Wiki Super Heavy/Starship - General Development Discussion

[Grendal]

Someone made a video simulation of a BFS landing on Mars. It's pretty cool.

To help put the pieces together, here is the IAC presentation introducing BFR/BFS:

The BFR "Earth to Earth" video:

This year was an update to the previous years presentation about "Making Life Multi-Planetary."

The earlier version of BFR, the ITS:

 

[HVM]

http://www.spacex.com/sites/spacex/files/making_life_multiplanetary-2017.pdf
The presentation notes of 2k17 BFR

 

[EchoDelta]

Is there a KSP version yet ?

 

[ecarfan]

Someone made a video simulation of a BFS landing on Mars. It's pretty cool.

Yes, cool. It appears that the video does not show the complete Mars landing maneuver sequence accurately. According to the simulation Elon showed at the last IAC, the BFS is planned to be nose down at an altitude of about 60km, gradually losing velocity, and then at less than 10km above the surface it will go nose up so the ablative heat shield is properly positioned to absorb the energy created as velocity is greatly reduced, and then the vehicle positions itself tail down for the landing burn. That video does not show the nose down phase. The BFS heat shield does not come into play until the vehicle is relatively close the surface because the Martian atmosphere is so thin compared to Earth. But there is enough atmosphere present for it to be very helpful in reducing vehicle velocity.

I know: picky, picky, picky.

 

[EchoDelta]

Yes, cool. It appears that the video does not show the complete Mars landing maneuver sequence accurately. According to the simulation Elon showed at the last IAC, the BFS is planned to be nose down at an altitude of about 60km, gradually losing velocity, and then at less than 10km above the surface it will go nose up so the ablative heat shield is properly positioned to absorb the energy created as velocity is greatly reduced, and then the vehicle positions itself tail down for the landing burn. That video does not show the nose down phase. The BFS heat shield does not come into play until the vehicle is relatively close the surface because the Martian atmosphere is so thin compared to Earth. But there is enough atmosphere present for it to be very helpful in reducing vehicle velocity.

I know: picky, picky, picky.

Had the same reaction : that sequence seems an approach for a much denser atmosphere, probably the author was inspired by a space shuttle reentry.
Maybe the author can change the script

 

[jkn]

For me both videos look more artistic projects than real simulations. Entry generates lot of heat energy. Distributing this energy for longer time interval lowers temperature. So deceleration must be as slow as possible. For that aerodynamic lift is needed to maintain max possible altitude. At those speeds lift can be generated only by keeping nose up, perhaps at 45⁰. 90⁰ nose up only after heating is not a problem and ship needs to avoid overshooting landing area.

 

[N5329K]

ship needs to avoid overshooting landing area.
...which better have an autonomous fuel depot very nearby, yes?
Also, I really don't buy landing directly on the tail. Too many things to hit, too much unintended energy to absorb. Look at the crush pads on Falcon's legs after a hot landing.
Robin

 

[ecarfan]

Also, I really don't buy landing directly on the tail.

Pretty sure the BFS will have massive landing legs capable of absorbing a lot of energy in a hard landing.

 

[N5329K]

I hope so. EM was suggesting that no landing legs will be required with suborbital BFR hops, because the landing evolution is so controlled and well-understood that the rocket can just land and mate up directly with the refueling points on the barge,
I respectfully would call major BS on that.
When pilots land an airplane, they try very hard to roll it on so the pax don't know they've arrived. Except when there's a crosswind and you need to dump lift now. Or have a short runway and need to stop now. Or because the wind shifts in the flare and you just thump it in and cringe. The runway centerline is there for a reason, and if the nosewheels don't straddle it pilots ding their performance. And don't get me started about stopping the airplane. There's a whole zen-thing about applying the brakes just so to keep anyone from feeling that natural little shudder of coming to a halt. In other words, there's the ideal (which is fine to aim for but not always achieved) and then there's the world.
Or in the case of the BFR, worlds.
Stuff happens and I would be very surprised (and impressed) if a huge ballistic object like the BFR could be brought down with that degree of unerring precision. Every time. To paraphrase one of Tesla's founders, Software is easy. Rockets are really, really hard.
Robin

 

[mongo]

I hope so. EM was suggesting that no landing legs will be required with suborbital BFR hops, because the landing evolution is so controlled and well-understood that the rocket can just land and mate up directly with the refueling points on the barge,
I respectfully would call major BS on that.
When pilots land an airplane, they try very hard to roll it on so the pax don't know they've arrived. Except when there's a crosswind and you need to dump lift now. Or have a short runway and need to stop now. Or because the wind shifts in the flare and you just thump it in and cringe. The runway centerline is there for a reason, and if the nosewheels don't straddle it pilots ding their performance. And don't get me started about stopping the airplane. There's a whole zen-thing about applying the brakes just so to keep anyone from feeling that natural little shudder of coming to a halt. In other words, there's the ideal (which is fine to aim for but not always achieved) and then there's the world.
Or in the case of the BFR, worlds.
Stuff happens and I would be very surprised (and impressed) if a huge ballistic object like the BFR could be brought down with that degree of unerring precision. Every time. To paraphrase one of Tesla's founders, Software is easy. Rockets are really, really hard.
Robin

BFR is the first stage, no passengers. The landings have been getting good enough to look at landing on the launch mount. Guessing it will have active alignment features to assist.

BFS is the second stage, with legs. It gets craned back onto the BFR at the destination (earth hops)

 

[N5329K]

BFR is the first stage, no passengers. The landings have been getting good enough to look at landing on the launch mount. Guessing it will have active alignment features to assist.

BFS is the second stage, with legs. It gets craned back onto the BFR at the destination (earth hops)

Thanks for the explanation. Legs are good.
Robin

 

[mongo]

Thanks for the explanation. Legs are good.
Robin

Yeah, they help keep the nozzles and fueling connections clear.
If you are landing on a non-prepared surface, how many to use? 5+ for redundancy and make them dynamic to keep the vehicle vertical?

Speaking of fueling connections on the Mars return trip will there be a robot arm to disconnect the CH4 and O2 feeds and move them out of the way pre launch? Or can they operate non supercooled and manually disconnect before take off? Or a second set on the side and a collapsible service tower in the cargo hold?

So many interesting things to look forward too!

 

[ecarfan]

EM was suggesting that no landing legs will be required with suborbital BFR hops, because the landing evolution is so controlled and well-understood that the rocket can just land and mate up directly with the refueling points on the barge,
I respectfully would call major BS on that.

Elon said in his most recent IAC presentation that he believed that the BRF would be able to “land back on its launch mounts”. Not “land and mate up directly with the refueling points”.

When the BFR/S “tanker” goes to LEO to refuel the BFS (Mars bound ship) the tanker will flip and “back in” to the BFS and the refueling lines will mate up in orbit. Maybe that is what you were thinking of?

 

[N5329K]

No, I understand the "love bug" in-orbit fuel transfer. I was under the impression that there was some standard issue tech hubris happening about how we are so good at landing on the pad we no longer need legs. Just drop her right down into the fuel pipes.
Which, as my daughter might say, makes a cool story, bro.
Robin

 

[Grendal]

Not a surprise. The government would like to have a piece of the action and then they get to claim some credit when BFR is a success.

SpaceX expects government support for development of BFR launch system - SpaceNews.com

 

[ecarfan]

SpaceX expects government support for development of BFR launch system - SpaceNews.com

The closing paragraph of that article is of the most interest to me. Quote:
“She [Gwynne Shotwell] said later that she expected the BFR system be used for lunar landing missions, likely before missions to Mars that have been the driving goal of SpaceX founder Elon Musk. “It appears to be a thrust of the current administration to go to the moon first, and we’re hoping that thrust is to develop a permanent presence on the moon,” she said. “And then from there we’re headed to Mars.””
————————————————————————-

I am not clear on who the “we” are that she refers to in that last sentence. “We” as in ‘the USA”? “We” as in “SpaceX”? I favor the former. I do not believe that Elon is going to wait for manned NASA missions to the Moon on a BFR to be completed before sending manned missions to Mars. That would greatly delay his timetable for beginning the colonization of Mars.

 

[adiggs]

“I don’t have any updates on that,” she said, but added there was more interest in such a flight than she expected. “The most surprising thing about that is that there are as many people as there are who want to go do that, and can seemingly afford to do that.”

This is the quote I found most interesting, though not particularly surprising to me. It'd be lovely if SpaceX could use space tourists to further fill and expand the launch manifest on a profitable basis (and of course, there's no reason to send somebody on a space tourist trip around the moon if it isn't VERY profitable for SpaceX).

There may not be a lot of billionaires on the planet, but once you're talking about individuals, you're talking about enough people to represent a LOT of entries on a launch manifest. Especially when the baseline is <2 dozen is the busiest year ever and puts a company in position to hold 50%+ market share.

More flights = cheaper flights for everybody else = more accessible to more and more uses (including entertainment).

 

[Bobfitz1]

This is the quote I found most interesting, though not particularly surprising to me. It'd be lovely if SpaceX could use space tourists to further fill and expand the launch manifest on a profitable basis (and of course, there's no reason to send somebody on a space tourist trip around the moon if it isn't VERY profitable for SpaceX). There may not be a lot of billionaires on the planet, but once you're talking about individuals, you're talking about enough people to represent a LOT of entries on a launch manifest. Especially when the baseline is <2 dozen is the busiest year ever and puts a company in position to hold 50%+ market share. More flights = cheaper flights for everybody else = more accessible to more and more uses (including entertainment).

When the BFR/BFS goes operational, I predict Bigelow Aerospace, Richard Branson or some group of billionaires are going to set up and operate the first of many LEO hotels. Bigelow has been developing expandable space habitation modules for many years. Their most advanced module (BEAM) was launched by SpaceX to ISS in 2016 and presumably has been in operational testing there since.
Robert Bigelow has deep pockets and has spent $350M to date. Hotels in LEO are definitely part of Bigelow's plans and once BFS is available, the per head cost to deliver passengers to one will drop low enough to be affordable to mere millionaires. I'd speculate that he has designs for a larger expandable module that can serve as the backbone and connector for many B330 modules to create the first LEO hotel. Bigelow Aerospace - Who We Are

Bigelow isn't waiting for SpaceX for some early use of his B330 module. They have begun working with ULA to put one in low Lunar Orbit.
Whether ULA will have Vulcan built and tested by end of 2022 is a question mark. There is nothing to stop him from partnering with SpaceX to put one or a few modules in LEO and open a basic hotel for multi millionaires before then. Then follow that with a much larger one to be orbited and served by BFS. It's easy to see thousands reserving in advance to visit a larger hotel and stay there one or a few weeks.

From News on Bigelow website:
Las Vegas, NV and Centennial, Colo. (Oct. 17, 2017) – Bigelow Aerospace and United Launch Alliance (ULA) are working together to launch a B330 expandable module on ULA’s Vulcan launch vehicle. The launch would place a B330 outfitted module in Low Lunar Orbit by the end of 2022 to serve as a lunar depot.

 

[jkn]

Payload to GTO from Wikipedia:
Vulcan: 15,100 kg (33,200 lb)
Vulcan Heavy: 23,000 kg (50,000 lb)

Falcon Heavy: 26,700 kg (58,900 lb)
Falcon Heavy reusable: 8000 kg

Falcon 9 expendable: 8300 kg
Falcon 9 reusable: 5300 kg

I doubt 8000 kg is too small for reusable Falcon Heavy. Reusing side boosters should be rather easy. Central booster has more speed.

Does not look good for Vulcan.

Vulcan (rocket) - Wikipedia
Falcon Heavy - Wikipedia
Falcon 9 - Wikipedia

 

[Bobfitz1]

Payload to GTO from Wikipedia:
Vulcan: 15,100 kg (33,200 lb)
Vulcan Heavy: 23,000 kg (50,000 lb)

Falcon Heavy: 26,700 kg (58,900 lb)
Falcon Heavy reusable: 8000 kg
Falcon 9 expendable: 8300 kg
Falcon 9 reusable: 5300 kg
I doubt 8000 kg is too small for reusable Falcon Heavy. Reusing side boosters should be rather easy. Central booster has more speed.
Does not look good for Vulcan.

Agree 100% that things don't look promising for ULA Vulcan and Vulcan Heavy. Especially by the time it is really ready to use.
I'm pretty sure Mr. Bigalow will drop ULA like a hot rocket once SpaceX has launch vehicles that will do what he wants.

The Falcon Heavy reusability penalty you cite from Wikipedia didn't seem reasonable to me so I did some research using non Wikipedia sources. I found that the Falcon 9 (not sure if block 3 or 4) has a max GTO payload of 8,300 kg expendable. If booster is recovered that drops to 5,500 kg. That works out to recoverable F9 boosters having about 66% of the absolute max payload.

Extrapolating that to Falcon Heavy (taking % to only 50% to give some leeway) calcs to 13,377 kg for recoverable booster FH.
That uses SpaceX website spec for FH of 58,860 lb max payload to GTO. I think that is using pre block 5 boosters, so block 5 FH may be higher. An interesting fact from one of my sources is that Echo Star 23 was one of the last expendable launches on SpaceX manifest, since block 5 boosters will be able to deliver ES 23 size loads with booster recovery.

In practice once FH is in service, there won't be many loads big enough to require expending the boosters. Especially if block 5 boosters take its max payload specs higher than website now shows.