-
#160
by
HarryM
on 06 Aug, 2009 20:13
-
One of the big questions is if the transit to Mars is in microgravity, how hard will it be for the crew to adapt quickly to Mars grav once on the surface and start to work. You wouldn't want them just sitting in the descent capsule trying to adapt for several days. One way to test might be a long (6 month) duration stay at ISS followed by a trip to the Moon as an analogue, though of course gravity is less, would probably be useful.
-
#161
by
Archibald
on 16 Sep, 2009 17:10
-
Yes, you can combine different propulsion systems.
LEO to higher rendezvous point (high circular or elliptical orbit, or a lagrange point) can be done chemically or by high-isp.
From there through TMI can likewise be done in a variety of ways- or combined with the first manoeuvre.
Arrival at Mars can be by direct entry and landing, or aerocapture, or a variety of propulsive methods.
Ascent from Mars surface obviously needs to be chemical propulsion, IMO it is virtually essential that this uses ISRU though, for a number of reasons.
From Mars orbit through TEI can be done chemically, either with Earth-sourced or Mars-sourced propellants, or by high-isp propulsion.
On arrival at Earth the options are similar to Mars arrival- direct entry, aerocapture, or chemical or high-isp propulsion.
FWIW, the original 'Mars Direct' scheme seems to be out of favour these days. It forces the return habitat vehicle to be far too small- you cannot live in an Orion for six months. More up to date plans involve rendezvous in Mars orbit with a return hab. This negates some of the advantages of using ISRU for the TEI burn because leaving it in Mars orbit becomes quite attractive.
Bringing the thread back to life...
I've dugged further electric/ chemical combinations. Found this
http://adsabs.harvard.edu/abs/2005AcAau..57..829MThis bring a question.
Electric propulsion trajectories are complex spirals (because thrust is too low to use the Oberth effect).
High-thrust trajectories are Hohmans.
Is there a way of combining the two into a electric-chemical trajectory ? For example, between Earth and MArs ?
-
#162
by
mmeijeri
on 16 Sep, 2009 17:33
-
SEP cannot do a Hohmann transfer because thrust is miniscule, but then again it doesn't have to because Isp is so high. The higher delta-v is more than compensated for by the higher Isp, it's the ratio delta-v/Isp that counts.
-
#163
by
Hop_David
on 16 Sep, 2009 21:48
-
Yes, you can combine different propulsion systems.
LEO to higher rendezvous point (high circular or elliptical orbit, or a lagrange point) can be done chemically or by high-isp.
From there through TMI can likewise be done in a variety of ways- or combined with the first manoeuvre.
Arrival at Mars can be by direct entry and landing, or aerocapture, or a variety of propulsive methods.
Ascent from Mars surface obviously needs to be chemical propulsion, IMO it is virtually essential that this uses ISRU though, for a number of reasons.
From Mars orbit through TEI can be done chemically, either with Earth-sourced or Mars-sourced propellants, or by high-isp propulsion.
On arrival at Earth the options are similar to Mars arrival- direct entry, aerocapture, or chemical or high-isp propulsion.
FWIW, the original 'Mars Direct' scheme seems to be out of favour these days. It forces the return habitat vehicle to be far too small- you cannot live in an Orion for six months. More up to date plans involve rendezvous in Mars orbit with a return hab. This negates some of the advantages of using ISRU for the TEI burn because leaving it in Mars orbit becomes quite attractive.
Bringing the thread back to life...
I've dugged further electric/ chemical combinations. Found this
http://adsabs.harvard.edu/abs/2005AcAau..57..829M
This bring a question.
Electric propulsion trajectories are complex spirals (because thrust is too low to use the Oberth effect).
High-thrust trajectories are Hohmans.
Is there a way of combining the two into a electric-chemical trajectory ? For example, between Earth and MArs ?
I can think of two ways to send an ion engine on a Hohmann trip: Tethers and railguns.
However exiting the Hohmann to achieve a capture orbit about the destination planet might be a problem with ion engines. I think it would be more doable for Jupiter, Saturn and beyond as the ship would hang around the destination for awhile after reaching apohelion.
-
#164
by
pmislov
on 20 Sep, 2009 14:59
-
hi people i am new in the forum and i registered because i love space and investigation for life and i was watching history chanel and all the misions to mars and they mentioned the mount olimpo and i wanted to know if there are any plans or idea coming or already done to send a ship to investigate what is inside like to send a shuttle inside the crater to see what is inside it and see if it can go to the nuk of the planet it would be 2 achievements
investigate mars underground and if lucky see for first time a planets nuk directly maybe at least reach some lava or any sign material inside it to take it and send it back to earth and investigate it and if mount olimpos crater is covered maybe the ship can have a drill or throw a bomb and take of that piece of rock covering it.
other idea i have is to throw a shuttle on its north pole on the white ``ice´´ and a hughe explosion blow its cover and lets the shuttle go in the ice as deep as posible
and the question is...
have they done any of those yet or is it planed to be done???
-
#165
by
Jim
on 20 Sep, 2009 15:20
-
no and no
-
#166
by
pmislov
on 20 Sep, 2009 15:22
-
is it posible to do any of the above with todays tech??
-
#167
by
Jim
on 20 Sep, 2009 15:22
-
is it posible to do any of the above with todays tech??
Nuking or bombing is a bad idea
-
#168
by
pmislov
on 20 Sep, 2009 15:27
-
one of my best friends father is president of a club of astronomy and he told me is posible i just called him
but to go inside the mount olimpo or the ice inside the poles can be done with todays tech and why havnt they done it??
p.s. my friends father said they did that to titan in saturn to go inside the ice
-
#169
by
AlexInOklahoma
on 20 Sep, 2009 16:40
-
Anything is possible (for the most part) if given enough money. There are plenty of companies that will do as you ask if you or friend's father want to pay for it ;-)
Ask your friend's Dad to give you the references of the Titan thing, please and review what it took to get there, etc (if such did occur - I am not sure of it myself) Returning samples from Mars, or any other planetary body, is currently in 'debate' stage as it is difficult to return things to Earth for a number of technical reasons (as well as $$).
I highly suggest 'researching' what you are asking about as you show a very low level of knowledge about such (not an insult, I promise you). Most of what you ask is all within this site and is very well explained as to possible or not, etc. Welcome to the site - and be glad that Jim was as nice as he was, LOL. You will find this site VERY educational as well as accessible, but you *will* need to check stuff out at least minimally before asking and then depending upon things you hear from friends that are not 'in the business' ;-) Your answers will likely come from folks that do such things professionally and know *exactly* what they are talking about - be wary about debating them if you have not done your homework (!!!!!!!!!)
Do a bit of googling about Mars and the active 'studies' happening..bet you will be surprised how much is actually happening right now and in the near future. Possibly some of what interests you is available already or will be soon (?) Heck, there is even an image of a 'lander' landing under parachute from an overhead satellite. Not real science in that image, but might help show just how well various things are being covered, IMO.
Again, welcome to NSF - the real Spaceflight site (at least as far as I am concerned),
Alex
-
#170
by
pmislov
on 20 Sep, 2009 18:31
-
ty!!!!
the next question will be how long it would take a suicide satelite or ship or wut ever to trhow it into a queasar or dark whole or a a worm tunel
btw sos for my english i am learning and i am a 13 yr old latin very interested on this =)
love dark wholes (FROM SPACE XD) and ty again
-
#171
by
Michael Bloxham
on 16 Oct, 2010 17:37
-
Using current technology limits, the entry vehicle cannot have a 'density' (mass/heatshield area) of more than about 150kg/m2, of else it hits the surface before it has slowed enough to deploy a parachute. So for something using a 10m PLF this would mean an entry mass of less than 12t.
Which is completely useable, if you use a little creativity ;-) (See the link in my sig.)
Hey guys, I was just looking for some good back-of-the-envelope figures to help me with my mental models.
1. So far I have been assuming 1/3.5 ratio of IMLEO to TMI (not including the mass of the spent TMI stage). For ~200 day trajectories at the reasonably opportunistic time periods, is this a reasonable figure?
2. Related to that, I have been trying to find the TMI payload for a J246. I tried to use the search but to no avail. Does anybody know it?
3. Also, what is a reasonable PMF (propellant mass fraction for those that are visiting Q&A) for a methane/LOX powered ascent vehicle to low-mars orbit, and also (3b) to an elliptical orbit suitable for rendezvous with an awaiting ERV?
4. What is a suitable PMF for a methane/LOX powered ERV for a nominal ~200 day return trajectory, from both a low-mars orbit and (4b) a higher-energy elliptical orbit?
I hope this is the right thread for these questions.
Thanks guys!
- Mike
-
#172
by
MickQ
on 15 Dec, 2010 06:18
-
Using current technology limits, the entry vehicle cannot have a 'density' (mass/heatshield area) of more than about 150kg/m2, of else it hits the surface before it has slowed enough to deploy a parachute. So for something using a 10m PLF this would mean an entry mass of less than 12t.
Which is completely useable, if you use a little creativity ;-) (See the link in my sig.)
Hey guys, I was just looking for some good back-of-the-envelope figures to help me with my mental models.
1. So far I have been assuming 1/3.5 ratio of IMLEO to TMI (not including the mass of the spent TMI stage). For ~200 day trajectories at the reasonably opportunistic time periods, is this a reasonable figure?
2. Related to that, I have been trying to find the TMI payload for a J246. I tried to use the search but to no avail. Does anybody know it?
3. Also, what is a reasonable PMF (propellant mass fraction for those that are visiting Q&A) for a methane/LOX powered ascent vehicle to low-mars orbit, and also (3b) to an elliptical orbit suitable for rendezvous with an awaiting ERV?
4. What is a suitable PMF for a methane/LOX powered ERV for a nominal ~200 day return trajectory, from both a low-mars orbit and (4b) a higher-energy elliptical orbit?
I hope this is the right thread for these questions.
Thanks guys!
- Mike
Mike.
I just discovered this thread and after reading it all I think it IS the right thread for these questions. I had been thinking that there should be one thread dedicated to ALL things MARS. It sometimes seems things get hashed and re-hashed over on multiple threads on different forums. Would it not be better to keep it all in one place ? Anyone ?
Mick.
-
#173
by
Kaputnik
on 15 Dec, 2010 09:33
-
1. So far I have been assuming 1/3.5 ratio of IMLEO to TMI (not including the mass of the spent TMI stage). For ~200 day trajectories at the reasonably opportunistic time periods, is this a reasonable figure?
Off-hand, I think the TMI burn is about 4km/s. Assuming an isp of 450s, that gives a basic ratio of 1:2.5. It would be reasonable (conservative?) to assume a dry stage mass of 10%, so the actual payload to IMLEO ratio becomes about 1:2.9
On some windows, and trajectories, TMI could be as little as 3.6km/s... using RL10B for 462s isp... and assume a lower dry mass stage... and you are optimistically looking at less than 1:2.5
2. Related to that, I have been trying to find the TMI payload for a J246. I tried to use the search but to no avail. Does anybody know it?
The exact figure would depend upon how fast a trajectory to Mars you wanted (e.g. minimum energy Hohmann transfer vs. a two year heliocentric free return to Earth). Plus the usual variation per launch year.
3. Also, what is a reasonable PMF (propellant mass fraction for those that are visiting Q&A) for a methane/LOX powered ascent vehicle to low-mars orbit, and also (3b) to an elliptical orbit suitable for rendezvous with an awaiting ERV?
As nobody has built one yet, cannot say definitively. I think you need the ascent vehicle to be capable of about 4.3km/s to reach low Mars orbit, and about another 1km/s got high orbit... but these are just the numbers I recall so don't take them as gospel.
4. What is a suitable PMF for a methane/LOX powered ERV for a nominal ~200 day return trajectory, from both a low-mars orbit and (4b) a higher-energy elliptical orbit?
Again, nobody has built one of these yet.
Best bet is probably to research the delta-v requirements for the two trajectories and then work out the numbers based on real life hardware. Bear in mind you may be asking your hypothetical vehicles to do more (e.g. longer storage of propellants etc) than existing stages and would need generous mass margins to cover than capability.
-
#174
by
Danderman
on 02 Mar, 2011 20:05
-
Will the MAVEN spacecraft carry a relay radio system for landers as to do the current Mars orbiters?
-
#175
by
Jim
on 03 Mar, 2011 00:17
-
Will the MAVEN spacecraft carry a relay radio system for landers as to do the current Mars orbiters?
yes
-
#176
by
scienceguy
on 17 Apr, 2011 21:28
-
Does anyone know of any studies analyzing the minimum amount of mass per person needed to get to and from Mars (assume ISRU)?
-
#177
by
grdja
on 14 May, 2011 17:54
-
Reading DRM5 and similar, I see that as in Apollo only thing that returns to Earth is the crew capsule. Six or seven monstrous Ares V launches; over thousand tons IMLEO and you recover and reuse nothing. Ok the hab stays on Mars; if you want your eventual second mission to go to very same place the first one did.
How much would departure vehicle mass IMLEO grow if you wanted to
return entire vehicle to say L1?
I understand there is very extreme and very widespread hatred for anything that can be mocked with "Battlestar" tag; but is it really economic to build thousand ton vehicles that cost tens of billions and then throw away every single part of them during one mission.
-
#178
by
clongton
on 14 May, 2011 18:20
-
BINGO! WE HAVE A WINNER!!!
-
#179
by
QuantumG
on 15 May, 2011 00:55
-
It's simply a fact that the majority of IMLEO is fuel.. you can't get around it (yet).
As for leaving the base on Mars.. I believe the idea with fixed-habitat-and-rover designs is to land your second habitat rover-range distance from the first habitat. Then land your third habitat rover-range distance from the first two, and so on. The result is an ever increasing base of operations.
Of course, to believe in that you have to think there will actually be more than one mission
