Science A visit to an NEO

[garyw]

Let's assume that it's 2018 or so, Obamas space plan has been a major success. Private space sector have worked out the bugs and NASA can buy launches to the ISS with no issues and NASA are just casting the first parts of a new vessel which will go visit an NEO.

Now, let's further assume that the goals for an NEO visit are:

1. Science - All that way to an NEO so it has to return something new.
2. Core Sample - You don't go all that way to take a photo.
3. Close enough to Earth that it's possible to get there and back within six months. (ISS increment time).
4. Big enough to be able to stick a flag in the "ground" and take photos.

If you were a mission planner, which NEO would you pick and why?

Discuss!!

 

[ar81]

I recall there was a group of asteroids (can't remember the name) that were supposed to be responsible for the dinosaur extinction. Not all of them have been tracked. I'd go for them.

That way you may scan nearby area to map them and see if they represent a threat and also yo may study their composition to evaluate the possible effects of another K-T like impact as you study them.

 

[jinglesassy]

2. Core Sample - You don't go all that way to take a photo.

WHAT?!?! NO APOLLO 8?!?! :lol:

I say Asteroid 2010 GA6

 

[Urwumpe]

If you were a mission planner, which NEO would you pick and why?

I would have three good candidates:

• Apophis - it passes very close, is a potential hazard for Earth.
• One of the Apollo asteroids, which is the group that ar81 means. Core sample could be helpful for getting more evidence on the CT event. Toutatis would be the favorite candidate there, though maybe a bit risk for its strange shape and chaotic orbit
• 101955 1999 RQ36, the NEO with the highest impact risk for the future. http://ssd.jpl.nasa.gov/sbdb.cgi?sstr=101955;orb=1 http://neo.jpl.nasa.gov/risk/a101955.html

 

[garyw]

I thought about Aphophis as well as as 3753 Cruithne. I figured that both would offer good science returns although 3753 Cruithne is probably easier to get to.

 

[2552]

The 2025 date Obama gave is likely for the NEO 1999AO10, from this NASA Flexible Path mission evaluation.

 

[Ark]

I'd personally like to see a mission to 3753 Cruithne, it seems like a good candidate with it's regular and predicable passes close to Earth.

 

[Piper]

The catch with going to an NEO, is that just because it comes close to Earth, it does not mean that it is easy to get to, doubly so if you want to come back. You got two burns to do to get a manned ship there, and Earth Ejection Burn (the easy one), and an Orbit Insertion Burn (the hard one). The first burn should generally not be much more difficult then a burn to get to the moon. However the second burn, the one to orbit the NEO, is the one that makes 99% almost impossible to get to with current rockets. The reason why so many are so hard to get to, are their high inclinations and eccentricities. The easiest asteroids to get to, will be the ones whose perihelion is close to 1au, and who have a relatively low inclinations. The aphelion can't be too big as well, nothing much past the orbit of Mars.

I did a search with my MPC Database Viewer, with the following search properties:

Perihelion: 0.9au to 1.1au
Aphelion: 0 to 1.5au (roughly the SMa of Mars)
Inclination: 0 to 5deg

Out of 6530 NEOs, only 53 fit those criteria. The largest of those was (10302) 1989 ML, at an estimated diameter of 432 meters (assuming an albedo of 15%). That's only 0.8% of all the NEOs. Even if we expand that search to inclinations up to 15 degrees, you still only get 155 (about 2.3%), the largest being (35107 )1991 VH at about 1.4km in diameter.

And if that wasn't difficult enough as it is, you got to take into account the time to get there, you may have to chase the asteroid 3/4 of its orbit before you catch up with it (or let it catch up with you), meaning you have to cruise through interplanetary space for almost a year. Not to mention doing that again to get back. So if you think you can just take a quick hop to an asteroid for a couple of weeks, you can kiss that fantasy good-bye.

People seem to think that just because an asteroid comes close to Earth, that it makes it easy (and quick) to get to, it doesn't. Sure, you can get to most of them easily, but 98% or them you won't be able to stop at, and the rest can take just as long to get to and from as it does to get to and from Mars.

 

[Sky Captain]

Could an electric propulsion help to cut down NEO mission time? If VASIMR test at ISS goes as planned and no major bugs that require reengineering of whole system appear it`s conceivable at 2020 - 2025 first VASIMR driven deep space vessel can be built for NEO missions.

 

[Piper]

Could an electric propulsion help to cut down NEO mission time? If VASIMR test at ISS goes as planned and no major bugs that require reengineering of whole system appear it`s conceivable at 2020 - 2025 first VASIMR driven deep space vessel can be built for NEO missions.

Yes it could, especially the trip there since they can generate much greater deltaVs. Instead of having to set up your transfer trajectory so that you arrive with as little deltaV as possible (which generally means a very long transfer), you can arrive there with a few thousands meters per second of relative velocity instead (which generally means much shorter transfers). Now, this still relies on how much thrust the engine generates in the time you have. VASIMR engines, like all low-thrust engines require time to build up velocity, and of course time is what you are trying to reduce.

 

[Sky Captain]

I don`t recall the source (I think it was related to claimed 40 day Mars mission time) but I somewhere read that VASIMR vith sufficient electrical power source could be capable of generating ~1 km/s of deltav per day so it would't take too long to accelerate and then deaccelerate at target.