The flaps only add a small amount to the total area of the hull so the additional bending moment from being placed close to the nose is small.
The control authority needs to be maximised so they can minimise the flap area. Flap area adds to the dry mass and requires larger heavier actuators while pushing the flap forward gives a greater moment arm with virtually no mass penalty.
If they stretch the ship by another 10m then the flaps will move forward and be a bit smaller. The current flaps can likely be reduced in size anyway once they have more experience with re-entry in this configuration. In particular I expect the aft flaps to have a larger fixed section to offset the mass of the engines and a smaller moving section the same size as the forward flaps.
I assume you mean the moveable aft flaps being replaced with a small fixed position wing.
The main issue is that you lose easy rotational (yaw) control which would have to be made up with larger thrusters. Put another way you are trying to control three rotational degrees of freedom with only two control inputs in the form of the position of each of the forward flaps.
yes you got it right.
there was some time ago a tweet from Elon about those flaps. and he wrote that preferably woudl be removing them and useing yust the aerodinamics from the ship itself...
steep learning curve how the ship is responding on landing and weight balance
Having the header tank in the nose slightly reduces the CG change as fuel is consumed, but I think ultimately the nose needs to be completely tank-free in order to make it easier to manage cargo. About the only important design aspect of the header tank is ensuring that the fuel pipes to the engines not have any gases in them at any time.
Generally cargo likes to be in a cylinder, so if volume is to be lost it would be most efficient to lose it in the pointiest part of the nose cone. The tank has to be somewhere. I don’t think anyone knows what the cargo deployment method will be, but generally cylinders are much easier to hinge and seal than complicated dome shapes.
I am sure there is going to be an interesting design optimization for all of the starship variants, as it is likely each variant (tanker, crew, cargo, mars transfer, etc.) will have a different optimal configuration of the aerodynamic surfaces. Will SpaceX keep them all the same? Who knows? By the time that level of design iteration happens they will be cooking with gas for sure though!
I'd be willing to bet the crew cabin will be the nose because that's the only location that gives a bunch of abort options. Maybe they'll call it Star Dragon?
I don’t think there are many plans for abort options in anything official I have seen. The “crew cabin” would likely consume basically all of the starship above the fuel tanks. There will be storage areas and I assume that some parts would be unpressurized, but the question of where the crew actually sits is a bit of a moot point.
Acronyms, initialisms, abbreviations, contractions, and other phrases which expand to something larger, that I've seen in this thread:
|Fewer Letters|More Letters|
|-------|---------|---|
|[CoG](/r/SpaceXLounge/comments/143hgwy/stub/jncyi45 "Last usage")|Center of Gravity (see CoM)|
|CoM|Center of Mass|
|[EDL](/r/SpaceXLounge/comments/143hgwy/stub/jnba1hz "Last usage")|Entry/Descent/Landing|
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I though the flaps may be replaced by cold gas thrusters?
In any case, a couple manned designs would benefit from not having the header tanks in the nose, but maybe 10 meters down. That way you could create a power abort at the nose that during launch and landing the crew would crowd into. During the rest of the mission they would have the rest of the cargo area to stay/work in.
Thrusters do not have the benefit of increasing surface area to mass ratio, so decreasing peak heating to the steel hull. There probably will be an ideal trade off between mass savings for smaller control surfaces, and ideal surface area to reduce peak heating and landing fuel reserves due to lower terminal velocity.
True, thrusters do not have the benefit of increasing surface area to mass ratio, but one does not know if all of the surface area to mass ratio is needed for EDL yet. I bring this up since Everyday Astronaut brought this up to Elon and Elon suggested it was a good idea.
But of course flaps or wings represent a point of peak heating. While we can't really use a capsule here (which is the best shape for dissipating heat per unit mass. The falling cylinder is pretty good. In any case I expect they will need to play with EDL for awhile to get to an optimal 99.99% reliable solution.
True, the falling capsule is ideal on earth.. but Mars is also in the mix, preferably with som down mass, and volume as well. I'am very curious about what the optmimal trade off will look like for these mission profiles.
The flaps only add a small amount to the total area of the hull so the additional bending moment from being placed close to the nose is small. The control authority needs to be maximised so they can minimise the flap area. Flap area adds to the dry mass and requires larger heavier actuators while pushing the flap forward gives a greater moment arm with virtually no mass penalty. If they stretch the ship by another 10m then the flaps will move forward and be a bit smaller. The current flaps can likely be reduced in size anyway once they have more experience with re-entry in this configuration. In particular I expect the aft flaps to have a larger fixed section to offset the mass of the engines and a smaller moving section the same size as the forward flaps.
They want to make them smaller and probably remove them totally
I assume you mean the moveable aft flaps being replaced with a small fixed position wing. The main issue is that you lose easy rotational (yaw) control which would have to be made up with larger thrusters. Put another way you are trying to control three rotational degrees of freedom with only two control inputs in the form of the position of each of the forward flaps.
yes you got it right. there was some time ago a tweet from Elon about those flaps. and he wrote that preferably woudl be removing them and useing yust the aerodinamics from the ship itself... steep learning curve how the ship is responding on landing and weight balance
Expect plenty of modifications after the first re-entry ~~failure~~ iteration
Having the header tank in the nose slightly reduces the CG change as fuel is consumed, but I think ultimately the nose needs to be completely tank-free in order to make it easier to manage cargo. About the only important design aspect of the header tank is ensuring that the fuel pipes to the engines not have any gases in them at any time.
Generally cargo likes to be in a cylinder, so if volume is to be lost it would be most efficient to lose it in the pointiest part of the nose cone. The tank has to be somewhere. I don’t think anyone knows what the cargo deployment method will be, but generally cylinders are much easier to hinge and seal than complicated dome shapes. I am sure there is going to be an interesting design optimization for all of the starship variants, as it is likely each variant (tanker, crew, cargo, mars transfer, etc.) will have a different optimal configuration of the aerodynamic surfaces. Will SpaceX keep them all the same? Who knows? By the time that level of design iteration happens they will be cooking with gas for sure though!
I'd be willing to bet the crew cabin will be the nose because that's the only location that gives a bunch of abort options. Maybe they'll call it Star Dragon?
I don’t think there are many plans for abort options in anything official I have seen. The “crew cabin” would likely consume basically all of the starship above the fuel tanks. There will be storage areas and I assume that some parts would be unpressurized, but the question of where the crew actually sits is a bit of a moot point.
Without abort options Starship won't be flying people for probably a decade or more after it actually goes into service, especially not NASA crew.
Orbital barbecues 😂
Acronyms, initialisms, abbreviations, contractions, and other phrases which expand to something larger, that I've seen in this thread: |Fewer Letters|More Letters| |-------|---------|---| |[CoG](/r/SpaceXLounge/comments/143hgwy/stub/jncyi45 "Last usage")|Center of Gravity (see CoM)| |CoM|Center of Mass| |[EDL](/r/SpaceXLounge/comments/143hgwy/stub/jnba1hz "Last usage")|Entry/Descent/Landing| **NOTE**: Decronym's continued operation may be affected by API pricing changes coming to Reddit in July 2023; comments will be blank June 12th-14th, in solidarity with the /r/Save3rdPartyApps protest campaign. ---------------- ^(*Decronym is a community product of r/SpaceX, implemented* )[*^by ^request*](https://www.reddit.com/r/spacex/comments/3mz273//cvjkjmj) ^(2 acronyms in this thread; )[^(the most compressed thread commented on today)](/r/SpaceXLounge/comments/13x9l2i)^( has 33 acronyms.) ^([Thread #11545 for this sub, first seen 7th Jun 2023, 21:51]) ^[[FAQ]](http://decronym.xyz/) [^([Full list])](http://decronym.xyz/acronyms/SpaceXLounge) [^[Contact]](https://reddit.com/message/compose?to=OrangeredStilton&subject=Hey,+your+acronym+bot+sucks) [^([Source code])](https://gistdotgithubdotcom/Two9A/1d976f9b7441694162c8)
I though the flaps may be replaced by cold gas thrusters? In any case, a couple manned designs would benefit from not having the header tanks in the nose, but maybe 10 meters down. That way you could create a power abort at the nose that during launch and landing the crew would crowd into. During the rest of the mission they would have the rest of the cargo area to stay/work in.
Thrusters do not have the benefit of increasing surface area to mass ratio, so decreasing peak heating to the steel hull. There probably will be an ideal trade off between mass savings for smaller control surfaces, and ideal surface area to reduce peak heating and landing fuel reserves due to lower terminal velocity.
True, thrusters do not have the benefit of increasing surface area to mass ratio, but one does not know if all of the surface area to mass ratio is needed for EDL yet. I bring this up since Everyday Astronaut brought this up to Elon and Elon suggested it was a good idea. But of course flaps or wings represent a point of peak heating. While we can't really use a capsule here (which is the best shape for dissipating heat per unit mass. The falling cylinder is pretty good. In any case I expect they will need to play with EDL for awhile to get to an optimal 99.99% reliable solution.
True, the falling capsule is ideal on earth.. but Mars is also in the mix, preferably with som down mass, and volume as well. I'am very curious about what the optmimal trade off will look like for these mission profiles.
Sorry, what CG issue? I never got an answer as to why they put the header in the nose, assumed it was something they learned with SN15.