New Mars Forums

All in all,  I think they may have fixed the leaks that caused engine bay fires during ascent,  and it would appear they have learned to start the flip early enough to compensate for an engine-out during the flip back upright and the touchdown burn.  They had to blow up three or four prototypes to learn those lessons!

But they still very clearly do not understand landing leg design!  They REALLY need to consult some engineers experienced at landing gear design for heavy vehicles,  and some other engineers experienced at foundation design for the soil bearing and penetration effects,  for making touchdowns not on a concrete pad or steel deck.  98+% of Mars and the moon is equivalent to a sand dune on Earth.  Including slopes and unevenness.  Not to mention rocks scattered all over the place,  up to the size of cars and houses.

What they have now on Starship resembles a real rough-field landing leg to about the same extent that that idiotic self-hammering "drill" on the Mars probe Insight bears to a real drill rig.  Most of you already know just how little I think of THAT design!  As far as I am concerned,  Starship's "landing legs" are just as idiotic a design,  if not more so.

They will need that issue addressed properly before they ever even approach low Earth orbit!  Did you not notice that one leg was about a meter from being off the pad and in the SOFT(!!!) mud?  Do they really have to blow more prototypes up to learn that lesson?  Really?

The video Spacenut provided the link for,  was full of talk about coming down evenly (or not) on all 6 legs at once.  In the real world,  that will just about NEVER happen,  no matter how precise and slowly the touchdown is made!  One leg will ALWAYS hit first,  then another "on the bounce",  and so on.  All 6 legs will experience very-highly magnified impact forces,  of highly-variable magnitude.  And relying on the crush of lunar regolith to absorb such impact energies (in the lunar lander version) is just plain nonsense!  Stupid is as stupid does!

One other thing:  I noticed they lost a tile.  They lost it experiencing cold,  and very modest wind scrubbing loads,  but no heating at all.  Entry with heating has way more thermal expansion (as well as VERY high wind scrubbing loads),  greatly raising the probability of losing a tile or tiles.  That WILL lead to a burn-through,  directly into a propellant tank full of vapor,  and perhaps some propellant liquids,  and depressurizing it to essentially vacuum conditions.  If not a tank,  then the cargo bay,  or the pressurized manned spaces.  Think about that!

I have to wonder how much they are depending upon tank pressurization for part of its structural strength.  Wind loads at way-hypersonic speeds,  even in the near-vacuum,  are quite high (near a ton per square foot or ten tons per square meter,  at a stagnation zone).  So the forces trying to crush and tear apart the structure are very high indeed!  Especially at near-broadside attitude (stated AOA is 60 degrees). 

If those forces were not high,  the vehicle would never decelerate.  But,  those high forces are EXACTLY why tumbling rocket stages break up on entry.  Note that I said "break up".  I did NOT say "burn"!  Skylab did NOT burn!  Neither did Cosmos 954!  Neither did shuttle Columbia!  Nor will the Chinese booster.

No more than they (Spacex) seem to know about landing gear,  I have rather low confidence in their ability to address issues they have never dealt with before,  like landing leg design for rough,  soft fields.  Or flying nearly broadside during entry.  No one has ever before flown a body broadside during entry,  much less simple supersonic flight well down into the atmosphere.  Their experiences with entry and landing Falcon cores will simply not apply to much of this:  those cores entered,  descended,  and landed rear-end-first,  end-on,  which is their strong direction.  MUCH DIFFERENT!

They (Spacex) have a very long row to hoe,  several of them actually,  before they can even realistically think about trying to fly this thing into orbit. I spent decades doing very similar flight vehicle development work,  including all sorts of flight tests.  I really do know something about this stuff.

GW

Not a firm number
https://www.cdc.gov/coronavirus/2019-nc … -large.jpg

old numbers

https://www.acsh.org/news/2020/06/23/co … race-14863

nearer to where we are
https://www.heritage.org/data-visualiza … hs-by-age/

True, water cannons were used for Mercury Redstone. But they work. It takes a lot of water to put out a fire. That means a hose or pipe of some sort. You want the suppression system to keep out of the way during launch. Of course Redstone didn't have a skirt, so everything was exposed. A water cannon had access to all of the rocket. But also realize putting out a fire is not just about separating fuel from oxygen, it's also about reducing temperature so the fire doesn't re-ignite. Hot metal from the fire could re-ignite the fire.

What started the fire? We all saw the fire start under the skirt. What burned? Considering this is a rocket, and heat involved with rocket engines, what inside the skirt was flammable? Landing will involve rocket flame being redirected by the concrete landing pad, so expect flame to be redirected up inside the skirt. So why was there something flammable in there? Also consider the rocket must vent methane after landing, any flame could ignite vented fuel. Looks like that's not what happened. We could hear noises that sounded like something burst. One vlogger said it sounded like COPV tanks bursting. If header tanks burst as a result of redirected flame from the concrete landing pad, then they have a design flaw.

By the way, you don't need a legged robot. If you want a robot of some sort, then a wheeled drone dragging a fire house could drive under the skirt and aim the nozzle. Of course the pressurized fire hose doesn't cause the drone to flop around like a rag doll, so that's an issue. I doubt a little CO2 bottle fire extinguisher would do much for a burst methane header tank.

Louis, GW (and others); thankyou for the support.  She has the MRI tomorrow.  My wife has long suspected that she suffers from an autoimmune condition.  It may be that the vaccine triggered this somehow.  We will have to wait for the results and diagnosis.

My own thoughts on the risk presented by coronavirus (and I am happy to be be proven wrong if someone can show me the statistics) is that the risk is real but quite small compared to other risks that we face in life.  The average age of death (in the UK) from coronavirus is 82 years of age.  I don't know what it is in the US, but I doubt that it is much different.  The response to the virus so far, appears to me at least to be grossly disproportionate to the real level of risk.  We will be burdened with the debt resulting from lockouts and other economically ruinous restrictions for decades to come.  Was it worth it?  There are sound reasons for doubting that it was.
https://www.dailymail.co.uk/debate/arti … RFORD.html

It is suspicious in my mind, that governments did not attempt to substantiate lockdowns and other restrictions with cost-benefit analysis.  Here's the bottom line: The coronavirus is a risk to public health and is one of many such risks.  Because it is a new virus without established immunity, it has a higher mortality rate than we are accustomed to from annual influenza cases.  That has gotten a lot of people scared.  And scared people aren't that interested in rational analysis or other people's rights.  There are things that can be done to reduce the risk, but they all come at a cost, both financial and in terms of loss of freedom for people having to tolerate enforced changes to their way of life and coercion into vaccination, which is not free from risk.

If you want to impose solutions on other people to reduce societal risk from this disease, then it is not unreasonable that you face a burden of proof in demonstrating that the reduction in total risk justifies whatever costs you are imposing on the people.  And the burden of proof absolutely should be on those that propose the enforced use of masks, restrictions on freedom of movement and association and of course vaccination, because these are deviations to normal life and they impose costs on people, some relatively small, others far less so.  It is simple really and it should be common sense: you need to demonstrate that what you are proposing is proportionate.  This is where cost-benefit analysis comes in.  It takes the emotion out of these decisions and gives you an answer based on arithmetic.  We use it for all sorts of complex decisions where we need to balance residual risks against the costs incurred by further risk reduction.

This is exactly the sort of cool headed approach that should be applied right now, before we trample over people's right to choose in order to mitigate a risk which may be much bigger in people's minds than it is in reality.  It may be that the use of masks, lockdown and vaccination, are fully justified by the results of a cost-benefit analysis.  Maybe not.  But without an evidence based justification, no one should be imposing the use of masks or vaccines on other people.

"No one aged 40 or below is at any risk from Covid if they are in they are neither obese nor with co-morbidities, so there is no reason for them to be advised to take the vaccine."

If that were true,  then why are the numbers of young adults and children that are sick with Covid-19 increasing in the US,  while the number of oldsters sickened is decreasing?  Them's the real numbers,  Louis! 

As for the difference between an "anti-vaxxer" and a "vaccine skeptic",  from my point of view,  there is no difference.  The outcome is the same:  they do not want the shot,  which makes them a contagion risk that threatens the rest of us.  If I were to threaten someone with a gun, I would be jailed.  There should be serious consequences for threatening with contagion.  Nuances of their reasons why they don't want the shot,  make no difference to that contagion threat outcome. 

As for the risks of the disease vs the vaccine,  I can only speak to the Pfizer,  Moderna,  and J&J shots.  There seem to be somewhere around 10 cases of bad blood clots with J&J,  and not very much other than 24-48 hours of feeling poor with the others.  That's out of around 100 million vaccinated so far in the US.  So the odds of a bad reaction are somewhere in the vicinity of 10/10^8 ~ 1/ten million.   Those are pretty good odds.  Compare that to the odds of a bad outcome from birth control pills: around 1/1000,  and people gladly accept those,  all the time. 

GW

Spacenut:

Makes me wonder if the post-landing fires are methane leaks from cracked engine bells (from slamming together).  The methane fuel is the regenerative coolant.  I guess it could be just the methane vapor vent catching fire,  though. 

Did you notice the landing leg about 1 m from the edge of the pad?  If it and 1 other had hit the soft dirt,  they'd sink in,  and topple the vehicle (a guaranteed explosion).  Lesson:  they nearly missed the hard pad,  located in an otherwise soft sea of mud.  That sort of landing leg is experimental-only.  They will soon need a real soft-dirt capability,  and will likely blow up at least a couple more,  before they finally learn that lesson. 

They do need better,  more-reliable camera coverage.  And (flight test 101) you do NOT do this stuff obscured by clouds!  You need ground-based photography,  too.  They obviously have NOT learned that lesson yet,  either.  Camera visuals really are your best diagnostic tool for problems,  especially the unexpected ones.

If this was the Boeing or Lockheed of half a century ago,  I'd say in 3 years they might reach operational orbital flight (if the Boeing or Lockheed of today,  NEVER!).  Spacex could probably beat that 3 years,  but not until they start learning flight test lessons faster. 

GW