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If solid rockets don't work then there is no pad abort for a Starship loaded up to 1400t with fuel.

You've over-constrained the problem.  You don't need 1400t of prop.  You don't even need cargo.  You need a ~20t crew module and just enough prop to get to LEO and do an EDL abort from orbit.  Once you're in LEO, you transfer to something else (an LSS or a fully-featured crew system suitable for either lunar surface or Mars journeys).  When you come back to LEO, the abort-safe crew version takes you back through EDL.

That said, 5 gee pull-away might not be adequate.  There might not be a viable way to launch a Starship from a mated SuperHeavy.  But even if you can get through these two problems, there are other abort modes that probably need an escape capsule.

your same arguments apply to having a crew dragon in the cargo compartment.

I don't understand what you're saying here.  If the argument is that you don't need robust abort modes for most if not all flight phases, then it's a tautology.  But if it's not then... you do?

Don't get too hung up on the D2.  But you need some kind of escape system if it's important to meet NASA pLOC standards--or responsible corporate standards, for that matter.

So if there is no pad abort, and ascent abort works with current design, and there is no ELD abort, I'm flummoxed as to what abort system there needs to be at all.

Again, you've constructed a tautology on a false premise.  It is of course true that if you need no abort contingencies, then you need no abort mechanism.

I don't see a reality where there isn't a viable pad abort.  All the flight failure trees get convolved with all the Stage 0 failure trees, and then there are any number of exogenous events.

And how did you make the leap to no EDL abort?  There may not be abort options through the entire hypersonic regime, but that's true for all human orbital spacecraft.  And you certainly need to deal with descent, landing, and nav contingencies. 

Landing abort is all that's left.   "can't get to catch tower" means water abort, which works with a robust cargo compartment.

First, I don't think it necessarily works with a robust nose.  It'll work if the entire ship is robust enough, but prop tanks tend to blow up if they rupture.

Second, what about "got to catch tower but catch failed"?

Failure to ignite or correctly use engines due to the remaining single points of failure (which is tank pressurization and gimbaling) happens at such a low altitude abort would be difficult.   Blasting a crew dragon horizontally won't be useful, and neither will solid rockets in the base.

Are you talking about ascent or descent here?  On descent, if you start the rotation high enough, there's absolutely nothing wrong with a horizontal D2 abort; it'll steer into the proper orientation for parachute opening.  And if the rotation is complete, then it's aborting vertically.

On the pad, failure to ignite isn't the problem.  A failure anywhere in the final launch sequence is a problem.

And a crew dragon wouldn't blast horizontally for any pad or ascent abort; it would go up vertically (or axially, after pitchover), after popping the fairing open.

I suspect gimbaling can be made redundant barring frozen parts1, so really we are just left with inadequate pressure in the header tanks as the remaining single point of failure.

If I ran a crew safety group, I'd have a jar where anybody who said the words, "Really we are just left with..." had to put $20.

Slosh causing gas ingestion into the turbines?
Eloneron failure during rotation?
Post-ignition engine explosion?
Nav/guidance failures?
Unexpected, large, cross-wind gusts?
Chopstick malfunctions?  Plain ol' catch failures?
Leg failures for uncaught landings?  Rough surface landings?
Foreign object damage on landing?

That's an off-the-top-of-my-head list.  I'm sure it can be made longer.

There is such thing as material annealing. The steel the ship is made from was hardened (it's cold rolled -- it's a type of work hardening; 300 series stainless hardens very well and its yield strength gets increased a few times). Stainless starts to slowly lose this strength above 700K and does so practically immediately above 1200K. But it's not melting point. 304 stainless steel melts at 1570K to 1630K. Shuttle tiles were to withstand 1530K. As far as we know Starship tiles are the same.

The vehicle needs its full strength primarily on ascent when its tanks are pressurized to 6bar while it faces ~35kPa max-q loads or 3.5g late booster burn load, all the while filled with 1200t of ascent propellant (so for example its skirt has to handle about 5000t load; 3.5g * ~1400t). But during EDL the vehicle is an order of magnitude lighter, dynamic loads are ~20kPa, tanks don't need high pressurization and likely are pressurized as little as possible because ullage gas has non-trivial mass. Suddenly skin doesn't have to survive stress of a 6bar, when the pressure is 2bar. Your skin structural margin increased from 40% to over 400%. The thing could become 4x weaker and it would still hold.

But after such overheating the vehicle would be a write-off (unless the overheating affected only a small patch, then a repair is an option). 300 series remains annealed after it's annealed, it doesn't heal (it doesn't age harden appreciably). You need to work harden it again (this is one of the reasons SpaceX had some initial trouble with popping tanks: weld's anneal the base material; they implemented a better controlled welding process and they also planish many welds which restores some of the strength, and they use weld doublers where fixing up seams is not feasible).

I don't buy this.

The RCC was for entry temperatures *above* 1530K.  You're equating that with a *melting* temperature in the same range.  These are NOT the same thing.  A material just below its melting point has lost most of its strength and will fail soon, if not immediately.  At 1000C 304 is 8 times weaker (lower yield stress) than at 600C.

We're talking about what to do in an off-nominal entry.  Off-nominal likely means damage (tiles or other) or loss of control.  I suspect in either case the assumption that there's nothing you can do is actually correct.  Damage will likely lead to burn through from loss of strength or full blown melting and that's worse on this vehicle than on Shuttle simply because burn through is on a pressurized tank you have to have to land safely.  Loss of control is probably worse.  So I seriously doubt that the intrinsic design of this vehicle makes it more robust against off-nominal entry conditions, and I certainly don't know of an abort option for that situation.

I'm not talking about RCC. There's no need for RCC on Starship because it doesn't have tight curvatures pointing into incoming air.

I'm talking about silica tiles, the ones which had limit of 1533K and didn't reach that on nominal entry.

Also in the localized HS failure you have the backside of an exposed skin fragment providing cooling, so the expected temperature is about 0.84 of a thermally insulated one. So burn through is less likely than it initially seems.
How fast they grow :)
Quite surprising to see the ESM for the Orion spacecraft to be used in the Artemis 5 mission getting ready to be shipped to Bremen ready for final integration just six months after the ESM component of the Orion spacecraft earmarked for the Artemis 4 mission left for the Airbus facility in Bremen.
Would be more believable with examples of “scooping.”
Hello everybody,

in order to understand the structure of the Door actuator pneumatic drive in detail and to be able to determine the dimensions of its individual parts, one cannot avoid looking at it from different perspectives with a higher magnification, e.g. as can be seen in the following images,

Source: NASA (STS-135)

here slightly larger, seen from the other side.

Source: NASA (STS-132)

This pneumatic drive is connected to the two screw jack bracket assemblies by the horizontal pipes of the pneumatic system, which extend forward and aft. When the door actuator system is activated in the horizontal configuration, the door actuator pneumatic drive pulls the screw jacks down vertically, tilting as necessary in their brackets,

Source: NASA (STS-126)

to clear the opening doors.

Source: NASA (STS-135)

Based on the determined dimensions, I've cut the corresponding individual parts,

Source: NASA (STS-126)

which can be seen in this image. The frame of the drive unit will be made from the smaller strips (0,25 mm x 0,5 mm), the longer strips (0,13 mm x 0,7 mm) should be used for the side retaining struts.

To get an idea of the size of the drive unit, I added a cuboid of the appropriate size,  but a few more details this White Box should get already.
Let's see if and how I will succeed in putting together this puzzle work.

Something unusual happening in the company? All the recent hit pieces in mass media about them going silent seems oddly timed...

I have not heard of anything unusual happening at the company.  Judging from LinkedIn, the company is pretty sizeable now (~300 employees) and the company is hiring quickly on the back of its Summer fundraising.  The business development manager most quoted in the press, Brian Gettinger, left the company in September.  So maybe some potential projects are getting less contact from the sales department.  Here's the replacement position...

Much of it seems to be just the normal hit piece avalanche that Musk attracts and can be safely ignored or adjusted 100x for significance.
Missions To The Moon (HSF) / Re: Artemis 1 Discussion Thread 2
« Last post by whitelancer64 on 12/05/2022 10:09 pm »
I am rather hesitant to ask this question in this group, because I can barely follow the headlines these months (too much work and other "higher priority distractions"). I tried to search this and other threads without success, but if this has been already discussed just point me in the right direction. Apologies if this is just "old stuff".

There is something bothering me regarding Artemis I re-entry. In this old post:

NASA stresses the fact that a "skip re-entry" is a novelty of this program and that:

Although the concept of the skip entry has been around since the Apollo era, it wasn’t used because Apollo lacked the necessary navigational technology, computing power, and accuracy.

To my knowledge, the Apollo CMC (Command Module Computer) had software to manage a skip re-entry with an initial entry into atmosphere, and the option for a skip-out maneuver followed by a ballistic phase (out of the atmosphere) and a subsequent re-entry. The decision to activate the skip-out maneuver was based on excess energy or the need to travel farther along-track. The entry profile was also guided laterally (or cross-track), and Apollo CMs always executed very precise water landings.

It could be that the new vehicle implements a more sophisticated lifted entry logic, and more sensors, but I am not sure that there is such a big difference between Apollo CM and Orion in terms of guidance schemes to say that it has never been implemented before. Maybe it has not been used in actual flight, but it has been designed, implemented and tested.

Is there more information on this topic?

Apollo did an aerodynamic "partial skip" or "lifting" reentry, extending the period of heating to reduce the peak heat load, but never actually leaving the atmosphere once reentry had begun.

... a lot of classified tests of nuclear warhead reentry vehicles demonstrated skip reentry or variations on it. You probably won't find much detail on that.

The Soviet-era Zond capsule and the Chinese Chang'e 5-T1 capsule both did skip reentry.
SFN Launch Schedule update, December 5:
Launch January 2023

Dec 15        Vand SLC-4E   SWOT
Dec 29        Vand SLC-4E   EROS C3 no. 1
NET Jan?   Vand SLC-4E   SDA Tracking Layer Tranche 0 Flight 1
General Discussion / Re: Predictions 2023
« Last post by CameronD on 12/05/2022 10:05 pm »
My Spaceflight Prediction for 2023:

A launch from somewhere in Australia that actually makes it to orbit.  8)

Cross-post re: Starlink 4-37, noting no changes today regarding Starlink 2-2:
SFN Launch Schedule, updated December 5:
Launch date TBD.  (No change to the Starlink 2-2 listing.)
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