Author Topic: Speculation thread: intermediate-lift Raptor-derived RLV  (Read 31075 times)

Offline sevenperforce

  • Full Member
  • ****
  • Posts: 746
  • Liked: 175
  • Likes Given: 220
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.

Offline guckyfan

  • Senior Member
  • *****
  • Posts: 6317
  • Germany
  • Liked: 1577
  • Likes Given: 1386
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.

Offline guckyfan

  • Senior Member
  • *****
  • Posts: 6317
  • Germany
  • Liked: 1577
  • Likes Given: 1386
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

  • Full Member
  • *
  • Posts: 142
  • Tokyo - Barcelona
  • Liked: 78
  • Likes Given: 79
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

  • Senior Member
  • *****
  • Posts: 2103
  • Liked: 374
  • Likes Given: 55
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

  • Fan boy at large
  • Global Moderator
  • Senior Member
  • *****
  • Posts: 8333
  • Saw Gemini live on TV
  • A large LEGO storage facility ... in Michigan
  • Liked: 5116
  • Likes Given: 3417
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

  • Full Member
  • ****
  • Posts: 746
  • Liked: 175
  • Likes Given: 220
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

  • Full Member
  • ****
  • Posts: 746
  • Liked: 175
  • Likes Given: 220
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

  • Armchair Rocketeer
  • Full Member
  • *
  • Posts: 113
  • Florida
  • Liked: 50
  • Likes Given: 87
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

  • Full Member
  • ****
  • Posts: 746
  • Liked: 175
  • Likes Given: 220
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.

Online Semmel

  • Full Member
  • ****
  • Posts: 1081
  • Germany
  • Liked: 768
  • Likes Given: 2219
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

  • Full Member
  • *
  • Posts: 142
  • Tokyo - Barcelona
  • Liked: 78
  • Likes Given: 79
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.

Iīm also dubious about mid size developments as per FH, thatīs 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

  • Full Member
  • *
  • Posts: 142
  • Tokyo - Barcelona
  • Liked: 78
  • Likes Given: 79
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

  • Senior Member
  • *****
  • Posts: 2120
  • East Alabama
  • Liked: 297
  • Likes Given: 191
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

  • Member
  • Posts: 92
  • Liked: 38
  • Likes Given: 77
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

  • Senior Member
  • *****
  • Posts: 2581
  • Liked: 1157
  • Likes Given: 731
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

  • Full Member
  • ****
  • Posts: 514
  • Liked: 513
  • Likes Given: 428
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

  • Senior Member
  • *****
  • Posts: 2103
  • Liked: 374
  • Likes Given: 55
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 »

Tags: