Re: I take objection to NASA's Mars plans!


Cardman wrote:
> On 1 Aug 2005 19:14:49 -0700, "William Mook"
> <william.mook@xxxxxxxxxxxxxxxxx> wrote:
>
> >Look, you can do a fly-by of Mars on a Mars-free-return trajectory, but
> >it would be a two-year ordeal, and give you a few hours near Mars, and
> >fly out into the asteroid belt at apo-helion.
> >
> >You could drop probes onto Mars' surface as you flyby, even control
> >them remotely as you fly by for a few weeks time.
> >
> >But you're still on board for two years.
>
> I can only feel that NASA would need to do a lot of long term space
> travel before doing such a 4 year mission.

Well, two years aboard the space station without supplies could precede
that!


> And yes even a 2 year fly-by Mars mission is an option. It is not
> their job to land on the surface, but to simply prove that they can
> make it out there and back.
>
> As if you want to jam people into a CEV derived system for two years,
> then you may as well send them somewhere interesting.

This was studied in 1965 using Apollo hardware;

* * * *

Mars flyby mission designed by NASA Huntsville in 1965 to use existing
Apollo hardware, allowing a manned flyby of Mars by 1975.

At the end of June 1964 Hans Koelle, Max Faget, and Wernher Von Braun
considered an early manned Mars flyby mission boosted by a Saturn V -
otherwise, as Faget conceded, "we'll never see a Mars expedition in our
lifetime". The mission, as conceived by Ruppe in February 1965, would
be launched by existing Saturn boosters in the mid- to late- 1970's.
The spacecraft would use Apollo hardware. An Apollo CSM would be housed
together with 4.5 tonnes of probes in a pressurised hangar. The crew of
three would be provided with a radiation shelter and a centrifuge to
maintain fitness during the voyage.

The spacecraft would be assembled in earth orbit using six Saturn V
launches followed by one Saturn IB launch. Launch 1 would orbit the
unpiloted flyby spacecraft. Launches 2 to 5 would be liquid oxygen
tankers. On Launch 6 a modified S-IIB second stage would place itself
in orbit with no payload or liquid oxygen residuals, but with 80 tonnes
of excess liquid hydrogen. Within 72 hours the four tankers would have
to successively dock with the S-IIB and pump liquid oxygen into its
oxidiser tank. Only then would a Saturn IB launch the crew aboard an
Apollo CSM into orbit.

The Service Module would be modified to be powered by an RL-10 liquid
oxygen/hydrogen engine in lieu of the standard storable propellant
engine. After separation from the S-IIB, the flyby spacecraft would
total 105 tonnes. During the Mars flyby the crew would drop 4.5 tonnes
of probes, fitted with 900 kg of instruments, into Mars orbit and the
Martian surface. As they approached the earth, the crew would enter the
Apollo CSM, undock from the spacecraft, fire the RL-10 engine to brake
the CSM to an acceptable re-entry velocity, re-enter the atmosphere,
and splashdown for recovery by an aircraft carrier. Total mission
duration would be 661 to 691 days.


-------------------------------------------------------------------------
NASA Mars Flyby 1965 Mission Summary:

Summary: Manned Mars flyby using Apollo hardware for earliest possible
mission (mid-1970's)
Propulsion: LOX/LH2
Braking at Mars: flyby
Mission Type: crocco
Split or All-Up: all up
ISRU: flyby
Launch Year: 1975
Crew: 3
Outbound time-days: 130
Mars Stay Time-days: 0
Return Time-days: 531
Total Mission Time-days: 661
Total Payload Required in Low Earth Orbit-tonnes: 550
Mass per crew-tonnes: 183
Launch Vehicle Payload to LEO-tonnes: 100
Number of Launches Required to Assemble Payload in Low Earth Orbit: 6
Launch Vehicle: Saturn V

Crew Size: 3. Design Life: 700 days. Basic Diameter: 6.90 m. Maximum
Diameter: 10.06 m. Mass: 600,000 kg. Main Engine: J-2. Main Engine
Propellants: LOX/LH2.

* * * *

> However, you are quite correct that landing on the surface is the
> ideal. They should certainly be able to handle landing no problem. I
> would say that launching from Mars (6794km diameter) should be
> somewhat interesting, when they have only launched from Earth and the
> Moon before.

Yes. This was also studied in the Early 1970s using Shuttle hardware
as a building block.

* * * *

Final NASA Mars expedition before the 1980's. The spacecraft would use
shuttle hardware, including SSME engines in the rocket stages.

In its final action after Nixon had killed any possibility of further
manned Mars spaceflight work, the nearly-defunct Planetary Missions
Requirement's Group called for NASA centres to sum up their work. NASA
Houston used the opportunity to take a new look at a Mars mission using
expected shuttle hardware in February 1971. A manned expedition to Mars
in 1987 lasting 570 days was envisioned. Six Chemical Propulsion System
liquid oxygen/liquid hydrogen stages, each equipped with a shuttle SSME
engine, would be assembled in low earth orbit. Each stage would be an
orbiter payload in place of the manned orbiter, having an empty mass of
27 tonnes and having 245 tonnes of liquid oxygen / liquid hydrogen
propellants. The tanks would be topped up in orbit by no fewer than 65
shuttle missions. A 50 tonne North American MEM lander, capable of
supporting three crew for 45 days on the surface, would be used. The
transit Mars Module would be lofted in a single shuttle launch, and be
20 m long, using a large solar array for power. The spacecraft would be
rotated in transit to provide 1/6 artificial G for the five-member
crew. The spacecraft would be placed in a 3200 x 16,000 km Mars orbit.
The landing crew would be provided with two single-man rovers, allowing
20,000 square km of the Martian surface to be explored. This was the
last of the NASA Mars expedition designs for decades.


-------------------------------------------------------------------------
NASA Mars Expedition 1971 Mission Summary:

Summary: First NASA Mars expedition design to use liquid oxygen/liquid
hydrogen propulsion and shuttle hardware elements.
Propulsion: LOX/LH2
Braking at Mars: propulsive
Mission Type: opposition
Split or All-Up: all up
ISRU: no ISRU
Crew: 6
Outbound time-days: 340
Mars Stay Time-days: 30
Return Time-days: 200
Total Mission Time-days: 570
Total Payload Required in Low Earth Orbit-tonnes: 1900
Total Propellant Required-tonnes: 1470
Propellant Fraction: 0.77
Mass per crew-tonnes: 316
Launch Vehicle Payload to LEO-tonnes: 30
Number of Launches Required to Assemble Payload in Low Earth Orbit: 71
Launch Vehicle: Shuttle

Crew Size: 5. Design Life: 460 days. Length: 140.00 m. Basic Diameter:
7.31 m. Maximum Diameter: 22.00 m. Mass: 1,900,000 kg. Main Engine:
SSME. Main Engine Propellants: LOX/LH2.

* * * *

Clearly, had we the willingness to go to Mars we could have been on
Mars already. Ideally, we could have used Apollo hardware to do a
flyby mission of Mars by the 1970s and then follow up with a landing by
the 1980s by the end of the decade of the 70s.

These things periodically raise their head depending on political
conditions. And that's the problem, they are dependent on political
conditions. It would be nice to create an economic basis for
investment in off-world development, but that would cause problems with
missile proliferation and long-term instability as space and planetary
colonies grew economically and politically. Which is the real reason
we don't carry out these sorts of programs;

* * * *

Joint Los Alamos/NASA design for a quick Mars flyby mission using
hardware planned for development by NASA in the 1990's, produced at the
urging of a Congressman in response to a perceived Soviet Mars
expedition plan. The Soviet Union, and the space hardware planned by
NASA, did not make it into the 1990's.

At the urging of ex-astronaut Harrison Schmitt, NASA and Los Alamos
National Laboratory jointly hammered out a Mars Manned Mission at a
seminar on 10-14 June 1985. The crash program was in response to the
possibility that the Soviet Union might mount a manned Mars expedition
as early as 1992 using its new Energia booster and experience with the
Mir station. A year-long flyby mission would be launched, requiring a
350 tonne spacecraft in low earth orbit. The spacecraft would have an
16.4 tonne Mission Module, two expendable propellant tanks, a 5.5 tonne
command module, and use two NASA-planned Orbital Transfer Vehicles with
a dry mass of 5.23 tonnes each. A total of 201 tonnes of liquid
oxygen/liquid hydrogen propellant would be loaded into the OTV's and
expendable tanks. A one hour OTV burn would place the spacecraft on its
trajectory. The empty lateral propellant tanks would be retained in
order to provide radiation and meteoroid protection for the crew. Six
months after launch the spacecraft would zoom pass Mars, in a flyby
phase lasting 150 minutes and beginning when the spacecraft was within
32,000 km of the planet. Closes approach to Mars would be 250 km. As
the spacecraft approached earth, a single OTV and the Command Module
would separate. Re-entry into the earth's atmosphere would come at 16.7
km/sec, a most difficult proposition as this was beyond OTV heat shield
limits. It would also subject a crew that had been in zero-G for months
to extremely high G forces. An alternative would be to use a fuelled
OTV to brake the CM from 16.7 km/sec to 10.6 km/sec before the CM
re-entered the earth's atmosphere. This was within the OTV's design
limits but would double the initial mass required in low earth orbit. A
Venus swing-by was not considered.

Mass: 325,000 kg.

* * * *

> >So, that's the point - do you spend two years aboard a spacecraft for a
> >few hours of remotely controlled systems - or spend four years aboard a
> >spacecraft for over a year on Mars' surface - you don't change much
> >with a flyby.
>
> It should be possible to go into Mars orbit. Stay for a few days. And
> then to break orbit and return.

You didn't read up on Hohmann transfer orbits. Its not possible to do
this because it takes too much energy. You can shed lots of energy in
the Mars atmosphere. You can't easily gain it back. If you're in Mars
orbit, then you have to break free of that orbit and you must follow
minimum energy back to Earth. This means you have to wait for
planetary alignment - which needn't take too long. But does take some
time.

> As it has been claimed that there is
> two ways to go to Mars. One week stay and then over a year stay.

The two week stay on the surface still spends time loitering in Mars
orbit for departure to Earth. There's no way around that - save vast
increases in mission delta vee.

> The Russians have always spoken about landing on Phobos before going
> to Mars. Sounds like an interesting idea, where this is a good Mars
> observation point. Just a shame that Phobos is a pebble. :-]

Landing on Mars' moons is an interesting possiblity to reduce delta vee
requirements. You could drop down remotely controlled probes or even
remotely controlled fliers - to explore Mars surface from orbit. Since
you don't have to bring those probes back, and since you don't have but
a few seconds lag time - this is an interesting approach to things.


> My point would not to be to land on Mars until they are ready. As four
> years is certainly a long time.

Okay. But whatever you do you can only do what's technically and
physically possible. And when limited to today's rocket capacity -
this means minimum energy interplanetary orbits, which entail long wait
times.

William

> Cardman.

.