Micro-Space >> Ultralight Manned Spaceflight

[Sid454]

hop - 26/1/2008  8:42 PM

It seems to me that anything involving the N word is pretty much out of the question for Mr. Specs concept of cheap, simple spaceflight developed by a small private organization on a shoestring.

Many of us find his proposals extremely dubious (and he has completely failed to address the problems pointed out earlier WRT aerocapture), but the idea of such an organization developing new nuclear propulsion systems is completely ridiculous.

Just the paperwork to obtain the materials, never mind develop, test and fly such a thing is beyond the reach of anything short of a major defense contractor or government program. Even getting RTGs or isotope heaters (which otherwise have the potential to work well in a minimal complexity mars mission) would be a major challenge.

I agree he also seems to not want to consider whats is common knowledge about human biology and psychology.

What about radiation it is a show stopper for a mars mission and going to mars is not like hiking up everest or a short scuba dive.

I wouldn't even consider locking someone inside something any smaller then a mir station core module for 7 months at a time.

His nautilus analogy is wrong if you want to spend 3 months on the bottom of the ocean you need the functional equivalent of the nautilus http://www.fas.org/man/dod-101/sys/ship/nr-1.htm

Heck to even visit the deeper levels and the bottom of the ocean you need something like this http://oceanexplorer.noaa.gov/technology/subs/alvin/alvin.html

As for RTGs they only produce at most a few hunderd watts which is nothing to a manned spacecraft.

 Even solar is a better option the arrays on ISS for example will still produce over 50 KW at mars thats still enough to run a VASIMR engine though not at as high thrust as a 300KW reactor.

Life support and making the spacecraft generally livable will use up about 15KW of that for a crew of four.

[rpspeck]

hop - 26/1/2008  8:42 PM
(and he has completely failed to address the problems pointed out earlier WRT aerocapture)

I noted in my 24/1/2008 posting: “I certainly see no reason to reject the conclusion of the authors of these three reports which were unanimously positive! All believed that these procedures were practical and should be employed. A few uncertainties requiring follow on study, or the demonstration spacecraft mentioned above, were spelled out in each report.”.  I intend a more detailed discussion, but that summarizes my current position.
 
If any of you want to challenge the competency of these authors, you are free to do so.  Having personally read the applicable parts of these papers, I agree with their conclusions.  I also agree that low cost operational demonstrations of these techniques are called for before embarking on a manned mission, and these certainly will be done.

I most certainly do not agree with the contention on this forum that DOUBLING or QUADRUPLING the launch mass and total cost of a Mars mission is a good alternative to doing these demonstrations!

I do agree that although unguided aerocapture is possible with zero lift (J.A. Mulqueen, page 62), it is undesirable.  The allowable “Vacuum Target Periapsis” increases from 0.5 km to 2.0 km when control of a low lift aerobrake is assumed.  Offset Center of Gravity with a spherical aerobrake, and roll control, can provide the lift assumed in that study and the control process is straightforward.  (The first inflection point of the deceleration gives a very clear prediction of the ongoing process, while only 1/6 of the delta V has occurred at that point and there is still time for corrections to take effect.)  I have always assumed that a “Pilot Aerobrake”, as called for in the Boeing paper, will be used as well.
 
Regarding “Cramped Quarters”, I have already mentioned that our composite materials allow a “Small Airliner” sized habitat to have a 50 pound mass.  One or two people can exist in such a volume, partitioned for private areas or just a “change of scenery”.  Many people can exist for a long time with endless Internet, Videos, video games, books on DVD and a torrent of  email and voice messages.  Things have changed from 100 years ago when small groups conducted similar duration Polar expeditions cut off from all contact!  

[rpspeck]

Sid454 - 25/1/2008  11:34 PM

GPS doesn't help find the station.
 
To catch ISS you also need a radar/lidar to know how fast you are closing with it.

Strapping a heat shield to an MMU will only give you 9 to 10 hours of life support so you'd have to use a three orbit skylab type rendezvous.

And no you can't just add O2 tanks it doesn't work that way for one you have to also drink....

 Also being in the pressure suit for 48 hours could cause pressure sores ...

It should be possible to get a small one place craft down to lets say 1500lbs which means a falcon 1 could be used.

Thank you for your conclusion!

Other notes: GPS DOES help you find the station if those on it will use theirs and radio you their position. (This won't work if they don't want to see you!) Several GPS units are presently used on ISS.

My computer can compare two GPS data sets, over a few seconds, and produce good 3D range and range rate data. (It is part of my “Northrup Grumman Lunar Lander” FAA tracking setup.)

Backpackers, mountaineers and Steve Fossett (who spent 67 hours circling the Earth in the cramped “Global Flyer” cockpit for its first  record) know about drinking, etc, and have lightweight solutions.

Pressure sores are hard to get and easy to avoid in zero G.

Regarding rendezvous, I keep forgetting that Manned launches have never occurred on time and some assume they never will.  Looking at the Dnepr launch accuracy specs (about +/- 5 km errors in 3 dimensions) rendezvous will be easy and require only a few meters per second of delta V.  BUT, each second of launch timing error produces a larger error!  Since 1 minute per orbit is about the limit for phasing adjustments in LEO, sizable launch time errors (+/- 45 minutes) will take days to correct.
 
RADICAL SOLUTION: Launch on time (as with an anti-ballistic missile).
 
TRADITIONAL SOLUTION: Launch astronauts in an RV, so they will be comfortable while they are waiting.  Cost doesn't matter, money grows on trees.
 
But money doesn't grow on MY TREE!  If I am going into space I am either going to put up with Fossett conditions, or insist on accurately timed launches!

[Jim]

rpspeck - 31/1/2008  8:52 PM

(This won't work if they don't want to see you!) Several GPS units are presently used on ISS.

But not "directly" linked to a radio.  The shuttle doesn't use it

[hop]

rpspeck - 31/1/2008  5:08 PM
Having personally read the applicable parts of these papers, I agree with their conclusions.  

So you agree that

J.A. Mulqueen, page 17
The thermal loads that are anticipated in most aerobrake applications require insulation materials which are at the limit of current technology
...
Unfortunately, the understanding of the thermal environments that will be encountered by aerobraked vehicles is not complete.

and

J.A. Mulqueen, page 85
The data that were developed showed that aerobrake trajectories are very sensitive to the
atmospheric entry conditions and the density variations within the atmosphere. This implies that a very responsive control scheme is required.

and (quoted earlier, but perhaps worth repeating)

Mary C. Lee and William T. Suit, page 3
Initially Mars entry runs were made trying to achieve capture with a single fixed bank
angle. The problem was extremely sensitive to changes in initial flight path angle and bank angle
and no combination of the two angles was found that would result in capture. Changes of the
order of .0001° would result in either impact or skip-out. At this point, the multiple bank angle approach was tried.

(My emphasis)

While at the same time claiming this is straightforward, with a few remaining uncertainties left to clean up ?

Finally

rpspeck
I do agree that although unguided aerocapture is possible with zero lift (J.A. Mulqueen, page 62),

Assuming you mean fig 4-9, the statement you "agree" with is not supported by the chart on that page, and is directly contradicted by the associated text:

1. Sensitivity of Trajectory to Entry Conditions and Vehicle Characteristics
Figures 4-5 through 4-11 show the sensitivity of the orbit apoapsis altitude at atmospheric
exit to target vacuum periapsis altitude for various ballistic coefficients and angles of attack for each of the aerobrake applications. These data were generated assuming a constant angle of attack for the entire aeropass. In reality, this would not be possible for reasons that will soon become obvious.

[Lampyridae]

rpspeck - 1/2/2008  10:08 AM
Regarding “Cramped Quarters”, I have already mentioned that our composite materials allow a “Small Airliner” sized habitat to have a 50 pound mass.  One or two people can exist in such a volume, partitioned for private areas or just a “change of scenery”.  Many people can exist for a long time with endless Internet, Videos, video games, books on DVD and a torrent of  email and voice messages.  Things have changed from 100 years ago when small groups conducted similar duration Polar expeditions cut off from all contact!  

The psychological impact of being away from Earth is going to be a whopper. Even if you propose that a learjet-sized cabin can be constructed for 50 pounds, and I think that it is wildly optimistic and unsafe, I would recommend double that as a bare minimum.

I have an idea regarding this. Assuming you use STP coupled with ammonia propellant (Isp 600s or so), you could build the propellant tank out of composites and then use it for habitat space. At 682kg / m3, 14 tonnes of propellant gets you about 20m3 of tankage. I would furthermore consider building this outbound tank inside the tank for the return propellant - ammonia can remain liquid at room temperature so the habitat wall can be in contact with it. Although that would require some extra strengthening... ammonia at 20C has a saturated vapour pressure of about 8 bars. Alternatively, plain old water would work as a return propellant. An ammonium/water solution would be a good compromise. That would get you some radiation shielding, maybe better than 15gm/cm2. Alternatively, have a storm shelter inside your return propellant tank. Mass ratios are not as effective but your LOC numbers probably go down from say 5 to about 10 or so. Radiation is one of the big hazards of spaceflight and even a year and a half outside of the Van Allen belts without shielding is going to wear down immune systems, bone density and so on on top of the zero g.

I would also ditch the idea of a Mars-first excursion and instead go for a Deimos mission with an opposition-type trajectory, swinging by Venus. You get higher thermal and radiation loads from the Venus swingby but you could have two firsts from one mission. Or a conjunction-class mission and see how your life support holds up for 3 years (but then artificial gravity is a must).

[rpspeck]

hop - 2/2/2008  6:01 PM

Mary C. Lee and William T. Suit, page 3
Initially Mars entry runs were made trying to achieve capture with a single fixed bank
angle. The problem was extremely sensitive to changes in initial flight path angle and bank angle
and no combination of the two angles was found that would result in capture. Changes of the
order of .0001° would result in either impact or skip-out. At this point, the multiple bank angle approach was tried.

This (unfootnoted) statement in the Lee & Suit 1989 "Preliminary Investigation..." ( .0001 degree) is so completely contradicted by the 1991 Mulqueen work (noted earlier) that it must be abandoned without further comment!  If the conditions which led to that conclusion were detailed, further analysis might be possible.  I do note that (starting 200 seconds before periapsis - at up to 1600 km distance) 1 km periapsis change corresponds to 0.04 degree change in entry angle, and that a “significant” 1/10 km corresponds to 0.004 degrees.  Thus changes significant in the Mulqueen work look quite small when reported in this form. (I have regularly assumed that .0003 degree aiming would be desired and know it to be available from optical systems we have produced and delivered.)  Considering the erratic and unpredictable guidance reported for successful simulations in the Lee and Suit preliminary report, I suspect that a roundoff error was involved in this early simulation software. In spite of this, Lee and  Suit concluded that this was a technique that was feasible and should be developed!
 
As planned in the Boeing report, a “Day Early” pilot probe would eliminate most of the uncertainty and generate a very useful prediction of the atmosphere to be encountered.  I have planned something similar from my earliest consideration of this technique.
 
The Mulqueen work of course includes the high C3 cases involved with expedited Mars transfer.  These resulted in marginal thermal conditions in the Boeing study, particularly with uncertainty about radiative transfer in a CO2 atmosphere.  The low C3 cases I am considering did not (in the Boeing study) as they create far less severe thermal conditions.
 
I am surprised that these encouraging but old studies were never followed up, but to an extent understand why they were not. They most certainly will  be, for low cost experiments can pave the way for major mission mass – and cost - reductions.  

[rpspeck]

Lampyridae - 4/2/2008  7:53 PM

a learjet-sized cabin ...

Assuming you use STP coupled with ammonia propellant (Isp 600s or so) ...

My model for a “Small Airliner” is the DC-3 cabin, far bigger than a Learjet. And the mass is a good number.
 
I appreciate the suggestions about Solar Thermal Propulsion.  The big problem I see with it is that it misses the Oberth Effect (Gravity Well Synergy).  It may offer 600 sec ISP at LOW thrust, but acceleration near Earth gives up to a 5x multiplication of Delta V, and cancels the advantage of STP.

I am very interested in Solar H2O electrolysis (with a gas combustion motor) since it can accumulate solar energy as H2 + O2 and burn these gases near Earth Perigee in an expanding elliptic orbit.  This should be a way to get “nonexplosive” microsatellites out of LEO.

Don't let me discourage the development of your expedition ideas!  I have a very narrow focus at the moment and know that Mountaineers and other Adventurers accept risks that NASA will never touch.    Some of them want to go into space and they will gladly swap the very real danger of avalanches and polar bears for a “3.5% risk of eventual cancer”.

[hop]

rpspeck - 4/2/2008  1:16 PM
This (unfootnoted) statement in the Lee & Suit 1989 "Preliminary Investigation..." ( .0001 degree) is so completely contradicted by the 1991 Mulqueen work (noted earlier) that it must be abandoned without further comment!

Which you earlier characterized as "agreeing with their conclusions". In any case, the different assumptions of the two papers make your claimed contradiction doubtful.

In spite of this, Lee and  Suit concluded that this was a technique that was feasible and should be developed!

This is a straw man. No one here has argued that aerocapture isn't workable, or isn't worth pursuing. On the contrary, there seems to be a clear consensus that it is a good idea, and no show stoppers have been identified.

What is in doubt is your claim that it is simple, or a straightforward extension of existing technology or experience. In particular, your insistence that you don't need very sophisticated hypersonic flight control seems utterly at odds with the literature.

The "pilot probe" doesn't negate this. Atmospheres are highly variable on many scales (both in time and space). You could encounter multiple +/- 50% density variations over the course of your flight profile, and by definition, your pilot probe will not have followed the same path.

I am surprised that these encouraging but old studies were never followed up...

Even a casual perusal of the NTRs will show you that this simply isn't true. For convenience, I linked the ones I found as free downloadable PDF and related to mars, which are mostly old. Hopefully something like http://ntrs.nasa.gov/search.jsp?N=0&Ntk=DocumentID&Ntx=mode%20matchall&Ntt=20060047563 will fly soon.

[rpspeck]

hop - 5/2/2008  6:21 PM
In any case, the different assumptions of the two papers make your claimed contradiction doubtful.

No one here has argued that aerocapture isn't workable, or isn't worth pursuing.

Hopefully something like http://ntrs.nasa.gov/search.jsp?N=0&Ntk=DocumentID&Ntx=mode%20matchall&Ntt=20060047563 will fly soon.

The UNSPECIFIED conditions in the preliminary paper which lead to the 0.0001 degree comment make it a useless reference, particularly when apparently refuted by a more detailed subsequent study.  

The fact that it is not a focus of the paper makes this doubly true.  Any unfootnoted comment, which is not examined in a paper, is open to question and may be dismissed without argument if contradicted by a more detailed and relevant study.   The 0.0001 degree number simply has no engineering significance.

The fact that the entry angle is critical and has little margin for error is acknowledged and needs no further discussion.

Some postings in this thread has argued that aerocapture is HARD and should be ABANDONED without further consideration.  Everything in spaceflight is hard, and I agree with you that this technique deserves consideration.   Just how hard is this?  Time will tell.

Thanks for another good reference.  These are very valuable to me.   I certainly do appreciate the fact that you are  providing accessible, high quality references!

[hop]

rpspeck - 5/2/2008  3:08 PM
Some postings in this thread has argued that aerocapture is HARD and should be ABANDONED without further consideration.

I haven't seen anyone say that. People have pointed out that it is much harder than you initially believed, and that your initial statements were based on a profound lack of understanding. This is undeniably true, given that your own position has changed from "proven" to "straight forward" to "some uncertainties remain" to "hard". It's still not clear that you have understood just how hard it is. Do you now acknowledge that you need hypersonic flight control as sophisticated as anything ever flown to successfully perform aerocapture ?

Anyway, here few more documents you may find interesting COST - BENEFIT ANALYSIS OF THE AEROCAPTURE MISSION SET

and (previously linked in a different thread in this forum ) Mars Exploration Entry, Descent and Landing Challenges

The second one isn't specifically about aerocapture, but provides a lot of interesting information on the current state of the art WRT landing on mars.

[Patchouli]

The 50lbs for a cabin sounds kinda impossible to me I mean you have a 18 cubic meter tank that has to hold at least 5psig thats if the skylab 74% O2 and 26% N2 atmosphere is used this is the lowest one can go for very long term it was tested to 81 days with skylab.
Then there is the micro meteor shields so it doesn't get punctured though there are lighter solutions then the Whipple shields used on most spacecraft.
Also you need insulation for thermo regulation a spacecraft with no thermo regulation and solar shielding would be a solar oven.
Now 500lbs to 1200lbs for the bare pressure vessel would sound believable even the little Genesis II module weighs 3,000lbs though thats a whole spacecraft.

[Patchouli]

The tank within a tank idea is pretty good that would solve the radiation issues.
Also any mass saving expedition concept should make use of the tanks as hab space as in the Apollo Venus flyby concept.
This also would give the crew some exercise room so they don't turn to jelly .
NASA's ESAS system may be very flawed but this doesn't mean everything NASA does is pointless the living space requirements were found the hard way by trial and error as they did start out with very small vehicles like Gemini.
Gemini was used for a 14day mission successfully http://en.wikipedia.org/wiki/Gemini_7
But much longer then that the crew would end up in very bad shape since they could not exercise to slow the physical degeneration from micro gravity.

Maybe if we could get rid of the mark I human body and replace it with a prosthetic body like ghost in the shell this would no longer be an issue but then all the NASA concepts even the 800ton all chemical propulsion 1989 study start to look like child's play when one considers stuff like that.

I know how to get 800T into orbit 6 to 8 SDVs or 30 F9-Hs/EELVs can do that but I have no idea how to fully eliminate atrophy in the human body in micro gravity other then that exercise can slow it
But artificial gravity can stop the atrophy you'll still need exercise space though.

[rpspeck]

Patchouli - 23/2/2008  12:50 AM

The 50lbs for a cabin sounds kinda impossible to me I mean you have a 18 cubic meter tank that has to hold at least 5psig thats if the skylab 74% O2 and 26% N2 atmosphere is used this is the lowest one can go for very long term it was tested to 81 days with skylab.
Then there is the micro meteor shields so it doesn't get punctured though there are lighter solutions then the Whipple shields used on most spacecraft.
Also you need insulation for thermo regulation a spacecraft with no thermo regulation and solar shielding would be a solar oven.
Now 500lbs to 1200lbs for the bare pressure vessel would sound believable even the little Genesis II module weighs 3,000lbs though thats a whole spacecraft.

Our "standard" number for a 9 cubic meter spacecraft (2 m diameter,* 3 meter long) is 60 pounds (27 kg).  This uses 1/2 millimeter thick, Kevlar/Epoxy composite and in this diameter would exceed 30 psi (2 atmospheres) bursting strength.  (A number of Epoxys have excellent stability in vacuum, just as the Kapton used on the outside of many spacecraft does - with some atomic Oxygen erosion in LEO).

We have made and tested hundreds of fuel tanks using exactly this construction (with 1/20 the diameter, and >20 times the burst pressure). These tanks (for equal length) run 3 pounds mass.  20 times the diameter, with equal length and wall thickness, gives the 60 pounds mass. These are MEASURED and TESTED numbers, not theory.  

The LDEF (Long Duration Exposure Facitily) with greater surface area experienced about 5 events in 5.4 years which would punch through the 1/2 mm walls.  Since this is for MANNED Missions, every few months the crew gets to patch one of the tiny sucking leaks with something (Duct Tape will work).

Note that your "Minimum Atmosphere" has 1.7 times the Oxygen partial pressure found in Vail Colorado, but people actually live there (as well as at much higher altitudes).  

White paint (>90 % thermal emissivity, 4%, or even 1% solar sbsorbtion) will be TOO COOL in sunlight in space.  Options, even for the Earth to Mars solar variation exist.

We are not talking about problems which would concern a terrestrial Adventurer.

[rpspeck]

I answered a follow up question (regarding my comments in the Question and Answer part of the Feb. 21, 2008 “Google Lunar X PRIZE” News Conference) on March 6, 2008 in another forum: http://spacefellowship.com/Forum/viewtopic.php?t=1155&start=225  .
 
That question asked for a time frame for the Ultralight Manned Lunar missions I mentioned at the Google Press Conference. Following a copy of that response,  I detail the present status of the Micro-Space hardware we intend to use for those flights.  

The time frame for Human Moon Missions, using Micro-Space hardware, is two to four years (subject to funding). Keep in mind that our planned "Deep Space" missions are all feasible with existing launch vehicles, although I often use cost estimates based on SpaceX promises.

About 70% of these mission costs will be for "Freight" service to LEO, with 30% or less for development, integration and production of customized spaceflight hardware.

The simplest, and nearest term Lunar flight would be simply circumlunar, allowing the next man, or first woman to travel around the Moon - the first such event this century and the first in more than 30 years. Micro-Space has many of the components required for this system in stock.

The most spectacular would be a solo human Moon landing. This would use many of the systems from the circumlunar craft and add a version of our Crusader HTS (Human Transport System) Lunar Lander, which itself uses many components we have in stock. This is the same lander we will use for the Google Lunar X PRIZE, and are actually preparing for flight tests.

The additional mass of the landers (two are actually used - the first one to land carries the fuel to take the astronaut back to lunar orbit). and Lunar orbit insertion increases the launch mass to at least half the capability of the Falcon 9.

I know that these promises are hard to believe, but in fact they primarily make use of lightweight mission concepts NASA extensively researched in past decades, but rejected in favor of less "austere" approaches.


We are finishing the welding on a batch of 14 of our bipropellant Liquid Fuel motors.  These are not optimized for vacuum use, but are similar to what we will use to accelerate from LEO to Lunar Transfer, brake into Lunar orbit, and descend to the Moon.  These motors will actually go into both level 1 and Level 2 “Northrup Grumman Lunar Lander competition” (NGLL) vehicles, and “Earth Launched” Space Diving demonstrators.  These spaceflight simulations – on Earth – are more demanding that actual spaceflight due to the lower ISP in air, the greater thrust required with one G, and the faster control dynamics.  (Other factors present in space are reduced or avoided.)

We have nearly 100 of our flight qualified, ultralight fuel tanks in stock.  These lightweight high pressure tanks make the high mass ratio (and low empty weight) of our pressure fed rocket systems possible: without this factor, our projected missions would be impossible.  Note that all our mass projections are based on measured systems mass, not theoretical predictions.

Our NGLL  systems use four to ten of these fuel tanks.  The Ten tanks hold up to 350 pounds of fuel, and (with less than 50 pounds system empty weight) this makes the landing of a 300 pound astronaut (with pressure suit and life support) on the Moon possible.  This is our Crusader HTS (Human Transport System) configuration.  

For the Google Lunar X PRIZE, we will cluster 30 fuel tanks (holding 1000 pounds of fuel) as a  Lunar Transfer Stage in a Falcon 1 payload.  ONE or TWO landers with reduced fuel load and rovers will be included.  This cluster will mass 500  pounds and be able to land 150 pounds on the moon.  With 50 pounds total empty weight, this will leave 100 pounds for rovers and other payload equipment.  

Our original concept (before the Google Prize) was to offer a single lander with 100 pound payload.  Standing seven feet tall on the Moon, and stabilized by locked landing legs, this could handle a drilling system for subsurface exploration on the Moon.  After successfully pulling the drill stem and instruments from one bore hole, the lander could then restart its motors and hop to additional test locations.  (Other instruments could of course analyze the surface close to the lander as well as analyze core samples.)  Using the remnant of the Transfer bus as a lunar relay satellite, the system could  link to landers at both the Lunar Poles, and Far-Side.

With the narrower focus of the Google competition, we prefer the concept of sending two lighter weight landers (same general size) to the Moon.  With lightweight (30 pound) rovers, either could complete the required image collection and transmission.  This increases the probability of success with a single Launch vehicle.  

A very important alternative mission for these components is the Human circumlunar flight described above.  Using the same Falcon 1, and 30 tank Lunar Transfer Stage,  a human astronaut can be accelerated to a circumlunar, free return orbit.  The 500 pound payload is sufficient for the traveler, life support, compact habitat and Earth reentry system.  Micro-Space has many of these components in stock and in operation.  

A Human lunar landing would require two Crusader HTS units (presumably successfully demonstrated by landing on the Moon in a Google effort), and much more fuel.  The total mass for a solo flight of this type would be at least ˝ the Falcon 9 payload.  Although the primary components for this system are also in production at Micro-Space, space validation of the lander and orbital rendezvous systems are called for.  

We are presently preparing for operational testing of both the lightweight and HTS landers for NGLL competitions, Google competition efforts and Human adventures.  The fact that all three use very similar systems and that the major components of these systems are already operational and in production, makes our short time projections possible.      

[tnphysics]

When will you have a flight?

[rpspeck]

We expect to achieve liftoff (in tethered flight) in about 4 weeks.

[rpspeck]

For anyone actually interested in DOING spaceflight, rather than just talking about it, please see the new Micro-Space thread "Astronauts Wanted".
 
http://spacefellowship.com/Forum/viewtopic.php?t=5551

This is a serious effort to show both sponsors and investors that “Adventurers” still exist.  Sponsors will be looking for people with the audacity and charisma of a Charles Lindbergh.  People willing to face both known and unknown risks with the ability to survive and later to talk about their experience.
 
Of course I know they exist,  as ocean sailors in tiny boats, mountain climbers and polar trekkers.  But do those actually exist  who are interested in space?  I know as well as anyone how our governments have quenched and beaten out of us our dreams of personal spaceflight.  But in actual fact “the road to space is open”.  It is a hard road (as many historic adventures have been),  it will for a time be expensive to travel there (which was also true for many historic adventurers), but interested sponsors will make that travel possible today just as they did yesterday.
 
A prerequisite for actual missions will be for a number of competent and qualified individuals to stand up and say: I Want To GO!  Only then will the media (including Popular Science and Popular Mechanics) pay attention to articles and drawings showing how it can be done.  IT CAN BE DONE!
 
It can be done at a practical cost: a cost a sponsor can pay in exchange for very valuable publicity.
 
Given the high cost of delivering mass to LEO, “Ultralight” design is necessary for acceptable cost. But since few dangers in space are avoided by heavy walled equipment, safety can be reasonable.
 
It can be done soon.  Who wants to GO?    

[Lampyridae]

rpspeck - 5/2/2008  6:54 AM

Lampyridae - 4/2/2008  7:53 PM

a learjet-sized cabin ...

Assuming you use STP coupled with ammonia propellant (Isp 600s or so) ...

My model for a “Small Airliner” is the DC-3 cabin, far bigger than a Learjet. And the mass is a good number.
 
I appreciate the suggestions about Solar Thermal Propulsion.  The big problem I see with it is that it misses the Oberth Effect (Gravity Well Synergy).  It may offer 600 sec ISP at LOW thrust, but acceleration near Earth gives up to a 5x multiplication of Delta V, and cancels the advantage of STP.

Oberth effect only applies for slingshot burns, not for actually leaving orbit. It helps make your trip shorter by a bit.

As for radiation shielding, superconducting coils can be used. Magnesium diboride is (reasonably) cheap. Higher temperature superconductors exist, up to 180K or so. Coated with copper wires and surrounded by a folded mylar jacket with a thin diamagnetic coating on the underside (e.g. pyrophoric or sheet carbon). Once in orbit, deploy the coils and pass current down the copper wires. The diamagnetic pushes the sheet carbon away and the mylar tube "inflates." Since there's vacuum between the mylar and conductor it's a great insulator. 99% of sunlight is reflected away. Use photovoltaics to gradually pump energy into the coils until the desired field strength is achieved. Using perigee assists with the magsail, you could raise your apogee until you could "kick off" with a hypergolic motor.

Getting to and from Mars is a matter of using the solar wind to accelerate / decelerate.

AFAIK, you don't even need to use superconducting cable, it just obviates the need for constantly pumping current into the wire. Plain old copper wire and solar panels should do just fine, without need for inverters or whatever. Required magnetic field strengths are in the order of about 10 microteslas. More is needed for getting out of magnetospheres, plus current needs.

[tnphysics]

Magnetic fields don't provide protection against polar radiation.

Superconductors with Tc>120K have not yet been created.