New Mars Forums

Starship SN-15 is scheduled for rollout to the launch pad either today or tomorrow. Musk claims that the leaks have been worked on "six ways to Sunday." "hundreds of new upgrades included..."

The landing pad is only one of the two thing SpaceX needs to be successful: the other is a buried glacier to make the retun propellat.
Is a buried glacier sufficiently stable for landing?
If the answer is "yes", what will happen to the starship when the astronauts melt the ice under her to make the return propellant?
If the answer is "no",  it is possible to make a concrete landing pad on a buried glacier, then melt the ice to get water without cracking the concrete?

Why not for SpaceX, once the landing issues are solved, to test the prototypes stability on terrains similar to Mars surface?

SpaceNut,

When the margin between victory and defeat can be as few as a hundred votes or less, widespread and pervasive fraud in every state of the union is not required.  Private citizens took it upon themselves to figure out if the addresses listed on ballots were valid.  They found that many of the addresses were simply empty parking lots where nary a resident was to be found.  The only reason Democrats don't find that problematic is because they won.  It's all a moot point now.  We now have a dementia patient running America, someone who doesn't know where he is, who he's currently speaking to, nor what he's currently doing.  He doesn't even remember the names of his cabinet secretaries.

This goes back to the possible claim that the vaccine gave me covid when in actuality you were ignoring the symptoms just to get the shot as a plausible means for the claim.
https://www.msn.com/en-us/health/medica … li=BBnb7Kz

Things are often not as "simple" as perceived.  That includes Spacex's "Starship".  It makes a pretty good design proposal for a transport to low Earth orbit.  That operation falls within its unrefueled capabilities.  But to get those capabilities,  you have to engineer both entry heat protection and terminal touchdown capabilities into what is otherwise just an upper stage pushing payload into orbit.  And you have to do it in a design capable of flying multiple times with minimal refurbishment between flights,  lest you lose all those advantages

Designs that can do all of that are NOT "simple".  Period!  Which is EXACTLY why all four prototypes so far flown have been lost to crashes,  post-landing fires-and-explosions,  or mid-air explosions. 

To go beyond low Earth orbit requires on-orbit refueling. With cryogenics,  not the storables the Russians have pioneered for ISS.  And which NASA (or anyone else) has NEVER YET done!   The number of refueling tanker flights is not trivial!  My numbers range from 4-5 tanker flights for a Mars mission flown at less-than-max propellant loadout and payload,  to ~8 tankers for a lunar landing flight,  at rather low delivered payload. 

To land such a craft on the moon or on Mars requires a rough-field capability that Spacex has yet to address,  at all!  So far,  their landing leg system designs,  whether Starship or Falcon core,  have ONLY landed on level,  smooth reinforced concrete pads,  or level-and-smooth hard steel decks! 

The moon and Mars require landings on what is essentially a soft sand dune,  and which is neither smooth nor level.   Even abort landings from orbit-only operations here on Earth have the same requirement.  Perhaps even soft mud landings!  I'm sorry,  but all those things are distinct possibilities!  Which makes them actually highly probable,  sooner or later.

Spacex's designs avoid the staging designs required of the Apollo LEM,  but at the cost of a far higher delivered Isp.  In turn,  that requires the most complicated rocket engine design ever attempted.  Anywhere in the world.  Period!  End of issue!  By definition,  not simple!

Docking two things together is not the most challenging thing to do anymore.  Apollo proved that,  although the initial feasibility was demonstrated earlier on Gemini.  It is still possible to screw that up,  as Boeing recently demonstrated with its CST design alternative to Dragon,  for manned missions to orbit.

Appearances are still quite deceiving,  Louis. 

GW

louis wrote:

Well I did specify a delta shaped aircraft which would clearly have a larger surface area.  In addition  above the cloud cover,  you could probably justify putting solar power film on the under-parts of the craft. Lastly, as I suggested, there is the possibility of the plane towing behind long solar "sails". We know small aircraft can tow behind advertising banners many times longer than the planes themselves. I don't know whether this would be practical but it might be. 

Clearly I wasn't suggesting that this approach would suffice to get the plane off the ground.  With VTOL craft, this might be something where that microwave/laser power could be used. Imagine a microwave or laser beam delivering energy to an onboard system till the plane is 5 miles high, at which point onboard batteries take over. This technology might become a reality, though I accept it isn't currently available.

Louis,

The first thing you need to accept is that there is no "winning" here, merely solutions that are more or less efficient than what we currently use, but all will have similar power requirements, because it takes power to move weight through the air at a given speed, period and end of story.  No matter what type of design you specify, solar panels can't come close to providing enough energy to keep all but the flimsiest, slowest, and lowest payload capacity aircraft airborne.  It's a basic physics problem that no amount of religious belief in "green energy" will ever overcome.

From the Wikipedia Article about Solar Impulse II:

The aircraft's major design constraint is the capacity of the lithium polymer batteries. Over an optimum 24-hour cycle, the motors can deliver a combined average of about 8hp (6kW), roughly the power used by the Wright brothers' Flyer, the first successful powered aircraft, in 1903. In addition to the charge stored in its batteries, the aircraft uses the potential energy of height gained during the day to power its night flights.

The Wright Flyer was about the size of a small 2 seat GA aircraft.  The time-averaged power output that could be generated by Solar Impulse II, over a 24 hour time period, was equivalent to what the Wright Flyer was able to generate.  In other words, something grossly insufficient to ever become an airliner.  8hp is sufficient to keep 1 pilot in the air inside a rather flimsy 2,000kg machine that was incapable of making subsequent flights due to flight loads / stresses placed upon an airframe design that was at the absolute limits of technological feasibility, without an unacceptable risk of structural failure in flight, using existing CFRP and thin film plastic technology.  Current CNT fabric could feasibly cut the airframe weight in half, which means an aircraft with a wingspan equivalent to an Airbus A380 that could carry a single pilot and a single passenger, but never fly more than a handful of times before flight stresses rendered the airframe too near to an impending in-flight structural failure for re-flight.

Solar Impulse II was equipped with 4 lightweight 10hp motors, for a total of 40hp.  That means it has a maximum power-to-weight ratio of 15kW per metric ton.  There is no such thing as an airliner with that kind of power-to-weight ratio, nor will there ever be.  The Boeing 747 has an average power requirement of 140MW during cruise, and that equates to generating an average of 314.6kW per metric ton during the cruise phase of the flight.  You can cut the airframe's empty weight in half with extensive use of CFRP, but that still leaves you more than an order of magnitude away from what you can supply using solar panels, and the batteries only exacerbate the weight problem, so now we're in a technological "corner", if you will, and we can't get out of it.  Flying a little slower always helps, but not enough to change the fact that current photovoltaics couldn't come close to supplying enough power if they were 100% efficient.

The Boeing 747 has 525m^2 of wing area, which is quite a bit.  At high noon, at the equator, with perfectly clear skies, it could generate 525kW from 100% efficient wing mounted thin film solar.  There's just one problem.  It still needs 70MW if it's made from CFRP and flying at airliner speeds.  If it flies a little bit slower, like the AGA-33 concept from France, it could get away with 45MW.  At that power level, the 747 needs 85.7 TIMES as much surface area to generate equivalent power output, but to cut the weight in half, we need to make the wing smaller so it generates less drag and requires less power to move it through the air.

Now let's consider your 100m "flying Dorito" / "flying wing" proposal. The surface area of that vehicle is 4,330m^2.  If it had 100% efficient thin film array (1,360W/m^2), it would generate 5,888,800W of power under the most ideal of conditions.  That sounds great, right?  That's quite a bit of power to be sure, but it's nowhere near 45MW.  Since our flying wing has an absolutely crazy amount of volume, it's a safe bet that it's going to weigh more to remain stiff enough to deal with flight loads, even at 450mph vs 600mph cruise speeds.  Even if we invoke CNT, we're still not light enough, and we can't decrease our surface area to reduce our power / thrust requirement to overcome viscous (pushing an object through a fluid) or induced (generating lift) drag, despite being lighter.

In short, making the aircraft larger will only make the power-to-weight problem worse, not better, because more structural weight is required to provide sufficient airframe stiffness as volume increases and you get more drag that you have to overcome to remain airborne.  If you increase the volume of the aircraft by using a "flying wing" or "flying Dorito" design, then it will have both a greater inert mass fraction and more skin drag (drag generated by pushing the airframe through a viscous fluid, aka "air") and more induced drag from generating more aerodynamic lift (which it must have to remain airborne- a blessing and a curse), and consequently require even more power to propel it through the air at a speed above its stall speed.

There are no banner towing planes that use less fuel (energy) when towing the banner than not towing the banner, so that eliminates the feasibility of towing a solar sail.  If the aircraft requires more surface area to generate more power from a skin-mounted solar array, then the most feasible engineering solution is to incorporate more surface area into the airframe design of the aircraft.  That's what the designers of Solar Impulse / Solar Impulse II actually did to create a solar-powered aircraft that could fly around the world while carrying a single pilot.  In fact, one could validly claim that they pretty much knew what they were doing and how to do it, and their bird made it around the world one time, just like Voyager, so mission accomplished.

There is one and only one practical way in which solar panels could ever generate enough power to propel an airliner-sized aircraft through the air, and that is if these "plasma engine" devices can be made sufficiently light / durable / powerful enough to use on an airliner-sized vehicle.  That's because they can generate 55 TIMES more thrust per kilowatt of input power than a turbofan engine.  The fly in the ointment is the special materials, making them lighter and more durable (not BBQ'ing the electrodes in operation), and having a vehicle with enough surface area to mount the thruster array (a "flying Dorito" would actually be a pretty good airframe design for something like this).  They also become less efficient as flight speeds increase.  If all those problems are solved and we come up with thin film that's dramatically more efficient than what we currently have, then we can reevaluate solar powered airliners.  We should see how this technology progresses over the next ten years or so, as it's still in its infancy.

A solar powered airship is perfectly feasible with current technology.  It's so feasible that Lockheed-Martin built and operated one for more than a year.

A solar powered train is perfectly feasible with current technology.  It's so feasible that it's providing routine passenger transport services in multiple cities around the world.

A solar powered ship might be feasible, although it's dubious as to whether or not we could use it in a practical way, and nobody has ever built one.

A solar powered car / truck / aircraft will never be feasible, let alone practical, even if we invoke 100% efficient solar panels and CNT composites.  Unfortunately, short of some heretofore unseen or unproven technology, it really doesn't matter what emerging technologies we invoke, because the power generated from the surface area available is grossly insufficient to move these vehicles at any appreciable speed.

Now that we've done enough simple math to know that we're never flying on a solar powered airliner, even if the solar panels are 100% efficient and CNTRP becomes as cheap and widely available as CFRP, unless those air breathing ion engines / plasma engines become practical, can we proceed to discuss some practical alternatives that could feasibly work using existing technologies?

There's plenty of practical applications for solar panels, but airliners aren't one of them.  I know it's a real drag, but all engineering has its limitations.  It's not a lack of imagination or a money problem, it's a physics problem.  The Sun only provides so many photons / Watts per square meter to play with.

In the general theme of US government support for private enterprise, which I think is a "good idea", I like the idea of allocating sufficient human resources to the SpaceX operation so there are no delays.  On the other hand, it seems to me we (forum members) have no idea what the responsibilities of the FAA may be, what the staffing level may be, or what the competing demands for specialist time may be.

What those of us who are US Citizens ** can ** do is to contact our local representatives to investigate to see if additional funding is needed, or if there might be other reasons why the supply of specialist services does not seem to be meeting the demand.

(th)

Regarding solar power satellites in GEO.  This is 36,000km above the equator.  Back around 2000, I can remember rectenna  arrays beings discussed on the Artemis e-mail forum.  The minimum size of a rectenna was estimated to be ~10km in diameter.  But that is at the equator.  If you are 45° North say, then the rectenna will need to be an ellipse some 14km long and 10km wide.  For most nations, this is still a relatively small area for the ~10GW of power it would provide.  But all the same, no one would want it in their back yard.

In Europe, we could probably fit at least a few rectennas in the southern part of the North Sea where the water is relatively shallow.  Dogger Bank is an option.  The US and Canada have huge amounts of desert areas that would be suitable, but putting a 10GW power receiver in the middle of nowhere would require spending a fortune on additional grid infrastructure.

Today, Monday: SN-11 test flight scrubbed.

Reason stated: No FAA inspector on-site to oversee the safety precautions followed. "he couldn't make it on time."

Good to hear Void.

Had found out second Friday back that brother was sick with covid and that by Wednesday he was admitted to the ICU for continued worsening symptom. They have thrown the kitchen sink at it and it would seem that he has lessening symptoms and was feeling a bit better.