Starship is Go...

SpaceNut · 2022-04-24 10:28:51

So we need to figure for what is the payload for the 100 per ship support since they will need to use the remaining for the build process.

What I do not see is the listing for coming home?

RobertDyck · 2022-04-24 12:59:35

Starship is designed to use liquid methane fuel since that can be manufactured on Mars. A propellant plant and depot will have to be built before any ships can return to Earth. I don't know about the heat shield; is Starship able to handle Earth atmospheric entry at interplanetary speed? Past depictions show a number of Starships delivering equipment ahead of the first humans, and those cargo landers were not intended to return.

I still argue that's not the way I would do it. I would scout Mars with Mars Direct first; a few missions. Send a rover with a multi-segment core drill to investigate before even the first human landing. After scouting and technology demonstration, send 2 Mars Direct habitats with 6 crew each, who would build a base for themselves using in-situ materials. That would require cargo landers to deliver tools, but start small and build larger tools using in-situ materials. After building a comfortable base for all 12 construction workers, then build habitation and life support for 100 more, as well as propellant production and storage. Only then send Starship with 100 settlers. Their job would be to expand mining/refining/manufacturing capacity, and build habitation and life support for 1,000 more. Only then would the Large Ship arrive.

RobertDyck · 2022-04-24 13:04:33

Ps. Elon Musk said ticket price for the first Starship would be higher, but after service to Mars becomes regular, ticket price would drop to $100,000 per person. I said lowest ticket price for the Large Ship would start higher, but drop to $100,000 per person. That's the same.

SpaceNut · 2022-04-24 13:10:55

The tonnage can be gotten for the fuel plant based on the work I did post 10 of topic as it contains the equipment and power requirements to make fuel for a single ships return. It does not include the mining equipment however.

80 mT, at 13,000 kwhr operating for co2 compression and electrolysis, cooling 6,696 kwhr to make 300 mT of fuel in a 2 years for 10 hours each day run

So if we can not fit all the people back into one ship for that 1,000; how many ships do we need to use as that is going to dictate the number of cargo units for refueling that need to be sent ahead of crew going to mars.

RobertDyck · 2022-04-24 14:03:06

You understand this is for settlement? Settlers travel one way, not returning. And all return propellant is made on Mars.

Mars Direct is a science mission, intended to return. That would bring hydrogen for ISPP: 1 ton of hydrogen becomes 18 tons of propellant. But Starship is intended for settlement, one-way only. Vehicles will return, settlers won't. And even hydrogen for return propellant will be made with Mars ice, so 100% ISPP. Starship is intended to carry 100 settlers to Mars. The Large Ship will carry 1,000 but it too is intended that most passengers are settlers, so crew and only a few passengers would return.

I'm not sure what you mean by "fit all people back into one ship". This is settlement. Elon's stated intent is a city of 1 million people. That can't be evacuated back to Earth, at least not quickly. Mars will require backups and contingencies on-site. And we can't ship all tools from Earth. We will send a minimal number of tools, as small as we can get away with, and use them to make more and larger and more diverse tools using in-situ materials. Remember historical analogies: Robert Zubrin compared the Lewis and Clark expedition to the Franklin expedition. Lewis and Clark lived off the land, while Franklin brought 2 ships packed with canned food and all the supplies they would need. Franklin's ships HMS Erebus and HMS Terror got trapped in ice, all crew died. Ironically if they hunted seal and caribou, learned to live like local Inuit, they would have lived. I use St. John's Newfoundland vs Roanoke and other failed government colonies as examples. Fishermen founded St. John's, ate fish they caught themselves, built the town with local resources. Roanoke and other government colonies depended on shipments of food from Europe. A Mars settlement must start small and grow using local resources.

SpaceNut · 2022-04-24 14:30:45

So what are the numbers since they are not coming back for each ship requires power to get to mars along with all the food and radiation shielding since its not going with AG. Of course musk says nothing about recycling of water or air in any of his videos.

We know that the Nasa food greenhouse post 205 in large ship topic for square foot print that can support a person is but need to find the shipping mass for each ship to have on the surface since its the only way that they will have enough.

RobertDyck · 2022-04-24 14:34:43

I assume Starship will use the same oxygen and water recycling as ISS. I posted details of that years ago. Light weight nuclear reactor, updating Mars Direct

Last edited by RobertDyck (2022-04-24 14:41:46)

SpaceNut · 2022-04-24 15:47:07

https://www.spaceworks.aero/spaceworks- … -habitats/

The final Mars Transfer Habitat design yielded a total mass of 200 t and power generation requirement of 300 kWe. This represents a significant reduction in the mass and power needs necessary for 100 inhabitants when compared to scaling current architectures for the human exploration of Mars. For reference, the in-space habitat mass for a settlement-class mission with – non-torpor approaches – was on the order of 700 t

TorporHabitatModule.jpg?resize=1024%2C691&ssl=1

http://www.sei.aero/eng/papers/uploads/ … 162015.pdf
Presentation: 100-Person Mars Transfer Vehicle using Torpor-Inducing Habitat

https://hobbyspace.com/Blog/?p=11618

http://www.sei.aero/eng/papers/uploads/ … 162015.pdf
Paper: 100-Person Mars Transfer Vehicle using Torpor-Inducing Habitats

https://adamjermyn.com/posts/mars_scales/

That means 3 cargo max payload 200mT to 1 crew of 100

GW Johnson · 2022-04-24 16:13:06

Here is what I have calculated as the velocity requirements for travel from low Earth orbit to direct entry at Mars. That is what Starship supposedly is designed to do, if refilled in low Earth orbit.

The departure delta-vee from low Earth orbit onto a Hohmann trajectory is 3.659 km/s at average planetary distances from the sun. For the two-year abort trajectory it is 4.859 km/s. If the burns are impulsive, the mass ratio-effective dV factor for these is 1.000.

You will need to make probably two course correction burns along the trip. I usually presume a dV budget of 0.2 km/s for these two burns, again with factor = 1.000 for impulsive burns.

Upon arrival at Mars, you will hit the atmosphere at about 135 km and 1-2 degrees below local horizontal, with 5.689 km/s speed off the Hohmann transfer, and about 7.403 km/s off the 2-year abort trajectory. There is no burn for this, you simply enter and hypersonically aerobrake, down to about local Mach 3 (0.7-ish km/s speed), coming out of the hypersonics traveling about 45 degrees downward at about 5 km altitude. Without intervention, you are roughly 10 seconds from impact at about Mach 3 (0.7 km/s).

Spacex’s Mars landing simulation showed a high angle-of-attack pull-up deceleration-to-transonic at about 10 km altitude, with flip and propulsive landing from just about that point. That’s about 0.25 km/s speed to “kill” propulsively, under circumstances demanding a factor of 1.5 to 2 to account for maneuvers, unforeseen difficulties, and whatnot. That adds around 0.37 to 0.5 km/s to your mass ratio-effective dV, to pull off the propulsive landing, if you believe their simulation.

I don’t believe it myself. I think they will have to fire up the thrust to augment the supersonic lift at high angle of attack, in order to make the pull-up to 10 km that decelerates them transonic. I think the landing mass ratio-effective dV allowance is probably closer to 0.7 to 1 km/s.

Let’s compromise, and call it 0.5 km/s worth of mass ratio dV for the landing. The course correction budget is near 0.2 km/s, and the departure dV is 3.659 to 4.859 km/s, depending upon which interplanetary trajectory you fly. The total is 4.359 km/s Hohmann, and 5.559 km/s for the fast 2-year abort flight to Mars. THAT is what you must have the mass ratio for! These burns all happen from the same Starship weight statement, so you can use this sum of dV’s to size things.

Any Starship that returns will need to reach orbit against gravity and drag losses totaling about 2% of low Mars orbit speed, plus enough dV at factor = 1.00 to reach the speed needed for the return trajectory. Thus a mass-ratio-effective value of about 5.800 km/s is needed for Hohmann to leave Mars, and something nearer 7.548 km/s to use the 2-year abort trajectory.

You still need a budget for a couple of course corrections on the way to Earth. I typically use the same as outbound: 0.2 km/s.

Upon arrival at Earth, you will hit the atmosphere at about 140 km and 1-2 degrees below local horizontal, with a speed of 11.572 km/s off the Hohmann trajectory at average planetary distance conditions, and 12.261 km/s off the 2-year abort trajectory at average conditions. These are above Earth escape speed (11.19 km/s at the surface). The worst possible case is closer to 17 km/s! These are free entries into the atmosphere, followed by hypersonic aerobraking to about local Mach 3, about 45 degrees downward, somewhere around 40 km altitude. There is plenty of room to decelerate further for a landing. THAT is the difference Earth’s far thicker atmosphere makes!

According to Spacex, the hypersonic aerobraking is flown at 60 degree angle-of-attack, increasing to 90-degree (dead-broadside) for the vertical “belly-flop”, after hypersonic entry aerobraking is done. As the air density increases with decreasing altitude, the dead-broadside ship decelerates well-subsonic, requiring only a thrusted flip and touchdown at the end. The mass ratio-effective dV for this is probably in the 0.25-0.30 km/s class.

So, for any Starship that returns to Earth, the mass ratio-effective dV budget is about 6.30 km/s for Hohmann transfer, and nearer 8.05 km/s for a fast return using the 2-year abort trajectory. Return is more demanding than the trip outbound, because of the surface launch from Mars! But THESE are the numbers you must have the mass ratio for! These burns all happen from the same Starship weight statement, so you can use this sum to size things.

That brings up the weight statement for Starship, which is burnout mass = inert mass plus payload mass, and ignition mass = burnout mass plus propellant mass. No ifs, ands, or buts. No exceptions. No wishful thinking. Nothing! THAT is the tyranny of the rocket equation!

A couple of years ago, I was using 120 metric tons inert mass for Starship, per comments made by Elon Musk himself in Boca Chica, in front of the very first prototype. The Spacex website said it would hold 1200 metric tons of propellant, and its payload to LEO was “over 100 tons”. These days, I have seen scuttlebutt (and scuttlebutt is all that it is) that the inert mass might be closer to 200 tons, and the propellant load closer to 1400 tons. There is no credible information to use anymore! Which is EXACTLY why I have not updated my estimates from those I made a couple of years ago!

A couple of years ago, the vacuum performance of a Raptor-1 vacuum-bell engine was listed on the Spacex website as 380 s Isp, corresponding to an effective exhaust velocity of 3.7265 km/s. Now there is scuttlebutt that the Raptor-2 version does even better, but there is no data available with any credibility at all. Again, that is EXACTLY why I never updated those estimates from 2 years ago!

So, I will use the more credible data from 2 years ago, just to find out what ballpark we might be playing in here. These data use 120 metric tons inert and (always) 1200 metric tons propellant aboard:
…………………………………..Req’dMR…Wpay,mton..MR………..surplus
Hohmann..outbound…...3.2211…..420……………3.2222……0.0011
Fast………….outbound…..4.4449……228……………4.4483……0.0034
Hohmann…return………..5.4227……151……………5.4280……0.0053
Fast………….return………..8.6729……36……………..8.6923……0.0194

My same numbers 2 years ago say that the Starship/Superheavy combination can only loft about 171 metric tons of payload to LEO. You simply cannot get to LEO while carrying the full max payload to Mars! The tyranny of the rocket equation forbids it! What that means is you only carry 171 metric tons of payload to Mars, but you can reduce the refilled on-orbit fuel load at departure from LEO to Mars. THAT is how you reduce the number of tanker flights needed to send one of these, one-way to Mars!

Payloads coming home from Mars to Earth are very much smaller. Quite trivial, if you try to use the fast trajectory home. The numbers make that very, very clear! You will NEVER evacuate a base or colony on Mars back to Earth, with this vehicle, should such a need ever arise! Better to face that now!

As to the heat shield: the simulations of the Mars landing that were on the Spacex website are based on roughly 7.5 km/s speed at entry interface, very close to my 7.403 km/s value off the fast trajectory! That is very slightly less than the 7.9 km/s at entry interface coming back from LEO. They are in the same ballpark! Anything that works from LEO is going to work for Mars entry off the fast trajectory, and certainly for entries off of Hohmann trajectories.

The ”killer” entry is the free return coming back from Mars to Earth, which is usually in the 12-13 km/s range. A couple of years ago, Spacex was saying its heat shield would withstand more than one entry from LEO, which seems to suggest they thought it might survive one free return from Mars. However, nobody yet really knows, because that vehicle and heat shield has yet to attempt its first return from LEO. We will see, if they ever get those orbital tests started.

GW

SpaceNut · 2022-04-24 18:12:10

That max to LEO of 171mT puts the fuel and payloads into the requirement of one more cargo rocket with nothing returning from mars.

4 cargo to 1 crew to land and make like tunnel rats to keep radiation levels to acceptable levels.

GW Johnson · 2022-04-25 12:02:33

Hi Spacenut:

Well, they think they can do better with revised stage designs and the Raptor-2 engines, whether SL or vacuum-fitted. Sooner or later, we will see.

The 171 m.ton figure comes from my 2+ year old data using Ra[tor-1 reverse-engineering estimates and 120 ton inert for Starship and about 200 ton for Superheavy. Back then, the propellant loads were listed as 1200 tons Starship and 3400 tons Superheavy. Now, no data are listed, and nothing I have seen elsewhere is very credible.

I think they (Spacex) are playing their cards a little closer to the chest because (1) the designs really are evolving, and (2) people like me get estimates that hit too close to the mark.

GW

GW Johnson · 2022-04-25 12:14:03

BTW, as a follow-up, again using the old data, here is what Starship might possibly be able to do as a single-stage round trip ferry operated between the surface and low Mars orbit.

Surf circ orbit speed eastward: 3.6 km/s, factor = 1.02 factored dV = 3.67 km/s
rendezvous and dock budget 0.2 km/s factor = 1
deorbit burn .05 km/s factor = 1
landing pull-up, flip, and touchdown near 0.4 km/s factor = 1.5 min, factored dV = 0.6 km/s

total factored dV = 4.522 km/s

vac Raptor Isp = 380 s, effective Vex = 3.7265 km/s

required MR = exp(dV/Vex) = 3.3651

propellant fraction = 1 - 1/MR = .7028 = Wp/Wign

if Wp = 1200 m.tons, Wign = 1707 m.tons, leaving inert + payload = 507 m.tons

if inert = 120 m.tons, then payload = 387 m.tons, which is much more than I really expected.

However, if the inert is higher, nearer 200 tons, then payload maxes-out at 307 m.tons. Still very attractive for ferry operations at Mars, loading/unloading a big ship in orbit!

So, what happens if the inert is higher to cover the legs needed to make rough-field landings on soft fine sand, AND the factored landing dV is higher, nearer 1 km/s, to be "safe" for human transport? Then:

dV =4.92

MR = 3.7444

propellant fraction = .7329

at 1200 tons propellant, Wig = 1637 m.tons

payload plus inert = 437 m.tons

if inert = 200 tons, them max payload = 237 m.tons. If the design proves out at all, that's pretty close to what I would expect from it.

GW

Last edited by GW Johnson (2022-04-25 12:22:28)

SpaceNut · 2022-04-25 20:31:52

Part of the issues for starship is the multi function design which makes it heavy if using an earth tile system that is capable of a lunar versus a one an done entry to mars, and that means a mass difference for tile thickness both for re-usability and for the higher peak heating seen for earth use.

10 seconds to go vertical for landing is not good so I agree that a powered lift up is required to break more speed and to set the rocket up to go from the flop to turning upward so as to be able to land. That means more fuel will be needed to get that higher payload to the surface.

That also means we need to have lots more testing of the engine combinations such as to be able to prove out the timing and engine strength.

GW Johnson · 2022-04-26 16:42:29

Spacenut:

The problem is that you could send a bunch of Starships one-way to Mars, but not know in advance exactly which one you might need to send back to Earth, for whatever reason. That unknown demands they all be capable of return.

Any ship known (for sure) in advance to be only one-way, can have a minimum heat shield capable of an Earth LEO entry (7.9 km/s), which is essentially identical to a Mars free-entry at 7.4-7.5 km/s. Any ship that might be called upon to return, must be capable of the Mars entry, plus a really harsh Earth free-return entry at 12-13 km/s, or perhaps even a bit faster.

That free return entry at Earth could be as bad as 17 km/s, if the planetary positions are closest to the sun, and you use a really high-speed trajectory. I'm talking faster than the 2 year abort trajectory.

Otherwise, free-return entry from Mars is still substantially more demanding than was Apollo returning from the moon. That was just a teeny bit under Earth escape at 10.9 km/s. Be aware that convective entry heating varies as velocity cubed, while radiational heating from the plasma sheath varies as velocity to the 6th power. Above 10 km/s, radiation dominates. Above 10 km/s, as radiation heating rapidly grows strong, the plasma sheath grows opaque to IR, so heat shield radiational cooling ceases. Only ablation is left to you.

The radio opacity of the plasma sheath starts much earlier. We have already seen the 3 minute radio blackout for Earth entries at 7.9 km/s,
since Mercury orbital flights starting in 1962.

GW

RobertDyck · 2022-06-15 12:30:43

Found this today. Directly from the FAA: SpaceX Starship Super Heavy Project at the Boca Chica Launch Site

Programmatic Environmental Assessment
The FAA published the Final Programmatic Environmental Assessment (Final PEA) and Mitigated Finding of No Significant Impact/Record of Decision (Mitigated FONSI/ROD) for the SpaceX Starship/Super Heavy Launch Vehicle Program at the SpaceX Boca Chica Launch Site in Cameron County, Texas (PEA) on June 13, 2022. The documentation is available for download below.
...
Mitigated Finding of No Significant Impact/Record of Decision
The FAA determined that the Proposed Action would not result in significant environmental consequences and has issued a Mitigated Finding of No Significant Impact/Record of Decision (FONSI/ROD). The Mitigated FONSI/ROD is available above. Required mitigation measures are listed throughout Chapter 3 of the final PEA. Should any future license or permit be issued to SpaceX to perform any aspect of the Proposed Action, the FAA will ensure that SpaceX implements these mitigation measures as conditions for licensure.

40-page official document: SpaceX Starship Super Heavy at Boca Chica FONSI ROD

SpaceNut · 2022-06-15 19:18:32

The environmental review is just one phase in SpaceX being granted a launch license US regulators find over 75 environmental hang-ups with SpaceX’s mega-rocket Starship

RobertDyck · 2022-06-15 20:22:23

I attended a conference where one speaker was the CEO of SpaceDev. That's the company that made the engine for SpaceShipOne, the spacecraft that won the X-Prize, and predecessor to SpaceShipTwo. He said sometimes you have to ask for forgiveness, not permission.

GW Johnson · 2022-06-16 07:34:48

You can only do the "ask forgiveness not permission" thing if they don't know what you are about to do. If they know, they will stop you. Spacex is already known to all the regulators.

Even so, it looks to me like Spacex will get to fly its Starship/Superheavy out of Boca Chica. That's fortunate, because NASA is now dragging its feet about them flying out of Canaveral.

NASA is belatedly (!!!) worried about an explosion or crash destroying the launch pad infrastructure. Makes you wonder why this wasn't the very first thing they thought about, doesn't it? That's a clue that this is bureaucratic foot-dragging, not anything technical.

GW

SpaceNut · 2022-06-16 18:55:09

Starship had already gotten its one pass at forgiveness with #8 or was it 10 in either case they need to do better or find another isolated place to launch from.

GW Johnson · 2022-06-17 07:16:09

Well, the risks are quite real with rocket vehicles. All we can do is minimize the probability, but sooner or later they do explode. And they throw shrapnel and start fires. That's the way of it.

I remember when more of the NASA and DOD launches out of Canaveral failed than flew. That was no different for Von Braun with the V-2 in WW2. It gets better as you learn more, but the problems never disappear entirely.

One of the problems any organization runs into is the passing-on of essential information from one person to another on-the-job. That's the art. Not everything is written down (the science) because managers really hate paying for that. Only about half the knowledge is written down. If turnover is high or there is age discrimination, the art may not ever get learned, and certainly does not get passed on effectively.

You can identify such organizations because the launch failure rate doesn't reduce as fast as it should, or starts to climb again. Confusing that is the break it/fix it/try again effect, which is a perfectly valid way to build up that art and science. The diagnosis is more certain if the failure rate starts to climb again.

Just some thoughts from someone who has watched this take place almost from the beginning.

GW

Last edited by GW Johnson (2022-06-17 07:16:29)

RobertDyck · 2022-06-17 15:10:06

GW Johnson wrote:

One of the problems any organization runs into is the passing-on of essential information from one person to another on-the-job.
...
You can identify such organizations because the launch failure rate doesn't reduce as fast as it should, or starts to climb again.

Boeing Starliner & 737 Max8

RobertDyck · 2022-06-17 15:13:18

GW Johnson wrote:

NASA is now dragging its feet about them flying out of Canaveral.

Details please. Reference?

kbd512 · 2022-06-17 17:55:27

I flew home from Chicago on a United-operated 737 Max8. I'm still alive.

RobertDyck · 2022-06-17 22:18:22

Ps. You never left.

SpaceNut · 2022-06-18 05:34:01

the cape is just feather ruffling since sls has been trouble pron with launching and not just a money siphoning machine.

boeing super max was the plane that auto crashed again by software issues, to say nothing about the starliner issues with the same...

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