Recent Posts

Pages: [1] 2 3 ... 10 Next
Hmm..  With all this talk of Mahia wildlife and a rocket that's taking it's jolly-old-time going anyplace, I do wonder what a stowaway possum might do to the rocket's trajectory if not spotted prior to lift-off.

How about bird poo? Can the avionics compensate for that??
Chinese Launchers / Re: OneSpace Corporation
« Last post by Asteroza on Today at 04:15 AM »
There's nothing wrong with recycling military ICBM's that are near the end of their shelf life. Minotaur/Taurus is a western example, and the rocket that really kicked the smallsat revolution into high gear was Dnepr. Whether that is actually a sustainable model is open for debate, both from a remaining stock perspective if no new boosters are made, and new production for a booster that may have not been produced in a while.
The original ITS concept from 2016 showed 3 landing legs (to be symmetric with the 6 engines) with very large footprints. The 2017 BFR concept, on the other hand, seems to show very small and stubby landing legs. The version shown ...

... Are those landing legs sufficient enough?

My advice: don't take the 2017 views of BFS as gospel. Things will change considerably once the details are being worked out.

Note:  FWIW, SpaceX changed their image policy a bit between Sep 2016 and Sep 2017.

For ITS2016,  SpaceX released a substantial number of images with CCxSA licenses, and Wikimedia has them.  This was consistent with something they had started some time before that of releasing a subset of SpaceX media in a license format that would allow it to be used in the various-language Wikipedias across the globe.

For ITS2017, and since, SpaceX has released none of the BFR images with a license sufficient to allow the emergent license guardians of the Wikiverse to allow any of SpaceX images of BFR in.  It was months after the announcement, and only under US Fair Use guidelines, that a single image made from a small-size screen grab from Musk's talk on BFR was able to stick, and not get removed a few weeks later by the image license patrollers.  Note that Fair Use is allowed by Wiki-guidelines only in the English Wikipedia, not in Wikemedia, so exceptions for the other-language Wikipedias have to be made on a language-Wiki by language-Wiki basis, and not all accept US-law Fair Use limited image use.

Wikimedia has not a single image of a BFR.

This is perhaps only a small thing, since many space media (including NSF ) articles will persist; but it seems to indicate that SpaceX media people have added some hurdles to use of the early approximate-design/details-not-all-tied-down images.  That fact may be relevant.
Dunning-Kruger specifically applies to imcompetent, poor performers.  While that might apply to some here, saying it applies to all seems like an unsupported generalization.  Many of the posters here are quite successful in various technical fields.  I've re-bolded your quote differently, to emphasize that DK applies to poor performers:

For those of you that have not read any of the links/papers I've posted about the Dunning-Kruger effect (originally published in 1999), I'll copy the abstract of the 2008 replication and meta-analysis below.

People are typically overly optimistic when evaluating the quality of their performance on social and intellectual tasks. In particular, poor performers grossly overestimate their performances because their incompetence deprives them of the skills needed to recognize their deficits.  Five studies demonstrated that poor performers lack insight into their shortcomings even in real world settings and when given incentives to be accurate. An additional meta-analysis showed that it was lack of insight into their own errors (and not mistaken assessments of their peers) that led to overly optimistic estimates among poor performers. Along the way, these studies ruled out recent alternative accounts that have been proposed to explain why poor performers hold such positive impressions of their performance.
If you are going to quote Dunning-Kruger, you also need to quote the opposite Imposter Syndrome.  This is where people who are actually competent doubt their own ability.  It can be defined as 'a feeling of “phoniness in people who believe that they are not intelligent, capable or creative despite evidence of high achievement.”'  They ascribe their own success to luck, or people somehow overlooking their obvious flaws.

Neither of these is a new observation.  As Yeats said in 1919, "The best lack all conviction, while the worst are full of passionate intensity."

If future Mars craft converge with BFS on anything, the most likely will be in-orbit refueling.

Maybe not. If SpaceX can crack second stage recovery and reuse, a (big!) two stage booster might be able to throw the BFS or similar on a direct trajectory. This may be more efficient.

Refueling is more efficient than a big two stage booster as there's less dry mass wastage. Also, you can go a lot faster with refueling also due to the lower dry mass.

I was thinking more financially efficient - one launch (admittedly of a bigger booster) instead of multiple.

How it is more financially efficient to launch a much bigger booster once instead of a smaller booster several times?

Historically, refueling has only ever been considered as a way to get round a lack of performance. I can't think of any study that proposed it because it was cheaper. This was because larger boosters were inherently more efficient in terms of $/kg to orbit (as long as their payload capacity was substantially fully utilised). However, these studies were based on expendable launchers and reusability may change things.

The argument is presumably that a smaller booster flying more often is cheaper because fixed costs can be shared among a greater number of flights. But you also have a greater number of flights per mission - each mission is therefore bearing multiple shares of those fixed costs. Also, the large booster may be being used only once per mission, but it's still reusable and it's difficult to see why the total number of flights in its career would be less.

All in all, there's a number of factors to take into account when carrying out a financial calculation, many of which factors are unclear at this time. Which is why I said 'may be more (financially) efficient'! :)
SpaceX BFR - Earth to Deep Space / Re: Elon The Boring Company
« Last post by wannamoonbase on Today at 03:05 AM »
I did some quick math, that even if they somehow managed to tunnel a mile a day and assume that a reinforcing ring is 4 feet wide (I think they are currently about 3 feet) that would be 1320 complete rings a day, 55 per hour, almost 1 ring per minute.   

That very quickly paints a picture of extreme material handling both in and out of the tunnel. 

Just the stock pile yard of tunnel segments that would need to be cast and stored while they reach strength (21-28 days likely) would require a huge laydown area.


It seems to really increase tunneling speed you can't get away from the idea of needing at least 2 parallel tracks, even if small, you need a constant flow of materials in and out of the tunnel.

I thought they ultimately want to make the tunnel reinforcements the same way they want to turn the excess materials into bricks. I saw mentioned somewhere that those bricks can be compressed to 2-3 times the density of the base material.
That get's rid of a lot of logistics.

For a 14 Feet diameter tunnel that ends up 12 Feet after reinforcements, and 2 times the density for the reinforments compared to the base material, that's less than half the amount you have to transport outside compared to traditional concrete segment reinforcement. And you don't need those 2-way logistics either.

Concrete is not just 'stuff from the ground'.  The portland cement, aggregate and pre-bent reinforcing bars are carefully specified and better be of consistent quality.  I can't imagine they will ever cast segments in place.  It'd be nice though.

I remain suspect of the blocks shown in the info session last week.  It's true that at times you will be boring through suitable material but other times you'll be in totally unsuitable materials.  the blocks they showed looked too smooth, no aggregate or reinforcing.

It's true that you can add accelerators or spec a stronger mix, but those do adds costs.  At one point I was a certified concrete field tester and worked on several large concrete jobs with various mix designs.  There are plenty of ways to configure concrete designs, but there is no free lunch. 

For precast buildings or structures, they can benefit from being strong enough to move and place but aren't subjected to a full load until they have cured.  I don't know if tunnel segments are immediately under full load, but it would seem prudent to assume so.

My original point was that the faster they dig tunnels the more lay down area they will need.  (That would be an awesome problem to have.) 
Ultimately, all this depends on how elastic the market for launches is ... if it's inelastic, this whole thing is futile as numbers won't go up. Personally, I think it *will* become elastic, but right now is just as constrained by essentially custom-built payloads, lovingly handcrafted.

I suspect this is an unstated motivation behind the Starlink project. Those satellites will be mass produced and once that is up and running you can think about diversifying into other market segments.

Especially if DoD is interested in these LEO constellations


What if warfighters could install an antenna on their F-16s, much like homeowners do on their roofs, and establish a commercial internet connection, allowing them to send critical battlefield information rapidly to the rest of the force?

The U.S. Air Force Research Laboratory (AFRL) is about to find out.

The Air Force is finally catching on to a revolution in the commercial small satellite world. Feb. 22 SpaceX launched a Falcon 9 rocket carrying two experimental satellites from Vandenberg AFB, California,...
To explore the art of the possible, AFRL is planning to contract with at least one commercial internet provider for a set of antennas that can be mounted onto Air Force test aircraft, Beal says. The team will then fly the aircraft, a Beechcraft C-12J based at Holloman AFB, New Mexico, directly under the associated satellites and establish a communications path.

That's a lot of rocket sheep (and rocket cows). :D
Also, several rocket horses.
 All I could get from the locals was that launch day travel by non residents down the 30km goat track to the site was strongly discouraged by the authorities. A phrase that means many things depending on where you are.
I'm not sure RL would appreciate term goat track, considering how much money was spent upgrading it.

Hope you are enjoying your holiday.

But thats where the Rocket Goats are  ;)
Where does the first stage get more wear?  Launch or re-entry and landing?  If the latter is the case, there may come a time in a Block 5's career that it might be sold as an expendable rather than a re-furbish.  If it's a draw or the launch imparts more stress, then I don't think a customer would want to buy.  I doubt if we have enough knowledge to answer this question (yet)!
If their models and inspections show it can’t handle landing, it won’t get launched. That’s a failure waiting to happen. That’s my bet. I wouldn’t want to launch on a rocket they aren’t sure will survive landing because I’d be concerned it wouldn’t survive launch.
So what IS behind the Backup Parachutes door/
Main chute anchor points.  See the video capture at
Pages: [1] 2 3 ... 10 Next