Plus the impact of the exhaust due to lack of flame trench.
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Informative new report from NSF about the current state of Starship development. I found this interesting, regarding the recent S24 static fire…
From the same NSF article:
What I don’t know is if an HLS Starship with no payload can, after reaching LEO, then do the TLI burn and then the de-orbit and landing burns to reach the lunar surface. For the lunar landing test missions it won’t require fuel to launch from the surface back into lunar orbit, the vehicle can just be left on the surface.
Or will it need to be re-fueled with a tanker Starship while still in LEO, before the TLI?
There has been a lot of discussion in the NSF forum about what is happening with S26 and S27. I of course have no special insight into what SpaceX’s plans are for those vehicles, but I have a slightly wild theory; they are HLS prototypes that will be sent to lunar orbit sometime in 2023 and used for the first lunar landing attempts (uncrewed, obviously). It’s the only reason I can think of for building a Starship without tiles or flaps. The HLS vehicle will never re-enter Earth atmosphere and does not require tiles or flaps to land on the Moon.
What I don’t know is if an HLS Starship with no payload can, after reaching LEO, then do the TLI burn and then the de-orbit and landing burns to reach the lunar surface. For the lunar landing test missions it won’t require fuel to launch from the surface back into lunar orbit, the vehicle can just be left on the surface.
Or will it need to be re-fueled with a tanker Starship while still in LEO, before the TLI?
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Could be orbital test tanks for refueling developmemt. HLS needs legs and high mounted supplementary engines.
Good points. Though right now we can’t rule out SpaceX adding legs and retro-rockets to S26 and S27, which are not yet completed. Or maybe the objective for the first two HLS test flights will simply be to get the vehicles to lunar orbit, and test landings will come later.
If those vehicles are planned to become prototype tanker Starships, they will need to be designed for re-entry and landing. I suppose they could be used only to test in-orbit refueling procedures and then they will be de-orbited into the ocean, like an F9 second stage.
Yeah, I was thinking the depo ships that just orbit and get refilled by multi-launch tankers then fill the cargo/ people carriers.
I think they need refueling to get a ship in lunar orbit versus free return loop.
I did not realize that a “depo ship” was part of the SpaceX in-orbit refueling plan. I thought that a tanker Starship went to LEO, transferred its extra O2/CH4 to a Starship and then returned to Earth.
What is the advantage of having a depo ship in orbit? It adds an additional step in the process of refueling a Starship before it leaves Earth orbit to go on to the Moon or Mars, and it means keeping O2/CH4 in orbit longer which means more boil off.
If you have a depot ship then you can know ahead of time that your cargo/ crewed ship can be refueled and the refurling can be done in one transfer. Otherwise, the cargo/ crew ship has to wait for and mate with 6 or however many tankers that each get launched after it.
Depot will have sun shades, radiators or such; but even without those, it's boil off (during active operations) would be similar to the cargo ship loitering.
Later, someone mentioned it looked like they were installing more bracing on the ship.
In a new paper from NASA about HLS and Artemis 3 there are images of the three Starship versions that will be part of the mission. I read about the paper on wccftech.com. That article includes this link Search - NASA Technical Reports Server (NTRS) but I can’t find the actual NASA paper.
This is from the NASA paper. It is the first time I’ve seen an image of the Starship Depot vehicle.
This is from the NASA paper. It is the first time I’ve seen an image of the Starship Depot vehicle.
Well.... I repeated it at least...You nailed it.The article at wccftech.com says:
A somewhat original thought I have had is to use a depot ship at an orbital first stage to increase useful mass and/or residual fuel of the cargo/ crewed Starship.
Need to rerun numbers to see how useful trading tanker launches for cargo is. At the exteme, if they could single stage a booster to orbit, it seems like at least 2km/s is possible with return. Starship solo is ~7km/sec.
Could also push a depot for remote refueling before in situ gets up and running.
Ben W
Chess Grandmaster (Supervised)
Ideally the orbital booster would have vacuum-optimized engines. I wonder about literally stacking two full-size boosters on top of each other for Earth launch, with the top booster only partially fueled, with vacuum engines and a nosecone. Just enough to get to orbit with no payload, then refuel there, and then attach an ordinary Starship on top. I wonder what sort of missions could be enabled this way?
While we're at it, what would stop one from stacking multiple such boosters on-orbit serially? Thinking of the super-long ship from 2001: A Space Odyssey. Could you make, say, a five-booster stack on-orbit, with a single Starship on top? That should enable some pretty quick trips through the solar system! And perhaps even reusable, if the boosters could retain enough fuel to get themselves back to reasonable orbits.
Double stacked booster is basically booster + depot. Yah, depot doesn't need sea level engines.
Additional stages of orbital boosters run into the same problem of diminishing returns as typical rockets as regards fuel. More mass to accelerate with each so decreasing gains.
Sadly, delta-v is a log function...
Ben W
Chess Grandmaster (Supervised)
No question the rocket equation is tyrannical. Maybe a five-booster stack would have twice the total delta-v of Starship alone, for a reasonable-size payload. But twice is still a lot! Sample-return from Pluto?
Ultimately it may make more sense to make e.g. a large ion-engine booster rather than a standard methalox one, although it couldn't assist in launching itself to orbit unless it were a hybrid booster with both ion engines and Raptors. Or one could launch it hybrid, then remove the raptors on-orbit to reduce mass, and refill the tanks with e.g. krypton. No shortage of potential solutions. But of course, let's get ordinary Starship to orbit (and back) first!
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At the risk of stating the overtly obvious, it’s worth noting that electric propulsion requires a massive amount of DC power to charge the field and huck molecules out the business end. The good news is that it’s a very compatible concept with communications satellites (most GEOs, most megaconstellations, etc) as they already have large power subsystems to supply the power hungry payloads….but for a mission that doesn’t otherwise need a ton of power (imaging sats, a fuel depot, etc) it can result in an EPS materially bigger than is otherwise necessary.
In the case of putting EP on Booster that would mean a massive solar array, batteries, chargers, etc. All totally doable for sure...its just going to be on an unprecedented scale. For reference, PPE--which near as I know is the largest contemplated EP system to-date--has something like a 50kW power subsystem and is going to push around 40T worth of mass. An EP Booster will be probably mass an order of magnitude or more higher.
From the internet engineering perspective Its also worth throwing in here that EP tanks are really high pressure--MEOP is in the 400+ bar range and the load is in the 300's. So...they kinda need their own tanks. In the contemplated re-use concept the pressurant tanks would likely suffice, though volume would likely be an issue.
And finally, just for funsies, its worth noting that both the Xenon and Krypton markets have been MASSIVELY impacted by Vlad's antics, since much of the world's supply--especially Xe--comes from the Ukraine. The price has gone up like 6-10x since he decided to wage not-war, and its super fluctuatey and generally difficult to procure. Plenty of folks are scrambling to develop alternatives but its not easy because the efficiency of Xe is hard to beat--that's why it was chosen in the first place for EP. Krypton is above Xe on the table and so its lower molecular mass makes it that much less efficient. Iodine is probably going to emerge as the winner (Busek is already advertising it) as its pretty heavy (its right next to Xenon on the table) and also can be stored as a solid so the reduction in storage vessels brings a lot of volume/mass upside there.
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