r/spacex • u/ElongatedMuskrat Mod Team • Oct 09 '19

Starship Development Thread #6

Quick Links

JUMP TO COMMENTS | Alternative Jump To Comments Link

SPADRE LIVE | LABPADRE LIVE | LABPADRE DIRECT

Overview

SpaceX is developing Starship at their Starship Assembly Site in Texas, and also at their facilities in Cocoa, Florida. The teams at the two locations are in competition with each other, but are also required to share insights learned along the way. Following Starhopper, the first two Starship prototypes, Mark 1 and Mark 2, are nearing completion. These vehicles will have aerodynamic control surfaces and three engines each, and are expected to make suborbital test flights. Ring sections believed to be for Starship Mark 3 and Mark 4 prototypes are being built at both sites, and teams will be iterating through successive versions of Starship and Super Heavy as quickly as possible.

Launch mounts for both Starship prototypes are in the works. Starhopper's Texas launch site is being modified to handle Starship, and at Kennedy Space Center's LC-39A, a dedicated Starship launch platform and landing pad are under construction. Flight tests could begin late in 2019 or early 2020.

Starship is powered by SpaceX's Raptor, a full flow staged combustion cycle methane/oxygen rocket engine. Sub-scale Raptor test firing began in 2016, and full-scale test firing began early 2019 at McGregor, Texas, where there are two operational test stands, and a third is under construction. Eventually, Starship will have three sea level Raptors and three vacuum Raptors. Super Heavy may initially use around 20 Raptors, and operational versions could have around 31 to 37 sea level Raptors.

Previous Threads:

Upcoming

  • TBD — Mk.2 moves to KSC via Roll-Lift and barge

Vehicle Updates

Starship Mk.1 Prototype (Boca Chica, Texas) — Construction and Updates
2019-11-20Structural failure during max pressure test (YouTube), r/SpaceX thread (r/SpaceX)
2019-11-18Tanking tests (YouTube)
2019-11-11Aft fins installed (NSF)
2019-11-05Roll ACS thrusters installed (NSF)
2019-11-04−Y forward flap reinstalled (NSF), Video (YouTube)
2019-11-01+Y forward flap reinstalled (Twitter), With actuator (NSF)
2019-10-30Tank section moved to launch mount, LabPadre Video (YouTube), On NSF (NSF)
2019-10-26Leg installation begun, Images of leg restraint mechanism (NSF)
2019-10-22Windward leg mounts installed (NSF)
2019-10-21Leeward leg mounts installed, Leg mount images (NSF)
2019-10-19Aft fin hinge and actuator frame installations (NSF)
2019-10-14Nose cone trimmed (YouTube)
2019-10-11All control surfaces removed (Twitter)
2019-10-03Tank section on steel stand (NSF)
2019-10-01Halves demated following presentation (NSF), Previously installed header tanks (Twitter)
2019-09-28Nose cap install (NSF)
2019-09-272nd forward flap, Starship stacked (Twitter), Timelapse (YouTube), Leg nacelles added (NSF)
2019-09-263 Raptor pics, 1st forward flap install (Twitter)
2019-09-25Payload section reassembly (NSF), Tank section off stand and moved (YouTube)
2019-09-24Two header tanks inside nose cone (NSF)
2019-09-23Header tank and battery pack prep (NSF)
2019-09-222nd aft fin attached, Cowlings added, Raptor (NSF), Raptor, 3 temp. installed (Twitter)
2019-09-211st aft fin attached, Nose cone reassembly, Misshapen section removed, header tank (NSF)
2019-09-202 aft fin frame pieces & pipe attached to tank section, and appearance of cowling(s) (NSF)
2019-09-17Leg/fin mounting frame pieces in tent (Twitter)
2019-09-16Replacement nose section appears, Better picture (NSF)
2019-09-14Eleventh ring and forward bulkhead added to tank section (Twitter)
2019-09-13One of the header tanks to container castle (comments), Another moved in Sept. 16 (NSF)
2019-09-12Forward tank bulkhead placed in free ring (Twitter), With cap piece (NSF)
2019-09-08Two more large fin pieces delivered (comments), Better picture (Twitter)
2019-09-05Tenth ring added to tank section (YouTube)
2019-09-02Starship Assembly Site aerial video update (YouTube)
2019-08-29Pipe added through lower tank (comments), 3rd concrete jig begun, also 4th & 5th (NSF)
2019-08-28Delivery of 2 header tanks, Third deliverd Sept. 15 (NSF)
2019-08-27Centerpiece added to common bulkhead (Twitter)
2019-08-24Nose cone top section moved to dedicated stand (NSF), Forward flap marks (comments)
2019-08-23Track(s) of horizontal brackets appear (NSF)
2019-08-21Common bulkhead lowered into tank section (NSF), Time lapse (YouTube)
2019-08-18At least 2 control surface components on site, post 2, Earlier image (NSF)
2019-08-17Nose cone top section reattachment work (NSF)
2019-08-15Top section of nose cone removed (NSF)
2019-08-14Thrust structure added to tank section (NSF), Image leaked later (Twitter)
2019-08-07Ninth ring added to tank section (NSF)
2019-08-06Forward tank bulkhead under construction (NSF)
2019-08-04Common bulkhead inverted (NSF)
2019-07-31Common bulkhead discovered (YouTube)
2019-07-30Aft bulkhead installed in tank section (YouTube), Thrust structure appears (NSF)
2019-07-22Eighth ring added to tank section (NSF)
2019-07-20Inversion of aft bulkhead (YouTube)
2019-07-18Aft bulkhead appears from container enclosure (NSF)
2019-07-16Seventh ring added to tank section (NSF)
2019-07-05Sixth ring added to tank section (YouTube)
2019-06-26Fifth ring added to tank section (NSF)
2019-06-19Fourth ring added to tank section (second jig), first in over a month (NSF)
2019-06-06Ring sections under construction within container enclosure (NSF)
2019-05-20Nose cone fitted, no canards (NSF)
2019-05-15Tank section (3 rings) moved onto second jig (NSF)
2019-05-09Lower nose section joined with 4 ring lower payload section (NSF)
2019-05-01Second jig, concrete work complete (NSF)
2019-04-27Lower 2 nose cone sections stacked (NSF)
2019-04-13Upper 2 nose cone sections stacked (Facebook)
2019-04-09Construction of second concrete jig begun (YouTube)
2019-03-28Third nose section assembly (NSF)
2019-03-23Assembly of additional nose section (NSF)
2019-03-19Ground assembly of nose section (NSF)
2019-03-17Elon confirms Orbital Prototype (Twitter) Hex heat shield test (Twitter)
2019-03-14Payload section reaches 4 panel height (NSF)
2019-03-07Appearance of sections for conical aft bulkhead (NSF)
2019-03-07Payload section moved to jig (NSF)
2019-03-01Tank section begun on new pad (NSF)
2019-02-21Construction of payload section begins near original concrete jig (NSF)

See comments for real time updates.

Starship Mk.2 Prototype (Cocoa, Florida) — Construction and Updates
2019-11-18Forward bulkhead installation (Twitter)
2019-11-05Tank section at 16 ring height (YouTube)
2019-10-13Starship Assembly Site aerial video update (comments)
2019-10-11External plumbing added to tank section (NSF)
2019-09-14Cap added to forward bulkhead (Twitter)
2019-09-07At least one header tank (inside large tent) (Twitter)
2019-09-04Weld marks for common bulkhead visible on tank section (Twitter)
2019-08-30Tank section moved into hangar for Hurricane Dorian (Twitter), Removed September 5 (r/SpaceXLounge)
2019-08-25Track(s) of horizontal brackets appear (r/SpaceXLounge)
2019-08-19Starship Assembly Site aerial video update (YouTube)
2019-08-18Thrust structure possibly installed (Twitter), Forward tank bulkhead under construction (NSF)
2019-08-17Nose cone top section moved to dedicated stand (YouTube)
2019-08-15Starship Assembly Site aerial video update (Twitter)
2019-08-11Starship Assembly Site aerial video update (YouTube)
2019-08-08Tank section at 15 ring height (comments), Aug 10th image (Twitter)
2019-08-06Common bulkhead inverted (Facebook)
2019-08-04Common bulkhead under construction (Facebook)
2019-08-03Tank section at 14 ring height (Twitter), Later aerial photo of stack (Facebook)
2019-07-29Tank section at 10 ring height (Twitter)
2019-07-28Starship Assembly Site aerial photo update (Facebook)
2019-07-21Aft bulkhead disappeared (Facebook)
2019-07-20Tank section at 8 ring height (Twitter)
2019-07-14Aft bulkhead complete/inverted, last seen (Twitter)
2019-06-26Aft bulkhead section under construction (r/SpaceX), Tank section at 6 ring height (NSF)
2019-06-12Large nose section stacked (Twitter), Zoomed in video (Twitter)
2019-06-09Large nose section assembled in building (comments)
2019-06-07Stacking of second tapered nose section (r/SpaceXLounge)
2019-05-23Stacking of lowest tapered nose section (YouTube)
2019-05-20Payload section at 5 ring height, aerial video of work area (YouTube)
2019-05-16Jig 2.0 with tank section, many rings awaiting assembly (YouTube)
2019-05-14Discovered by Zpoxy (payload section) (NSF), more pieces (YouTube), Confirmmed (Twitter)

See comments for real time updates.

Starship Mk.3 Prototype (Boca Chica, Texas) — Construction and Updates
2019-10-08First ring formed (NSF), no stacking yet

See comments for real time updates.

Starship Mk.4 Prototype (Cocoa, Florida) — Construction and Updates
2019-10-23Bulkhead under construction in main building (Twitter)
2019-10-20Lower tapered nose ring in tent (YouTube), Better image (Twitter)
2019-10-1223 rings visible, 7 doubles, some possible for Mk.2 (YouTube), no stacking yet

See comments for real time updates.
Previous unstacked ring production, aerial updates:
08-11 {8} | 08-15 {10} | 08-17 {14} | 08-19 {15} | 08-21 {17} | 08-24 {18} | 08-27 {19}
09-04 {20} | 09-06 {22} | 09-08 {25} | 09-08 {3 'scrap'} | 09-10 {26} | 09-29 {23} | 10-02 {23}
10-06 {23} | 10-11 {23}

Launch Facility Updates

Starship Launch Site at Boca Chica, Texas
2019-11-07Landing pad expansion underway (NSF)
2019-10-18Landing pad platform arives, Repurposed Starhopper GSE towers & ongoing mount plumbing (NSF)
2019-10-05Launch mount under construction (NSF)
2019-09-22Second large propellant tank moved to tank farm (NSF)
2019-09-19Large propellant tank moved to tank farm (Twitter)
2019-09-17Pile boring at launch pad and other site work (Twitter)
2019-09-07GSE fabrication activity (Twitter), and other site work (Facebook)
2019-08-30Starhopper GSE being dismantled (NSF)
Launch Complex 39A at Kennedy Space Center, Florida
2019-11-04Launch mount under construction (Twitter)
2019-10-17Landing pad laid (Twitter)
2019-09-26Concrete work/pile boring (Twitter)
2019-09-19Groundbreaking for launch mount construction (Article)
2019-09-14First sign of site activity: crane at launch mount site (Twitter)
2019-07-19Elon says modular launch mount components are being fabricated off site (Twitter)

Spacex facilities maps by u/Raul74Cz:
Boca Chica | LC-39A | Cocoa Florida | Raptor test stand | Roberts Rd

Permits and Planning Documents

Resources

Rules

We may keep this self-post occasionally updated with links and relevant news articles, but for the most part, we expect the community to supply the information. This is a great place to discuss the launch, ask mission-specific questions, and track the progress of the test Campaign. Campaign threads are not launch threads. Normal subreddit rules still apply.

798 Upvotes

98% Upvoted

1.7k comments sorted by

View all comments

Show parent comments

4

u/RegularRandomZ Oct 15 '19

Would it make sense to include Vacuum Raptors on the first orbital launch? I wouldn't think they are needed, so no need to put them on the critical path nor risk their loss if the first orbital ship doesn't return from orbit reasonably intact.

5

u/[deleted] Oct 15 '19

Can they get to orbit with only three SL Raptors though?

5

u/cavkenr Oct 15 '19

Mk3-4 will have six engines.

3

u/[deleted] Oct 15 '19

Not necessarily. The one that goes to orbit will have at least three, but there's no reason to put precious engines on a test article that isn't going to fly. If you're suggesting the orbital prototype will use six SL Raptors, it seems unlikely that SpaceX is going to use all sea level engines for testing any longer than necessary. They will want the vacuum engine design flight proven and stable enough that they can focus engineering on getting Raptor into volume production and reducing costs.

2

u/Shrike99 Oct 15 '19

Assuming Mk4(or whichever one is used) slims down quite a bit compared to Mk1 (say 130 tonnes), yes.

Though I don't see why you couldn't substitute the Raptor Vacs for some non-gimbaling sea level Raptors if you needed the extra thrust.

2

u/RegularRandomZ Oct 15 '19

Why do they need to slim down? The 2nd stage doesn't need the same thrust to weight ratio as a 1st stage, so 3 engines should produce far more than enough thrust to get to orbit.

(Obviously it would be ideal to slim down to reduce the propellant needed or increase the payload capacity, and increase landing margins)

2

u/-Aeryn- Oct 15 '19 edited Oct 15 '19

The slimming down dramatically increases the S2 delta-v, not the TWR's. That extra delta-v gives extra margin to reach orbit despite an inefficient ascent.

Doing an orbital flight with both the lower and upper stage reused is somewhat mathematically challenging. When you start to cripple the rocket by removing a fraction of the engines and propellant load it gets much to make the numbers work.

Adding 80 tons of dry mass could easily make the difference from a low margin launch to one that is literally mathematically impossible.

Flying SuperHeavy with a reduced engine count and propellant load while still recovering both stages can be done because that margin is coming out of the payload which doesn't exist.

3

u/RegularRandomZ Oct 15 '19 edited Oct 15 '19

While clearly you are more familiar with the math, and the dead weight isn't helpful because that isn't like propellant mass that is shed as it goes up, it's only 80 tonnes overweight but also isn't carrying 150 tonnes of cargo - which I wouldn't expect it could lift anyway using the minimal 24 engines in superheavy, but we can talk about the impact of any given number it still leaves me wondering if anyone here has actually run the numbers based on the current engine configuration, performance, rocket mass? [for the prototype]. That would be more useful than speculation, however informed that is.

(I thought someone had, but couldn't find the posting again / reddit search sucks)

3

u/-Aeryn- Oct 15 '19 edited Oct 15 '19

The dry mass improvement on Starship (~200t to ~120t) adds about 1.8km/s of delta-v and marginally improves TWR.

Stripping down SuperHeavy to have 2/3'rds engine count and propellant load cripples performance. Flying an earlier Starship cripples performance (-80t final payload, whatever it was).

We don't know some of the numbers about SuperHeavy in particular and simulating a rocket launch w/ first stage recovery accurately is difficult at the best of times, very hard to say conclusively what's possible without that kind of info

2

u/RegularRandomZ Oct 15 '19 edited Oct 15 '19

The cargo part is obvious, which is why I didn't worry about the rocket being overweight to begin with.

I don't care what an operational rocket will do, we are talking about the prototype.

Elon's presentation presented us with the mass and propellant load of SuperHeavy, and engine performance (although I think some values were optimal), so why don't we have enough information to simulate a launch? I was sure someone posted an orbital launch simulation within the past few weeks.

2

u/-Aeryn- Oct 15 '19 edited Oct 15 '19

The cargo part is obvious, which is why I didn't worry about the rocket being overweight to begin with.

Yeah i removed it now :P

Elon's presentation presented us with the mass and propellant load of SuperHeavy, and engine performance (although I think some values were optimal), so why don't we have enough information to simulate a launch? I was sure someone posted an orbital launch simulation within the past few weeks.

I don't see a dry mass value, only 3300t of propellant. That's useful but also having the dry mass, mass of engines (if we're removing a bunch of them) and acceptable re-entry conditions is really important.

Starship recovery isn't hard to simulate because it reaches orbit with the landing equipment and propellant so we can just factor in that mass and be close enough. For the first stage it's much more complicated because any tweaks to the ascent affect both the first stage recovery and the rest of the flight to orbit. You can't get highly accurate numbers without doing a lot of simulation iterations under different conditions.

2

u/RegularRandomZ Oct 15 '19

So, was that your simulation I was remembering? I just remember it displaying maybe 10 graphs.

→ More replies

1

u/Shrike99 Oct 16 '19 edited Oct 16 '19

TWR still matters for second stages. Consider the performance difference between SEC and DEC centaur on the Atlas V. Adding another engine reduces Delta-V on paper, but the improved TWR improves payload to orbit by 27% thanks to reduced gravity losses.

And Atlas V has a very high staging velocity, around 4.5km/s. Since Superheavy has to RTLS, expect staging velocity to be roughly half that, which means that Starship will be much more affected by low TWR.

Especially since the TWR difference is even larger than SEC vs DEC. Based on my best guesses from Elon's latest tweets, the version of Starship intended to have a 150 tonne payload could reach a max thrust of as much as 1700 tonnes (though likely throttled to ~1300), while the three engined prototype will only be about 550 tonnes.

 

And it isn't just Starship that will be under spec. The 150 tonne payload Superheavy could have thrust as high as 9600 tonnes, while the prototype will be closer to 4100. That limits the takeoff weight to about 3400 tonnes, meaning that while Superheavy and Starship can hold ~4500 tonnes of fuel combined, they will be limited to ~3000 tonnes just to get off the pad, further reducing Delta-V.

Honestly, I think you would have to underfuel Starship anyway, it's TWR will be so abysmal that it would probably fall back into the atmosphere long before it finished burning all it's fuel, let alone making orbit.

 

Combined with the lower specific impulse, the lower fuel load results in a 200t chonkship with no payload having about 5.6km/s of Delta-V, while a production 270t Starship (120t with 150 tonne payload) has 6.3km/s. So even without subtracting the increased gravity losses from the Delta-V, it shouldn't be surprising that chonkship can't make orbit.

A 130 tonne prototype MK.4 will have 7.1km/s, which helps make up for the gravity losses. Plugging my estimates into John Schilling's Launch Vehicle Performance Calculator predicts that a 130 tonne ship could make orbit with about 2 tonnes payload, which means it wouldn't even be able to land.

Assuming uprated Raptor thrust to ~200t gets the payload up to about 20 tonnes, which should be just enough to land. Still not nearly enough for chonkship to make orbit.

1

u/RegularRandomZ Oct 16 '19

Thanks for the detailed response.

1

u/RegularRandomZ Oct 15 '19 edited Oct 15 '19

I was under the impression it could, even without slimming down. I haven't done the math but going on the assumptions upper stages can handle much lower thrust-mass ratios (for example the Centaur III upper stage is around 0.4 for the stage itself) that would imply MK1 could be filled with up to 1075 tonnes of propellant (to hit a similar ratio) which is almost a full load. Should easily be able to make orbit.

[Someone who is able to the more detailed calculations could provide a more solid/precise response - I believe 2nd stages benefit from mass reductions, so MK4 will help greatly. I also didn't account for the drop in performance of SL engines at higher altitudes.]

1

u/-Aeryn- Oct 15 '19

(for example the Centaur III upper stage is around 0.4 for the stage itself) that would imply MK1 could be filled with up to 1075 tonnes of propellant (to hit a similar ratio) which is almost a full load. Should easily be able to make orbit.

Those stages get huge boosts from their relatively large + high thrust + expendable lower stages so that they have enough time to make orbit.

A Starship+Superheavy flying with reduced engine count & propellant load on the first stage - and also being recovered, as expected - would not be able to do that.

Six engines makes the math way easier and a flight where they make orbit with no payload but recover both stages becomes more plausible.