waterways, so factory doesn't have to be at or near the launch pad.  However, a new pad and facilities would have to be developed. 

Mini-ITS to me would be about 7-8m in diameter and be able to launch 75 tons to LEO fully reusable.

(A)But then you would still need to develop a separate full size cargo version, full size crew version and full size tanker version. (B)Whereas if you went straight for a full size cargo version, it would likely be significantly less complex than the full size crew version, with less required functionality, no life support, far simpler internal design and far more cargo capability.

(C)And it would then retire the mini version, making all of that interim development work a wasted exercise.

I think not.
(A) you wouldnt NEED to develope any arbitrary size. 75 tons is more than enough for any of the suggested uses. IF there will still be a need for bigger loads, it will be so much later that a seconed generation will be designed anyway.
(B) I totaly agree that a cargo version will be easier than a crew version, that goes without saying. But that means nothing about full size vs smaller size. I think that the sheer size of ITS is its biggest hurdle.
(C) big rockets don't retire smaller ones unless they are better or cheaper at the job. 747 dont retire 737.
Raptor boosters are supposed to fly 1000x (maybe even more with major overhauls).
Merlin boosters are supposed to fly 100x before major overhauls.
737 and 747 use the exact same fuel, Jet A. M1D and Raptor don't.
Even IF M1D upper stages can be reused, there every expectation that they will require far more refurb / replacement for 100 flights.
The total gamuth of orbits used by rockets represent far lesser destinations than aircraft has routes.
Hence the two comparisons are invalid.
Most launches are to GTO. If ITS can deliver at least 6 satellites per launch directly to GTO, the use of F9/FH for GTO launches is gone.
The full blown Mars ITS can be used for CRS and CCS missions once approved by NASA, perhaps with a single launch per year to service ISS without practical payload or seats limitations.
Meanwhile, 737 and 747 are expected to fly nearly daily.
Lets be a bit more thorough in our thoughts gentleman, space isn't airline transportation. Completely different reality.
The airline scenario analogy stops with the argument that we must reuse rockets to bring down costs, everything else is different.
« Last Edit: 05/04/2017 08:56 AM by macpacheco »
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Offline M.E.T.

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Re: Speculation thread: intermediate-lift Raptor-derived RLV
« Reply #112 on: 05/04/2017 09:09 AM »
I think the Mini-ITS would cost less overall to develop and can be developed more quickly.  Infrastructure for one.  A Mini-ITS can use existing pad 39A or B and would cost less to modify than a whole new launch pad.  Transportation from any factory along the waterways would be easier. 

I reading so much, I don't really know which ITS version is going to be developed.  The 12m version can take advantage of the existing river and intercoastal waterways, so factory doesn't have to be at or near the launch pad.  However, a new pad and facilities would have to be developed. 

Mini-ITS to me would be about 7-8m in diameter and be able to launch 75 tons to LEO fully reusable.

(A)But then you would still need to develop a separate full size cargo version, full size crew version and full size tanker version. (B)Whereas if you went straight for a full size cargo version, it would likely be significantly less complex than the full size crew version, with less required functionality, no life support, far simpler internal design and far more cargo capability.

(C)And it would then retire the mini version, making all of that interim development work a wasted exercise.

I think not.
(A) you wouldnt NEED to develope any arbitrary size. 75 tons is more than enough for any of the suggested uses. IF there will still be a need for bigger loads, it will be so much later that a seconed generation will be designed anyway.
(B) I totaly agree that a cargo version will be easier than a crew version, that goes without saying. But that means nothing about full size vs smaller size. I think that the sheer size of ITS is its biggest hurdle.
(C) big rockets don't retire smaller ones unless they are better or cheaper at the job. 747 dont retire 737.
Raptor boosters are supposed to fly 1000x (maybe even more with major overhauls).
Merlin boosters are supposed to fly 100x before major overhauls.
737 and 747 use the exact same fuel, Jet A. M1D and Raptor don't.
Even IF M1D upper stages can be reused, there every expectation that they will require far more refurb / replacement for 100 flights.
The total gamuth of orbits used by rockets represent far lesser destinations than aircraft has routes.
Hence the two comparisons are invalid.
Most launches are to GTO. If ITS can deliver at least 6 satellites per launch directly to GTO, the use of F9/FH for GTO launches is gone.
The full blown Mars ITS can be used for CRS and CCS missions once approved by NASA, perhaps with a single launch per year to service ISS without practical payload or seats limitations.
Meanwhile, 737 and 747 are expected to fly nearly daily.
Lets be a bit more thorough in our thoughts gentleman, space isn't airline transportation. Completely different reality.
The airline scenario analogy stops with the argument that we must reuse rockets to bring down costs, everything else is different.

Something which has been bothering me is how they would get around the lack of a launch escape system to satisfy NASA crew transportation needs. Is there an envisaged solution to this in the ITS architecture? Like a pod or something which can eject from the upper stage during a launch malfunction?

Otherwise NASA may continue to insist on Falcon usage for crew transportation to the ISS.

Offline macpacheco

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Re: Speculation thread: intermediate-lift Raptor-derived RLV
« Reply #113 on: 05/04/2017 09:31 AM »
Something which has been bothering me is how they would get around the lack of a launch escape system to satisfy NASA crew transportation needs. Is there an envisaged solution to this in the ITS architecture? Like a pod or something which can eject from the upper stage during a launch malfunction?

Otherwise NASA may continue to insist on Falcon usage for crew transportation to the ISS.
By virtue of being fully and quick reusable launch systems, ITS can be tested to exhaustion.
The notion of a launch escape system made every sense in expendable stacks.
Once you can do over a dozen test flights on the same booster/spaceship combination (without any refurb) as a means of initial certification and perhaps 1 or 2 unmanned test flights on each brand new booster/spaceship units changes a lot of the safety calculations that mandates LAS.
There's an implicit assumption that boosters can randomly go kaboom due to hidden design issues/fabrication issues.
And lets not forget that the ITS upper stage itself might be your escape system protecting from booster problems.
Its a brave new world when all components of a launch system can be fully, rapidly and easily reused again and again and again.
I think ITS will make it viable to keep operating ISS for a long time, until its replaced with something much bigger (or a bunch of similar sized space hotels/stations).
« Last Edit: 05/04/2017 09:37 AM by macpacheco »
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Online hkultala

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Re: Speculation thread: intermediate-lift Raptor-derived RLV
« Reply #114 on: 05/04/2017 09:46 AM »
Something which has been bothering me is how they would get around the lack of a launch escape system to satisfy NASA crew transportation needs. Is there an envisaged solution to this in the ITS architecture? Like a pod or something which can eject from the upper stage during a launch malfunction?

Otherwise NASA may continue to insist on Falcon usage for crew transportation to the ISS.
By virtue of being fully and quick reusable launch systems, ITS can be tested to exhaustion.
The notion of a launch escape system made every sense in expendable stacks.
Once you can do over a dozen test flights on the same booster/spaceship combination (without any refurb) as a means of initial certification and perhaps 1 or 2 unmanned test flights on each brand new booster/spaceship units changes a lot of the safety calculations that mandates LAS.

R-7-derivates have flown about 2000 times and they still use LAS on soyuz.

Quote
There's an implicit assumption that boosters can randomly go kaboom due to hidden design issues/fabrication issues.
And lets not forget that the ITS upper stage itself might be your escape system protecting from booster problems.

No, it's too slow to start and it has too bad T/W for that. Escape rockets needs to have T/W considerably better than the rocket it is trying to escape, and they need to start IMMEDIATELY, not after few seconds.

Offline macpacheco

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Re: Speculation thread: intermediate-lift Raptor-derived RLV
« Reply #115 on: 05/04/2017 10:27 AM »
Something which has been bothering me is how they would get around the lack of a launch escape system to satisfy NASA crew transportation needs. Is there an envisaged solution to this in the ITS architecture? Like a pod or something which can eject from the upper stage during a launch malfunction?

Otherwise NASA may continue to insist on Falcon usage for crew transportation to the ISS.
By virtue of being fully and quick reusable launch systems, ITS can be tested to exhaustion.
The notion of a launch escape system made every sense in expendable stacks.
Once you can do over a dozen test flights on the same booster/spaceship combination (without any refurb) as a means of initial certification and perhaps 1 or 2 unmanned test flights on each brand new booster/spaceship units changes a lot of the safety calculations that mandates LAS.

R-7-derivates have flown about 2000 times and they still use LAS on soyuz.

Quote
There's an implicit assumption that boosters can randomly go kaboom due to hidden design issues/fabrication issues.
And lets not forget that the ITS upper stage itself might be your escape system protecting from booster problems.

No, it's too slow to start and it has too bad T/W for that. Escape rockets needs to have T/W considerably better than the rocket it is trying to escape, and they need to start IMMEDIATELY, not after few seconds.
It would be impossible economically to do 100 test flights on soyuz+R7.
To do that with ITS the biggest issue would be having a dedicated launch pad.
I'm not saying my assumptions will hold in the eyes of NASA, but I am saying that your argument 100% ignores the massive difference in testing/certifying a system that is fully reusable (reflying dozens of times with zero refurb).
As long as ITS can refly dozens of times without refurb and does so without any failures and non destructive testing proves everything is still within margins and within predicted wear levels changes everything (in theory).
At some point the paradigm will change.
Lets keep it in perspective that there were just 135 STS missions.
If NASA is willing to pay US$ 1 billion for testing ITS, 135 test launches is in theory possible (but illogical).
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Offline dror

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Re: Speculation thread: intermediate-lift Raptor-derived RLV
« Reply #116 on: 05/04/2017 12:16 PM »
Something which has been bothering me is how they would get around the lack of a launch escape system to satisfy NASA crew transportation needs. Is there an envisaged solution to this in the ITS architecture? Like a pod or something which can eject from the upper stage during a launch malfunction?

Otherwise NASA may continue to insist on Falcon usage for crew transportation to the ISS.
By virtue of being fully and quick reusable launch systems, ITS can be tested to exhaustion.
The notion of a launch escape system made every sense in expendable stacks.
Once you can do over a dozen test flights on the same booster/spaceship combination (without any refurb) as a means of initial certification and perhaps 1 or 2 unmanned test flights on each brand new booster/spaceship units changes a lot of the safety calculations that mandates LAS.

R-7-derivates have flown about 2000 times and they still use LAS on soyuz

Each rocket have flown once. Flight proven vehicles may ease the pressure

Offline dror

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Re: Speculation thread: intermediate-lift Raptor-derived RLV
« Reply #117 on: 05/04/2017 12:20 PM »
I think the Mini-ITS would cost less overall to develop and can be developed more quickly.  Infrastructure for one.  A Mini-ITS can use existing pad 39A or B and would cost less to modify than a whole new launch pad.  Transportation from any factory along the waterways would be easier. 

I reading so much, I don't really know which ITS version is going to be developed.  The 12m version can take advantage of the existing river and intercoastal waterways, so factory doesn't have to be at or near the launch pad.  However, a new pad and facilities would have to be developed. 

Mini-ITS to me would be about 7-8m in diameter and be able to launch 75 tons to LEO fully reusable.

(A)But then you would still need to develop a separate full size cargo version, full size crew version and full size tanker version. (B)Whereas if you went straight for a full size cargo version, it would likely be significantly less complex than the full size crew version, with less required functionality, no life support, far simpler internal design and far more cargo capability.

(C)And it would then retire the mini version, making all of that interim development work a wasted exercise.

I think not.
(A) you wouldnt NEED to develope any arbitrary size. 75 tons is more than enough for any of the suggested uses. IF there will still be a need for bigger loads, it will be so much later that a seconed generation will be designed anyway.
(B) I totaly agree that a cargo version will be easier than a crew version, that goes without saying. But that means nothing about full size vs smaller size. I think that the sheer size of ITS is its biggest hurdle.
(C) big rockets don't retire smaller ones unless they are better or cheaper at the job. 747 dont retire 737.
Raptor boosters are supposed to fly 1000x (maybe even more with major overhauls).
Merlin boosters are supposed to fly 100x before major overhauls.
737 and 747 use the exact same fuel, Jet A. M1D and Raptor don't.
Even IF M1D upper stages can be reused, there every expectation that they will require far more refurb / replacement for 100 flights.
The total gamuth of orbits used by rockets represent far lesser destinations than aircraft has routes.
Hence the two comparisons are invalid.
Most launches are to GTO. If ITS can deliver at least 6 satellites per launch directly to GTO, the use of F9/FH for GTO launches is gone.
The full blown Mars ITS can be used for CRS and CCS missions once approved by NASA, perhaps with a single launch per year to service ISS without practical payload or seats limitations.
Meanwhile, 737 and 747 are expected to fly nearly daily.
Lets be a bit more thorough in our thoughts gentleman, space isn't airline transportation. Completely different reality.
The airline scenario analogy stops with the argument that we must reuse rockets to bring down costs, everything else is different.

The discussion is about full size ITS vs intermediate size RLV. F9\FH is irrelevant

Offline macpacheco

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Re: Speculation thread: intermediate-lift Raptor-derived RLV
« Reply #118 on: 05/04/2017 01:09 PM »
The discussion is about full size ITS vs intermediate size RLV. F9\FH is irrelevant
It is relevant if it makes the premise goal of this thread pointless, which is the point I'm making.
If the best choice is pure M1D F9/FH transitioning directly to ITS/mini ITS, then this thread is pointless.
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Offline dror

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Re: Speculation thread: intermediate-lift Raptor-derived RLV
« Reply #119 on: 05/04/2017 02:57 PM »
The discussion is about full size ITS vs intermediate size RLV. F9\FH is irrelevant
It is relevant if it makes the premise goal of this thread pointless, which is the point I'm making.
If the best choice is pure M1D F9/FH transitioning directly to ITS/mini ITS, then this thread is pointless.
It depends on your definition of mini ITS

Offline GWH

In considering the launch costs of ITS vs a miniITS spaceship I think one should look at F9 development and reuse.

SpaceX didn't just slap some legs and grid fins on the F9, land it and reduce the costs of launch through reuse the moment they did that. It's been, and still is, a long journey and many lessons learned in the process.  The block 5 is supposed to get them to the point of rapid and economical booster reuse.  There will be new challenges in upper stage reuse, particularly when there is so much new tech involved in the ITS. See the shuttle orbiter for example.  It will not be easy to get the reflight rates and low refurb of the ITS that makes the per launch cost as low as they want.  There may be a lot of value in learning some of those lessons at a smaller scale.

But to make this argument that the first flight of ITS is going to instantly flip the cost equation on its head is, in my opinion, rubbish.  Just like with F9, it will take a while until they reach that point of operational reusability of a complete new system to reach the cost/flight goals that are projected.

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Re: Speculation thread: intermediate-lift Raptor-derived RLV
« Reply #121 on: 05/05/2017 11:08 AM »
In considering the launch costs of ITS vs a miniITS spaceship I think one should look at F9 development and reuse.

SpaceX didn't just slap some legs and grid fins on the F9, land it and reduce the costs of launch through reuse the moment they did that. It's been, and still is, a long journey and many lessons learned in the process.  The block 5 is supposed to get them to the point of rapid and economical booster reuse.  There will be new challenges in upper stage reuse, particularly when there is so much new tech involved in the ITS. See the shuttle orbiter for example.  It will not be easy to get the reflight rates and low refurb of the ITS that makes the per launch cost as low as they want.  There may be a lot of value in learning some of those lessons at a smaller scale.

But to make this argument that the first flight of ITS is going to instantly flip the cost equation on its head is, in my opinion, rubbish.  Just like with F9, it will take a while until they reach that point of operational reusability of a complete new system to reach the cost/flight goals that are projected.
You must assume SpaceX needs to learn things all over again to design a new LV that's fully reusable from the get go.
Rocket design is engineering rather than experimentation. Experimentation is done when there's no / little data. But F9 / FH reuse experience provides a lot of valuable data and experience that makes ITS design far closer to 100% engineering rather than experimentation.
I agree with you that many more lessons will be learned from Block IV and Block V ops, but its very likely mini ITS / ITS construction will only begin 12-24 months after Block V starts flying, which might provide SpaceX around 25 flights worth of Block V flight/re flight.

People insist on thinking they understand SpaceX modus operandi while ignoring Elon Musk's style and track record.
He's as ballsy as they get. He's also a perfectionist. He won't start cutting ITS / mini ITS metal until the design is up to his standards which are quite high.

If you can't put yourself inside E.M.'s head your predictions are very very likely wrong.
My opinion (as well as yours) isn't worth much if you're assuming things will be done they way you like, they will be done like E.M. likes is. Embrace that.
« Last Edit: 05/05/2017 11:12 AM by macpacheco »
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Online guckyfan

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Re: Speculation thread: intermediate-lift Raptor-derived RLV
« Reply #122 on: 05/05/2017 12:04 PM »
People insist on thinking they understand SpaceX modus operandi while ignoring Elon Musk's style and track record.
He's as ballsy as they get. He's also a perfectionist. He won't start cutting ITS / mini ITS metal until the design is up to his standards which are quite high.

In all speculation we need to remember a reusable second stage is announced for end of next year. I can not believe that at this stage they will spend all the needed engineering effort for developing a new Merlin upper stage. I am convinced it will be a Raptor upper stage. Up until that reusable upper stage was announced I liked to speculate but did not believe in a Raptor upper stage for Falcon. But the reusable announcement has changed that.

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Re: Speculation thread: intermediate-lift Raptor-derived RLV
« Reply #123 on: 05/05/2017 01:36 PM »
People insist on thinking they understand SpaceX modus operandi while ignoring Elon Musk's style and track record.
He's as ballsy as they get. He's also a perfectionist. He won't start cutting ITS / mini ITS metal until the design is up to his standards which are quite high.

In all speculation we need to remember a reusable second stage is announced for end of next year. I can not believe that at this stage they will spend all the needed engineering effort for developing a new Merlin upper stage. I am convinced it will be a Raptor upper stage. Up until that reusable upper stage was announced I liked to speculate but did not believe in a Raptor upper stage for Falcon. But the reusable announcement has changed that.

I would call it a recoverable upper stage rather than a reusable one. A first step. Precisely where SX needs to experiment with techniques.
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Offline JamesH65

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Re: Speculation thread: intermediate-lift Raptor-derived RLV
« Reply #124 on: 05/05/2017 01:48 PM »
People insist on thinking they understand SpaceX modus operandi while ignoring Elon Musk's style and track record.
He's as ballsy as they get. He's also a perfectionist. He won't start cutting ITS / mini ITS metal until the design is up to his standards which are quite high.

In all speculation we need to remember a reusable second stage is announced for end of next year.

No not really. They said they hope to do something that may or may not be a reusable second stage, hopefully maybe by the end of next year.

I can not believe that at this stage they will spend all the needed engineering effort for developing a new Merlin upper stage. I am convinced it will be a Raptor upper stage. Up until that reusable upper stage was announced I liked to speculate but did not believe in a Raptor upper stage for Falcon. But the reusable announcement has changed that.

I don't think there is any evidence at all to support a Raptor U/S. Not to say it won't happen, just that there is nothing to indicate that it will. If nothing else, the cost to infrastructure to support it will be pretty high. Will the Raptor even be ready by end of next year?


Online hkultala

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Re: Speculation thread: intermediate-lift Raptor-derived RLV
« Reply #125 on: 05/05/2017 01:57 PM »
People insist on thinking they understand SpaceX modus operandi while ignoring Elon Musk's style and track record.
He's as ballsy as they get. He's also a perfectionist. He won't start cutting ITS / mini ITS metal until the design is up to his standards which are quite high.

No, the only reason he's not cutting ITS metal is because it's made of carbon fiber, not metal.

Related to his perfectionism, exactly the opposite. He knows that the best way to get something done is to start experimenting, get your hands dirty. And they ALREADY both made and broke one ITS tank.



« Last Edit: 05/05/2017 02:00 PM by hkultala »

Offline spacenut

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Re: Speculation thread: intermediate-lift Raptor-derived RLV
« Reply #126 on: 05/05/2017 02:10 PM »
I still think a Mini-ITS/BFR should be built to be able to take advantage of pad 39A at 12 million lbs thrust or less.  More than Saturn, but less than a full blown 28 million they have been speculating for the BFR.  ITS or Mini ITS would be sized to fit this 12 million lb thrust rocket.  That way SpaceX can take advantage of the existing pad and infrastructure.  Same with transportation infrastructure. 

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Re: Speculation thread: intermediate-lift Raptor-derived RLV
« Reply #127 on: 05/05/2017 02:30 PM »
No, the only reason he's not cutting ITS metal is because it's made of carbon fiber, not metal.

Related to his perfectionism, exactly the opposite. He knows that the best way to get something done is to start experimenting, get your hands dirty. And they ALREADY both made and broke one ITS tank.

F9 Block II easily took at least an extra year to fly because Musk demanded M1D engines had to had the margins to fly 100 times, several things on the F9 Block II were very overdesigned because of reuse, although they knew they wouldn't be recovering and reflying Block II for a while.

And now SX already has a line of rockets flying, generating revenue, certified with USAF.

The earlier you fix issues the cheaper the fix is to implement.

The full ITS set (1 booster, 1 tanker, 1 spaceship) is expected to cost over half a billion USD.
I'd say even Elon Musk isn't going to build the first one in a hurry. The man has a degree in economics. He's aggressive but certainly not stupid.
If its a mini ITS that might be able to launch from LC39A at a reasonable cost of upgrades, that's one thing, but if its the full size ITS, I don't think your argument holds water.
« Last Edit: 05/06/2017 09:06 AM by macpacheco »
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Offline spacenut

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Re: Speculation thread: intermediate-lift Raptor-derived RLV
« Reply #128 on: 05/14/2017 12:58 PM »
One of the reasons I believe a "Raptor 9" based rocket would be beneficial is not only taking advantage of existing infrastructure, but the following.

Say a 7m diameter Raptor 9 is built.  A 7 meter upper stage could also be built to be reusable, based on ITS design, only smaller about half scale.

A Raptor 9 would generate about 6 million lbs thrust.  This would get an expendable version payload to 80-90 tons.  Ok you make the entire rocket reusable and you can match Falcon heavy expendable.  Falcon heavy, according to Musk, is "hard".  A single stick rocket would be easier?  Probably. 

This rocket could do moon and Mars, with extensive building of an in space infrastructure to use fuel depots, SEP tugs, among other things. 

Sure you only can get about 30-40 tons of payload to Mars, maybe more, but that is doable sooner.  With SEP tugs and fuel depots, even more payload may could be landed. 

This rocket would compete, (with various upper stages) with SLS and New Glenn, and be more capable.  Falcon Heavy would not be needed. 

Shear cost is another reason to take advantage of existing infrastructure.  Pads 39A or B could either be used to launch without building a new launch facility. 

This rocket with the ability to launch the Constellation by carrying 20-30 or more satellites in one launch.  Cost to launch a large single stick shouldn't be more than Falcon Heavy is to be, so launch costs would drop. 

This rocket would be in the range of payload and capabilities of the old "Direct" rocket, at about half the price. 

It could fill and nich and still get us to Mars with refueling.  So, it may take 3 times as many launches as a full blown ITS, but should cost less than half to get going.   

Online guckyfan

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Re: Speculation thread: intermediate-lift Raptor-derived RLV
« Reply #129 on: 05/14/2017 03:05 PM »
I think the remark FH is "hard" gets interpreted wrong. Sure the design was hard. But like Tom Mueller said about Merlin 1D, the design was hard. Now that it is designed, building and flying it is no longer hard. The same will apply for FH. FH will be replaced, but not earlier than phasing out the whole Falcon family, IMO.

Offline AncientU

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Re: Speculation thread: intermediate-lift Raptor-derived RLV
« Reply #130 on: 05/14/2017 10:01 PM »
One of the reasons I believe a "Raptor 9" based rocket would be beneficial is not only taking advantage of existing infrastructure, but the following.

Say a 7m diameter Raptor 9 is built.  A 7 meter upper stage could also be built to be reusable, based on ITS design, only smaller about half scale.

A Raptor 9 would generate about 6 million lbs thrust.  This would get an expendable version payload to 80-90 tons.  Ok you make the entire rocket reusable and you can match Falcon heavy expendable.  Falcon heavy, according to Musk, is "hard".  A single stick rocket would be easier?  Probably. 

This rocket could do moon and Mars, with extensive building of an in space infrastructure to use fuel depots, SEP tugs, among other things. 

Sure you only can get about 30-40 tons of payload to Mars, maybe more, but that is doable sooner.  With SEP tugs and fuel depots, even more payload may could be landed. 

This rocket would compete, (with various upper stages) with SLS and New Glenn, and be more capable.  Falcon Heavy would not be needed. 

Shear cost is another reason to take advantage of existing infrastructure.  Pads 39A or B could either be used to launch without building a new launch facility. 

This rocket with the ability to launch the Constellation by carrying 20-30 or more satellites in one launch.  Cost to launch a large single stick shouldn't be more than Falcon Heavy is to be, so launch costs would drop. 

This rocket would be in the range of payload and capabilities of the old "Direct" rocket, at about half the price. 

It could fill and nich and still get us to Mars with refueling.  So, it may take 3 times as many launches as a full blown ITS, but should cost less than half to get going.   

If you are going to build a completely new rocket to take advantage of existing infrastructure, why just go incrementally better than FH?  So you've obsoleted your own rocket... not a reason to celebrate.

New intermediate-sized Raptor rocket should maximize capability of LC-39A and B.  Build a 12+Mlbf booster (19 engines in three ring -- 1-6-12 -- hex pattern  would be my choice) with both a conventional second stage and fairing, plus a follow-on mini-ITS spaceship second stage.  Core diameter would be around 9m (8-10).  Reusable booster mode payload would be around 200t.

Probably could find a few uses... everything you said x 2.  And obsolete someone else's rocket.
« Last Edit: 05/14/2017 10:07 PM by AncientU »
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Re: Speculation thread: intermediate-lift Raptor-derived RLV
« Reply #131 on: 05/15/2017 08:20 AM »

If you are going to build a completely new rocket to take advantage of existing infrastructure, why just go incrementally better than FH?  So you've obsoleted your own rocket... not a reason to celebrate.

FH covers almost the entire need for lifting in cislunar space. No need to build a bigger rocket than this. Except for the ITS which can take care of everything too large for the smaller vehicle.

New intermediate-sized Raptor rocket should maximize capability of LC-39A and B.  Build a 12+Mlbf booster (19 engines in three ring -- 1-6-12 -- hex pattern  would be my choice) with both a conventional second stage and fairing, plus a follow-on mini-ITS spaceship second stage.  Core diameter would be around 9m (8-10).  Reusable booster mode payload would be around 200t.

Probably could find a few uses... everything you said x 2.  And obsolete someone else's rocket.

This would be a rocket oversized for most launchs. They are already developing an oversized rocket, why another?

Offline spacenut

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Re: Speculation thread: intermediate-lift Raptor-derived RLV
« Reply #132 on: 05/15/2017 11:52 AM »
A 12 million lb thrust or lower would take advantage of existing infrastructure.  Give us a big rocket to match or exceed SLS at a lower cost.  Allow for a Mini-ITS which would give us 50 tons or 50 people to Mars instead of 100.  Allow us to get there quicker as no new infrastructure would have to be built (except at Boca Chica maybe).  This rocket could become a workhorse for moon as well as Mars missions.  Multiple satellite launcher.  Deep space probe launcher. 

The width of railroad tracks haven't changed since the 1880's when they standardized the track nationwide.  Engines have increased in size as well as railcars.  Why not build a rocket to take advantage of infrastructure built to handle the Nova rocket of the 1960's that was never built.  Same with highways.  Trucks have gotten larger but not the highway widths.  Two pads can already handle 12 million lbs.  Existing barges in the inland waterways of America can handle 10-12m maximum diameter.  Don't know the maximum length. 

With the BFR/ITS, the factory will be limited to near the pad.  Due to the massive power of this rocket, a huge radius would need to also be clear for each launch.  The Cape has this but at 12 million lbs.  The Mini-BFR factory and the Mini-ITS factory could be built anywere along the inland or intercoastal waterway, like in states that are more manufacturing friendly and have less regulations than California, and are also nearer potential launch locations and LNG facilities. 

Again taking advantage of existing infrastructure from factory to transportation to launch site has to be a cost consideration, not just the biggest rocket you can build on paper, but as big as you can reasonably build cost wise and still get to Mars. 

Offline macpacheco

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Re: Speculation thread: intermediate-lift Raptor-derived RLV
« Reply #133 on: 05/15/2017 01:31 PM »
If you are going to build a completely new rocket to take advantage of existing infrastructure, why just go incrementally better than FH?  So you've obsoleted your own rocket... not a reason to celebrate.

New intermediate-sized Raptor rocket should maximize capability of LC-39A and B.  Build a 12+Mlbf booster (19 engines in three ring -- 1-6-12 -- hex pattern  would be my choice) with both a conventional second stage and fairing, plus a follow-on mini-ITS spaceship second stage.  Core diameter would be around 9m (8-10).  Reusable booster mode payload would be around 200t.

Probably could find a few uses... everything you said x 2.  And obsolete someone else's rocket.
Raptor's better ISP and double T:W are huge benefits, both for upper stable and booster.

Just as importantly F9 and FH were designed aiming for re-use but they couldn't take reuse for granted.
Designing a rocket from the ground up for reuse allows such things as much more expensive but lighter carbon composite structures, giving up on road transport.
Its funny the list has been enumerated over a dozen times by several people, but some guys have locked their thought process in a path that doesn't actually make sense.

The fundamental FACT is F9 with upper stage expendability is a very capable rocket that can handle the vast majority of SpaceX manifest.
Designing a Raptor upper stage will deliver more performance, but at what fabrication cost vs F9 upper stage ?
SpaceX stated main upper stage reuse path involves putting same fuel vacuum and SL engines on the upper stage, there's not enough room to do that with road transport limits.
So if you open your mind to the give and take of:
1 - The end game is ITS and ITS style reuse
2 - Raptor is already being tested, for nearly 6 months, Raptor is a very real rocket engine !
3 - Raptor is designed for perhaps 100 mission firings per refurb, 10x as many as M1D (key, key, key issue) Just the refurb savings on the booster already shoots down your idea !
4 - In the short run, F9 as is can handle the manifest economically, with FH handling the balance
5 - There's a lot of economical benefit on a larger rocket that can deliver a handful of GEO satellites at a time to a far more convenient orbit than today. Don't loose sight that most of SpaceX's current revenue is toward GEO launches
6 - A fully reusable SLS sized booster will... KILL SLS ! There's a chance SpaceX can finally be recognized as the path to the Mars, the Moon, the outer planets. What if SpaceX started getting a US$ 1 billion / yr subsidy to build the full sized ITS ? (Ok, I'm probably dreaming)
7 - A mini ITS / Raptor 9 rocket would actually have the lifting and payload bay/fairing size to deliver perhaps even 3x as many CommX satellites per launch.

And you're blatantly ignoring the FACT that SpaceX / Elon Musk doesn't think small. Yep, you're thinking way too small. You're idea doesn't fit SpaceX  M.O.
« Last Edit: 05/15/2017 01:44 PM by macpacheco »
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Offline spacenut

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Re: Speculation thread: intermediate-lift Raptor-derived RLV
« Reply #134 on: 05/15/2017 02:24 PM »
Maybe not, but it is more practical and can be done sooner rather than later.  We still need the raptor engines, not matter what rocket they are used on.  I know this is a speculation thread, but no infrastructure exists for the proposed BFR/ITS yet.  That will take 3-5 years to build and maybe an extra billion.  2 years to modify pad 39 they already have maybe and probably a couple hundred million.  They could even use the McCloud facility in Louisana to build and intermediate lift of 12 million lbs or less or anywhere else for that matter.  LNG can be either shipped in or piped into the Cape.  A pipeline company might even build the pipeline into the cape from an existing pipeline just for the sale of the gas, and maybe even the LNG facility.  Before I retired from my gas company a pipeline for natural gas was being laid under the Gulf from Louisiana to Tampa for power generation.  From this pipeline alone LNG could be made during off peak hours at a power plant. 

Also, if the intermediate 10-12 million lb thrust Raptor derived vehicle is built, it would be less costly than SLS for the same or larger payload, putting SLS out of business.  This rocket could be built within 5 years, not 10 for BFR/ITS.  Also, Musk might need another influx of capital to get this big project up and running.  With an intermediate Raptor derived rocket, he could begin on his own. 

For practical purposes, I think large SEP tugs should be built to carry non perishable and non human cargo to Mars.  A Mini ITS system could be left at Mars and not return to earth to dock and bring down the SEP cargo to Mars, SEP could then return to Earth for more cargo.  The intermediate vehicle can launch the SEP tugs, cargo and propellant on a continuous bases to Mars.  Mini-ITS would bring people and several used and Mars transport between Mars and high Mars orbit.  SEP tugs could use argon from Mars or Earth to refuel since Mars atmosphere had quite a bit of argon.  Or they could use an oxygen supplied SEP tug with excess oxygen created in methane production on Mars to supply the fleet of Mini-ITS. 

 

Offline philw1776

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Re: Speculation thread: intermediate-lift Raptor-derived RLV
« Reply #135 on: 05/15/2017 04:20 PM »

Again taking advantage of existing infrastructure from factory to transportation to launch site has to be a cost consideration, not just the biggest rocket you can build on paper, but as big as you can reasonably build cost wise and still get to Mars.

That was a major factor when SpaceX was sending new cores to FL for every launch and even sending flight proven cores back to Texas for static firings then back to FL.  An ITS will be transported once, from the nearby factory and then used many tens of times plus without further transportation.
I don't see how a wide 12 million LB rocket uses existing transportation.
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Offline dror

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Re: Speculation thread: intermediate-lift Raptor-derived RLV
« Reply #136 on: 05/18/2017 12:54 PM »
One of the reasons I believe a "Raptor 9" based rocket would be beneficial is not only taking advantage of existing infrastructure, but the following.

Say a 7m diameter Raptor 9 is built.  A 7 meter upper stage could also be built to be reusable, based on ITS design, only smaller about half scale.

A Raptor 9 would generate about 6 million lbs thrust.  This would get an expendable version payload to 80-90 tons.  Ok you make the entire rocket reusable and you can match Falcon heavy expendable.  Falcon heavy, according to Musk, is "hard".  A single stick rocket would be easier?  Probably. 

This rocket could do moon and Mars, with extensive building of an in space infrastructure to use fuel depots, SEP tugs, among other things. 

Sure you only can get about 30-40 tons of payload to Mars, maybe more, but that is doable sooner.  With SEP tugs and fuel depots, even more payload may could be landed. 

This rocket would compete, (with various upper stages) with SLS and New Glenn, and be more capable.  Falcon Heavy would not be needed. 

Shear cost is another reason to take advantage of existing infrastructure.  Pads 39A or B could either be used to launch without building a new launch facility. 

This rocket with the ability to launch the Constellation by carrying 20-30 or more satellites in one launch.  Cost to launch a large single stick shouldn't be more than Falcon Heavy is to be, so launch costs would drop. 

This rocket would be in the range of payload and capabilities of the old "Direct" rocket, at about half the price. 

It could fill and nich and still get us to Mars with refueling.  So, it may take 3 times as many launches as a full blown ITS, but should cost less than half to get going.   

If you are going to build a completely new rocket to take advantage of existing infrastructure, why just go incrementally better than FH?  So you've obsoleted your own rocket... not a reason to celebrate.

New intermediate-sized Raptor rocket should maximize capability of LC-39A and B.  Build a 12+Mlbf booster (19 engines in three ring -- 1-6-12 -- hex pattern  would be my choice) with both a conventional second stage and fairing, plus a follow-on mini-ITS spaceship second stage.  Core diameter would be around 9m (8-10).  Reusable booster mode payload would be around 200t.

Probably could find a few uses... everything you said x 2.  And obsolete someone else's rocket.

Now, you see where this leads?
This is, as guckyfan suggested, a very Big FR.
I agree these are very reasonable advantages, and I too think this is a more logical size for the BFR, but it will only push the full size further away.
An intermediate vehicle needs to serve the later design, not compete with it.
It needs to be drastically simpler in order to remove 'design roadblocks', to make the impossible possible.

Sevenperforce's design is just that-
You start with a spaceship that lanches on FH, develope all hardware and architecture on smaller scale and realistic budjet and timescale while being usefull.
IF necessary, then move on to an improved booster and develope the needed hardware, again, on smaller scale.
Only then you move on to a big freaking rocket, with your development process sped up.

On that note, I do think that 4 meters is too small for the spaceship which needs to be at least as big as a a F9 fairing.
« Last Edit: 05/18/2017 03:20 PM by dror »

Offline spacenut

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Re: Speculation thread: intermediate-lift Raptor-derived RLV
« Reply #137 on: Today at 02:53 AM »
12m would use existing barge transportation on rivers and the inter-coastal waterway.  The VAB and pads 39A and 39B were designed for 12m Nova rocket to replace Saturn V.  Nova was to have 8 F1 engines and develop 12 million lbs thrust which is what the pads and the VAB were designed to handle. 

I do not think the existing barge and inter-coastal waterway can handle anything larger than 12m due to bridges and standard barge sizes.  15m ITS will require ALL new infrastructure.  Transportation from factory to launch pad, and launch pad itself, as well as distance for the shock wave of the blast off.   The cape offers this from the old Saturn pads.  The VAB could be used for assembly and the old Saturn transporter could be used for ITS because ITS is liquid fueled, thus will be lighter than solids.   

Offline macpacheco

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Re: Speculation thread: intermediate-lift Raptor-derived RLV
« Reply #138 on: Today at 05:05 AM »
Think about how large a rocket that would still cost less per launch than F9, as long as:
F9 booster requires a little refurb each launch, a lot of refurb every 10 launches and must be rebuild/thrown away every 100 launches.
F9 upper stage is still thrown away except when launched on a FH with very little payload but FH launches incur 3x faster usage of boosters.

Meanwhile a very large rocket consumes far more O2 and CH4, but those are both very cheap, the booster flies 100x between refurbs, 1000x total, the upper stage flies say 20x between refurbs and 100x total. The cost to build the launch stack and refurb should still dominate.

Even a rocket with SLS size expendable performance could be cheaper or at least similar cost per launch with F9.
It both casts a shadow over SLS, but also directly replaces all FH launches and could also replace the vast majority of F9 launches.

I also suggest thinking about launch pad congestion if the predicted launch volume materializes.
F9/FH are stepping stones onto large raptor rockets, they are not going to hang around once mini ITS is flying and its certified with NASA/USAF.
« Last Edit: Today at 05:08 AM by macpacheco »
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Tags: Raptor ITS BFR