Author Topic: NEP AG transit to Mars (Read 59045 times)

Chris Bergin · « **on:** 01/09/2006 01:09 pm »

In works with a powerpoint presentation and animation to download.

We're going to do a short lead in article to bring those people from the news site (still more than the forum - for a strange reason I can't work out) to the forum.

I'll scan some images from the powerpoint I've acquired via the FTP section.

Note this is a March 2003 report, but very interesting reading - noting the devil's advocate approach to the ESAS NTR approach to Mars transit. One for you all to discuss, obviously. Ironically, it has the appearance of the ESAS approach with the landers etc.

Chris Bergin · « **Reply #1 on:** 01/09/2006 01:38 pm »

Here's the vehicle from the animation video showing the rotation.

Chris Bergin · « **Reply #2 on:** 01/09/2006 01:46 pm »

The report is Earth-Mars Artificial-G NEP Architecture Sun-Earth L2 Architecture (3-Week Parametric Trade Study)

This is an example of one of the pages from the 71 pages in this powerpoint presentation. As mentioned, I'll make it available on the FTP server (I have to given the server loads, and guests taking the link and throwing it on other sites that then use our FTP server externally).

Chris Bergin · « **Reply #3 on:** 01/09/2006 02:04 pm »

Here's the link to the download area.
http://forum.nasaspaceflight.com/forums/thread-view.asp?tid=1219&start=1 - which is for presentations and video in L2.

Mark Max Q · « **Reply #4 on:** 01/09/2006 02:15 pm »

Seems a little like the SDLV plan, with the CEV being another SDLV. Interesting.

Chris Bergin · « **Reply #5 on:** 01/09/2006 04:02 pm »

We're placing another Powerpoint presentation on to the download section - this is from slightly earlier (2002) but has good explantatory background.

58 pages.

Jason Sole · « **Reply #6 on:** 01/09/2006 04:26 pm »

Very interesting, and one hell of a read. Might have some comments tomorrow, but impressive to see this was/is/maybe a serious consideration.

rsp1202 · « **Reply #7 on:** 01/09/2006 06:04 pm »

Graphics indicate masts, etc., are deployable. I hope that means self-deployable or with minimal number of astronaut EVAs for on-orbit assembly, unlike on ISS. There was a shuttle flight or flights that tested deploying such structures.

David AF · « **Reply #8 on:** 01/09/2006 07:52 pm »

This is some read and a serious presentation on both reports. Interesting as I think it's useful for seeing how NTR compares?

nacnud · « **Reply #9 on:** 01/09/2006 08:05 pm »

I like the picture from 2001, especaly as during that part of the film was supposed to be in zreo g and velcro shoes were simulating gravity.

Not a good start to the report

Chris Bergin · « **Reply #10 on:** 01/09/2006 08:17 pm »

Typical, as soon as I use that image on the outline story (which was basically "here's some things mentioned, go read the PowerPoint presentations") you go and say that about the image

Chris Bergin · « **Reply #11 on:** 01/09/2006 09:23 pm »

Quote

nacnud - 9/1/2006 9:05 PM

I like the picture from 2001,

And I thought you were joking, only to hear it was from the film. I only seem to remember HAL

Mark Max Q · « **Reply #12 on:** 01/09/2006 09:37 pm »

Ok, still going over these documents. Firstly what is the reason for moving from NEP to NTR in the ESAS report, compared to where NASA was with the 2002 and 2003 reports?

HarryM · « **Reply #13 on:** 01/09/2006 10:09 pm »

Maybe since NERVA went so far along and ground-tested they considered NTR technology more mature.

Mark Max Q · « **Reply #14 on:** 01/09/2006 10:19 pm »

Quote

HarryM - 9/1/2006 5:09 PM

Maybe since NERVA went so far along and ground-tested they considered NTR technology more mature.

Thanks. Following that up, if given the option with both NEP and NTR, with both along the same level of testing, which is preferable?

HarryM · « **Reply #15 on:** 01/09/2006 11:29 pm »

For manned missions the ~12 month NEP transit to Mars (versus the commonly quoted 3 months for NTR) is a big disadvantage. I know which one I'd prefer to be on. NEP certainly has uses in unmanned deep space, like in the original JIMO concept.

HarryM · « **Reply #16 on:** 01/10/2006 12:02 am »

12 month is what the mentioned PP presentation says (700 days in transit, round trip).

A "fast" Mars mission, Mars Direct with NTR, http://www.astronautix.com/craft/marirect.htm

Mars Direct Nuclear Thermal Mission Summary:

Summary: Low cost; no orbital rendezvous or assembly; dependent upon ISRU propellant production for return; Chemical and NTR options
Propulsion: Nuclear thermal
Braking at Mars: aerodynamic
Mission Type: conjuction
Split or All-Up: split
ISRU: ISRU
Launch Year: 1997
Crew: 4
Mars Surface payload-tonnes: 30
Outbound time-days: 100
Mars Stay Time-days: 550
Return Time-days: 130
Total Mission Time-days: 780
Total Payload Required in Low Earth Orbit-tonnes: 220
Mass per crew-tonnes: 55
Launch Vehicle Payload to LEO-tonnes: 105
Number of Launches Required to Assemble Payload in Low Earth Orbit: 2
Launch Vehicle: Ares

simonbp · « **Reply #17 on:** 01/10/2006 12:50 am »

But the magic is in the thrust; whereas an NTP or chemical manned Mars mission would depart directly from LEO, a practical ion-engine-based mission (solar or nuclear) would have significantly lower thrust, and thus acceleration, and thus spend a significant amount of time climbing up through the Van Allen belts before reaching escape velocity. The spindly NEP spacecraft I've seen also have the distinct disadvantage of being both hard to construct in space (meaning beyond simple docking manoevers) and being to unwieldly for aerobraking (let alone aerocapture) meaning they need a lengthly decceleration burn in order to enter Mars orbit. All this adds up to NEP generally requiring more launches, longer flights, and thus more money.

Could you get around these problems by building a more powerful electric thruster? Yes, that's VASMIR. Would such a rocket plus the nuke to power it end up smaller and more powerful than just an NTR? I doubt it...

Getting back on topic: The trussed, rotating AG would be interesting (for both NEP and NTP) if combined with a direct-entry crew capsule; shortly before reaching Mars, the crew capsule detaches from the truss, gets a distance away from it, and does either a direct atmospheric entry or a series of aerobraking orbits followed by final entry. This might freak out the greens as if the reactor is not on just the right course to skip out on a heliocentric trajectory, it could end up as a radioactive crater...

Simon

JonClarke · « **Reply #18 on:** 01/10/2006 07:02 am »

Quote

HarryM - 9/1/2006 7:02 PM

12 month is what the mentioned PP presentation says (700 days in transit, round trip).

A "fast" Mars mission, Mars Direct with NTR, http://www.astronautix.com/craft/marirect.htm

Mars Direct Nuclear Thermal Mission Summary:

Summary: Low cost; no orbital rendezvous or assembly; dependent upon ISRU propellant production for return; Chemical and NTR options
Propulsion: Nuclear thermal
Braking at Mars: aerodynamic
Mission Type: conjuction
Split or All-Up: split
ISRU: ISRU
Launch Year: 1997
Crew: 4
Mars Surface payload-tonnes: 30
Outbound time-days: 100
Mars Stay Time-days: 550
Return Time-days: 130
Total Mission Time-days: 780
Total Payload Required in Low Earth Orbit-tonnes: 220
Mass per crew-tonnes: 55
Launch Vehicle Payload to LEO-tonnes: 105
Number of Launches Required to Assemble Payload in Low Earth Orbit: 2
Launch Vehicle: Ares

Astronautix is an invaluable site but unfortunately the section on Mars missions is full of typos.

The "fast" NTR Mars direct trajectory was 180 days, not 100, the same as the chemical one. Zubrin used NTR to reduce the LEO mass from 140 to 110 tonnes.

As fars as the NEP proposal goes, it is good to see alternatives to NTR are being considered. However, the spin gravity idea is completely unnecessary, IMHO.

Jon

nacnud · « **Reply #19 on:** 01/10/2006 11:40 am »

Agreed, for a conjunction type mission with a fast transfer in both directions of 180 days the exposure to micro gravity shouldn't present too much of a problem. This coupled with a long surface stay means you can allow time after landing for adaptation to Martian gravity, if needed.

However for an opposition class mission, where out the out bound journey is still only 180 days there is the short surface stay of 30 days and the long journey home to consider. The short surface stay means that any time needed to recover after a micro gravity transfer has a real impact on the time available for mission objectives. Also the long return leg of 430 days could also be problematic on returning to Earth.

I think the solution is not to use an opposition class mission

Oh and I had to look up the difference between the conjunction and opposition class missions, if anyone is interested this is what I found.

Quick Facts from Red Colony

Quick Facts
	Conjunction	Opposition
Outbound Transit Time	180 Days	180 Days
Inbound Transit Time	180 Days	430 Days
Mars Stay Time	500 Days	30 Days
Total Mission Time	910 Days	640 Days
Delta V	6.0 km/s	7.8 km/s
Venus Flyby Needed	No	Yes
Average Radiation Dose	52 Rem	58 Rem
Zero Gravity Exposure	360 Days	610 Days

Diagrams redrawn from International Academy of Astronautics (IAA) Web Site