View Full Version : Landing on Mars

22nd Nov 2018, 11:19
As there is another lander about to hopefully have a successful landing on the red planet.

It has been stated that it needs to decelerate from 6 X the speed of a rifle bullet to walking pace in just under 6 minutes.
With this in mind. what are the G forces involved, and would a human withstand said forces?

Sorry no Brexit involved :D


22nd Nov 2018, 11:30
I haven't calculated the effects on the human body, but I hope the mission will be successful. This is the first mission (other than the unsuccessful Beagle mission) that has the equipment to see if there was life on Mars - or even if it still exists.

22nd Nov 2018, 11:35
Mars Rover Curiosity by Rob manning goes into a lot of detail on the issues. Which aren't just the deceleration forces lots of lateral as well

rifle bullet 1200 m/s x 6 is 7200 m/s in 360 seconds which is 20 m/s/s aka only 2.1 G average.

Peak G alot higher and short duration. He seemed to think they could get a human down safely.

Its a good book written by the chief engineer of the project.

22nd Nov 2018, 12:28
The main problem isn’t the deceleration, it’s trying to achieve the deceleration in such a th8n atmosphere. Hence the use of inflatable heat shields to increase the surface area.

22nd Nov 2018, 13:21
rifle bullet 1200 m/s x 6 is 7200 m/s in 360 seconds which is 20 m/s/s aka only 2.1 G average.
Peak G alot higher and short duration. He seemed to think they could get a human down safely.InSight speed will be around 5.5km/s and peak deacceleration will be 7.4g, occurring 4 minutes before landing.

22nd Nov 2018, 13:39
During the decent, the max G-force value depends on the lander (or orbiter) L/D (lift-to-drag ratio). That is why Space Shuttle and Buran could provide comfortable G-profile for the crew (around 2g). Soyuz capsule (having L/D less than 1) makes it with 4+g nominally and with a so-called ballistic descent (rotation around X-axis and zero L/D) the crew faces up to 9g.

If the future manned Mars lander will be fully ballistic, it would also reach 8-9 g, as far as I remember.

Those interested may take a look at the following presentation concerning the ExoMars mission with many plots and data:

22nd Nov 2018, 14:02
Thanks for the replies
Although the g forces aren't dramatically high, even the peaks. 7.4g
They are high enough after 9 plus months of weightlessness to be dammed uncomfortable I should imagine


22nd Nov 2018, 14:28

Please note that g is not a force.

22nd Nov 2018, 14:51

Please note that g is not a force.


only a spot

hat, coat, door

22nd Nov 2018, 15:51
As G is a measure of gravity and there will be very little in space, will there any major 'force' to experience?

22nd Nov 2018, 17:47
G is an acceleration. Which can be linked to energy which the body can deal with. The limits of which have been established by German car makers during the second world war using concentration camp prisoners with what the human body can take.

22nd Nov 2018, 17:57
G is an acceleration..


We can all play this game.. G is the universal gravitational constant......a constant of proportionality, not an acceleration.


22nd Nov 2018, 18:20
well if your a physicist like my Phd dad. I am just a thick mech eng trained pilot. I suppose if your designing for American cabin crew and punters with standard punter and crew weights G gravitation constant maybe an issue to the rest of us G in social media or little g is 9.81 m/s/s when we are actually doing real shite is good enough.

But as my bosses want fuel density recorded to 3 decimal places.... the bowser has 2% tolerance on out put and the fuel gauges have 5% tolerance under EASA maint regs…. I really can't be f'd arguing the toss.

22nd Nov 2018, 18:42
And BTW big G is also a energy constant..... in fact everything in eng is energy. Those that have a clue what they are doing quickly realise engineering is just making everything to work out to zero...…. it doesn't matter what flavour you are it still the same bullpoo.

Apart from civils of course...…. for them its how many animals they can have sex with and still sign the job off. And how many inverted slop tests they can perform in one day. The hard core civils of course its only tonnage of shite that counts of course. And to be honest those "shite" engineers are the only civils that seem to have a clue what they are doing.

22nd Nov 2018, 19:00
Those that have a clue what they are doing quickly realise engineering is just making everything to work out to zero...….


22nd Nov 2018, 19:11
that's not really what I was on about :D

Its more engineering accountancy of energy. If it doesn't equal zero your missing some which may result in a bang or a twang.

Although we were taught quantum physics my point that if we ever get something going fast enough for quantum to apply we have surely screwed up got me pointed towards FEA and high energy structural stuff, the paint brush euro Disney engineering I was never involved with thankfully. I fact did once get hired when announcing that I considered anything under a M20 bolt as macro engineer and really didn't understand why any one would spek less if there was room for them to fit. I had had a few beers though.

22nd Nov 2018, 20:01
well if your a physicist like my Phd dad.Seeing as this thread has gone down the silly pedantry route: The D is capitalised in PhD.:ok:

22nd Nov 2018, 20:46
Actually his cert has a small d I really don't have a clue why..... his was all to do with radio nuclides and dispersion through water from the Russians dumping cores in the water.

My sisters PhD cert has a large D but hers is some Biology shite to do with shite eating bacteria in sewage farms.

Myself I didn't write up due to it being really not cost effective as I wasn't interested in going academic like the rest of them in the family. But my stuff was critical cracking and stress relief using natural frequency of residual stress relief of pressure vessels. Walked away but still being quoted due to the "numbers" being used in ASME codes.

I might add out of 4 family members I am the only one without a PhD,as a pilot I out earn all of them by some 40k euro a year and that's with all their salaries combined. Mum has a PhD as well in some education bollocks.

22nd Nov 2018, 21:18
Dad accounts for 50% of the combined incomes mainly due to being a RPA, sister is some lab water quality bollocks for a water board manager , and mother is a senior exam type for science and a principle. Me I pass the check's and medicals and drink tea...……. but I do have to get up at 4am a few times a month....

Mr Optimistic
23rd Nov 2018, 09:57
A Lockheed Martin lander is supposed to plonk down on Monday. Focus is geology and subsurface stuff.

23rd Nov 2018, 14:02
That's the subject of this thread :)
Worth pointing out that Lockheed Martin are the contractor for the lander itself, but most of the instruments onboard are European (mainly through CNES and DLR), including one (SEIS) with strong connections to the UK (Imperial and Oxford Universities). LM will get much of the credit for the landing, if it works, but the mission itself is truly international.

Mr Optimistic
23rd Nov 2018, 14:28
Ah, should pay more attention. Couple of cubes two.

Loose rivets
24th Nov 2018, 00:25
As mentioned, G is usually used as the Gravitational constant. g for acceleration and the associated inertia. The word, force, is commonly used - but that is true for gravity, which is better described as a pseudo force.

Now, if you want to be truly amazed, read up on Col. (Flight surgeon) John Stapp. One report imagined, that can't be un-imagined, is 'His eyes were engorged with blood.'Pascual Jordan (https://en.wikipedia.org/wiki/Pascual_Jordan) first suggested that since the positive energy of a star's mass and the negative energy of its gravitational field together may have zero total energy, conservation of energy would not prevent a star being created by a quantum transition of the vacuum. George Gamow (https://en.wikipedia.org/wiki/George_Gamow) recounted putting this idea to Albert Einstein (https://en.wikipedia.org/wiki/Albert_Einstein): "Einstein stopped in his tracks and, since we were crossing a street, several cars had to stop to avoid running us down".[3] (https://en.wikipedia.org/wiki/Zero-energy_universe#cite_note-3)
That story of Einstein always gives me the image of the now ageing professor half way across a road - in Princton IIRC. It really is an astonishing concept and the notion of the Singularity sits well in a pre-vacuum reality where you need to build a universe without paying for bricks.

24th Nov 2018, 06:43
Some considerations concerning future (and so long awaited) manned missions to Mars.

The peak acceleration during the descent phase could be reduced to 30-40 m/s**2 due to a proper aerodynamic form of the landing module. This force is similar to what Soyuz crews are experiencing. Uncomfortable, but quite survivable and no danger to health even after 6-12 months in weightlessness as already proved by dozens of Russian cosmonauts and many US and other nations astronauts since late 70's when such expeditions started. The record was set in '94-'95 onboard the Mir station - 437 days in space that is quite comparable to the round trip to Mars.

However, the main problems will come later, immdediately after the landing. Soyuz crews usually need assistance of the rescue team to get out of the capsule after landing. Assume the designers could make the exit from the Mars lander much easier, but the crew members can hardly walk and cannot do any work for a few days. Of course the Mars gravity is just 38% of the Earth's but yet no one knows how much would it ease the human's activity after landing.

An ideal situation would imply that after the landing the crew would make an easy transfer to a habitat that is already deployed and ready to provide comfortable conditions for accommodation during the first week as minimum. I.e. no need to carry, install, test etc. anything. Hospital or profilactorium-like activities only. This means that before the crew is sent to Mars the habitat infrastructure should be built and tested.

Transportation from the lander to habitat is another critical issue. A rover is needed, absolutely. And unlike the Moon landing, bringing a rover together with the crew lander is not feasible. It should be ready in advance and be part of the habitat infrastructure. It should be able to move autonomously to the landing point (through a not well-known terrain), pick up the crew and bring them to the habitat.

With all that said, we will first see many (10+ IMHO) unmanned missions to Mars to prepare a site for the crew.

26th Nov 2018, 20:01
It has landed and apparently - still serviceable.
Pics should be forthcoming soon.

Juliet Sierra Papa
26th Nov 2018, 20:04
Awesome job well done so far, first pics returned.

clark y
26th Nov 2018, 20:06
Was just watching it live. It has even sent back first image.

It was interesting reading and watching the feed as the actual event had happened a few minutes earlier.

26th Nov 2018, 20:27
Jet Morgan and crew managed it in 1971.
Listen again! (https://www.oldtimeradiodownloads.com/sci-fi/journey-into-space/2)

26th Nov 2018, 22:28
For all of our flaws and foibles, we sure can land functional spacecraft on other planets. (And are grateful for assistance rendered from our fellow humans - their countries do not matter!)

Yes! I am certainly proud to be an American! Moreso to be a member of a species who takes the first small steps to find our origins and to discover where we shall journey not so long from now. We muster courage and curiosity together...

Well done us! :D

- Ed