Winged vs. propulsive landing of rockets

publiusr

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Aldebaran next please.

Now…how about a winged SuperHeavy? Redundant to be sure…but maybe not too limber. I read at Macleans.ca that Nuytten at Nuytco was allowed to use recently declassified submarine steel secrets released to industry for his Exo Suit 2000…and I think it was the July 2021 issue of the Journal of Spacecraft and Rockets that had a bit on metallic heat shields for winged designs that used…what was it…304 stainless.


Put this all together and you would have Boeing’s Space Freighter…just without the Boeing.

Might save on the cranes at least.
 
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publiusr

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One last aside if I may...about the possibility of a winged SLS....

Buran T was a winged Energia after all: http://www.astronautix.com/b/buran-t.html


But then I remembered this:
View: https://www.youtube.com/watch?v=S9LfDM0l-XY



I had no idea that strap-ons could be so widely based...and wondered...could those attachment points be inside a wing? The forward attachment points inside canards.

SRBs would be at the wingtips now.

The payload would be in a Hustler type pod so the SRBs would have the center of gravity through them. Do-able?
 

RanulfC

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Hazegrayart did it again ! top notch

Yes but he DID miss the fly-back engines required for the concept :)
Still a LOT better than the folks who are still passing around a flyback S1 as a "flyback Atlas" illustration :)

Aldebaran next please.

Now…how about a winged SuperHeavy? Redundant to be sure…but maybe not too limber. I read at Macleans.ca that Nuytten at Nuytco was allowed to use recently declassified submarine steel secrets released to industry for his Exo Suit 2000…and I think it was the July 2021 issue of the Journal of Spacecraft and Rockets that had a bit on metallic heat shields for winged designs that used…what was it…304 stainless.


Put this all together and you would have Boeing’s Space Freighter…just without the Boeing.

Might save on the cranes at least.

Musk doesn't like wings, he's specifically rejected them as a possible recovery system. (Say's they are to expensive, which is questionable, and to heavy which has some merit but isn't as clear) The boost-back and landing propellant are said to 'trade' as about equal to wings-wheels in payload penalty but I'm not so sure and it's not even clear if they every considered anything BUT a rocket powered landing approach. (A set of tip-turbine 'fans' powered by the RCS monopropellant instead of the grid gins would be possible and allow a more accurate and controlled landing but I'm not even sure if anyone has even suggested such a set up) This is mostly about landing places OTHER than Earth which doesn't actually apply to the SuperHeavy.

One last aside if I may...about the possibility of a winged SLS....

Buran T was a winged Energia after all: http://www.astronautix.com/b/buran-t.html


But then I remembered this:
View: https://www.youtube.com/watch?v=S9LfDM0l-XY



I had no idea that strap-ons could be so widely based...and wondered...could those attachment points be inside a wing? The forward attachment points inside canards.

SRBs would be at the wingtips now.

The payload would be in a Hustler type pod so the SRBs would have the center of gravity through them. Do-able?

Not really, 'wings' don't normally have that much structural strength and the stress' would be tremendous due to the drag/thrust of the SRB's. Yes those are pretty 'spaced' out, (no pun intended :) ) but they would still be pretty narrow for wings to have enough lift to support the vehicle on reentry, flight and landing. Possible? Yes, but I wouldn't want to try to engineer that to work if I didn't have to :)

You'd also still have to have the payload on the 'nose' to keep the CG/CP balance I'd think.

Just put bigger wings and a nuclear engine on the payload... Wait, I think I've heard of that one before...
1631401132979.png


Randy
 

publiusr

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I don’t think anyone thought to put SRB supports inside wings…maybe a smaller design like Ariane 5?
 

TomcatViP

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Wings induce lift, a force that has to be taken into account designing the rocket structure. The induced torque is significant and alters the simplicity of a rocket design, adding complexity and cost when a set of wings only serve the purpose of landing.
Mass wise, it is then more practical to carry an extra volume of fuel for a boosted recovery.

One parameter that is scarcely taken into account is that wings for rockets are not wings as you have in an airplane. The total lift is only a fraction of the takeoff mass and, when coupled with a small trick that I may post one day, only a percentage of the landing mass.
I think that Musk is pretty spot on when he says that wings are costly.

However, the complexity of having to catch a huge booster during recovery might change his view on this IMOHO. Even if the cost of the ground installation is fixed and can be amortized on multiple launches, the added reliability risks (something reset to zero on every launches) might offset any advantages regarding a simpler winged landing.
 

publiusr

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Wings wouldn’t do him any good on Mars…which is his end goal…so VTOVL all the way for him…but ULA could at least have done a winged Pyrios fly-back in place of Vulcan. Two or three F-1 Bs…J-2 upper stage…low part count…
 

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I had no idea that strap-ons could be so widely based...and wondered...could those attachment points be inside a wing? The forward attachment points inside canards.
They were spaced to fit on the shuttle MLP
 

martinbayer

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Wings induce lift, a force that has to be taken into account designing the rocket structure. The induced torque is significant and alters the simplicity of a rocket design, adding complexity and cost when a set of wings only serve the purpose of landing.
Mass wise, it is then more practical to carry an extra volume of fuel for a boosted recovery.

One parameter that is scarcely taken into account is that wings for rockets are not wings as you have in an airplane. The total lift is only a fraction of the takeoff mass and, when coupled with a small trick that I may post one day, only a percentage of the landing mass.
I think that Musk is pretty spot on when he says that wings are costly.

However, the complexity of having to catch a huge booster during recovery might change his view on this IMOHO. Even if the cost of the ground installation is fixed and can be amortized on multiple launches, the added reliability risks (something reset to zero on every launches) might offset any advantages regarding a simpler winged landing.
Wings do not "only serve the purpose of landing" - they are also instrumental for reentry, glideback, and TAEM, see Shuttle CONOPS. Musk understandably chose VTVL simply because there are no substantial atmosphere and landing strips on Mars (or the Moon, for that matter). Circumstances are a bit different here on Earth. Another important aspect is that wings (apart from moveable aerodynamic controls) are largely a passive structure, whereas rocket engines are highly energetic machines, with cumulative burn time being a limiting factor. From a basic engineering perspective, it makes sense to add comparatively simple structures to decelerate a reusable vehicle rather than waste propulsion system life on something environmental friction can easily take care of for you.
 

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I do agree @martinbayer but we are discussing here a winged first stage. Hence my take on it.

We will see what's the value of Musk's reentry technique. Even if I think it's a great idea it still haven't been fully demonstrated. The main negative point being the vertical landing and the cost of fixed infrastructure that are needed. So wings on rockets are probably there to stay for a long time when mission perspectives dictates.
 

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I do agree @martinbayer but we are discussing here a winged first stage. Hence my take on it.

We will see what's the value of Musk's reentry technique. Even if I think it's a great idea it still haven't been fully demonstrated. The main negative point being the vertical landing and the cost of fixed infrastructure that are needed. So wings on rockets are probably there to stay for a long time when mission perspectives dictates.
My arguments above hold true for orbiters as well as boosters.
 

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Wings do not "only serve the purpose of landing" - they are also instrumental for reentry, glideback, and TAEM, see Shuttle CONOPS. Musk understandably chose VTVL simply because there are no substantial atmosphere and landing strips on Mars (or the Moon, for that matter). Circumstances are a bit different here on Earth. Another important aspect is that wings (apart from moveable aerodynamic controls) are largely a passive structure, whereas rocket engines are highly energetic machines, with cumulative burn time being a limiting factor. From a basic engineering perspective, it makes sense to add comparatively simple structures to decelerate a reusable vehicle rather than waste propulsion system life on something environmental friction can easily take care of for you.
Not true. From a basic engineering perspective when engines are inexpensive and easily replaceable, it makes more sense to use them than carry needless mass around. Also don't have the additional cost of managing large area of TPS. Instead of burning propellant to haul needless wings and TPS, use it for landing.

The basic structure of the vehicle is enough to provide drag without adding more mass. No need for aero TAEM.

And wrong about substantial atmosphere on Mars, it will still provide the bulk of the braking.

Wings on a booster are a waste, and more so for orbiters.
 

martinbayer

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Wings do not "only serve the purpose of landing" - they are also instrumental for reentry, glideback, and TAEM, see Shuttle CONOPS. Musk understandably chose VTVL simply because there are no substantial atmosphere and landing strips on Mars (or the Moon, for that matter). Circumstances are a bit different here on Earth. Another important aspect is that wings (apart from moveable aerodynamic controls) are largely a passive structure, whereas rocket engines are highly energetic machines, with cumulative burn time being a limiting factor. From a basic engineering perspective, it makes sense to add comparatively simple structures to decelerate a reusable vehicle rather than waste propulsion system life on something environmental friction can easily take care of for you.
Not true. From a basic engineering perspective when engines are inexpensive and easily replaceable, it makes more sense to use them than carry needless mass around. Also don't have the additional cost of managing large area of TPS. Instead of burning propellant to haul needless wings and TPS, use it for landing.

The basic structure of the vehicle is enough to provide drag without adding more mass. No need for aero TAEM.

And wrong about substantial atmosphere on Mars, it will still provide the bulk of the braking.

Wings on a booster are a waste, and more so for orbiters.
Blithely asserting that liquid rocket engines are "inexpensive and easily replaceable" is quite a tall tale, especially compared to passive structures or TPS, since liquid propulsion systems are inherently more complex. TPS has also come a long way since the Shuttle - note that Musk is using an innovative version as well. In addition, every single in flight rocket engine reignition is a potential risk event. Also, compare how many SpaceX boosters have been lost to date during landing as opposed to how many Shuttle, X-37B, or Buran missions during the same flight phase - the DC-XA comes to mind as well. While the upper atmosphere of Mars is dense enough for aerobraking, the lower layers would require inordinately large wings for aerodynamic flight of any large craft, so that rationale still stands as well. But I'm sure Musk would be absolutely fascinated to learn that having aerodynamic surfaces on the Starship is a waste :D ...
 
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RanulfC

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Wings do not "only serve the purpose of landing" - they are also instrumental for reentry, glideback, and TAEM, see Shuttle CONOPS. Musk understandably chose VTVL simply because there are no substantial atmosphere and landing strips on Mars (or the Moon, for that matter). Circumstances are a bit different here on Earth. Another important aspect is that wings (apart from moveable aerodynamic controls) are largely a passive structure, whereas rocket engines are highly energetic machines, with cumulative burn time being a limiting factor. From a basic engineering perspective, it makes sense to add comparatively simple structures to decelerate a reusable vehicle rather than waste propulsion system life on something environmental friction can easily take care of for you.
Not true. From a basic engineering perspective when engines are inexpensive and easily replaceable, it makes more sense to use them than carry needless mass around.

So jets instead of rockets to land with, that makes some sense as we've known that jets are vastly cheaper and more reliable than rockets and use less propellant fraction. Bonus if you cut them down to just the 'fan' stages. Somehow though I don't think that's where you were going though :)
Also don't have the additional cost of managing large area of TPS. Instead of burning propellant to haul needless wings and TPS, use it for landing.

Large area TPS is actually easier to do than low area TPS though, especially if you design towards a more lower-mass/higher surface area design. "Needless" isn't a 'fact' btw it's really a matter of opinion and design philosophy.

Randy
 

publiusr

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Wing-mass allows orbiter to be a more flat, stable platform than capsules. Wings are even better for fly-back boosters in that you only light the engines once-and the engines have a much more benign thermal environment upon return than VTOVL designs like Musk's first stages endure. The wing's inert mass is a feature-not a bug...especially if it pays for itself as a kerosene wet wIng. The engines will last longer...
 

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As an aerospace engineer, before a systematic parameter driven case specific evaluation, I'm completely agnostic to a trade between turbojets/turbofans/rockets for booster reentry ballistic/glide return based on cost/mass/reliability/environmental pre-screening.
 

Byeman

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Wings do not "only serve the purpose of landing" - they are also instrumental for reentry, glideback, and TAEM, see Shuttle CONOPS. Musk understandably chose VTVL simply because there are no substantial atmosphere and landing strips on Mars (or the Moon, for that matter). Circumstances are a bit different here on Earth. Another important aspect is that wings (apart from moveable aerodynamic controls) are largely a passive structure, whereas rocket engines are highly energetic machines, with cumulative burn time being a limiting factor. From a basic engineering perspective, it makes sense to add comparatively simple structures to decelerate a reusable vehicle rather than waste propulsion system life on something environmental friction can easily take care of for you.
Not true. From a basic engineering perspective when engines are inexpensive and easily replaceable, it makes more sense to use them than carry needless mass around.

So jets instead of rockets to land with, that makes some sense as we've known that jets are vastly cheaper and more reliable than rockets and use less propellant fraction. Bonus if you cut them down to just the 'fan' stages. Somehow though I don't think that's where you were going though :)
Also don't have the additional cost of managing large area of TPS. Instead of burning propellant to haul needless wings and TPS, use it for landing.

Large area TPS is actually easier to do than low area TPS though, especially if you design towards a more lower-mass/higher surface area design. "Needless" isn't a 'fact' btw it's really a matter of opinion and design philosophy.

Randy
Not really. Jet engines are almost as useless as wings. The rocket engines are just as cheap for the same equivalent thrust and not useless mass for the bulk of the ascent or descent. And jet engines add more complexity to the design.
 

publiusr

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But jets last longer. Wings with jets means the rockets ignite only once-and then well above a flame trench absent on drone ships. The rockets just need be in a package that a heavy forklift can remove at ground level. That may allow easier handling than, say, moving a lighthouse around as SpaceX does?
 

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Not really. Jet engines are almost as useless as wings. The rocket engines are just as cheap for the same equivalent thrust and not useless mass for the bulk of the ascent or descent. And jet engines add more complexity to the design.

Rockets are NOT 'as cheap' nor do they have the same lifetime. Also they don't have to be that complex or massive. As I've noted elsewhere replacing the grid-fins with tip-turbine fans would allow a more controlled and easier landing. If we were talking something like "torch-igniters" or such you'd probably have a point about the ease and complexity but SpaceX for example uses a chemical igniter which it both limiting and dangerous.

Randy
 

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Rockets are NOT 'as cheap' nor do they have the same lifetime. Also they don't have to be that complex or massive. As I've noted elsewhere replacing the grid-fins with tip-turbine fans would allow a more controlled and easier landing. If we were talking something like "torch-igniters" or such you'd probably have a point about the ease and complexity but SpaceX for example uses a chemical igniter which it both limiting and dangerous.

Randy
How much do you think a merlin costs? It is much less than $ 6 million apiece. Less than a CFM 56 engine. Raptor will be also.
The shorter life time doesn't matter, as long as they last as long as the LV airframe (which is going to be shorter than an aircraft)

"tip-turbine fans would allow a more controlled and easier landing." Unsubstantiated. And would be more complex than grid fins and more maintenance. The landing is already very controlled and easy. It has been done more than 80 times.

Raptor uses torch lighters. But dealing with the TEA/TEB is not a big deal. It is highly automated and only one ground tank is filled for the Booster. It is easier to manage than hydrazine.
 

publiusr

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A winged craft might be faster to turn around. Lying on its side--a forklift can drive up to the back and slide a whole boat-tail out and slide a new one in. No need to move a lighthouse. Merlins are pretty cheap in some respects, but won't last as long as a fly-back turbojet.

Again--fly-back rocket engines are spared the hoverslam--they have a more benign thermal environment in only igniting over a flame trench and not an unyielding pad. Thus a longer service life.

If a Falcon is good for 10 flights--a fly-back should at least double that--easily.
 

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1. A winged craft might be faster to turn around. Lying on its side--a forklift can drive up to the back and slide a whole boat-tail out and slide a new one in. No need to move a lighthouse. Merlins are pretty cheap in some respects, but won't last as long as a fly-back turbojet.

2 Again--fly-back rocket engines are spared the hoverslam--they have a more benign thermal environment in only igniting over a flame trench and not an unyielding pad. Thus a longer service life.

If a Falcon is good for 10 flights--a fly-back should at least double that--easily.
1. Wrong. It wouldn't be quicker. Moving a lighthouse is easier than stacking and dealing with a winged vehicle. Flyby turbojet is dead mass on ascent and require complex coverings for launch and entry.

2. Unsubstantiated. The hoverslam doesn't bother the engines. And the engines are not dead weight like wings.

3. Your math is wrong. 2, 3 or X Falcons is cheaper than one flyback. And flyback requires more maintenance between flights.

You really don't get it.
 

martinbayer

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1. A winged craft might be faster to turn around. Lying on its side--a forklift can drive up to the back and slide a whole boat-tail out and slide a new one in. No need to move a lighthouse. Merlins are pretty cheap in some respects, but won't last as long as a fly-back turbojet.

2 Again--fly-back rocket engines are spared the hoverslam--they have a more benign thermal environment in only igniting over a flame trench and not an unyielding pad. Thus a longer service life.

If a Falcon is good for 10 flights--a fly-back should at least double that--easily.
1. Wrong. It wouldn't be quicker. Moving a lighthouse is easier than stacking and dealing with a winged vehicle. Flyby turbojet is dead mass on ascent and require complex coverings for launch and entry.

2. Unsubstantiated. The hoverslam doesn't bother the engines. And the engines are not dead weight like wings.

3. Your math is wrong. 2, 3 or X Falcons is cheaper than one flyback. And flyback requires more maintenance between flights.

You really don't get it.
You're actually the one with the spurious math. "X Falcons is [sic] cheaper than one flyback"? Since X can obviously be *any* number, for example ten, one hundred, or one thousand (need I go on?) Falcons would *still* be cheaper than one flyback? I don't think so. It would be extremely helpful for your credibility if you could provide at least one verifiable documented quantitative comparison/trade study of flyback or glideback VTHL vs. VTVL RLV from a credible source that supports your handwaving qualitative assertions with respect to relative cost, performance, etc..
 
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Byeman

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1. A winged craft might be faster to turn around. Lying on its side--a forklift can drive up to the back and slide a whole boat-tail out and slide a new one in. No need to move a lighthouse. Merlins are pretty cheap in some respects, but won't last as long as a fly-back turbojet.

2 Again--fly-back rocket engines are spared the hoverslam--they have a more benign thermal environment in only igniting over a flame trench and not an unyielding pad. Thus a longer service life.

If a Falcon is good for 10 flights--a fly-back should at least double that--easily.
1. Wrong. It wouldn't be quicker. Moving a lighthouse is easier than stacking and dealing with a winged vehicle. Flyby turbojet is dead mass on ascent and require complex coverings for launch and entry.

2. Unsubstantiated. The hoverslam doesn't bother the engines. And the engines are not dead weight like wings.

3. Your math is wrong. 2, 3 or X Falcons is cheaper than one flyback. And flyback requires more maintenance between flights.

You really don't get it.
You're actually the one with the spurious math. "X Falcons is [sic] cheaper than one flyback"? Since X can obviously be *any* number, for example ten, one hundred, or one trillion Falcons would *still* be still cheaper than one flyback? I don't think so. It would be extremely helpful for your questionable credibility if you would provide at least one verifiable documented quantitative comparison of flyback or glideback VTHL vs. VTVL from a reputable source that supports your handwaving qualitative assertions with respect to relative cost, performance, etc..
You don't really understand how cheap Falcon 9s are? Even an expendable one? A new Falcon 9 price (not cost) is around $65 million. Reused price is around $50 million. Either way, the price includes an expended second stage.

Show me the price of a VTHL booster with equivalent performance. And its reflight price?
It would be like making a Boeing 737-800/900 or 757-200 into a booster (same diameter as Falcon9, similar length,41m. They cost around a 100 million but with no rocket engines, TPS or proper aerodynamics. It has to carry extra propellant to offset the additional mass of wings and landing gear. Maybe another engine. I could see this costing 300 to 400 million. Flyby requires more infrastructure for maintenance.

The different between a Falcon 9 expendable and reusable is fairly minor.

The 10 uses per booster is not limit. They will keep flying them until they can't
 

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1. A winged craft might be faster to turn around. Lying on its side--a forklift can drive up to the back and slide a whole boat-tail out and slide a new one in. No need to move a lighthouse. Merlins are pretty cheap in some respects, but won't last as long as a fly-back turbojet.

2 Again--fly-back rocket engines are spared the hoverslam--they have a more benign thermal environment in only igniting over a flame trench and not an unyielding pad. Thus a longer service life.

If a Falcon is good for 10 flights--a fly-back should at least double that--easily.
1. Wrong. It wouldn't be quicker. Moving a lighthouse is easier than stacking and dealing with a winged vehicle. Flyby turbojet is dead mass on ascent and require complex coverings for launch and entry.

2. Unsubstantiated. The hoverslam doesn't bother the engines. And the engines are not dead weight like wings.

3. Your math is wrong. 2, 3 or X Falcons is cheaper than one flyback. And flyback requires more maintenance between flights.

You really don't get it.
You're actually the one with the spurious math. "X Falcons is [sic] cheaper than one flyback"? Since X can obviously be *any* number, for example ten, one hundred, or one trillion Falcons would *still* be still cheaper than one flyback? I don't think so. It would be extremely helpful for your questionable credibility if you would provide at least one verifiable documented quantitative comparison of flyback or glideback VTHL vs. VTVL from a reputable source that supports your handwaving qualitative assertions with respect to relative cost, performance, etc..
You don't really understand how cheap Falcon 9s are? Even an expendable one? A new Falcon 9 price (not cost) is around $65 million. Reused price is around $50 million. Either way, the price includes an expended second stage.

Show me the price of a VTHL booster with equivalent performance. And its reflight price?
It would be like making a Boeing 737-800/900 or 757-200 into a booster (same diameter as Falcon9, similar length,41m. They cost around a 100 million but with no rocket engines, TPS or proper aerodynamics. It has to carry extra propellant to offset the additional mass of wings and landing gear. Maybe another engine. I could see this costing 300 to 400 million. Flyby requires more infrastructure for maintenance.

The different between a Falcon 9 expendable and reusable is fairly minor.

The 10 uses per booster is not limit. They will keep flying them until they can't
Do you think Musk is dead wrong in using aerodynamic surfaces on the Starship, since in your categorical view such structures, whether they're called wings, fins or canards, seem to be an expensive waste? I'm pretty sure that cost, functionality and performance considerations and trades for a fully reusable TSTO did enter his mind. Comparing an only partly reusable Falcon 9 to a fully reusable VTHL TSTO conveniently leaves out the fact that such a design could return payloads Shuttle orbiter style, while second stage reusability for the Falcon 9 seems to have been completely abandoned, and the split fairing is only designed to return itself, so the low price of the Falcon 9 comes at the cost of additional mission capabilities offered by a true RLV. A much better and fairer comparison would be between the Starship and a broadly similar design, with the main difference being that both stages of the alternative would perform unpowered horizontal landings.
 
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publiusr

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SILENCE! No one may ever question Jim-the-wise! The sunburst that Lockheed and Boeing feel "secure" has aged just so well....right guys? Back on topic...if you were to total up the surface area of all the fins-you don't have much less than some of the more spartan winged designs. Yes it would need some more bracing...and Musk wants commonality with Mars designs-but you may want more surface area there too.
 

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How much do you think a merlin costs? It is much less than $ 6 million apiece. Less than a CFM 56 engine. Raptor will be also.

SpaceX says a Merlin costs "less than $1 million dollars" but that's been disputed with good reason. The CFM 56, (odd choice) costs around $8.7 million but has a vastly longer life time (and far less between flight maintenance and operations costs) than the Merlin. (Raptor is "supposed" to cost less than the Merlin and so far I've found very few that believe that, not to mention they are a lot shorter life time and a lot more failure prone)

I noted above the CFM 56 is an odd choice as it meets none of the criteria needed. A Falcon 9 first stage dry weight is around 25,600kg/56,400lb so you need about that much thrust (at least 1/1 TW) to land the stage. The CFM only produces 34,000lbf so you'd need at least two and frankly there are more compact and better engines available. (Specifically it should be noted that 90% of the thrust of this engine is generated by the single fan so one could argue if you cut down the REST of the engine to something that JUST drove that fan and used them you could mount four of them instead of the grid fins and fly the stage anywhere you wanted it to land)

The shorter life time doesn't matter, as long as they last as long as the LV airframe (which is going to be shorter than an aircraft)

Well yes but so far they need major maintenance between flights whereas jets do not and that's part of that whole "lifetime" metric. Sure the main stage airframe is only good for about 10 flights but the Merlin's are supposed to be capable of more and a jet engine life is measured in thousands of hours. Something else to consider is that rocket engines need a lot of inspection and maintenance between flights, (part of the whole issues with the idea of 'rapid turn around') whereas jets/fans are vastly easier and cheaper to maintain. Also there's the benefit of getting more performance out of the rocket engines because the jets/fans will use vastly less fuel to land (and therefore you get back some of that 15% payload hit recovery takes out) and avoiding that 'suicide burn' will always be a good thing.

"tip-turbine fans would allow a more controlled and easier landing." Unsubstantiated. And would be more complex than grid fins and more maintenance. The landing is already very controlled and easy. It has been done more than 80 times.

No the landing is NOT 'very controlled and easy' not even SpaceX says that for a good reason. The main issues is that the Merlin is incapable of being throttled enough for a "very controlled and easy" landing hence the need for the suicide burn itself. Unsubstantiated? Er, you've never seen a quad-or-multi-rotor drone fly? A Harrier? A helicopter? Heck they were pretty easily landing jet-thrust vehicles in the late 40 and early 50s never mind today. More complex? Not really. If you look you'll find that tip-turbine rotors have been experimented with for decades. Specifically there was a concept of using them to land space capsules they looked into in the 60s as a possible follow-on to Apollo using essentially the RCS propellant as a monopropellant to drive a fan based landing system. It was a toss up if it was more economical than just using an off-the-shelf jet engine and kerosene but it was far less complex than the jet engine. (Fewer parts) The single-stage fan of the CFM 56 is about the same size as the current grid fins at about 2m so it wouldn't be that much of a burden and would need a 'feed' line for propellant similar to the current hydraulic fluid line. (Again pretty easy to combine with the RCS system if you really want to go simple)

Raptor uses torch lighters. But dealing with the TEA/TEB is not a big deal. It is highly automated and only one ground tank is filled for the Booster. It is easier to manage than hydrazine.

TEA/TEB is toxic and difficult to handle, it also limits the re-lights of the engine. It's about as hard to use as hydrazine, (which is handled for the RCS anyway) and about as toxic. Dealing with both TEA/TEB IS a 'big deal' and always will be given their toxic nature part of the reason that they are moving away from such propellants. Nature of the beast but there are better choices it's just that SpaceX has stopped most improvements to the Falcon series which is a shame given it still has a lot of capacity left in the design.

Randy
 

RanulfC

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1. A winged craft might be faster to turn around. Lying on its side--a forklift can drive up to the back and slide a whole boat-tail out and slide a new one in. No need to move a lighthouse. Merlins are pretty cheap in some respects, but won't last as long as a fly-back turbojet.

2 Again--fly-back rocket engines are spared the hoverslam--they have a more benign thermal environment in only igniting over a flame trench and not an unyielding pad. Thus a longer service life.

If a Falcon is good for 10 flights--a fly-back should at least double that--easily.
1. Wrong. It wouldn't be quicker. Moving a lighthouse is easier than stacking and dealing with a winged vehicle. Flyby turbojet is dead mass on ascent and require complex coverings for launch and entry.

2. Unsubstantiated. The hoverslam doesn't bother the engines. And the engines are not dead weight like wings.

3. Your math is wrong. 2, 3 or X Falcons is cheaper than one flyback. And flyback requires more maintenance between flights.

You really don't get it.

Ahm, your point (1) is pretty far off base as the Falcon 9 is NOT 'moved' like a light house but moved into a horizontal position and loaded on a truck and the driven back to the hanger. Two more steps than an already landed "horizontal" lander has to go through. (Attach tow bar, drive back to prep-hanger. A LOT more simple and easier)

You then STILL have to deal with 'stacking' the launch vehicle so there's no savings there either. And again the 'covering' depends greatly on the way it's designed. Note this is not considered an 'issue' with Starship. (I have doubts, specifically since the current vehicle is not weighted and balanced as an operational vehicle would be which means the TPS could be vastly under-rated)

"Hover-slam" SPECIFICALLY 'bothers' the engines as they are exposed to a very high heat pulse as the flames of the landing engine are recirculated around the other engines and hardware that has no active cooling at this point in flight unlike on take off. (This specifically has been a perennial problem with all the "Starship" landings we've seen. Not really sure why SpaceX is ignoring the large body of work that has shown "engine bays" do not work well with back-flame and have always tended to overheat and/or catch fire. Kind of good reason why no one else proposes using them in a flight vehicle) Wings don't have to be 'dead-weight' by the way. In fact many kerolox LV designs planned on using them to carry part of the kerosene load since packing kerosene into wings is very much a known and well understood technology. More so the 'wet' wings (and less fuselage tankage) means a lighter vehicle during reentry which cuts down on TPS requirements. Again this isn't something that isn't well known and understood.

Lastly the "math" is spurious as you can find plenty of examples where it works for wings BETTER than a powered landing. Specifically we KNOW why SpaceX chose powered landing and it has nothing to do with 'economics' specifically. Musk wanted powered landing because "wings-and-wheels" don't work off-Earth. The rather simple counter to this is that the Falcon 9 will never be USED off-Earth so vertical rocket landing isn't really being 'traded' at all as it's a "requirement" imposed from outside on the design. Period.
Even the argument of being needed to 'return-to-the-launch-site' for reuse is unsupported given the number of times they have landed down-range and had to 'ship' the booster back. If they were really going with that logic then winged, jet fly back makes vastly more sense which is the reason it was the main way considered for so long.

We very much know and understand how to get a winged booster back to the landing site and with todays technology it's easier than ever but that's not what (or why) Falcon 9 ended up the way it did. Musk wanted rocket powered landing so that's what they did and we can't really 'argue' with that because it's not at all based on anything OTHER than that requirement.

Yes, we very MUCH "get it" because many of us have spent far longer than the self-taught Musk looking and studying the actual problems and trade-offs.

Randy
 

RanulfC

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You're actually the one with the spurious math. "X Falcons is [sic] cheaper than one flyback"? Since X can obviously be *any* number, for example ten, one hundred, or one thousand (need I go on?) Falcons would *still* be cheaper than one flyback? I don't think so. It would be extremely helpful for your credibility if you could provide at least one verifiable documented quantitative comparison/trade study of flyback or glideback VTHL vs. VTVL RLV from a credible source that supports your handwaving qualitative assertions with respect to relative cost, performance, etc..

To be fair, (and no I don't want to be but... :) ) he's assuming that everything that comes out of Musk/SpaceX is "fact" rather than a lot being 'supposition' because SpaceX/Musk don't HAVE to tell anyone the real numbers. Secondly Musk specifically said at one point that he/they had 'traded' flyback but dropped it early on with no actual evidence they did. (And frankly a lot they didn't as it would have been a very different design from the get go it they had and since they were aiming for 'simple' rather than most efficient it's likely they didn't really do any significant trade work. More specifically as noted Musk wasn't interested)

VTHL would have required more aerodynamic work to be done and they could more easily take existing booster work and use that to base the Falcon 9 on. Which is what they did and why the initially looked towards parachutes and water landing. VTVL came about from the work Musk wanted to do for Mars and in context it makes sense but it has it's drawbacks which pretty much show why they didn't do any actual 'trades'. (A 15% payload loss isn't minor after all)

You don't really understand how cheap Falcon 9s are? Even an expendable one? A new Falcon 9 price (not cost) is around $65 million. Reused price is around $50 million. Either way, the price includes an expended second stage.

Show me the price of a VTHL booster with equivalent performance. And its reflight price?

The XS-1 was to have a turn around cost of less than $5 million and the 'operational' booster less than $10 million per flight. Well never know for sure but DARPA and NASA both agree the prices were likely correct given the parameters. Total launch costs were aimed at less than $50 million (with expendable upper stage included) for the expected flight rate. Other studies of such VTHL boosters came out to around the same prices.
The thing is that with a reusable first stage the overall utility is dependent on the flight rate and currently SpaceX has not actually shown that reusability has enough economic impact to actually reduce the costs.

It would be like making a Boeing 737-800/900 or 757-200 into a booster (same diameter as Falcon9, similar length,41m. They cost around a 100 million but with no rocket engines, TPS or proper aerodynamics. It has to carry extra propellant to offset the additional mass of wings and landing gear. Maybe another engine. I could see this costing 300 to 400 million. Flyby requires more infrastructure for maintenance.

Apples and oranges actually as the 737 is vastly more economic and efficient than the Falcon 9 can every hope to be. Even comparing the X-15 to the Falcon 9 isn't applicable due to the more specialized and experimental nature of the X-15. Operations and maintenance costs of VTVL and VTHL are likely to be almost the same though most of the infrastructure and operations already exists in depth for VTHL and not for VTVL so the economics is likely better for the former than the later. Development costs will be a bit higher due to the nature of VTHL flight but unlike the Falcon 9 the VTHL will by design be reusable from the very start so the overall construction and operations costs will likely be lower. Flyback actually requires LESS specialized infrastructure and gains operational savings from being more similar to aircraft operations, (no aircraft are not spacecraft nor are spacecraft aircraft there's just some cross over for a winged/wheeled design :) ) than VTVL.
The different between a Falcon 9 expendable and reusable is fairly minor.

There is no difference, it's a choice to expand the booster or not. That's kind of the point in that they simple use a 'reusable' booster and expend it rather than recovering it. They just don't use some systems in the expendable case, they don't remove them.

The 10 uses per booster is not limit. They will keep flying them until they can't

The thing is that they don't know whereas actually calculating the life time of a VTHL is pretty straight forward and something that's pretty easy to determine during flight testing. (A very good reason for reuse from the start as an actual program goal :
Do you think Musk is dead wrong in using aerodynamic surfaces on the Starship, since in your categorical view such structures, whether they're called wings, fins or canards, seem to be an expensive waste? I'm pretty sure that cost, functionality and performance considerations and trades for a fully reusable TSTO did enter his mind. Comparing an only partly reusable Falcon 9 to a fully reusable VTHL TSTO conveniently leaves out the fact that such a design could return payloads Shuttle orbiter style, while second stage reusability for the Falcon 9 seems to have been completely abandoned, and the split fairing is only designed to return itself, so the low price of the Falcon 9 comes at the cost of additional mission capabilities offered by a true RLV. A much better and fairer comparison would be between the Starship and a broadly similar design, with the main difference being that both stages of the alternative would perform unpowered horizontal landings.

(Ok why it lets me collapse 'some' responses and doesn't others.... :) )

To be clear there's a reason Musk is adamant that those 'aerodynamic surfaces' are NOT "wings" since he's come out against the very idea of a lifting reentry and landing. (Hence "skydiver-not-glider" and all that bunk :) )

Yes he thought about a fully reusable TSTO, rather obviously given the initial idea of reusing the Falcon 9 Upper Stage, the problem is it doesn't work well with the VTVL concept as the Upper Stage gets too heavy to fast and ends up with little or no payload unless you 'trick' things out. (Such as changing propellants, using lifting reentry and non-propulsive landing, etc) Nothing Musk was willing to invest in for the Falcon when he'd moved on to Starship.
(Again a missed opportunity since it would have arguably been rather straight forward to do so but it's not like he's going to let anyone else use the Falcon so...)

In context, payload return is a 'niche' capability and frankly not something that SpaceX has seriously considered beyond what Dragon can do. For most other missions it's a distraction and not worth the effort or payload losses. Arguably some "simple" modifications (note those quotes :) ) to the upper stage would allow enough margin to incorporate reusability to some extent but keeping in mind that in MOST missions, (Starlink in LEO is really an outlier and more akin to a Dragon/ISS mission than the 'usual' GTO missions) Coming back from GTO is arguably harder than coming back from LEO but again there's a number of ways that could be explored to make this pretty doable. But again not something Musk is interested in. I can't agree enough that the Falcon 9 is being used far less than it is capable of being but again that's directly in Musk's hands unless SpaceX (or Falcon) gets spun off and that's unlikely in the extreme.

I've argued elsewhere that you can actually replace the Falcon 9 Upper Stage with a variety of different upper stages for different tasks in a fairly straightforward manner, (fully reusable, partially reusable {Dragon} or fully "expendable" with a varying degree of 'expandable' given some uses on-orbit) but it would take time and effort that Musk isn't willing to spend. I also have come to dislike, but understand, the general "popularity" of VTVL reusability given a focus on more than just landing on Earth. (As noted 'wings-and-wheels' don't work so hot on the Moon or Mars though to be honest Kraft Ehricke's Lunar Slide-Out Lander isn't as far out as one might think :) )

Still in any case a winged VTHL booster has always made a lot of sense as it's not going to the Moon or Mars in any case and that's why it keep coming up over and over again. Unfortunately it's unlikely we'll see another set of government spending to develop new boosters and as noted the 'utility' of reusability is still in doubt unless the overall flight rate goes way up so I don't see any of the other booster makers taking the leap.

SILENCE! No one may ever question Jim-the-wise! The sunburst that Lockheed and Boeing feel "secure" has aged just so well....right guys?

Actually correct as has been noted the actual utility of reusability isn't proven yet and it's not likely to be given the current flight rates. Personally I favor reusability as much as possible but it's not as clear cut as many make it out to be.

Back on topic...if you were to total up the surface area of all the fins-you don't have much less than some of the more spartan winged designs. Yes it would need some more bracing...and Musk wants commonality with Mars designs-but you may want more surface area there too.

"Technically" it's not as the area isn't near enough to get more than some very basic control at low speeds. And arguably nothing we've seen indicates it has really any use at high speeds so... Fully deployed there's no landing that survivable if the rockets don't work so they aren't really 'useful' anywhere outside the narrow parameters of the 'planned' flight profile. Yes they could use a LOT more area to cut down on the Mars landing velocity but it's not likely to happen. They are going to "simple" despite the drawbacks in a hope to keep the costs down but it will all depend on how good, (and how robust) the TPS ends up being. There's a good argument for 'flattening' (and broadening the edges) of the upwind side of the Starship to give it better hypersonic aerodynamics but that would add complexity and cost despite the advantages of lower peak thermal pulse and better handling during reentry. (It would also fully protect the fins and canards from reentry heating but again there's trade offs :) )

There's also a half dozen promising reentry technologies I'd be throwing money at were I Musk but in context he'd not be 'in charge' if he did so, so I can see why he'd not be interested at this point :)

Randy
 

publiusr

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Now has anyone thought about inflatable inserts with Starship's control surfaces so as to extend them at Mars? There was that recent thread here with the lunar lander that almost looked like wings. One of the reasons I liked OTRAG, the Bono saucer and side-mount/piggyback modularity is that wide monolithic aerobrake disks with inflatable extensions can be had. I see the best Mars craft as wider than it is tall. The top side of the disk has the small hab cylinder dead center....with loosely folded parachutes of great size atop the upper surface of the disk...but with the risers hooked more directly to the hab to pull it free of the disk after the combined package slows a bit...the hab doing a final burn.The disk or disk pie-slices are side mounted in place of an American Buran, say?
 
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martinbayer

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@RanulfC : VTHL does not works on the moon?

Check this:

It also can work on earth (300m landing distance). So far I haven't run a Simulation for Mars.
Ok, so it's a low touchdown speed variant of Krafft Ehricke's Lunar Slide Lander (LSL) concept, see https://www.lpi.usra.edu/publications/books/lunar_bases/LSBchapter12.pdf and https://selenianboondocks.com/wp-content/uploads/2015/08/SlideLander.png for a better illustration, but like for the original concept you need a smooth, homogeneous (albeit significantly shorter) surface landing strip without any rocks or boulders before the very first landing of such a system. What specific advantages is this particular approach supposed to offer over a traditional VTVL that you need anyway for the preparatory moonscaping effort, especially since the final approach velocity (50 km/h vs. 5,500 km/h for the LSL) seems low enough to be handled by purely propulsive means without significantly impacting overall mass?
 
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TomcatViP

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@martinbayer : thanks, I wasn't aware of Ehricke's Lunar lander concept.

In anyway, however, the idea here is different. We are here in the terminal phase of the landing after the vehicle has been slowed down and is guided for terminal touchdown (remember Apollo video when the LEM begin the final approach gliding down the surface before landing vertically).
The goal of the Squirrel Moonwalk is to allow a massive rocket (285 metric tons) to land in a short distance (100m) without blasting half the moon surface back into orbit (no brownout condition) with its inherent hazard of damages from puncturation, offer a better way to handle cargo operations (the lean down attitude at rest), minimize fuel consumption and offer a similar rock blast free takeoff.

The essential parameters that are beneficial for this is the low lunar gravity and the properties of Lunar grounds (as characterized by the Apollo missions). But there is a possibility to land similarly on earth, albeit on longer distance and with partial lift (70% was studied).

The Squirrel Moonwalk use a glide down approach with a VTOL aggravated slope that alleviate the need for lift propulsion and better landing precision. There is two boost involved: one (throttle down) around the deployed leg contact to blast the landing surface and clear it from small rocks but also to initiate terminal vehicle rotation and, one, once the attitude of the rocket ship is horizontal to brake to rest (full power).

That way, the landing distance is kept under the targeted minimal (100m). The sim has three line markers that you can see: one at 0 meters (touchdown point), the middle one at 50 meters and the last one at 100m.

As you can guess, there is a lot of mission advantages in the system: risks reduced, lower fuel consumption (friction coefficient are not affected by gravity) and cargo handling (increases safety for the astronauts and decreases the mass to orbit).
 
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martinbayer

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@martinbayer : thanks, I wasn't aware of Ehricke's Lunar lander concept.

In anyway, however, the idea here is different. We are here in the terminal phase of the landing after the vehicle has been slowed down and is guided for terminal touchdown (remember Apollo video when the LEM begin the final approach gliding down the surface before landing vertically).
The goal of the Squirrel Moonwalk is to allow a massive rocket (285 metric tons) to land in a short distance (100m) without blasting half the moon surface back into orbit (no brownout condition) with its inherent hazard of damages from puncturation, offer a better way to handle cargo operation (the lean down attitude at rest), minimize fuel consumption and offer a similar rock blast free takeoff.

The essential parameters that are beneficial for this is the low lunar gravity and the properties of Lunar grounds (as characterized by the Apollo missions). But there is a possibility to land similarly on earth, albeit on longer distance and with partial lift (70% was studied).

The Squirrel Moonwalk use a glide down approach with a VTOL aggravated slope that alleviate the need for lift propulsion and better landing precision. There is two boost involved: one (throttle down) around the deployed leg contact to blast the landing surface and clear it from small rocks but also to initiate terminal vehicle rotation and, one, once the attitude of the rocket ship is horizontal to brake to rest (full power).

That way, the landing distance is kept under the targeted minimal (100m). The sim has three line markers that you can see: one at 0 meters (touchdown point), the middle one at 50 meters and the last one at 100m.

As you can guess, there is a lot of mission advantages in the system: risks reduced, lower fuel consumption (friction coefficient are not affected by gravity) and cargo handling (increases safety for the astronauts and decreases the mass to orbit).
You seem to assume that you can safely (and repeatedly?) land a "massive rocket" horizontally on a completely unprepared strip, even if it's only 100 m long - in my view a very risky notion. On one hand you appear concerned about blast effects disturbing the lunar surface (although "blasting half the moon surface back into orbit" seems a bit overblown) and creating a brownout (which can't happen anyway, since there is no atmosphere that could support the kind of conditions that can generate brownouts for terrestrial helicopters in dusty environments), yet on the other hand you deliberately seem to plan to use those very same effects to "blast the landing surface and clear it from small rocks" - seems pretty contradictory to me. I don't recall ever reading or hearing of observed actual damages from puncturation occurring on any of the LEMs, which seems unlikely anyway, since the engine blast would blow any debris away from the vehicle, and I also don't recall any of the Apollo astronauts complaining about poor surface visibility conditions during final descent and landing being a problem. And what's driving the very specific landing mass of 285t? As you can guess, I don't see any mission advantages in the system.
 
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TomcatViP

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1. there is no landing sideways. The landing axis being the longitudinal axis of the rocket.
2. Mass is Starship category as mission specified
3. with ~300t on landing, you can expect a much greater blast effect on the surface that is dusty and littered with small rocks (read sciences mission reports) than with a LEM or a small rover.
4. The plume will blast the surface near tangentially and then parallel to the surface. Anything lifted by the exhaust plume will be pushed away from the vehicle and won't endanger future missions (imagine the case where hundreds of Starships are landing every year)
5. The brownout mentioned is a generic term. There is no recirculation obviously (no need to take other for stupids) but "Picking some dust" was the call...
6. the direct trajectory saves fuel (see below)

View: https://youtu.be/nOcDftgR5UQ?t=78


View: https://youtu.be/FlpstXNjImY?t=895
 
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Byeman

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Do you think Musk is dead wrong in using aerodynamic surfaces on the Starship, since in your categorical view such structures, whether they're called wings, fins or canards, seem to be an expensive waste? I'm pretty sure that cost, functionality and performance considerations and trades for a fully reusable TSTO did enter his mind. Comparing an only partly reusable Falcon 9 to a fully reusable VTHL TSTO conveniently leaves out the fact that such a design could return payloads Shuttle orbiter style, while second stage reusability for the Falcon 9 seems to have been completely abandoned, and the split fairing is only designed to return itself, so the low price of the Falcon 9 comes at the cost of additional mission capabilities offered by a true RLV. A much better and fairer comparison would be between the Starship and a broadly similar design, with the main difference being that both stages of the alternative would perform unpowered horizontal landings.
Wings provide lift. Fins or canards only provide control. I was specifically calling out wings.
 

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Well yes but so far they need major maintenance between flights whereas jets do not and that's part of that whole "lifetime" metric. Sure the main stage airframe is only good for about 10 flights but the Merlin's are supposed to be capable of more and a jet engine life is measured in thousands of hours. Something else to consider is that rocket engines need a lot of inspection and maintenance between flights, (part of the whole issues with the idea of 'rapid turn around') whereas jets/fans are vastly easier and cheaper to maintain. Also there's the benefit of getting more performance out of the rocket engines because the jets/fans will use vastly less fuel to land (and therefore you get back some of that 15% payload hit recovery takes out) and avoiding that 'suicide burn' will always be a good thing.

"tip-turbine fans would allow a more controlled and easier landing." Unsubstantiated. And would be more complex than grid fins and more maintenance. The landing is already very controlled and easy. It has been done more than 80 times.

No the landing is NOT 'very controlled and easy' not even SpaceX says that for a good reason. The main issues is that the Merlin is incapable of being throttled enough for a "very controlled and easy" landing hence the need for the suicide burn itself. Unsubstantiated? Er, you've never seen a quad-or-multi-rotor drone fly? A Harrier? A helicopter? Heck they were pretty easily landing jet-thrust vehicles in the late 40 and early 50s never mind today. More complex? Not really. If you look you'll find that tip-turbine rotors have been experimented with for decades. Specifically there was a concept of using them to land space capsules they looked into in the 60s as a possible follow-on to Apollo using essentially the RCS propellant as a monopropellant to drive a fan based landing system. It was a toss up if it was more economical than just using an off-the-shelf jet engine and kerosene but it was far less complex than the jet engine. (Fewer parts) The single-stage fan of the CFM 56 is about the same size as the current grid fins at about 2m so it wouldn't be that much of a burden and would need a 'feed' line for propellant similar to the current hydraulic fluid line. (Again pretty easy to combine with the RCS system if you really want to go simple)


TEA/TEB is toxic and difficult to handle, it also limits the re-lights of the engine. It's about as hard to use as hydrazine, (which is handled for the RCS anyway) and about as toxic. Dealing with both TEA/TEB IS a 'big deal' and always will be given their toxic nature part of the reason that they are moving away from such propellants. Nature of the beast but there are better choices it's just that SpaceX has stopped most improvements to the Falcon series which is a shame given it still has a lot of capacity left in the design.

Randy
No, Merlins do not need "lot of inspection and maintenance between flights"
80 successful landings means they are "very controlled and easy"
Falcon does not use hydrazine.
TEA/TEB is easier to use than hydrazine. It does not require SCAPE gear.
 

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1. A winged craft might be faster to turn around. Lying on its side--a forklift can drive up to the back and slide a whole boat-tail out and slide a new one in. No need to move a lighthouse. Merlins are pretty cheap in some respects, but won't last as long as a fly-back turbojet.

2 Again--fly-back rocket engines are spared the hoverslam--they have a more benign thermal environment in only igniting over a flame trench and not an unyielding pad. Thus a longer service life.

If a Falcon is good for 10 flights--a fly-back should at least double that--easily.
1. Wrong. It wouldn't be quicker. Moving a lighthouse is easier than stacking and dealing with a winged vehicle. Flyby turbojet is dead mass on ascent and require complex coverings for launch and entry.

2. Unsubstantiated. The hoverslam doesn't bother the engines. And the engines are not dead weight like wings.

3. Your math is wrong. 2, 3 or X Falcons is cheaper than one flyback. And flyback requires more maintenance between flights.

You really don't get it.

Ahm, your point (1) is pretty far off base as the Falcon 9 is NOT 'moved' like a light house but moved into a horizontal position and loaded on a truck and the driven back to the hanger. Two more steps than an already landed "horizontal" lander has to go through. (Attach tow bar, drive back to prep-hanger. A LOT more simple and easier)

You then STILL have to deal with 'stacking' the launch vehicle so there's no savings there either. And again the 'covering' depends greatly on the way it's designed. Note this is not considered an 'issue' with Starship. (I have doubts, specifically since the current vehicle is not weighted and balanced as an operational vehicle would be which means the TPS could be vastly under-rated)

"Hover-slam" SPECIFICALLY 'bothers' the engines as they are exposed to a very high heat pulse as the flames of the landing engine are recirculated around the other engines and hardware that has no active cooling at this point in flight unlike on take off. (This specifically has been a perennial problem with all the "Starship" landings we've seen. Not really sure why SpaceX is ignoring the large body of work that has shown "engine bays" do not work well with back-flame and have always tended to overheat and/or catch fire. Kind of good reason why no one else proposes using them in a flight vehicle) Wings don't have to be 'dead-weight' by the way. In fact many kerolox LV designs planned on using them to carry part of the kerosene load since packing kerosene into wings is very much a known and well understood technology. More so the 'wet' wings (and less fuselage tankage) means a lighter vehicle during reentry which cuts down on TPS requirements. Again this isn't something that isn't well known and understood.

Lastly the "math" is spurious as you can find plenty of examples where it works for wings BETTER than a powered landing. Specifically we KNOW why SpaceX chose powered landing and it has nothing to do with 'economics' specifically. Musk wanted powered landing because "wings-and-wheels" don't work off-Earth. The rather simple counter to this is that the Falcon 9 will never be USED off-Earth so vertical rocket landing isn't really being 'traded' at all as it's a "requirement" imposed from outside on the design. Period.
Even the argument of being needed to 'return-to-the-launch-site' for reuse is unsupported given the number of times they have landed down-range and had to 'ship' the booster back. If they were really going with that logic then winged, jet fly back makes vastly more sense which is the reason it was the main way considered for so long.

We very much know and understand how to get a winged booster back to the landing site and with todays technology it's easier than ever but that's not what (or why) Falcon 9 ended up the way it did. Musk wanted rocket powered landing so that's what they did and we can't really 'argue' with that because it's not at all based on anything OTHER than that requirement.

Yes, we very MUCH "get it" because many of us have spent far longer than the self-taught Musk looking and studying the actual problems and trade-offs.

Randy
The "moving a light house" is an idiotic comment publiusr made about Starship and its booster.
Hover slam bothers the engines no more than entry does.
And wrong, powered landing for boosters has nothing to with landing on other bodies. It was specifically for booster reuse, because parachuting without entry burn didn't work.

VTVL boosters will always be cheaper than VTHL booster because of the minimalistic structure. The amount of mass needed to make a expendable booster a VTVL is much less than a VTHL

 

martinbayer

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1. there is no landing sideways. The landing axis being the longitudinal axis of the rocket.
2. Mass is Starship category as mission specified
3. with ~300t on landing, you can expect a much greater blast effect on the surface that is dusty and littered with small rocks (read sciences mission reports) than with a LEM or a small rover.
4. The plume will blast the surface near tangentially and then parallel to the surface. Anything lifted by the exhaust plume will be pushed away from the vehicle and won't endanger future missions (imagine the case where hundreds of Starships are landing every year)
5. The brownout mentioned is a generic term. There is no recirculation obviously (no need to take other for stupids) but "Picking some dust" was the call...
6. the direct trajectory saves fuel (see below)

View: https://youtu.be/nOcDftgR5UQ?t=78


View: https://youtu.be/FlpstXNjImY?t=895
1. I automatically assumed that for landing horizontally the forward flight path of the rocket would align with the longitudinal axis of its body as well as with the direction of the landing strip as shown in your animation.
2. If this is Starship in disguise, how exactly will takeoff be accomplished?
3. That's a given, but does not change my argument. If you're concerned about potential damage to nearby structures or other vehicles, protection can be achieved through either distance and/or berms.
4. I'm not sure how pushing dirt around in real time would endanger future missions, since when the next lander comes around (even if that's just 10 minutes later), the dust will long have settled. Anything lifted by the exhaust plume of a VTVL lander will be pushed away from the vehicle as well and also won't endanger future missions.
5. While it's technically true that brownout is a generic term that can also describe an intentional or unintentional drop in voltage in an electrical power supply system, I assumed you meant the phenomenon related to helicopters and propeller aircraft operating in dusty environments, which is a rather specific meaning. Please explain what exactly you mean by "picking some dust" - potential electrostatic cling? I note that that never seemed to come up as an issue for the LEM ascent stage (other than its interior, but that issue is landing/takeoff mode agnostic) either.
6. I also note that you use Apollo 11 as the example for a fuel saving trajectory, which only seems to support my argument for an ultimately vertical touchdown (to quote Charlie Duke in your first video snippet: "down like a helicopter")...
 
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martinbayer

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Do you think Musk is dead wrong in using aerodynamic surfaces on the Starship, since in your categorical view such structures, whether they're called wings, fins or canards, seem to be an expensive waste? I'm pretty sure that cost, functionality and performance considerations and trades for a fully reusable TSTO did enter his mind. Comparing an only partly reusable Falcon 9 to a fully reusable VTHL TSTO conveniently leaves out the fact that such a design could return payloads Shuttle orbiter style, while second stage reusability for the Falcon 9 seems to have been completely abandoned, and the split fairing is only designed to return itself, so the low price of the Falcon 9 comes at the cost of additional mission capabilities offered by a true RLV. A much better and fairer comparison would be between the Starship and a broadly similar design, with the main difference being that both stages of the alternative would perform unpowered horizontal landings.
Wings provide lift. Fins or canards only provide control. I was specifically calling out wings.
Good to see that even in your universe there is still room for some aerodynamic surfaces, since control can also be provided by an RCS ;).
 

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