I for one, hope it works as planned. Carbon fiber will make it lighter.
As mentioned SpaceX has landing covered, and engine reuse covered, and very well made engines.
Solar power for long duration missions of course. They still have to master bringing the whole ship back from space, and land. I think this will be done many times before allowing people to fly.
This is inaccurate.Methalox is BETTER for an VTOL SSTO than LH2. It's denser and permits much better TWR.And one-use SSTO is easy. Falcon 9 boosters/FH side boosters can already do it, with aluminum structures and gas-generator low pressure engines.
The SSME was designed in the 1970s. Later blocks had updates for better reusability. Merlin is reusable without rebuilding. Raptor will be built to the same goals. And FFSC methalox is easier on the turbines than FRSC hydrolox.
This is the major outstanding question for BFS. PICA-X is certainly up to the reentry task, but will it last many flights? And how durable is it on the ground?
Fly lots of flights, obviously. BFR is designed for turnaround and reflight in hours. It could in principle fly more in 3 months than the Shuttle did in 30 years.
Shuttle was limited by power from the fuel cells and reaction control hydrazine, neither of which could be replenished in space.
BFS will use solar panels for power (unlimited endurance) and boiloff from the main tanks for RCS (unlimited, with orbital refueling).
...1. SSTO
2. Engine reuse.
3. Thermal protection system:
4. Safety.
5. Remain in space time
The hubris around BFR is a bit like that around the shuttle in the 1970s.
Hopefully SpaceX can overcome these issues and launch BFR/BFS around the same time as SLS They can prove me wrong like they proved most people wrong with Falcon 9. But how?
And of course, even if, like the shuttle, BFR/BFS ends up 10 times the target price, it's still competitive with every launch system apart from Falcon 9 Block 5 (and New Glenn and Skylon).
Quote from: spacenut on 05/15/2018 12:47 pmAs mentioned SpaceX has landing covered, and engine reuse covered, and very well made engines. For the booster stage.Remember they want to land the US on a fully loaded booster stage. That's never been done anywhere ever.
Remember they want to land the US on a fully loaded booster stage. That's never been done anywhere ever.
*snip*1. SpaceX claim that their BFS (without booster) will be able to make it to orbit and back with a tiny payload. This is an extraordinary claim as SSTO has been a dream for many decades, and often regarded as unachievable. *snip*
Quote from: alexterrell on 05/15/2018 07:49 am*snip*1. SpaceX claim that their BFS (without booster) will be able to make it to orbit and back with a tiny payload. This is an extraordinary claim as SSTO has been a dream for many decades, and often regarded as unachievable. *snip*Just a technical point. There have been several rocket first stages capable of doing SSTO - as early as the 1960s, with the Titan II. I've heard the Atlas V booster could do so as well, as could the F9 first stage. The issue is useful payload, which is small to non-existent. The SSTO "dream" is something like the VentureStar, or Skylon - capable of taking a payload to orbit, but also returning again, for full reuse of the LV, which reduces launch costs. Of course, If you can do that with a TSTO (two stage to orbit), it's actually more efficient because you're not cutting into your payload capacity as much by flying the entire thing into orbit. The Shuttle had a similar issue, as a rocket system it had an enormous payload capacity, but the Shuttle took up so much of it.
Good points - if the payload drops to 50 tons, the cost per kg triples.
I fail to see how the expressed skepticism is helpful and for whom it is helpful. This topic seems like a re-phrasing of risk assessment topics discussed previously.Anyhow, going with the topic given how BFS/BFR is all about engineering and no use of unobtanium, I see the risks as or I'm most skeptical/concerned about...1. Funding BFR/BFSWill ongoing NASA contracts, launch revenue and external private investment provide R&D cash sufficient to meet aspirational schedules?I say likely not quite enough, such that development will be cash constrained. Not a real "Problem" except resultant schedule delays frustrate us amazing peoples & girls.2. RUD(s)Can't afford RUD(s) as they pole huge holes in revenue streams. Related to issue #1. I expect something(s) to go awry between now & 2022 aspirational causing delays. RUDs are worse now with higher #s of employees to pay.3. Generic re-use without major refurb (affects cost/flight)Biggest risk here in my opinion is not Raptor engines but TPS. How many re-entries before ablative systems like PICA-X+ need something substantive done? I have no idea. Maybe they're looking at alternative approaches. Technical risk higher with approaches at lower TRLs.Regarding long term Mars plans beyond one or two oppositions I'm back to funding issues again. If the Skynet, I mean StarLink, program doesn't produce many billions of revenue, ongoing Mars missions face financial starvation.As a financial aside, i'd like Musk to sell Tesla to say Apple, and then focus on SoaceX and have liquid billions to self fund SpaceX.
Announcing crazy, ‘aspirational’, goals is standard operating procedure for Elon, but SpaceX has shown that they can execute with Falcon 9.I think it’s reasonable to be skeptical of any hard numbers right now (when BFS will fly, how much payload it will carry, how much it will cost, etc) but to be confident that the overall vision/concept will be eventually achieved in some way or another, and that is pretty dang exciting!
An academic reactor or reactor plant almost always has the following basic characteristics: (1) It is simple. (2) It is small. (3) It is cheap. (4) It is light. (5) It can be built very quickly. (6) It is very flexible in purpose. (7) Very little development will be required. It will use off-the-shelf components. (8 ) The reactor is in the study phase. It is not being built now.On the other hand a practical reactor can be distinguished by the following characteristics: (1) It is being built now. (2) It is behind schedule. (3) It requires an immense amount of development on apparently trivial items. (4) It is very expensive. (5) It takes a long time to build because of its engineering development problems. (6) It is large. (7) It is heavy. (8 ) It is complicated.
Quote from: philw1776 on 05/15/2018 04:09 pmI fail to see how the expressed skepticism is helpful and for whom it is helpful. This topic seems like a re-phrasing of risk assessment topics discussed previously.Anyhow, going with the topic given how BFS/BFR is all about engineering and no use of unobtanium, I see the risks as or I'm most skeptical/concerned about...1. Funding BFR/BFSWill ongoing NASA contracts, launch revenue and external private investment provide R&D cash sufficient to meet aspirational schedules?I say likely not quite enough, such that development will be cash constrained. Not a real "Problem" except resultant schedule delays frustrate us amazing peoples & girls.2. RUD(s)Can't afford RUD(s) as they poKe huge holes in revenue streams. Related to issue #1. I expect something(s) to go awry between now & 2022 aspirational causing delays. RUDs are worse now with higher #s of employees to pay.3. Generic re-use without major refurb (affects cost/flight)Biggest risk here in my opinion is not Raptor engines but TPS. How many re-entries before ablative systems like PICA-X+ need something substantive done? I have no idea. Maybe they're looking at alternative approaches. Technical risk higher with approaches at lower TRLs.Regarding long term Mars plans beyond one or two oppositions I'm back to funding issues again. If the Skynet, I mean StarLink, program doesn't produce many billions of revenue, ongoing Mars missions face financial starvation.As a financial aside, i'd like Musk to sell Tesla to say Apple, and then focus on SoaceX and have liquid billions to self fund SpaceX.1. Funding prediction: SpaceX will have the means to develop and build BFR+BFS, but not the means (or full ability) to outfit them for crewed Mars expeditions. For this they'll need to draw on the expertise and funds of other entities.2. RUDs are to be expected in the development of any new vehicle, especially one this ambitious. Are you saying they can't afford any RUDs, ever, or only once the vehicle becomes operational? If the latter, the question shifts to a ratio of accidents amidst a given flight campaign. Honestly, if you're searching for something along these lines to center concern upon, a loss of crew specifically seems far more likely to impact and delay the program.3. Good point, and agree that it's a risk, but there is nuance. We have three TPS concerns: booster, tanker, and spaceship. SpaceX must obtain reuse with minimal refurb for the first two only, as they'll both fly an order of magnitude more than the BFS. SpaceX have and will continue to prove out booster TPS with Falcon and Block 5. Tanker will be tricker, but it's only returning from LEO and, again, SpaceX will be learning from its Falcon US return+reuse efforts.
I fail to see how the expressed skepticism is helpful and for whom it is helpful. This topic seems like a re-phrasing of risk assessment topics discussed previously.Anyhow, going with the topic given how BFS/BFR is all about engineering and no use of unobtanium, I see the risks as or I'm most skeptical/concerned about...1. Funding BFR/BFSWill ongoing NASA contracts, launch revenue and external private investment provide R&D cash sufficient to meet aspirational schedules?I say likely not quite enough, such that development will be cash constrained. Not a real "Problem" except resultant schedule delays frustrate us amazing peoples & girls.2. RUD(s)Can't afford RUD(s) as they poKe huge holes in revenue streams. Related to issue #1. I expect something(s) to go awry between now & 2022 aspirational causing delays. RUDs are worse now with higher #s of employees to pay.3. Generic re-use without major refurb (affects cost/flight)Biggest risk here in my opinion is not Raptor engines but TPS. How many re-entries before ablative systems like PICA-X+ need something substantive done? I have no idea. Maybe they're looking at alternative approaches. Technical risk higher with approaches at lower TRLs.Regarding long term Mars plans beyond one or two oppositions I'm back to funding issues again. If the Skynet, I mean StarLink, program doesn't produce many billions of revenue, ongoing Mars missions face financial starvation.As a financial aside, i'd like Musk to sell Tesla to say Apple, and then focus on SoaceX and have liquid billions to self fund SpaceX.
First off, I'm a fan of SpaceX....
The hubris around BFR ...
Quote from: alexterrell on 05/15/2018 07:49 amFirst off, I'm a fan of SpaceX....QuoteThe hubris around BFR ...(firmly wearing my fan hat)Almost stopped reading when I saw the first quoted part, as usually people who start posts saying they are a fan of Z ... aren't fans of ZBut I stuck it out till I saw the second quoted part. Really? Fan me has now dismissed the opening post as completely not value added.(mod hat) How is this different than umpteen prior threads? Also, looks like all the objections have been addressed, no?
I'm probably the most critical guy on Elon's nonsense who still claims the title of huge fan. In a way, I'm like those people who write to serial killers in prison My opinion on BFR is: wow! I wouldn't design anything like it. I'm amazed that it's actually being built (and yes, it is!) and I simply can't wait to see it flying (and I think it will!)Will it hit all the targets that Elon has suggested it will? No way. I feel perfectly safe making that prediction - it's Elon's way to overpromise and underdeliver, usually with a schedule that's massively different to what he claims. The fact that Elon has already downgraded his original claims (twice?) is evidence, to me, that he'll do it again.Still, a fully reusable rocket doesn't exist yet. The idea that one* will soon exist is going to change everything, even if only 50% of Elon's aspirations come to fruition.* Two? Yes, SpaceX are experimenting with recovering the upper stage of the Falcon family and may actually reuse it too. Amazing!
I'd say possibly 2 with Blue Origin's New Glenn.I don't expect SpaceX to do 2nd stage recovery & re-use. It's an engineering study project to learn.
Quote from: philw1776 on 05/15/2018 11:41 pmI'd say possibly 2 with Blue Origin's New Glenn.I don't expect SpaceX to do 2nd stage recovery & re-use. It's an engineering study project to learn.New Glenn isn't even intended to be fully reusable... so that seems unlikely.It's interesting for some projects Elon promises the moon (or Mars ), but for other projects they sandbag.