Author Topic: An asteroid mission may be harder than going to Mars  (Read 4951 times)

Offline Blackstar

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That's just a snarky way of me saying you can broaden the search parameters somewhat and have plenty of targets to choose from. If you're picky, you're picky and likely to have to settle with just a handful (or one).

I've been hanging out with the people who were advocating a human mission to an asteroid since BEFORE it was Obama's policy (there were a few people at JSC who were studying this issue in 2007-2008, loosely connected to some people at JPL and a few others, like Tom Jones). It's not just being "picky." Over 9000 NEOs have been tracked. That's not a lot considering how big space is and how rarely these things get near Earth. There just aren't many good candidates in that number, even if you opened the selection criteria up. And you cannot open the criteria up very much. For instance, you cannot realistically say that you'll accept candidates where the round-trip human mission is a year or two. We're not going to fly that kind of mission. You cannot accept candidates with high spin rates. And it would not make any sense to go to an asteroid that is smaller than your spacecraft. Just about the only criteria that you could play around with from an operational standpoint is the year--instead of 2025, try to find a good candidate between 2025 and, say, 2050. Twenty-five years would give you more options. But that's not politically acceptable because the President made a speech.

Now there are of course hundreds of thousands of NEOs (probably millions, if you want to include really really small stuff). The problem is we cannot see them. Earth based telescopes are not big enough, and they're not well suited to the task (because they're on Earth, and that's not where you want to be to look for these things, the geometry is wrong).
« Last Edit: 02/07/2013 02:30 AM by Blackstar »

Offline Robotbeat

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Re: An asteroid mission may be harder than going to Mars
« Reply #21 on: 02/07/2013 02:55 AM »
Blackstar:

I don't see why a mission of, say, 390 days should be off the table. I also don't see why the target can't be around the same size as the spacecraft... Objects about that size are still plenty big to threaten cities, we can still study them scientifically, and (further in the future here) they would still have lots of raw minerals to mine (and, of course, half the reason to go is to prepare for a Mars orbit/surface mission). Rotation rate poses some problems, but most of the objects which aren't super small have reasonable rotation rates. And even fitting the parameters you describe, I was still able to come up with several candidates: http://neo.jpl.nasa.gov/cgi-bin/nhats?dv=9&dur=390&stay=8&launch=2025-2030&H=22&occ=7&sort=n_via_traj&sdir=DESC&action=Display+Table#top
(BTW, Apophis seems to be one of the best in this list! Pretty low delta-v, if you start at EML1/2 and are using electric propulsion, as Boeing has suggested.)

Again, I completely agree we should improve the candidate list with an extensive survey effort, but I definitely do not think we have such a dearth of candidates that we are in any danger of not finding one. And yes, I think folks worrying about this too much are over-constraining the mission parameters.
« Last Edit: 02/07/2013 03:30 AM by Robotbeat »
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Online mlindner

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Re: An asteroid mission may be harder than going to Mars
« Reply #22 on: 02/07/2013 05:24 AM »
Here's an idea. Can you find an asteroid thats large enough you can orbit it, but small enough that you can jump from the surface and with the help of a MMU (the astronaut RCS backpacks) can return to orbit?
« Last Edit: 02/07/2013 05:24 AM by mlindner »
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Offline Proponent

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... surveying all the NEAs is perhaps the clearest, most direct, and least expensive way for NASA to contribute to the continued health, safety, prosperity, and survival of humanity.)

And it would be cheap compared to the cost of pulling off a crewed NEA mission.  It's a real shame it's not being done.

Offline Proponent

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Re: An asteroid mission may be harder than going to Mars
« Reply #24 on: 02/07/2013 08:28 AM »
Here's an idea. Can you find an asteroid thats large enough you can orbit it, but small enough that you can jump from the surface and with the help of a MMU (the astronaut RCS backpacks) can return to orbit?

At constant density, surface escape velocity and circular speed in low orbit for spherical bodies scale linearly with radius.  Bodies about 10-ish km in diameter or smaller will tend to meet your escape-velocity criterion.

Orbiting, though, is probably another matter.  Since small bodies are often quite non-spherical, staying in orbit will probably require a lot of station-keeping.  But then, the delta-V required to station-keep with or with "orbit" is so small that it doesn't really matter.

Landing on an NEA is likely to be more like docking with it.  An NEA EVA is likely to be more like an ISS EVA than a lunar one.

Offline Proponent

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The article is highly misleading, but if you read it closely, you can see how the author might have gone off-track. In short, he is reporting about something that Marcia Smith said during a telecon discussion last week about something that Bill Gerstenmaier said to a committee in July 2012 OVER SIX MONTHS AGO. If you stop and think about it a bit, you might ask why the reporter didn't simply call up Gerstenmaier himself and ask him.

Furthermore, the sentiment the article attributes to Gerstenmeier is that "in many respects, it's easier to go to Mars, because we know a lot about Mars."  He may also hold that in many other respects, it's easier to go to an NEA.

Quote
Bottom line, it's a crappy article.

Yup.

EDIT:  "may" -> "many" in last sentence of penultimate paragraph.
« Last Edit: 02/07/2013 05:35 PM by Proponent »

Online MATTBLAK

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Re: An asteroid mission may be harder than going to Mars
« Reply #26 on: 02/07/2013 08:57 AM »
The article's not great. And lately, I've been pushing the idea that the first manned mission beyond L-2 should be to Phobos and Deimos - we'd get two asteroidal bodies for the price of one (sort of) and Mars as well if sample return probes are scooped up near Phobos.
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Offline spectre9

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Re: An asteroid mission may be harder than going to Mars
« Reply #27 on: 02/07/2013 09:15 AM »
Poor 1999 AO10 gets no love when it's obviously the main target.

It's much easier to get to than Mars.

Missions can be around 200 days which is much shorter than a Mars flyby.

But why flyby Mars when you can enter orbit and visit Deimos? Obviously that takes much more propellant than an asteroid mission.

There are other targets past 2025 but the timescale NASA is on is already much too long for my liking and there's no reason why the date should be pushed even farther to the right.

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Re: An asteroid mission may be harder than going to Mars
« Reply #28 on: 02/07/2013 09:29 AM »
One reason why some NEAs might not be 'getting any love' is that imagine the reaction when Astronauts are on TV and photographed next to a knotty, grey rock not much bigger than their own spacecraft!

"We forked out $10 billion dollars to send these guys to a rock the size of a Hollywood mansion?! If they wanted samples; wouldn't it have been cheaper to send a robot?"

No: Astronauts need to be seen cavorting around a really big body the size of a small mountain or better to be seen getting 'bang for buck'. And if you think the reasons I just stated doesn't matter or is irrelevant - think twice...
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Offline spectre9

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Re: An asteroid mission may be harder than going to Mars
« Reply #29 on: 02/07/2013 09:51 AM »
1999 AO10 is around 50m diameter.

I wouldn't say that's small especially when it's still frontier land.

The 5 month mission will be much quicker than any trip to Mars.

Uninspiring? Maybe so but it's easy and if NASA can't do it given over a decade of preparation there's no way they'll make it to Mars orbit in 2033.

Robotic precursors will be sent first.

The thing with Mars is that those precursors have already been sent, heaps of them too.

Offline alexterrell

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Re: An asteroid mission may be harder than going to Mars
« Reply #30 on: 02/07/2013 10:12 AM »
Poor 1999 AO10 gets no love when it's obviously the main target.

It's much easier to get to than Mars.

Missions can be around 200 days which is much shorter than a Mars flyby.

But why flyby Mars when you can enter orbit and visit Deimos? Obviously that takes much more propellant than an asteroid mission.

There are other targets past 2025 but the timescale NASA is on is already much too long for my liking and there's no reason why the date should be pushed even farther to the right.

Does it require less propellent than Phobos or Deimos?

If you can employ the tactics of Aerocapture and the Oberth Effect, then Phobos should have a lower delta v than most NEOs. (6.2km/s according to Wikipedia - better than most, but not all NEOs in the list)

The other advantage is that it can be revisited every 26 months. An NEO can typically be revisited once every few decades.

True - mission duration is going to be longer. A key criteria is whether artifical gravity is needed.

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